diff --git a/routes/adjustmentMethods/AdjustmentMethod.ts b/routes/adjustmentMethods/AdjustmentMethod.ts
index 374f260..3416a2a 100644
--- a/routes/adjustmentMethods/AdjustmentMethod.ts
+++ b/routes/adjustmentMethods/AdjustmentMethod.ts
@@ -1,27 +1,26 @@
-import { GeoCoordinates, WateringData } from "../../types";
+import { BaseWateringData, GeoCoordinates, PWS } from "../../types";
 import { WeatherProvider } from "../weatherProviders/WeatherProvider";
 
 
 export interface AdjustmentMethod {
 	/**
 	 * Calculates the percentage that should be used to scale watering time.
-	 * @param adjustmentOptions The user-specified options for the calculation, or undefined/null if no custom values
-	 * are to be used. No checks will be made to ensure the AdjustmentOptions are the correct type that the function
-	 * is expecting or to ensure that any of its fields are valid.
-	 * @param wateringData The basic weather information of the watering site. This may be undefined if an error occurred
-	 * while retrieving the data.
+	 * @param adjustmentOptions The user-specified options for the calculation. No checks will be made to ensure the
+	 * AdjustmentOptions are the correct type that the function is expecting or to ensure that any of its fields are valid.
 	 * @param coordinates The coordinates of the watering site.
-	 * @param weatherProvider The WeatherProvider that should be used if the adjustment method needs to obtain any more
+	 * @param weatherProvider The WeatherProvider that should be used if the adjustment method needs to obtain any
 	 * weather data.
+	 * @param pws The PWS to retrieve weather data from, or undefined if a PWS should not be used. If the implementation
+	 * of this method does not have PWS support, this parameter may be ignored and coordinates may be used instead.
 	 * @return A Promise that will be resolved with the result of the calculation, or rejected with an error message if
 	 * the watering scale cannot be calculated.
 	 * @throws An error message can be thrown if an error occurs while calculating the watering scale.
 	 */
 	calculateWateringScale(
 		adjustmentOptions: AdjustmentOptions,
-		wateringData: WateringData | undefined,
 		coordinates: GeoCoordinates,
-		weatherProvider: WeatherProvider
+		weatherProvider: WeatherProvider,
+		pws?: PWS
 	): Promise< AdjustmentMethodResponse >;
 }
 
@@ -53,6 +52,8 @@ export interface AdjustmentMethodResponse {
 	 * user-configured watering scale instead of using the one returned by the AdjustmentMethod.
 	 */
 	errorMessage?: string;
+	/** The data that was used to calculate the watering scale, or undefined if no data was used. */
+	wateringData: BaseWateringData;
 }
 
 export interface AdjustmentOptions {}
diff --git a/routes/adjustmentMethods/ManualAdjustmentMethod.ts b/routes/adjustmentMethods/ManualAdjustmentMethod.ts
index d584f83..7c9e8f7 100644
--- a/routes/adjustmentMethods/ManualAdjustmentMethod.ts
+++ b/routes/adjustmentMethods/ManualAdjustmentMethod.ts
@@ -6,7 +6,8 @@ import { AdjustmentMethod, AdjustmentMethodResponse } from "./AdjustmentMethod";
  */
 async function calculateManualWateringScale( ): Promise< AdjustmentMethodResponse > {
 	return {
-		scale: undefined
+		scale: undefined,
+		wateringData: undefined
 	}
 }
 
diff --git a/routes/adjustmentMethods/RainDelayAdjustmentMethod.ts b/routes/adjustmentMethods/RainDelayAdjustmentMethod.ts
index 56b1406..bfa1348 100644
--- a/routes/adjustmentMethods/RainDelayAdjustmentMethod.ts
+++ b/routes/adjustmentMethods/RainDelayAdjustmentMethod.ts
@@ -1,17 +1,20 @@
 import { AdjustmentMethod, AdjustmentMethodResponse, AdjustmentOptions } from "./AdjustmentMethod";
-import { WateringData } from "../../types";
+import { GeoCoordinates, ZimmermanWateringData } from "../../types";
+import { WeatherProvider } from "../weatherProviders/WeatherProvider";
 
