Exceptionally dry conditions this winter have heightened the risk of summer wildfires
In California, May typically marks the beginning of a warm and dry summer season. This year, however, things are different. Not only has it been warm and dry for the past couple weeks; it’s been warm and dry for months. So dry, in fact, that officials are warning the risk of wildfires across much of the state is going to be much worse than usual, for several months to come.
According to their most recent outlook, the National Interagency Fire Center predicts that large parts of southern and central California, along with forests throughout the Sierra Nevada, are likely to see more wildfires than normal, particularly later this summer.
“A big chunk of the state is looking at above-average wildfire risk,” said Rob Krohn, a meteorologist with the U.S. Forestry Service’s Predictive Services Branch in Riverside. According to Krohn, the exceptionally dry conditions in California during most of this winter have left many areas parched and vulnerable to ignition from both human and natural causes.
This summer’s increased threat of wildfires is something Californians can expect to see more often in coming decades. Climate researchers predict that over the next 75 years, a combination of warmer winters, reduced snowpack, earlier snowmelts, and hotter, drier summers will lead to more wildfires in forested parts of the state. Year-to-year variations in the weather will still heavily influence fire risk in the future, as it has this year, but just how devastating this year’s wildfires are in California will be a warning of the forests’ vulnerability to the developing warmer, drier climate.
The past few years have been relatively quiet for wildfires in California, following two devastatingly dry years in 2007 and 2008, when more than 800,000 acres burned.
“December  was the second driest December in over a hundred years,” Anderson said. Several areas of the state received only 5-to-10 percent of their usual rainfall in December and heading into mid-January, it appeared California might have its driest winter on record.
A few days of heavy rain in late January brought a spot of relief. Then, a wetter than usual March boosted total winter precipitation. Nevertheless, all but the most northern parts of California still registered well below average total rain and snowfall, Anderson said.
And in terms of wildfire risk, Krohn said the wet weather in March and early April came too late. By then the damage was done. While the rain may have helped prevent spring wildfires from starting — to date this year only about 1,000 acres have burned in California, well below normal — plants and trees rely heavily on the rain that falls early in the season to help them stay moist and healthy throughout the dry summer season. Without moisture from early rain, the plants simply haven’t been taking up water that fell later in the spring.
Despite the arid winter, California water supplies are in generally good condition leading into summer. Thanks to record wet conditions last year, most groundwater basins and reservoirs are still high, and the California Department of Water Resources says most people — and farmers — won’t suffer from this winter’s drier than normal conditions.
Unfortunately, these reservoirs have little influence on the wildfire risk, And more often that not in California, Krohn said, predictions for bad wildfire years tend to come true.
“Odds are that these conditions will translate into above normal fire activity this year,” Krohn said. The U.S. Forest Service, along with the National Weather Service, will continue to revise the wildfire outlook throughout the summer, and Krohn said there is a small chance that heavy rains later this summer could develop, which would dampen this fire season.
It’s more likely, however, that local officials will begin to implement burning restrictions across much of the state, particularly as the wildfire risk worsens later this summer.
A version of this post also appears at Climate Central, a content partner of Climate Watch.