They will be perfectly fine for a day without a warm spot to bask and 90 is far from being too hot if it warms up. Think about where they come from in the wild. There are cloudy, cool, rainy days and times where the snakes can't find an ideal basking spot. Being out of what we as humans have deemed their 100% perfect environment (even though we don't know for sure that what we provide is what they would truly prefer) for a day won't cause any issues, lasting or temporary. Have fun finding something to do yourself! Maybe it's time to bust out a good book!?