My neurologist prescribed slurpees...seriously...so I keep flavorice or some kind of popsicles in the freezer for those times when the heat hits me and exacerbates my symptoms.
Also, there are products with beads in them that you soak in cold water and wrap around your neck. Or keep a wet washcloth or hand towel in the freezer and do the same-make sure your pulse points in your neck are covered by it. It lowers your core body temp quickly.
I think MS patients get a tax break for ACs...I can't live without it. I go in the basement during the summer if the AC isn't doing the job...