Hotter and drier — those are the new normals for Southern California.
Hotter especially in the late summer and fall months, and drier especially in November and March, traditionally the start and end of the region’s rainy season. More triple-digit temperatures each year, too.
That assessment comes from the National Oceanic and Atmospheric Administration, which recently updated what it considers “normal” weather at thousands of locations across the country. The new normals, based on the weather from 1991 to 2020, replace old normals based on conditions from 1981 to 2010.
The Southern California News Group analyzed data from the 68 stations across Los Angeles, Orange, Riverside, and San Bernardino counties that had both temperature and precipitation normals for both eras to compare how “normal” is changing.
“There’s been quite a bit of warming and quite a bit of drying on Southern California, that’s for sure,” said Michael Palecki, project manager for the climate normals at NOAA’s National Center for Environmental Information.
People concerned about the effects of climate change, Palecki said, are “righteously alarmed at the situation we’re facing.”
Michael Jerrett, co-director of UCLA’s Center for Healthy Climate Solutions, hopes that as people start noticing the changes in weather norms and experience more extreme events, they are moved to not just believe in climate change but do something about it.
“All of these things I think are getting through to people. People are starting to realize climate change isn’t some hoax,” he said. “It’s not a hoax, it’s real and it’s happening.
“We have to affect the behavior of millions and millions of individuals,” Jerrett said. “People have to think this is a serious problem, and I think they’re starting to feel that way.”
If you didn’t enjoy the heat waves that blistered Southern California in June and July, the new normals include some bad news: On average across the 68 weather stations analyzed, the region is seeing about five more 100-degree days than it used to.
It’s worse in the desert.
Twentynine Palms formerly experienced about 63 triple-digit days per year. That’s now up to 89, according to the new weather normals. That represents the largest increase of any station analyzed, but Joshua Tree and one of two stations in Barstow are also getting more than 20 more triple-digit days than they used to.
There are now about 36 triple-digit days per year in Woodland Hills, compared to 21 before. The number nearly doubled in Van Nuys (from eight to 15) and Chino (from 13 to 23).
Of the 68 stations, 59 are seeing more 100-degree days than before, while seven — all near the coast or in the mountains — are unchanged. Only two — Victorville and Trona, both in San Bernardino County — are seeing fewer.
(The most 100-degree days? The new normal is 131 of them per year at a station in Blythe near Riverside County’s border with Arizona, up from 121 in the old normals.)
Heatwaves “are one of the leading causes of weather-related deaths in the United States,” according to the U.S. Centers for Disease Control and Prevention. CDC data shows hundreds of people die each year from heat-related illnesses, including more than 600 in California from 2010 to 2019.
Studies have shown that extreme heat has all sorts of other negative effects on people, said UCLA’s Jerrett. For example, work-related accidents — not just heat-related, but all types of accidents — go up and academic performance goes down, he said.
Even outside of extreme heat events, Southern California is getting hotter, the new normals show.
The average annual temperature — which takes into account the highs and lows on every day of the year — has increased at 67 of the 68 weather service stations analyzed. The only exception was the Tustin Irvine Ranch station, one of two near Irvine’s Great Park, which is 0.6 degrees cooler than before. (The other Irvine Ranch station, however, is 0.9 degrees warmer than before.)
Other stations range from 0.3 degrees warmer in places like Pomona and Wrightwood to 1.6 degrees warmer in Hemet and Ontario, with the largest increase being 1.7 degrees at one of Riverside’s weather stations.
The average increase across the 68 stations analyzed is 0.7 degrees.
That may not sound like much, but actually is “a pretty substantial rate of increase,” Palecki said. He noted that the eras covered by the old normals and new normals have 20 years in common.
“You’re really looking at the differences between the 1980s and 2010s, divided by three,” he said. In other words, a 0.7-degree rise between the two eras means the 2010s were 2.1 degrees hotter than the 1980s in Southern California.
“So that means that we’re really increasing at quite a rapid rate,” Palecki said.
