Rain, heat, repeat: What does erratic weather mean for California drought and fires?
The pendulum of Northern California weather is getting ready to swing once again, from rain, hail, thunderstorms and snow showers at the start of this week to sunny and much warmer than average temperatures by the weekend.
Temperatures near Sacramento are expected to soar from a forecast high of 65 degrees Tuesday to 92 degrees by Saturday, staying in the upper 80s to low 90s early next week, according to the National Weather Service.
Daytime highs near South Lake Tahoe will jump from the mid-30s Tuesday to the mid-70s this coming weekend. Both are roughly 10 degrees hotter than normal for this time of year.
The latest turnaround brings the same pair of questions Californians have grown used to asking: What do the latest weather trends mean for the drought, and for wildfire risk?
Drought and summer water supply
In a California hydrology report Friday, state water officials wrote that April finished with “near average conditions,” but that this “ultimately did little to offset the precipitation deficit caused by near record-breaking dry conditions to start 2022.”
Sacramento and the central Sierra Nevada mountains each broke all-time records for the least precipitation ever recorded between the start of January and the end of March.
Just a couple of weeks after winter storms dumped on the central Sierra Nevada in late April, statewide snowpack has melted down to 22% of average as of Tuesday, falling from 35% on April 26, according to the state Department of Water Resources. The southern Sierra range is now at just 9% of average.
“As we get that snowpack building through winter and it gets to spring, the snowmelt becomes that foundation of your summer supply,” Michael Anderson, the state climatologist, said in a media briefing with reporters Tuesday on drought conditions. “As that melts out, then you move into storage until those fall rates return and the cycle starts over.”
But as temperatures and precipitation patterns bounce between extremes, Anderson said, this normal cycle is disrupted.
“We used to not have to worry about warm anomalies in the wintertime drying out the landscape. That was a summertime thing,” Anderson said. “Now it really is, we get these long breaks (in precipitation) like we saw this year.”
Anderson noted the stark comparison between March in the first year of the current drought, 2020, and March 2022. Statewide precipitation in March 2020 reached 95% of average; this year, it was just 30%. March 2020 was 1.3 degrees cooler than average; March 2022 was 3.6 degrees warmer than average.
He said the state’s snowpack peaked about a month earlier than normal, in early March rather than early April.
Climate change is a large part of those anomalies, state water officials on Tuesday’s briefing said.
The anomalies are impacting reservoir levels as well. Eleven of the state’s 17 reservoirs are below 80% of average, according Department of Water Resources data updated Tuesday. The two largest, Lake Shasta and Lake Oroville, were at 48% and 70% of average, respectively.
Wildfire risk
Fire agencies and climate experts have advised that this year’s wildfire season figures to be a long and difficult one for California.
That hasn’t materialized yet, with mild temperatures and scattered showers in recent weeks having helped delay severe wildfire weather conditions in the short term.
In early April, the weather service issued its earliest-ever spring red flag warning for interior Northern California due to dry, hot and windy conditions.
But the Sacramento Valley has not been under red flag conditions in more than a month since then, thanks largely to off-and-on rain that has fallen just frequently enough to keep fire fuels from drying out.
That streak won’t continue forever. As summer months arrive, bringing more consistent heat as precipitation peters out, the low existing supply of snowmelt and snow runoff will fade, leading to drier and more receptive wildfire fuels in many parts of the state.
In the immediate short term, the National Weather Service Storm Prediction Center’s fire weather outlook as of Tuesday showed no heightened fire risk within California.
Those forecasts do, though, show “critical” fire weather elsewhere in the West, across wide swaths of New Mexico, Arizona and Colorado over at least the next few days, along with “elevated” fire risk in other parts of those states and in Nevada and Utah.
California’s most dangerous wildfire conditions in recent years have often come not during the hottest point of the year, but rather in early autumn, when lingering heat tends to coincide with gusty winds and dry vegetation.
This story was originally published May 11, 2022 at 5:00 AM.
