If you really want to wear foundation, I warmly recommend you the Shiseido sun-protection compact foundation, it has a high SPF and doesn't feel cacky or anything. You can apply it with the sponge that comes with it, dry or wet (for a better covering effect).
But if the weather is that hot, you'd better not wearing any foundation and go for a good sunscreen and just a little bit of powder where it's needed. Your skin will thank you for that at the end of the summer, believe me