If you're playing atm 9 (or between 7 and 9), occultism and evilcraft have methods of controlling the weather. Occultism has dry, rainy, thunderstorm and even time so day or night. The hourly weather forecast graphs out temp/dewpoint, wind, rain/snow, etc., which is really handy if you wanna get a quick idea of what to expect at a given time.
They really don't have as much data to get their version of. Weather underground has, by far, the best data and accuracy, in part because it has a network of tens of thousands of personal weather stations (pws). Quick question, after you use the env variable command, does weather still rotate randomly after x amount of time passes using the command weather?
Check current conditions or forecasts with data points from 250,000+ personal weather stations across the globe. The vast amount of weather data they collect only becomes meaningful when combined with the scientific expertise that their team of meteorologists provide.