Summer heat

Okay, so I am 22 weeks pregnant with my second child and this is also my second summer pregnancy. But something about this pregnancy is making it very very difficult for me to tolerate the heat. I live in Texas so it's 100° every day right now and every time I spend any kind of time in the heat I feel like I'm going to pass out. I didn't have this with my first pregnancy and I don't know what to do with this... Help!?