S. led to well-above average temperatures across Southern California, as well as elevated thunderstorm convection.
Every event with a place to put it; 11 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 area of upper-level high pressure centered over the southwestern U.S. led to well-above average temperatures across Southern California, as well as elevated thunderstorm convection. Fog along the coast caused travel disruptions.
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 Mar 31, 7:58 PM PST, 4 hours 2 minutes earlier.
Area Forecast Discussion National Weather Service San Diego CA 858 PM PDT Wed Mar 31 2021 .SYNOPSIS... Thursday will be another warm day with highs in the 70s and 80s in many areas. A weak upper level disturbance will bring scattered high clouds and a chance for light showers, mainly over the mountains. Friday through Sunday will be unseasonably warm except near the coast where areas of fog and a shallow marine layer will keep temperatures lower. Early next week a trough will move inland across California for cooler weather, breezy onshore winds and a deeper marine layer. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Update: An upper low centered about 350 miles southwest of San Diego will move northeast over northern Baja and far southern California Thursday afternoon/evening. There is actually some lightning west of San Clemente Island this evening. The evening San Diego sounding continued to show very dry air in place, but an increase in moisture in the 600-400 mb layer. Even so, am not anticipating anything overnight here as that moisture is limited and the upper low remains offshore, but as this upper low feature approaches on Thursday, there is a slight chance of thunderstorms, mainly over the mountains. Previous Discussion: Warm, downslope Santa Ana winds west of the mountains today resulted in higher temperatures in the coastal and valley zones than in the deserts. At 1 PM the temperatures at Camp Pendleton (89), Fullerton (88), Long Beach (87), and Montgomery Field (85) were all higher than in Palm Springs (83). The temperature at the San Diego Airport reached 83 at Noon, one degree shy of the record. The temperature fell to 82 at 1 PM. The airmass was also very dry with dew points of 7 at Long Beach, 2 at Ontario, and -7 at Big Bear. Relative humidities were in the single digits at these sites. The Santa Ana winds will decrease through evening as the 1033 mb surface high over northern Utah weakens. Peak gusts through 1 PM were 65 mph at Highland Springs and 57 mph at Sill Hill Skies tomorrow will have more clouds than today as a compact shortwave 450 miles southwest of San Diego this afternoon moves northeast across northern Baja Thursday. Steepening mid-level lapse rates and an influx of mid-level moisture will produce clouds and virga Thursday. The rain will most likely evaporate in the dry sub- cloud layer before reaching the ground, but a few areas may get a few raindrops, mainly in the mountains. There is a small chance for a thunderstorm. Friday will trend cooler in the coastal zones from increasing onshore flow and the return of a shallow marine layer. Dense fog over the coastal waters Thursday night may reach the beach Friday morning. It will spread a little farther into the coastal zones Saturday morning. Farther inland the mountains and deserts will continue to warm Friday and Saturday. It will actually be hot in the lower deserts Saturday and Sunday with highs from 95 to 100. The outlook for next week shows a cooler weather pattern as a Pacific trough moves inland across California. This trough will bring stronger onshore flow, a much deeper marine layer, and high temperatures back closer to the seasonal norms of 60s at the coast, the low 70s in the valleys, and the low 80s in the lower deserts. && .AVIATION... 010345Z...Mostly clear skies through this evening. SCT-BKN AOA 15,000 FT will move into the region through the night and persist into Thursday. Breezy N-NE winds will continue with surface gusts near 25-35 kts, which will lead to areas of MOD-STG up/downdrafts and LLWS possible on the leeward side of the mtns. Winds will slowly diminish by sunrise Thursday. && .MARINE... No hazardous marine conditions are expected through Sunday morning. Breezy northwest winds will develop Sunday night and will persist into early next week. && .FIRE WEATHER... Santa Ana winds continue to subside with only minor humidity recovery overnight. The offshore winds will be lighter Thursday but the humidities will remain very low, from 6 to 12 percent. On Thursday, an upper level disturbance moving in from the southwest may trigger a thunderstorm with dry lightning in the afternoon. Moisture is limited and wetting rains are unlikely. Humidity will slowly increase from the coast into the valleys Friday through Sunday. && .SKYWARN... Skywarn activation is not requested. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && PUBLIC...Gregoria (Update)/Moede (Previous Discussion) AVIATION/MARINE...APR
The national radar mosaic for the moment the first event began.
8 excessive heat, 1 astronomical low tide, 1 wildfire, 1 dense fog. Local standard time, as filed.
High temperatures occurred in the upper 80s to low 90s. John Wayne airport reached 90 degrees.
Temperatures peaked in the upper 80s and lows 90s. Oceanside airport reached 88 degrees.
Temperatures reached the mid 90s in some spots, including San Pasqual Valley.
Temperatures reached into the upper 80s and the low 90s, including Fullerton Airport at 92 degrees.
High temperatures reached into the upper 80s and low 90s.
The area saw temperatures near 90 degrees.
Hot temperatures occurred with plentiful 90s and even 100 degrees at Palm Springs Airport and 102 degrees at Thermal Airport.
Oceanside fire reports a lightning strike started a fire. The fire was about one quarter acre and burned some surrounding vegetation and fencing near homes. No homes were burned and the crew took about an hour to mop up the scene.
Areas of the desert saw temperatures reach into the upper 80s.
Areas of the SD deserts saw temperatures over 100 degrees, including Ocotillo Wells at 102 degrees.
CHP and news outlets report fatal crash in Carlsbad along Interstate 5 south of Tamarak Avenue. The driver went crashed his car into the center median and was pronounced dead at the scene. Carlsbad Airport reported visibility near one quarter mile in dense fog.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
| Event | Date | Age | Sex | Where | Kind |
|---|---|---|---|---|---|
| Dense Fog, San Diego County Coastal Areas | 2021-04-04 | 23 | Male | Vehicle/Towed Trailer | Indirect |
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, April 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: 954848, 954849, 954850, 954852, 954853, 954855, 954856, 954931, 954857, 954858, 955368.