 
 /**
  * Only delays watering if it is currently raining and does not adjust the watering scale.
  */
-async function calculateRainDelayWateringScale( adjustmentOptions: RainDelayAdjustmentOptions, wateringData: WateringData | undefined ): Promise< AdjustmentMethodResponse > {
+async function calculateRainDelayWateringScale( adjustmentOptions: RainDelayAdjustmentOptions, coordinates: GeoCoordinates, weatherProvider: WeatherProvider ): Promise< AdjustmentMethodResponse > {
+	const wateringData: ZimmermanWateringData = await weatherProvider.getWateringData( coordinates );
 	const raining = wateringData && wateringData.raining;
-	const d = adjustmentOptions && adjustmentOptions.hasOwnProperty( "d" ) ? adjustmentOptions.d : 24;
+	const d = adjustmentOptions.hasOwnProperty( "d" ) ? adjustmentOptions.d : 24;
 	return {
 		scale: undefined,
 		rawData: { raining: raining ? 1 : 0 },
-		rainDelay: raining ? d : undefined
+		rainDelay: raining ? d : undefined,
+		wateringData: wateringData
 	}
 }
 
diff --git a/routes/adjustmentMethods/ZimmermanAdjustmentMethod.ts b/routes/adjustmentMethods/ZimmermanAdjustmentMethod.ts
index e5268c0..e8fea63 100644
--- a/routes/adjustmentMethods/ZimmermanAdjustmentMethod.ts
+++ b/routes/adjustmentMethods/ZimmermanAdjustmentMethod.ts
@@ -1,13 +1,20 @@
 import { AdjustmentMethod, AdjustmentMethodResponse, AdjustmentOptions } from "./AdjustmentMethod";
-import { WateringData } from "../../types";
+import { GeoCoordinates, PWS, ZimmermanWateringData } from "../../types";
 import { validateValues } from "../weather";
+import { WeatherProvider } from "../weatherProviders/WeatherProvider";
 
 
 /**
  * Calculates how much watering should be scaled based on weather and adjustment options using the Zimmerman method.
  * (https://github.com/rszimm/sprinklers_pi/wiki/Weather-adjustments#formula-for-setting-the-scale)
  */
-async function calculateZimmermanWateringScale( adjustmentOptions: ZimmermanAdjustmentOptions, wateringData: WateringData | undefined ): Promise< AdjustmentMethodResponse > {
+async function calculateZimmermanWateringScale(
+	adjustmentOptions: ZimmermanAdjustmentOptions,
+	coordinates: GeoCoordinates,
+	weatherProvider: WeatherProvider,
+	pws?: PWS
+): Promise< AdjustmentMethodResponse > {
+	const wateringData: ZimmermanWateringData = await weatherProvider.getWateringData( coordinates, pws );
 
 	// Temporarily disabled since OWM forecast data is checking if rain is forecasted for 3 hours in the future.
 	/*
@@ -15,7 +22,8 @@ async function calculateZimmermanWateringScale( adjustmentOptions: ZimmermanAdju
 	if ( wateringData && wateringData.raining ) {
 		return {
 			scale: 0,
-			rawData: { raining: 1 }
+			rawData: { raining: 1 },
+			wateringData: wateringData
 		}
 	}
 	*/
@@ -33,42 +41,40 @@ async function calculateZimmermanWateringScale( adjustmentOptions: ZimmermanAdju
 		return {
 			scale: 100,
 			rawData: rawData,
-			errorMessage: "Necessary field(s) were missing from WateringData."
+			errorMessage: "Necessary field(s) were missing from ZimmermanWateringData.",
+			wateringData: wateringData
 		};
 	}
 
 	let humidityBase = 30, tempBase = 70, precipBase = 0;
 
