User blog comment:MidnightShadow07/Stupid Question/@comment-11100467-20150410034050

Transformers are definitely affected by lightning, but the only accounts of them being harmed is when some Decepticons such as Overcast manipulate the weather. A lucky strike could probably harm them. With other types of weather they don't seem to be harmed by them. Manipulation could disorient them, but overall they don't seem to be affected by rain or snow (unless of course they were crushed by a giant snowball).

Cold weather can affect them though.