Sunny and clear weather in Pokemon GO gives boosts to the same types of Pokemon.
It depends on where a trainer lives, but many places will most commonly see their in-game weather listed as Clear/Sunny. Those two types of weather in Pokemon GO deliver some significant boosts.
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The boosts are for those types of Pokemon and moves in battle and an increase in those types of Pokemon spawning. Clear/Sunny weather in Pokemon GO increases the spawn rates of Grass, Fire, and Ground-types.
Top 5 Pokemon that appear during Sunny weather in Pokemon GO
#5 - Lombre

Lotad and Lombre have appeared much more frequently in Pokemon GO as of late. Sunny weather only boosts those appearances.
Lombre is a great Pokemon to catch, as it will eventually evolve into Ludicolo. Farming Lotad Candy by catching a ton of them or Lombre will lead to Ludicolo, who as a Grass/Water-type can be very good in battle.
#4 - Nidoking

Nidoking is one of the most influential and intimidating Pokemon of all time. With boosted encounters in Sunny weather, securing a Nidoking is a necessity.
Catching one with good stats outright instead of evolving it from a Nidorino is excellent because it allows Pokemon GO trainers to save Candy to power up the Nidoking.
#3 - Growlithe

Growlithe is an extremely common Fire-type in Pokemon GO. Sunny weather boosts its common spawn even further. Incredibly, it only takes 50 Growlithe Candy to evolve it into Arcanine.
Catching a ton during Sunny weather, and using Pinap Berries, will allow for that evolution in no time. Getting a hold of Arcanine will do any trainer well.
#2 - Roselia

With 100 Candy and a Sinnoh Stone, Roselia evolves into the mighty Roserade. Roselia is a great Pokemon all on its own, but Roserade is on a completely different level.
Farming Roselia Candy with Sunny Weather Encounters will give players a chance to obtain Roserade and perhaps the newest Pokemon GO attack, Leaf Storm.
#1 - Rhydon

Rhydon is a solid middle evolution Rock/Ground-type. Trainers should keep an eye on Sunny weather and hope for a huge number of Rhydon encounters. Getting that precious Rhydon Candy will soon lead to an evolution.
That evolution delivers Rhyperior, one of the most dangerous Pokemon available. It is a wonderful choice for PVP battles and the GO Battle League.
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