Dean Ashford, a 3rd year video game art student from Southampton Solent University, is working on his own YouTube channel dedicated to tips and tricks on different game development aspects. He is always ready to cover new topics and problematic questions, so feel free to contact him.
Take a look at his UE4 guides on weather effects below.
Simple Rain Particles
Rain Particles and Material
Snow Particle System
Vertex Paint Rain Material
Dean’s tutorials are focused on Unreal Engine 4, but you could probably ask him to tell you about another package. You can find tons of tutorials on complex materials, special effects and other UE4 aspects here.