Cooling towels will become your best friend. I used to live in N. California and although the days will be hot the evening will cool. I agree that you should plan your day around how your body will feel when you head outside.

I went to NYC last year at the end of summer and the heat was crazy. I carried a cooling towel in my bag along with disposable cooling packs that I got at Walgreen that I could pop open when sitting down at lunch when I was resting.

I bought cooling down the day I moved to HOT Phoenix, Az. It gets up to 117 here! I stay inside as much as possible during hottest part of the days!! Just go out when there some relief from awful weather!! At least it stays lighter out later to be able to go grocery shopping, I also do my pick up at Fry's ( you can shop for groceries online under Fry's website, then pay by credit card. Also schedule a day and time!) It took me awhile to get the hang of it though, if there's a will there's a way!! Good luck ♥️

Ice vest cool neck fan . Long white dress I pack my hydro pack with sonic ice . It lays on my spine . I pass out have a stroke . The heat is not fun anymore

I wear loose fitting mostly linen clothing or a light cotton. I don’t have a cooling jacket but I think they are a great idea. I stay indoors during the hottest part of the day. Wear my hair up, take lots of cold showers, rest frequently, I make a lot of smoothies with almond milk, mango nectar, frozen tropical fruit and spinach, try to avoid cooking, eat salads and sandwiches as my staples in the summer, fans, air conditioning, bring changes of clothing with you if you need an emergency change, I’ve put my under garments in the freezer, carry around ice packs wrapped in a towel, and going to bed I do tha same, wrap a towel around a cold pack and cuddle, wash my hands with cold, cold water, try to get my walks in just as dawn is breaking as it’s the coolest part of the day. Research where you will be going to see if places offer handicapped accommodations to avoid exertion, try to avoid stressful situations, make sure you get a good nights rest each night, those mini fans you can stash in your purse or backpack, avoid alcohol, avoid spicy food, definitely plan ahead, stay in the shade as much as you can, choose to visit out door places in the morning, indoor place with air conditioning during the day, stay well hydrated, drink as much water as you can, this is just what I could think of off the top of my head, oh!! and if you’re flying, call the reservation desk, let them know in a guarded way, could you please be seated first, even look into regular sports clothing they now have this wicking fabric to keep moisture away from your skin.,,
I hope this helps!!

Oh yes heat effects MS terribly. They have special hats and towels that help to keep you cooler. Good luck and enjoy your trip