Yes, tire pressures typically drop by about 3 psi from summer pressures due to colder air in the winter. Can it cause a flat? Very unlikely, though there is a very (and mean very) small chance that the change in temperature caused the rubber to contract a bit and lose the seal against the rim of the wheel. I would say that there is a 99.9% chance that the flat is unrelated to temperature change though.
Zenmervolt