An upper level high pressure system allowed for a combination of above average temperatures and high humidity to produce an elevated heat risk for inland areas August 20-24. This was locally enhanced by heat bursts produced by shower activity in the coastal and valley areas on the afternoon of August 23.
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 high pressure system allowed for a combination of above average temperatures and high humidity to produce an elevated heat risk for inland areas August 20-24. This was locally enhanced by heat bursts produced by shower activity in the coastal and valley areas on the afternoon of August 23.
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 Aug 21, 1:06 PM PST, 1 hour 54 minutes earlier.
Area Forecast Discussion
National Weather Service San Diego CA
206 PM PDT Thu Aug 21 2025
.SYNOPSIS...
Strong high pressure over the region will continue the warmer than
average weather pattern through the weekend. Monsoonal moisture
will continue to increase Friday into early next week, leading to
daily chances for storm activity each afternoon and evening over
the mountains and deserts. The marine layer will be very thin,
leading to minimal clouds and fog through Saturday with better
cloud coverage near the coast by early next week. The area of high
pressure will continue to weaken later next week, leading to a
lesser chance of storms and cooler weather.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
An increase in monsoonal is seen on satellite in the form of
cumulus clouds bubbling over the mountain crests. Though we have
some moisture in place, it won't be enough to form any storms over
the region. Hot temperatures like today's will continue into
Friday as the high pressure peaks in intensity. Friday will be a
bit different though as an increase in monsoonal moisture will
make it feel more humid, especially across the lower deserts.
Chances for storms increase across the mountains and locally into
the deserts by Friday afternoon. Elevated convection is seen on
local hi-res models Friday night into Saturday, which may produce
some light showers across this region. These showers may maintain
themselves into valleys west of the mountains, mainly the Inland
Empire. Saturday and Sunday afternoon will see daily storm chance
across the mountains and deserts. Rain rates through the weekend
are low to moderate confidence, but most rates will be near one
quarter to one half inch per hour.
Confidence lowers on exact mountain and desert locations will see
shower and storm activity, but chances remain 20-50% per NBM
through Wednesday. High pressure will weaken through early next
week, prompting temperatures to lower near average. Ensemble
models show a continued weakening of this area of high pressure
along with a trough that may form offshore. This trend would lead
to a further cooling trend and lower chances for thunderstorm
activity.
&&
.AVIATION...
212045Z...Coast/Valleys...FEW low clouds with bases around 700 ft
MSL currently at the beaches in southern San Diego County. Low
clouds and fog return to the immediate coast 09Z-16Z Friday with
about a 30 percent chance for CIG/VIS impacts at KSAN and 10-20
percent chance at KCRQ and KSNA. Expect clearing to the beaches by
17Z Friday.
Mountains/Deserts...SCT-BKN clouds 15-20kft MSL through tonight. CU
and possible TCU over the mountains this afternoon.
&&
.MARINE...
No hazardous marine conditions are expected through Tuesday.&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Heat Advisory until 8 PM PDT Saturday for San Bernardino and
Riverside County Valleys-The Inland Empire.
Heat Advisory until 8 PM PDT Friday for Orange County Inland
Areas-Riverside County Mountains-San Bernardino County
Mountains-San Diego County Mountains-San Diego County
Valleys-Santa Ana Mountains and Foothills.
Extreme Heat Warning until 8 PM PDT Saturday for Apple and
Lucerne Valleys-Coachella Valley-San Diego County Deserts-
San Gorgonio Pass near Banning.
PZ...None.
&&
PUBLIC...APR
AVIATION/MARINE...PGThe national radar mosaic for the moment the first event began.
5 heat. Local standard time, as filed.
Tied daily record high temperature of 93 at Palomar Mountain. Daily record high of 106 at Campo. Daily record high of 96 at Lake Cuyamaca.
Tied daily record high temperature of 107 at San Jacinto.
Daily record high temperature of 100 at Anaheim.
Daily record high temperature of 110 at Escondido. Tied daily record high temperature of 103 at Ramona.
Daily record high temperature of 100 at Vista. Daily record high temperature of 94 at Chula Vista.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2025Every state in 2025This day in weather historyWarnings in California, August 2025
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: 1293495, 1293497, 1293498, 1293499, 1293500.