I've noticed this as well. This morning it was cloudy but the ground was wet so it just rained and in the game it showed rainy which is fine for me i don't expect the game to be 100% accurate it's close enough but 30 minutes later its saying "clear" when we still have full overcast of clouds. like.. bruh...
Pokémon GO weather rant as a meteorologist
I've been traveling and experienced in real life: sunny, partly cloudy, cloudy, snow, windy. In Pokémon GO, however, I never saw Cloudy and Windy, and when there was Snow in the game and in reality, it did not spawn any Ice and Metal types, and soon enough Extreme was active. I've seen Extreme in clear or partly cloudy, freezing conditions and I traveled 20 km by train to a place with identical weather and the Extreme disappeared.
Currently I am siting under 8/8 Altostratus in northeastern Spain which is a solid cloud cover, yet it is perfectly Sunny/Clear in the game. There is no way a forecaster would predict sunny conditions with so much cloudiness in the region on satellite images.
Something tells me they either fake the weather because they do not have real-time input, or their input is a very bad substitute for actual weather conditions.
Answers
I'm in sunny So Cal, and the weather has been pretty much spot on. But, it's always sunny here so I guess that's not saying much. We did have some wind recently. I went to an area where I can usually catch 1 or maybe 2 dratini if I'm lucky thinking dragon and flying should be spawning like crazy. Not 1 dratini.