Heat causing contractions?

I've been having really bad "cramps" for the past few days and baby hasn't been as active as usual so I called and was told to come in for a non-stress test. Baby boy is doing great and My cervix is high and closed and just a little effaced but they said I was having mild contractions caused by the heat. Anyone else experiencing this? I'll be 31w on weds this little man needs to stay put for 9 more!!