Sarah is right, the fluffy undercoat is actually protective; the dark longer guard hairs absorb the heat and the fluff keeps the heat away from the body! They can actually over-heat if shaved and get skin cancers. Dog groomers are notorious for shaving huskies, you have to be very insistent they must not shave them -some are famous for ignoring you though. Petsmart has a few class action suits growing against them for this.
That doesn't mean they can go mushing and romping in the summer, keep activity low. My dogs love their swimming pool, a cool dark hole they've dug and air conditioning vents. I take walks in the early morning hours and bring lots of water, unless we are walking near a stream. They sleep a lot and act like they are lounging lions on the Serengeti LOL
so, no jogging on hot days with huskies or shaving!
make sure they have lots of water! they may only stand in the water or lie in it
-they often do not like to swim just the feet and belly -some will swim though. Quinn likes to stick his head under water and blow bubbles!
We have a screen room with ceiling fans they love to lie in even when it's too hot for me! Tala lies belly up under the fans.
Each dog has a favorite air conditioning vent
No unoccupied cars, even with windows cracked open it will still get too hot!
So, basically, have lots of water available, shade and either ceiling fans or air conditioning. Here in North Carolina they hibernate for the summer LOL