It would seem our mild climate would make thunderstorms hard to develop. What allows them to form?
We certainly don't have the hot, muggy air followed by abrupt cooling that breeds the powerful thunderstorms farther east, mainly east of the Rockies. Thunderstorms here are most common from late spring to early fall. The sun is more direct then, better able to heat the ground. That results in a sharp decrease in temperature from ground to altitude (when colder air moves in aloft). That's the definition of an unstable air mass; a sharp decrease in temperature with altitude. Another factor is that our mountains can give moist, unstable air more of a push upward. Even if conditions are marginal for thunderstorms, that upward boost can make the difference.