are there places you can go swimming? When it is hot over summer we would go out for a walk etc early on & be home by noon & then go swimming in the afternoon.
Do you have somewhere shady out doors that you can do water play?
Also are there airconditioned shopping centres, I have spend many an afternoon having a milkshake out with the boys just to get us out of the house, we'd often go to the Library (air conditioned) & then afterwards go & have a milkshake.
Not sure what time it gets cooler in the day, but I know when my 2 were younger it was worth having them have shorter night sleep & a nap in the middle of the day so we could enjoy things in the cooler evening... I think why some countries have siestas