We made bubble snakes a couple of days ago, that was fun. Cut a plastic bottle in half, and use the top part, i.e. the part that you'd usually drink out of. Cover the cut end with a jay cloth, and secure with an elastic band. Dip the jay cloth end in a solution of washing up liquid and water, and blow into the bottle from the drinking end. See who can make the longest bubble snake (the fan might add a new dimension!).
Other hits here: board games, snap, Hama beads, shrinkies, sticky mosaics, fuzzy felt, 'science experiments' (get a book, we have the Usborne Big Book of Science Things to Make and Do, or google), junk modeling, good old fashioned drawing. We also do (loosely speaking) topics, where we'll read about / draw things to do with a topic for a week or so - maybe Space, or the season, or a country, or recently sealife (DS's choice!), and look up info on the computer, then make fact sheets over the course of a few days.
DS has a few apps on the iPad too - some educational and some just fun.
Set4Sport has some good "sporty" ideas using household stuff, although you may struggle to summon up the energy in the heat.
We are about to move back to somewhere that level of hot, and I plan to resort to my old trick of sitting with my feet in a basin of cold water while I do stuff at the table...