 	// Get baseline conditions for 100% water level, if provided
-	if ( adjustmentOptions ) {
-		humidityBase = adjustmentOptions.hasOwnProperty( "bh" ) ? adjustmentOptions.bh : humidityBase;
-		tempBase = adjustmentOptions.hasOwnProperty( "bt" ) ? adjustmentOptions.bt : tempBase;
-		precipBase = adjustmentOptions.hasOwnProperty( "br" ) ? adjustmentOptions.br : precipBase;
-	}
+	humidityBase = adjustmentOptions.hasOwnProperty( "bh" ) ? adjustmentOptions.bh : humidityBase;
+	tempBase = adjustmentOptions.hasOwnProperty( "bt" ) ? adjustmentOptions.bt : tempBase;
+	precipBase = adjustmentOptions.hasOwnProperty( "br" ) ? adjustmentOptions.br : precipBase;
 
 	let humidityFactor = ( humidityBase - wateringData.humidity ),
 		tempFactor = ( ( wateringData.temp - tempBase ) * 4 ),
 		precipFactor = ( ( precipBase - wateringData.precip ) * 200 );
 
 	// Apply adjustment options, if provided, by multiplying the percentage against the factor
-	if ( adjustmentOptions ) {
-		if ( adjustmentOptions.hasOwnProperty( "h" ) ) {
-			humidityFactor = humidityFactor * ( adjustmentOptions.h / 100 );
-		}
+	if ( adjustmentOptions.hasOwnProperty( "h" ) ) {
+		humidityFactor = humidityFactor * ( adjustmentOptions.h / 100 );
+	}
 
-		if ( adjustmentOptions.hasOwnProperty( "t" ) ) {
-			tempFactor = tempFactor * ( adjustmentOptions.t / 100 );
-		}
+	if ( adjustmentOptions.hasOwnProperty( "t" ) ) {
+		tempFactor = tempFactor * ( adjustmentOptions.t / 100 );
+	}
 
-		if ( adjustmentOptions.hasOwnProperty( "r" ) ) {
-			precipFactor = precipFactor * ( adjustmentOptions.r / 100 );
-		}
+	if ( adjustmentOptions.hasOwnProperty( "r" ) ) {
+		precipFactor = precipFactor * ( adjustmentOptions.r / 100 );
 	}
 
 	return {
 		// Apply all of the weather modifying factors and clamp the result between 0 and 200%.
 		scale: Math.floor( Math.min( Math.max( 0, 100 + humidityFactor + tempFactor + precipFactor ), 200 ) ),
-		rawData: rawData
+		rawData: rawData,
+		wateringData: wateringData
 	}
 }
 
diff --git a/routes/weather.spec.ts b/routes/weather.spec.ts
index a979773..3964910 100644
--- a/routes/weather.spec.ts
+++ b/routes/weather.spec.ts
@@ -9,7 +9,7 @@ process.env.WEATHER_PROVIDER = "OWM";
 process.env.OWM_API_KEY = "NO_KEY";
 
 import { getWateringData } from './weather';
-import { GeoCoordinates, WateringData, WeatherData } from "../types";
+import { GeoCoordinates, ZimmermanWateringData, WeatherData } from "../types";
 import { WeatherProvider } from "./weatherProviders/WeatherProvider";
 
 const expected = require( '../test/expected.json' );
@@ -81,7 +81,7 @@ export class MockWeatherProvider extends WeatherProvider {
         this.mockData = mockData;
     }
 
-    public async getWateringData( coordinates: GeoCoordinates ): Promise< WateringData > {
+    public async getWateringData( coordinates: GeoCoordinates ): Promise< ZimmermanWateringData > {
         const data = this.mockData.wateringData;
         if ( !data.weatherProvider ) {
             data.weatherProvider = "mock";
@@ -101,6 +101,6 @@ export class MockWeatherProvider extends WeatherProvider {
 }
 
 interface MockWeatherData {
-    wateringData?: WateringData,
+    wateringData?: ZimmermanWateringData,
     weatherData?: WeatherData
 }
diff --git a/routes/weather.ts b/routes/weather.ts
index 1401c77..fe313e5 100644
--- a/routes/weather.ts
+++ b/routes/weather.ts
@@ -5,13 +5,14 @@ import * as SunCalc from "suncalc";
 import * as moment from "moment-timezone";
 import * as geoTZ from "geo-tz";
 
