IS IT EASIER TO BECOME OVERHEATED WHILE PREGNANT?

I works at a elementary school. It is to help with recess and only lasts 3 hours. Today it was 85 and muggy. I was in the shade most of the day. I started sweating and all of a sudden I felt weak. I felt like I was going to throw up in front of all of the children. So I told another teacher I needed to sir down. I went to my car sat in the airconditioner answer a snack. I still felt weak but much better. Is this a sign of over heating?? I have never had anything like this happen before. I am around 15 weeks. Thanks so much.