California, with its Mediterranean climate, generally has mild, wet winters, but this winter has been warm and dry, prompting our plants to sprout as if it were spring.
This spring behavior is best seen in deciduous plants. Below, a cercis occidentalis, western redbud, is flowering and budding.
A ribes sanguineum ‘White Icicle’, white flowering currant, is also sending out flowers and buds. In the background are the faint flower stalks of the festuca californica, California fescue. All three are California native plants.
How warm and dry has it been? Here’s some weather data for Los Altos, my home town, located in Silicon Valley, just south of San Francisco, California. The first chart shows the average high temperatures (red lines) and average low temperatures (purple lines). The solid lines show our actual temperatures, and the dashed lines show the historic temperatures. Our actual high temperatures (solid red line) track the historic averages (dashed red line) until January 2014, where the actual monthly temperature is seven degrees higher than normal and equal to the high temperature for March.
Our actual low temperatures (solid purple line) are usually higher than the historic averages (dashed purple line). The actual low temperature for January is four degrees higher than normal and equal to the historic average temperature for March. Our January high and low temperatures matched what we expect for March! No wonder the plants think it’s spring.
Rainfall is the other aspect of our California winter. The next chart compares our monthly average rainfall (blue bars) to the actual rainfall (red bars) from January 2013. We’ve had much less rain than normal. Actuals are shown through January 2014. I show average rainfall through June because we get most of our rainfall in the winter, and long-term weather forecasts call for our dry spell to last another couple months.
California’s governor recently declared a drought. The cumulative rainfall for Los Altos shows the depth of the drought. The blue line is the sum of the historic average rainfall, about 16 inches a year. The red line is the sum of our actual rainfall — we had 3.08 inches of rain in 2013, and 2014 is starting out dry. If the forecast is accurate, we’ll miss the winter rains and go into the dry summer without moisture in our plants and soil, except for irrigation.
This year looks like very dry, and this would be California’s third dry year in a row.
In summary, we had spring temperatures in January and little rain, and the long-term forecast is for more of the same. For California, whose winter is characterized by cold temperatures and rain, it’s shaping up to be a year with no winter.
For folks interested in the source data, I used wunderground.com for the actual weather data for Moffett NAS, an airport several miles from Los Altos.