The very first day they had the weather it was sunny, then rainy, then snowy. Nothing lasted long enough for anything to spawn. And even then it's still freezing outside no matter the weather, really wish they would have released gen 3 in November.
Now it's stuck on cloudy and partly cloudy most of the time which are terrible weathers because they feature normal and poison, and unfortunately the common Pokemon like Weedle, Venonat, Spinarak, Rattata, Pidgey and Sentret are normal and poison. The rock and fairy are getting maybe 1 here or there and the fighting is at 0%. Have yet to see a Ralts even though fairy has increased spawns.
I thought the weather would make fighting types more common since I still need 175 of those for the gold metal. Machop or Meditite's would be great. But it's just whatever species are common for your area. I am seeing some Slakoth and Zigzagoon's though so those help, well until I get Slaking and Linoone.
They actually left 4 types out of the weather, kind of wish they had removed Normal, Poison and Bug and added some of those in.