Update: in May 2018, Weather Underground has stopped issuing weather API keys. Existing keys that have been issued still work, but they have changed business and will no longer offer free API keys. We have switched weather service provider to OpenWeatherMap (OWM). The OpenSprinkler weather algorithm no longer requires a weather API key -- however, if you provide a WU key (under the Advanced tab in Edit Options), the weather algorithm will automatically use WU data. 

The description below is no longer relevant.


OpenSprinkler's weather adjustment feature relies on real-time data obtained from the Weather Underground (http://www.wunderground.com) website. To use this feature, you need to apply for Wunderground API Key. There is no cost to apply for a basic key, which is more than sufficient for personal use. 

Follow the steps below:

  1. Create a free Weather Underground account here: https://www.wunderground.com/signup. Enter your email address and a password (this is NOT your API Key), then click the “Sign up for free” button.

  2. Weather Underground will immediately send you an email with an activation link. You must click this link within the email to activate your account (you’ll be brought back to the login screen).

  3. Next, open the following URL https://www.wunderground.com/weather/api/d/pricing.html and click the "Purchase Key" button at the top or bottom of the page (you will not be asked for a method of payment).

  4. Weather Underground will ask you to fill out a simple form in order to complete your request. 
  • When asked about web address, fill in any web address, such as 'www.opensprinkler.com'
  • When asked where the API will be used, answer “Other”.
  • When asked if the API is for commercial use, answer “No”.
  • When asked if the API is for chip processing, answer “No”.

After submitting the form, you should see a page with a green bar that says “Success!”. Below it you’ll see a field called “Key ID”. This is the API Key you need to provide to your OpenSprinkler device. Write down your code or copy it somewhere so you can transfer it to OpenSprinkler.

You can now log out of Weather Underground. Keep your login credentials somewhere secure in case you ever need to access your account again to get a new API Key at some point in the future.