Many GMs ignore weather when running their games. Everything seems to happen on a perpetually fine late spring day when it's never too cold or too hot.

This is a mistake. Just think of all the combat penalties you can heap on players fighting on slippery ground, with wet hair flicking into their eyes, lightning temporarily blinding them, and water getting onto their bowstrings or into their electrically powered weapons.

Transcript

{Obi-Wan races on to the platform to arrest Jango Fett}
Boba Fett: Dad! Look!
Jango Fett: Boba, get on board.
[SFX]: Kablam! {Jango fires at Obi-Wan}
[SFX]: Whoom! {Obi-Wan pulls out his laser sword}
Obi-Wan: Not going to come peacefully, hey?
[SFX]: Blam!
Jango Fett: Arrest me? I should be arresting you...
Jango Fett: In 4 minutes and 33 seconds.
Jango Fett: So, you've decided attack is the least feeble form of defence, Kenobi?
Jango Fett: You still don't understand the magnitude of your sin.
Obi-Wan: Look, if I've somehow inadvertently offended you, I apologise.
[SFX]: Whoom!
[SFX]: Whoom!
[SFX]: Blam! Blam!
Jango Fett: Oh, that's sweet. Maybe I'll spare one planet.
Jango Fett: Let's see... Alderaan.
Obi-Wan: Nooooooo!
Obi-Wan: Hang on, do I know Alderaan?
Jango Fett: No.