I wouldn't drop the temperatures hoping he heads for a warm spot, because if he's holed up far enough away, he won't try to find it, he would
probably just stay curled up & cold wherever he is.
Darn! I sure hate playing hide & seek w/ snakes, they're SO GOOD at it. Just keep looking...especially at night, when he's more likely to hunt.
The worst (most dangerous) room for a loose snake is probably the kitchen: they can be attracted to the warm motor of a refrigerator & get
killed, they can get into the stove...& maybe into the walls of house, if there's a gap behind the stove where it's hooked up. Cupboards: at
floor level, there is often a dark inviting crawl space up behind the bottom cupboard doors, where they can get under the bottom of the cupboard
& the floor...I once had an adult bull snake get loose & hibernate there for 6 months before she emerged unscathed & ready for food & company.
Washer & dryer, also dishwashers, often have access at floor level, behind them etc.
Good luck & don't give up!