I had the same problem this July...the house is 124 years old and not insulated except for the ceiling and the bathroom we gutted. Ironically, in my friend's care the tadpoles were fine, but the cats got out . Do you have a friend or neighbor with a cooler house that would be willing to take them, if the basement suggestion doesn't work out? If they only just started sprouting back legs, you do have a bit of time, depending on water temperature. My water was always between 74 - 80 degrees F. Let me check my log and I can give you a time frame between when they got back legs and when front legs appeared.

I do have another idea, but I still strongly recommend cooling them, and even then there's a possibility of drowning if they morph. I had to resort to it on my camping trip, but all did just fine.