Rain at Chautauqua apartments.
Davis receives nearly 20 inches of rain annually, which is a quite a bit compared to many cities throughout the state, but not that much from a national perspective.
Local soils can only absorb 1/2" to 1" of rainfall before water starts to run off. Runoff will puddle or run into storm drains. If the drains are blocked with leaves, water will back up onto surface streets. Soil along county roads becomes saturated after just a few inches of rain. Your car will very likely get stuck in the mud if you pull off onto a dirt shoulder.
Not all puddles are the result of rain, some are year round.
(* A ton of rain is approximately equal to one inch of rainfall on 400 square feet.)
Significant rainfall episodes, and otherwise, in Davis:
January 3 - 10, 1995: 6.75" of rain.
January 1 - 31, 2007: no measurable rainfall.
Average monthly rainfall:
June - September: negligible.
November 19, 2013 was the first rain of the 2013-2014 wet season. The storm was relatively minor, dropping 0.03 inches of rain.
Rain on Nov 2nd 2006, first storm of the season