-import { GeoCoordinates, TimeData, WateringData, WeatherData } from "../types";
+import { BaseWateringData, GeoCoordinates, PWS, TimeData, WeatherData } from "../types";
 import { WeatherProvider } from "./weatherProviders/WeatherProvider";
 import { AdjustmentMethod, AdjustmentMethodResponse, AdjustmentOptions } from "./adjustmentMethods/AdjustmentMethod";
 import ManualAdjustmentMethod from "./adjustmentMethods/ManualAdjustmentMethod";
 import ZimmermanAdjustmentMethod from "./adjustmentMethods/ZimmermanAdjustmentMethod";
 import RainDelayAdjustmentMethod from "./adjustmentMethods/RainDelayAdjustmentMethod";
-const weatherProvider: WeatherProvider = new ( require("./weatherProviders/" + ( process.env.WEATHER_PROVIDER || "OWM" ) ).default )();
+const WEATHER_PROVIDER: WeatherProvider = new ( require("./weatherProviders/" + ( process.env.WEATHER_PROVIDER || "OWM" ) ).default )();
+const PWS_WEATHER_PROVIDER: WeatherProvider = new ( require("./weatherProviders/" + ( process.env.PWS_WEATHER_PROVIDER || "WUnderground" ) ).default )();
 
 // Define regex filters to match against location
 const filters = {
@@ -42,7 +43,7 @@ async function resolveCoordinates( location: string ): Promise< GeoCoordinates >
 	}
 
 	if ( filters.pws.test( location ) ) {
-		throw "Weather Underground is discontinued";
+		throw "PWS ID must be specified in the pws parameter.";
 	} else if ( filters.gps.test( location ) ) {
 		const split: string[] = location.split( "," );
 		return [ parseFloat( split[ 0 ] ), parseFloat( split[ 1 ] ) ];
@@ -121,7 +122,7 @@ function getTimeData( coordinates: GeoCoordinates ): TimeData {
  * @param weather Watering data to use to determine if any restrictions apply.
  * @return A boolean indicating if the watering level should be set to 0% due to a restriction.
  */
-function checkWeatherRestriction( adjustmentValue: number, weather: WateringData ): boolean {
+function checkWeatherRestriction( adjustmentValue: number, weather: BaseWateringData ): boolean {
 
 	const californiaRestriction = ( adjustmentValue >> 7 ) & 1;
 
@@ -154,7 +155,7 @@ export const getWeatherData = async function( req: express.Request, res: express
 	const timeData: TimeData = getTimeData( coordinates );
 	let weatherData: WeatherData;
 	try {
-		weatherData = await weatherProvider.getWeatherData( coordinates );
+		weatherData = await WEATHER_PROVIDER.getWeatherData( coordinates );
 	} catch ( err ) {
 		res.send( "Error: " + err );
 		return;
@@ -181,6 +182,7 @@ export const getWateringData = async function( req: express.Request, res: expres
 		location: string | GeoCoordinates	= getParameter(req.query.loc),
 		outputFormat: string				= getParameter(req.query.format),
 		remoteAddress: string				= getParameter(req.headers[ "x-forwarded-for" ]) || req.connection.remoteAddress,
+		pwsString: string					= getParameter( req.query.pws ),
 		adjustmentOptions: AdjustmentOptions;
 
 	// X-Forwarded-For header may contain more than one IP address and therefore
@@ -211,22 +213,24 @@ export const getWateringData = async function( req: express.Request, res: expres
 		return;
 	}
 
