In origins you can upgrade the storm power to slow down your enemies, as though they were walking in a storm! It even has the expensive cgi showing stormy weather too!
How about havings maps that affect your own troops? (Hero/reinforcements/barracks).
For example, a desert map that makes your troops move and attack slower due to the heat? There could be a wavy pattern across the screen to make out that its really hot...
It doesnt have to just be their movement however, it could affect their stats directly.
It could also affect the enemies too.