Davis has a Mediterranean climate, meaning that almost all rainfall comes during the cooler part of the year (roughly November through March), and especially during the winter months of December, January, and February. During the warmer half of the year it seldom rains, and if it does it is light and brief.
Davis receives an average of 20 inches (~500 mm) of rain annually, which is around average for a California city, but low from a national perspective. Most rains are light or moderate in intensity, and separated by at least a day of dry weather. Nevertheless, during some winters, Davis receives a ton of rain, and that along with the fog makes for very dismal conditions, in stark contrast with the sunny weather that prevails the rest of the year. This can take newcomers a while to get used to.
Local soils can only absorb 1/2" to 1" (13-25 mm) 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.
For an example of natural drainage methods used in Davis, check out the ecologically designed neighborhood of Village Homes, which does NOT have ANY storm drains. Rather it makes use of swales (ditches on contour) that slow, spread, and sink the water into the soil to replenish groundwater, rather than contribute to storm water flood control. In the 1980s during a particularly bad flood year, the neighborhood actually helped absorb flood water from neighboring subdivisions, whose storm drains were overwhelmed. If you're into the idea of natural drainage, read up on permaculture or call up Whole System Designs, a local landscape contractor that designs and installs swales and other water harvesting earthworks. They also install rainwater catchment tanks/cisterns and have thousands of gallons of water already captured in El Niño 2016! For every 1000 sq feet of catchment area, you can expect to capture 600 gallons of water per inch of rain!
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: October: 0.9" (23 mm) November: 2.4" (61 mm) December: 3.5" (89 mm) January: 3.9" (99 mm) February: 4" (102 mm) March: 2.8" (71 mm) April: 1.2" (30 mm) May: 0.6" (15 mm) June - September: negligible.
- Very heavy rain combined with small hail (and a single thunderclap), "deluge", on January 19, 2017 in the late morning. Never seen anything like it since I started living in Davis (October 2011).
- March 20-21, 2016: Two days of light showers dropped 0.15 inches of rain over Davis.
- March 10-13, 2016: Four days of wet weather brought in some 1.90 inches of rain to Davis. Excess runoff in the Sacramento River also began flowing over the Fremont Weir into the Yolo Bypass.
- March 4-5, 2016: A two day storm brought in some 1.87 inches of rain, 1.50 inches of which fell on Saturday alone. A very intense band of rain, paired with heavy gusts of wind, swept through the valley around 10pm Saturday night, knocking out power in many places, including parts of Davis. City and PG&E crews were active through out the night in Davis, clearing fallen tree limbs and tending to power outages.
- February 2, 2016: Light morning showers dropped 0.04 inches of rain.
- January 29, 2016: Modest showers dropped a small amount of rain, 0.04 inches, over Davis.
- January22-23, 2016: A moderate storm brought in 0.31 inches over two days. Most of the rain (0.29 inches) fell during the 22nd.
- January 13-19, 2016: A series of El Nino driven systems brought in 2.39 inches over the 7 day period. The average daily precip. was 0.34 inches per day. The wettest day was the 19th with 0.97 inches for the day.
- January 4-9, 2016: Nearly a week's worth of precipitation brought in a reported 2.57 inches of rain for Davis, including 1.32 inches on January 6th alone.
- December 18-21, 2015: Four days of showers dropped 0.56 inches of rain over Davis.
- December 13, 2015: An early morning storm brought in 0.55 inches of rain.
- December 10, 2015: Light showers brought 0.19 inches or rain.
- November 8-9, 2015: Scattered showers brought 0.09 inches or rain over two days.
- November 1-2, 2015: First storm of the 2015-2016 wet season. Brought in 0.75 inches over two days.
- December 11-12, 2014: Medium sized storm dropped 1.19 inches of rain over Davis. (Storm was overly-hyped by the news media as a potentially devestating storm for California, but ended up being kind of a normal storm for Tinytown).
- Late November/Early December 2014 Rain came (in spades) starting during Black Friday (November 28) 2014. Rain levels are now at normal (at least in the Bay Area) for this year.
- February 25-March 04 2014: Two large storm systems passed through Davis, dropping a total of 1.90 inches of rain. The first system peaked on Wednesday, Feb 26th, dropping approximately 0.42 inches of rain, and the second system peaked on Friday, Feb 28th with 1.14 inches. Miscellaneous showers contributed to the remaining precipitation.
- February 6-9 2014: A series of storms brought in 1.78 inches of rain.
- November 19, 2013: November 19, 2013was the first rain of the 2013-2014 wet season. The storm was relatively minor, dropping 0.03 inches of rain.
Also see: Thunderstorms