Not so much in summer, but spring is always a good time to shop for waterproofs and warm clothing, most of the outdoor shops knock a fair bit of money off to get rid of their last winter coats and things, so as long as you're not looking for anything too specific then there are bargains to be had.
Helps if you're a weird size too, they struggle selling that stuff and you can get it cheap.
Summer fruits are cheap in season, so if you can preserve them by freezing, drying, canning or making jams and jellies then you can keep yourself in fruit over the winter.
I personally love dried cantaloupe or galia melon, it's fragrant, sweet and lovely, so if you have a dehydrator then give it a go, they're cheaper in summer so I make a load and that keeps me until they're cheap again.
Was out in a new bit of countryside today, met up with a chap that I met though my YouTube channel and there were wild (or possibly feral) raspberries everywhere, so I'm going to head back up there with some tubs and pick some to preserve. Summer fruit might be cheap in season, but free is even better.

That is not dead which can eternal lie, and with strange aeons even death may die.