And as Jerrett pointed out, “We’re not going to see this affect all people equally.”
Those most vulnerable to the effects of increased heat are people with preexisting health conditions, the elderly, people who are socially isolated, and Black and Latino communities, he said.
Not only are people in lower-income and minority communities less likely to have air conditioning and more likely to have preexisting conditions, but Jerrett said their neighborhoods tend to have less green space and more structures and concrete, which actually makes them hotter.
In fact, a UC San Diego study released in July found the land surface can be up to 7 degrees warmer in high-poverty neighborhoods than in the wealthiest neighborhoods in the same county.
The new normals show that every month of the year has gotten a little bit warmer in Southern California, but heat is being turned up more in late summer and fall — the months of August through November are each up by 0.9 to 1.0 degrees, on average across the 68 stations. May saw the lowest increase, only 0.1 degrees.
Broken down by geography, temperatures increased most at the inland stations — those more than about 5 miles from the coast but south and west of the mountains — than they did at stations close to the coast, in the mountains, or in the deserts on the other side of the mountains.
July and August are Southern California’s hottest months, but just how hot varies widely by location. July’s new normal high temperature is 69.4 degrees at the Santa Monica Pier, but over 100 at most desert stations, and a withering 110.5 degrees in Needles.
Looking for some chilly weather? Head to the mountains for the region’s lowest average temperatures. In Big Bear Lake, for example, the normal lows are below freezing for half the year.
Less rain (and snow, too)
On average, the 68 weather stations are getting about 0.9 inches less rainfall each year, the new normals show.
That reduction isn’t spread evenly throughout the year. March and November are each getting about a quarter of an inch less precipitation, while April, August, September, and October are each getting about one-tenth less.
Only eight stations are getting more rain than before, and half of those are getting only a few hundredths of an inch more. Sandberg, in L.A. County’s far northwest corner, is up about eight-tenths of an inch, the Getty Center is up about 0.6 inches and Van Nuys is up 0.4 inches.
On the other end of the spectrum, a station on Mount Wilson is getting 3.8 inches less rain, and stations at the airports in Burbank, Ontario, Chino, and Riverside also show a decline of at least 3 inches.
Only 13 stations analyzed had snowfall data. On average, they’re getting a bit over an inch less snow per year than before.
The largest decline was at Big Bear Lake — home to several ski resorts — whose normal annual snowfall dropped from 65.7 inches to 58.6 inches.
Wrightwood, which also offers skiing, is now snowier than Big Bear, according to the NOAA data. Its new normal snowfall is 61.8 inches per year, just a small decline from 62.3 inches before.
‘Perfect conditions for wildfires’
The timing of the hotter, drier conditions is particularly unfortunate for wildfire season. Less rain in March means vegetation can start drying out sooner, hotter fall temperatures can turn more vegetation into wildfire fuel just as destructive Santa Ana winds arrive and a drier November means less rain to help put out conflagrations.
“Those are perfect conditions for wildfires, definitely,” said Tirtha Banerjee, an assistant professor of civil and environmental engineering at UC Irvine who studies how fires move.
Climate change certainly isn’t the only factor in the increasing destructiveness of Western wildfires — more people are living in and visiting wildlands, which increases the risk, and people have been suppressing wildfires for so many years that there’s an abundance of fuel to burn.
But the cycle of hotter temperatures and dryer conditions increases wildfire risks “substantially,” Jerrett said.
“I don’t think it’s a doomsday scenario,” Banerjee said. “We have to start with the fact that fires are not necessarily all bad.”
Many ecosystems depend on fires, he noted, so wildfires aren’t disasters if they aren’t threatening people.
The question needs to be, “How do we live with fire?” Banerjee said. “We cannot afford to lose lives or property, so how do we manage ecosystems better?”
One answer is having more prescribed fires, which he said will reduce the amount of fuel available to burn in wildfires and, in turn, lower their intensity. Engineers can work to “harden” the infrastructure so it’s at less risk of burning, and officials can help communities become more prepared.
Source: Nikie Johnson, OC Register