-	// Continue with the weather request
 	let timeData: TimeData = getTimeData( coordinates );
-	let wateringData: WateringData;
-	if ( adjustmentMethod !== ManualAdjustmentMethod || checkRestrictions ) {
+
+	// Parse the PWS information.
+	let pws: PWS | undefined = undefined;
+	if ( pwsString ) {
 		try {
-			wateringData = await weatherProvider.getWateringData( coordinates );
+			pws = parsePWS( pwsString );
 		} catch ( err ) {
-			res.send( "Error: " + err );
+			res.send( `Error: ${ err }` );
 			return;
 		}
 	}
 
+	const weatherProvider = pws ? PWS_WEATHER_PROVIDER : WEATHER_PROVIDER;
 	let adjustmentMethodResponse: AdjustmentMethodResponse;
 	try {
 		adjustmentMethodResponse = await adjustmentMethod.calculateWateringScale(
-			adjustmentOptions, wateringData, coordinates, weatherProvider
+			adjustmentOptions, coordinates, weatherProvider, pws
 		);
 	} catch ( err ) {
 		if ( typeof err != "string" ) {
@@ -244,7 +248,19 @@ export const getWateringData = async function( req: express.Request, res: expres
 	}
 
 	let scale = adjustmentMethodResponse.scale;
-	if ( wateringData ) {
+
+	if ( checkRestrictions ) {
+		let wateringData: BaseWateringData = adjustmentMethodResponse.wateringData;
+		// Fetch the watering data if the AdjustmentMethod didn't fetch it and restrictions are being checked.
+		if ( checkRestrictions && !wateringData ) {
+			try {
+				wateringData = await weatherProvider.getWateringData( coordinates );
+			} catch ( err ) {
+				res.send( "Error: " + err );
+				return;
+			}
+		}
+
 		// Check for any user-set restrictions and change the scale to 0 if the criteria is met
 		if ( checkWeatherRestriction( req.params[ 0 ], wateringData ) ) {
 			scale = 0;
@@ -429,3 +445,21 @@ function getParameter( parameter: string | string[] ): string {
 	// Return an empty string if the parameter is undefined.
 	return parameter || "";
 }
+
+/**
+ * Creates a PWS object from a string.
+ * @param pwsString Information about the PWS in the format "pws:API_KEY@PWS_ID".
+ * @return The PWS specified by the string.
+ * @throws Throws an error message if the string is in an invalid format and cannot be parsed.
+ */
+function parsePWS( pwsString: string): PWS {
+	const match = pwsString.match( /^pws:([a-f\d]{32})@([a-zA-Z\d]+)$/ );
+	if ( !match ) {
+		throw "Invalid PWS format.";
+	}
+
+	return {
+		apiKey: match[ 1 ],
+		id: match[ 2 ]
+	};
+}
diff --git a/routes/weatherProviders/DarkSky.ts b/routes/weatherProviders/DarkSky.ts
index 843678c..a5c3746 100644
--- a/routes/weatherProviders/DarkSky.ts
+++ b/routes/weatherProviders/DarkSky.ts
@@ -1,6 +1,6 @@
 import * as moment from "moment-timezone";
 
-import { GeoCoordinates, WateringData, WeatherData } from "../../types";
+import { GeoCoordinates, WeatherData, ZimmermanWateringData } from "../../types";
 import { httpJSONRequest } from "../weather";
 import { WeatherProvider } from "./WeatherProvider";
 
@@ -16,7 +16,7 @@ export default class DarkSkyWeatherProvider extends WeatherProvider {
 		}
 	}
 
-	public async getWateringData( coordinates: GeoCoordinates ): Promise< WateringData > {
+	public async getWateringData( coordinates: GeoCoordinates ): Promise< ZimmermanWateringData > {
 		// The Unix timestamp of 24 hours ago.
 		const yesterdayTimestamp: number = moment().subtract( 1, "day" ).unix();
 		const todayTimestamp: number = moment().unix();
diff --git a/routes/weatherProviders/OWM.ts b/routes/weatherProviders/OWM.ts
index 0d32d8f..939cfa0 100644
--- a/routes/weatherProviders/OWM.ts
+++ b/routes/weatherProviders/OWM.ts
@@ -1,4 +1,4 @@
-import { GeoCoordinates, WateringData, WeatherData } from "../../types";
+import { GeoCoordinates, WeatherData, ZimmermanWateringData } from "../../types";
 import { httpJSONRequest } from "../weather";
 import { WeatherProvider } from "./WeatherProvider";
 
