A strong upper level ridge and offshore flow brought very hot temperatures and low relative humidity to areas west of the mountains. Temperatures ranged from 85 along the coast to 105 degrees in the San Diego County valleys and Inland Empire.
Every event with a place to put it; 1 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.
A strong upper level ridge and offshore flow brought very hot temperatures and low relative humidity to areas west of the mountains. Temperatures ranged from 85 along the coast to 105 degrees in the San Diego County valleys and Inland Empire.
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 Sep 25, 3:42 AM PST, 4 hours 18 minutes earlier.
AREA FORECAST DISCUSSION
National Weather Service San Diego CA
442 AM PDT SUN SEP 25 2016
.SYNOPSIS...
Strong high pressure aloft off the California coast and surface
high pressure over the Great Basin will bring dry and warmer
weather through Monday with periods of gusty northeast winds near
the coastal foothills. Hottest days and strongest winds are expected
on Today and Monday. Upper level low pressure over northern Baja will
bring increasing moisture and slow cooling for Tuesday into
Wednesday. Onshore flow and seasonal temperatures return for the
latter half of the week as a developing trough of low pressure moves
inland through the western states.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
.SHORT TERM (TODAY THROUGH TUESDAY)...
Strong high pressure off the California coast will peak
today...then weaken Monday and Tuesday as an upper level low
pressure system develops over northwest Mexico and moves into
northern Baja. Surface high pressure over the Great Basin will
bring gusty northeast winds near the coastal foothills and below
passes and canyons into the inland valleys and inland Orange
County with strongest gusts to around 55 mph. The flow will become
more easterly tonight into Monday with the stronger winds
continuing near the coastal foothills of the San Diego County
mountains...and in the far inland Inland Empire below the Banning
Pass. Locally gusty east winds will continue into Tuesday...
especially for inland San Diego County.
The high pressure aloft combined with the offshore flow will push
hot temperatures toward the coast today with high temperatures
Monday a few degrees higher. This will push high temperatures into
the 90s towards the coast...to near 100 in the San Diego County
mesas and western valleys...and to 100 to 105 for inland Orange
County and the western Inland Empire. A heat advisory is in effect
for these areas today and Monday. Slow cooling will begin on
Tuesday.
Upper level low pressure over northern Baja will begin to draw
some mid level moisture into far Southern California Monday night
and Tuesday with some mid clouds and very small chances for
precipitation.
&&
.LONG TERM (WEDNESDAY THROUGH SATURDAY)...
Upper low low pressure pressure over Southern California and
northern Baja will slowly weaken with cooling developing and
continuing in the next weekend. Residual mid level moisture will
bring some clouds and small chances of precipitation into
Wednesday and Thursday. Toward next weekend...a low pressure
system moving inland through the western states will bring a
return of onshore flow with gusty west winds in the mountains and
deserts...cooling to near seasonal levels...and a return of night
and morning coastal low clouds and patchy fog.
&&
.AVIATION...
250935Z...N to NE winds will strengthen later this morning. Local
surface gusts of 30-40 kt are possible below the passes and canyons,
and along coastal mountain slopes and foothills. Winds peaking 13-
20Z, weakening some during the afternoon and becoming easterly
overnight. STG-SVR LLWS and up/downdrafts likely over and SW/W of
the mountains, including near KONT.
Otherwise mostly clear with unrestricted vis through Monday morning.
&&
.MARINE...
No hazardous marine weather is expected through Thursday.
&&
.BEACHES...
A long-period south swell from 200 degrees will create elevated surf
of 4 to 7 ft along southwest-facing beaches in Orange County, and 3
to 5 ft along San Diego County beaches today. Strong and dangerous
rip currents are expected with the elevated surf. A Beach Hazards
Statement remains in effect through 8 PM this evening. Swell and
surf will begin to subside tonight into Monday.
&&
.FIRE WEATHER...
Strong high pressure aloft off the California coast and surface
high pressure over the Great Basin will combine to bring dry and
warmer weather through Monday with periods of gusty northeast
winds near the coastal foothills and into portions of the inland
valleys. The most critical combination of highest temperatures...lowest
humidities...and strongest winds is expected today with slight
recovery in humidities on Monday...especially in the mountains.
Areas of greatest impact will be the coastal mountain slopes into
the inland valleys, as well as inland Orange County. Weaker
offshore flow will continue into Tuesday and Wednesday with some
moderation in the heat...humidities...and winds expected.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX Watches/Warnings/Advisories...
CA...Red Flag Warning until 3 PM PDT Monday for Orange County Inland
Areas-Riverside County Mountains-Including The San Jacinto
Ranger District Of The San Bernardino National Forest-San
Bernardino County Mountains-Including The Mountain Top And
Front Country Ranger Districts Of The San Bernardino
National Forest-San Bernardino and Riverside County Valleys
-The Inland Empire-San Diego County Inland Valleys-San
Diego County Mountains-Including The Palomar And Descanso
Ranger Districts of the Cleveland National Forest-San
Gorgonio Pass Near Banning-Santa Ana Mountains-Including
The Trabuco Ranger District of the Cleveland National
Forest.
Wind Advisory until 5 PM PDT Monday for San Diego County
Mountains-San Diego County Valleys.
Wind Advisory until 4 PM PDT this afternoon for Orange County
Inland Areas-Riverside County Mountains-San Bernardino
County Mountains-San Bernardino and Riverside County
Valleys-The Inland Empire-Santa Ana Mountains and Foothills.
Heat Advisory from 11 AM this morning to 8 PM PDT Monday for
Orange County Coastal Areas-Orange County Inland Areas-San
Bernardino and Riverside County Valleys-The Inland Empire-
San Diego County Coastal Areas-San Diego County Valleys-
Santa Ana Mountains and Foothills.
Beach Hazards Statement through this evening for Orange County
Coastal Areas-San Diego County Coastal Areas.
PZ...None.
&&
PUBLIC/FIRE WEATHER...17
AVIATION/MARINE/BEACHES...SSThe national radar mosaic for the moment the first event began.
1 heat. Local standard time, as filed.
A survey of 19 local hospitals indicated 20 heat related 911 calls over two days, with 3 heat related injuries and 1 death. These numbers do not include urgent care facilities and are therefore likely underdone.
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 |
|---|---|---|---|---|---|
| Heat, San Diego County Valleys | 2016-09-25 | Unknown | Direct |
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2016Every state in 2016This day in weather historyWarnings in California, September 2016
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: 661640.