I was previously convinced that taking cold showers was my only saving grace during hot summers, but this year I got the advice to try to take a warm shower a short while before bed, and I'm surprised to say that it has helped. This is for high 20s though so YMMV for sure.
Other things that help:
- Open windows when outdoor temperature is lower than indoor temperature, and try to get a cross breeze going if possible
- Keep light out of the house by closing blinds during the day
- Wear linen clothing and use linen bedding, this material works better for warm conditions
- Fans help reduce perceived temperature by several degrees