@@ -14,7 +14,7 @@ export default class OWMWeatherProvider extends WeatherProvider {
 		}
 	}
 
-	public async getWateringData( coordinates: GeoCoordinates ): Promise< WateringData > {
+	public async getWateringData( coordinates: GeoCoordinates ): Promise< ZimmermanWateringData > {
 		const forecastUrl = `http://api.openweathermap.org/data/2.5/forecast?appid=${ this.API_KEY }&units=imperial&lat=${ coordinates[ 0 ] }&lon=${ coordinates[ 1 ] }`;
 
 		// Perform the HTTP request to retrieve the weather data
diff --git a/routes/weatherProviders/WUnderground.ts b/routes/weatherProviders/WUnderground.ts
new file mode 100644
index 0000000..854af36
--- /dev/null
+++ b/routes/weatherProviders/WUnderground.ts
@@ -0,0 +1,44 @@
+import { GeoCoordinates, PWS, WeatherData, ZimmermanWateringData } from "../../types";
+import { WeatherProvider } from "./WeatherProvider";
+import { httpJSONRequest } from "../weather";
+
+export default class WUnderground extends WeatherProvider {
+
+	async getWateringData( coordinates: GeoCoordinates, pws?: PWS ): Promise< ZimmermanWateringData > {
+		if ( !pws ) {
+			throw "WUnderground WeatherProvider requires a PWS to be specified.";
+		}
+
+		const url = `https://api.weather.com/v2/pws/observations/hourly/7day?stationId=${ pws.id }&format=json&units=e&apiKey=${ pws.apiKey }`;
+		let data;
+		try {
+			data = await httpJSONRequest( url );
+		} catch ( err ) {
+			console.error( "Error retrieving weather information from WUnderground:", err );
+			throw "An error occurred while retrieving weather information from WUnderground."
+		}
+
+		// Take the 24 most recent observations.
+		const samples = data.observations.slice( -24 );
+
+		// Fail if not enough data is available.
+		if ( samples.length !== 24 ) {
+			throw "Insufficient data was returned by WUnderground.";
+		}
+
+		const totals = { temp: 0, humidity: 0, precip: 0 };
+		for ( const sample of samples ) {
+			totals.temp += sample.imperial.tempAvg;
+			totals.humidity += sample.humidityAvg;
+			totals.precip += sample.imperial.precipRate;
+		}
+
+		return {
+			weatherProvider: "WUnderground",
+			temp: totals.temp / samples.length,
+			humidity: totals.humidity / samples.length,
+			precip: totals.precip,
+			raining: samples[ samples.length - 1 ].imperial.precipRate > 0
+		}
+	}
+}
diff --git a/routes/weatherProviders/WeatherProvider.ts b/routes/weatherProviders/WeatherProvider.ts
index 4826df2..895bbab 100644
--- a/routes/weatherProviders/WeatherProvider.ts
+++ b/routes/weatherProviders/WeatherProvider.ts
@@ -1,14 +1,16 @@
-import { GeoCoordinates, WateringData, WeatherData } from "../../types";
+import { GeoCoordinates, PWS, WeatherData, ZimmermanWateringData } from "../../types";
 
