An upper-level ridge centered over the western United States led to excessive heat across the High Deserts and the lower deserts of Southern California from June 1 to June 5. Hot temperatures and very dry conditions primed the region for enhanced fire weather; a wildfire was reported in Riverside County.
Every event with a place to put it; 5 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS SGX wrote it up.
An upper-level ridge centered over the western United States led to excessive heat across the High Deserts and the lower deserts of Southern California from June 1 to June 5. Hot temperatures and very dry conditions primed the region for enhanced fire weather; a wildfire was reported in Riverside County.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS San Diego, CA wrote its last area forecast discussion before the first event at May 31, 8:15 PM PST, 3 hours 45 minutes earlier.
Area Forecast Discussion National Weather Service San Diego CA 915 PM PDT Mon May 31 2021 .SYNOPSIS... A stagnant weather pattern will be in place over the West this week with low pressure over Baja and high pressure over the Great Basin. Midlevel moisture in easterly flow aloft will produce clouds over the mountains each day. A persistent marine layer will keep June gloom in place in the coastal areas. Temperatures will be seasonal near the coast, while the valleys, mountains and deserts will warm through Friday. Next weekend a trough will bring cooling through early next week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Evening Update: June gloom was already in place in the coastal zones this evening with a solid overcast extending 100 miles west over the ocean. Farther inland scattered convective clouds developed over the mountains this afternoon, most widespread over the San Bernardino Mountains where small cumulus towers formed with the heat of the day. The weather pattern won't change much this week. Cool marine air and low clouds will persist in the coastal zones, while it will turn a little warmer in the valleys, mountains and deserts as higher pressure builds in from the north. Tropical Storm Blanca was located 600 miles south of Cabo this evening. It will drift slowly west this week before dissipating over the weekend. *From Previous Discussion* High pressure will be building aloft over the Great Basin this week as a weak, stalled low pressure center spins over Baja. The resulting easterly flow over SoCal will continue to bring in mid and high level moisture, resulting in some clouds over the mountains each day. Meanwhile, over the coastal basin, a strong inversion has kept some clouds along the immediate coast into the early afternoon. Onshore flow has weakened considerably, compared to the past few days, but further heating of the deserts each afternoon will ensure some gusty sea breezes develop each afternoon and make it into the desert passes be early evening. The marine layer will likely decrease a bit more this week, but remain deep enough to keep coastal and western valley area temperatures closer to average, even as it warms above average farther inland. Warmest days inland should be Wed-Fri before the ridge aloft weakens and gradual cooling begins. The global models show increasing troughing along the West Coast by the weekend and into early next week. Exact details remain elusive, but the ensemble trends are clearly cooler in all 12Z Global model runs. There will also be a switch in wind direction aloft to W-SW late this week, which will cut-off any further influx of mid/high level moisture. && .AVIATION... 010340Z...Coast/Valleys...Stratus with bases 1300-1800 ft MSL will continue to spread inland this evening, reaching portions of the inland valleys overnight, including KONT. Vis 3-5 sm in BR/HZ likely where stratus nears terrain in the valleys. Clouds/vis restrictions clearing inland 15-17Z and near the coast 17-20Z. The immediate coast will remain mostly BKN-OVC through the afternoon. Clouds will begin to spread back into the coastal areas after 23Z Tue with bases near 1000-1500 ft MSL. Otherwise FEW-SCT clouds AOA 10,000 ft MSL and unrestricted vis through Tuesday evening. Mountains/Deserts...FEW-SCT clouds AOA 10,000 ft MSL and unrestricted vis through Tuesday evening. SCT shallow cumulus may develop over the mountain crests again Tuesday afternoon with bases near 8,000 ft MSL. && .MARINE... No hazardous marine conditions are expected through Saturday. && .BEACHES... A long-period south swell of 3 ft/15-17 sec from 190 degrees will bring elevated surf of 4-6 feet to much of Orange County Wednesday through Saturday. The higher surf and high rip current risk will create dangerous swimming conditions. && .FIRE WEATHER... Building high pressure over the Great Basin and stalled low pressure over the Baja Peninsula is resulting in easterly flow aloft over southern California. Moisture in that flow will create some cumulus clouds over the higher mountains each day through midweek. There is a slight chance that enough instability and moisture could create a brief, high-based thunderstorm or two in the late afternoons/early evenings. The threat with these would be isolated, dry lightning and locally gusty, erratic winds. Based on the current short-range models and available data, the chance for these isolated thunderstorms each of then next several days is ten percent or less. The interior valleys, mountains and deserts will be heating up through midweek with daytime maximum temperatures expected to be from 5-10 degrees above average. This will drive stronger sea breezes through the desert passes with local gusts of 25-35 MPH where RH values will initially be from 10-20 percent. With the unseasonably dry fuels, this will create an elevated fire weather potential late each day, especially near and below the passes. West of the mountains, the marine layer and onshore flow will maintain higher humidity and winds will not be as strong. && .SKYWARN... Skywarn activation will not be needed this week. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && EVENING UPDATE...Moede PUBLIC/FIRE WEATHER...10 AVIATION/MARINE/BEACHES...SS
The national radar mosaic for the moment the first event began.
4 heat, 1 wildfire. Local standard time, as filed.
Excessive heat was reported across the Apple and Lucerne Valleys. The heat peaked on Wednesday, June 2, with a high temperature of 104 degrees reported in Apple Valley and a temperature of 97 degrees reported in Hesperia.
Excessive heat occurred across the Coachella Valley through this event. The high temperature peaked in Palm Springs on Friday, June 4 when temperatures reached 109 degrees. Thermal and Indio reported their peak temperatures on June 5, with highs of 108 and 107, respectively. Indio also reported an overnight low temperature of 84 degrees on June 5. The Excessive Heat Warning expired on the evening of June 4, so the hottest day of the event for some locations occurred after the expiration.
Excessive heat occurred across the San Diego County Deserts through this evening. Ocotillo Wells reported the highest temperature of the event at 111 degrees on June 5. The heat peaked in Borrego Springs on June 4, when temperatures reached 108 degrees. The Excessive Heat Warning was allowed to expire on the evening of June 4, so the peak heat that occurred on June 5 was not covered by the heat warning.
Numerous heat-related 911 calls were reported across San Diego County from June 2 through June 4. Several were reported due to walking/hiking in the desert. All cases had experienced mild heat-related symptoms.
The spruce wildfire located 3 miles east of Riverside started around 5 pm local time and was extinguished around 8 pm after burning approximately 12.5 acres. Evacuation orders issued for nearby homes with no structures damaged.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2021Every state in 2021This day in weather historyWarnings in California, June 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 965751, 965752, 965753, 965750, 965754.