California pipes freeze because most homes here weren’t built with extensive freeze protection, since prolonged cold weather is uncommon. When temperatures drop to 32 degrees or below—even briefly—pipes in unheated spaces or along exterior walls can freeze quickly.
The problem is often made worse by small air leaks around windows, doors, and foundations that allow cold air to reach pipes inside walls. Even if your thermostat reads 50 degrees, temperatures inside exterior walls can be 20-30 degrees colder, putting pipes at risk during overnight temperature drops.
Additionally, pipes that work fine in normal weather may have vulnerabilities that only show up during cold snaps. Poor insulation, drafty areas, or pipes running through unheated spaces create perfect conditions for freezing when temperatures drop, even temporarily.