 export class WeatherProvider {
 	/**
-	 * Retrieves weather data necessary for watering level calculations.
+	 * Retrieves weather data necessary for Zimmerman watering level calculations.
 	 * @param coordinates The coordinates to retrieve the watering data for.
-	 * @return A Promise that will be resolved with the WateringData if it is successfully retrieved,
-	 * or rejected with an error message if an error occurs while retrieving the WateringData or the WeatherProvider
+	 * @param pws The PWS to retrieve the weather from, or undefined if a PWS should not be used. If the implementation
+	 * of this method does not have PWS support, this parameter may be ignored and coordinates may be used instead.
+	 * @return A Promise that will be resolved with the ZimmermanWateringData if it is successfully retrieved,
+	 * or rejected with an error message if an error occurs while retrieving the ZimmermanWateringData or the WeatherProvider
 	 * does not support this method.
 	 */
-	getWateringData( coordinates : GeoCoordinates ): Promise< WateringData > {
+	getWateringData( coordinates: GeoCoordinates, pws?: PWS ): Promise< ZimmermanWateringData > {
 		throw "Selected WeatherProvider does not support getWateringData";
 	}
 
diff --git a/routes/weatherProviders/local.ts b/routes/weatherProviders/local.ts
index 71e4798..1a12eca 100644
--- a/routes/weatherProviders/local.ts
+++ b/routes/weatherProviders/local.ts
@@ -1,6 +1,6 @@
 import * as express	from "express";
 import { CronJob } from "cron";
-import { GeoCoordinates, WateringData } from "../../types";
+import { GeoCoordinates, ZimmermanWateringData } from "../../types";
 import { WeatherProvider } from "./WeatherProvider";
 
 const count = { temp: 0, humidity: 0 };
@@ -46,9 +46,9 @@ export const captureWUStream = function( req: express.Request, res: express.Resp
 
 export default class LocalWeatherProvider extends WeatherProvider {
 
-	public async getWateringData( coordinates: GeoCoordinates ): Promise< WateringData > {
-		const result: WateringData = {
-			...yesterday as WateringData,
+	public async getWateringData( coordinates: GeoCoordinates ): Promise< ZimmermanWateringData > {
+		const result: ZimmermanWateringData = {
+			...yesterday as ZimmermanWateringData,
 			// Use today's weather if we dont have information for yesterday yet (i.e. on startup)
 			...today,
 			// PWS report "buckets" so consider it still raining if last bucket was less than an hour ago
diff --git a/types.ts b/types.ts
index 8dbe9f5..72a480d 100644
--- a/types.ts
+++ b/types.ts
@@ -1,6 +1,9 @@
 /** Geographic coordinates. The 1st element is the latitude, and the 2nd element is the longitude. */
 export type GeoCoordinates = [number, number];
 
+/** A PWS ID and API key. */
+export type PWS = { id: string, apiKey: string };
+
 export interface TimeData {
     /** The UTC offset, in minutes. This uses POSIX offsets, which are the negation of typically used offsets
      * (https://github.com/eggert/tz/blob/2017b/etcetera#L36-L42).
@@ -50,22 +53,25 @@ export interface WeatherDataForecast {
     description: string;
 }
 
+export interface BaseWateringData {
+    /** The WeatherProvider that generated this data. */
+    weatherProvider: WeatherProviderId;
+    /** The total precipitation over the window (in inches). */
+    precip: number;
+}
+
 /**
  * Data from a 24 hour window that is used to calculate how watering levels should be scaled. This should ideally use
  * historic data from the past day, but may also use forecasted data for the next day if historical data is not
  * available.
  */
-export interface WateringData {
-    /** The WeatherProvider that generated this data. */
-    weatherProvider: WeatherProviderId;
+export interface ZimmermanWateringData extends BaseWateringData {
     /** The average temperature over the window (in Fahrenheit). */
     temp: number;
     /** The average humidity over the window (as a percentage). */
     humidity: number;
-    /** The total precipitation over the window (in inches). */
-    precip: number;
     /** A boolean indicating if it is raining at the time that this data was retrieved. */
     raining: boolean;
 }
 
-export type WeatherProviderId = "OWM" | "DarkSky" | "local" | "mock";
+export type WeatherProviderId = "OWM" | "DarkSky" | "local" | "mock" | "WUnderground";