A strong ridge of high pressure and a dry airmass helped temperatures sore in inland areas from the 16th through the 27th. The heat was most intense in the deserts on the 20th, 24th, and 25th with Palm Springs reaching 122 degrees on all three days.
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.
A strong ridge of high pressure and a dry airmass helped temperatures sore in inland areas from the 16th through the 27th. The heat was most intense in the deserts on the 20th, 24th, and 25th with Palm Springs reaching 122 degrees on all three days. Temperatures peaked in the 100-110 degree range over the San Diego County Valleys and Inland Empire on the 20th, 24th and 25th. Flex Alerts were issued asking customers to conserve power.
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 Jun 17, 1:00 PM PST, 1 hour earlier.
Area Forecast Discussion
National Weather Service San Diego CA
200 PM PDT Sat Jun 17 2017
.SYNOPSIS...
Very hot weather will prevail over the deserts under strong high
pressure aloft through at least next Thursday, with Tuesday and
Wednesday likely the hottest days when a few locations could exceed
120 degrees. Mild weather will occur along the coast with low clouds
and fog at times during the late nights and early mornings, locally
dense. The inland valleys will hot at times, with peak heat there
Tuesday and Wednesday as well. Slight cooling will occur early next
week.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Marine layer was a little deeper this morning, with cloud tops as
high as around 1500 feet. Latest aircraft soundings show the
inversion base around 700 feet above sea level. Locally dense fog
occurred on the San Diego County mesas and over nearby higher
terrain this morning, and this will be the case again late tonight
and early Sunday. In most cases, temperatures were within 2-3 deg F
of those from 24 hours ago.
A 592 DM high was centered over the Central Coast of California with
ridging southeast through NW Mexico. The axis of the high will
gradually shift east to Nevada-Arizona-Chihuahua through Sunday and
then strengthen through Tuesday over Arizona where it could reach
598 DM. Over our area, there will be variations of the theme, with
very hot weather with very low humidities in the desert but a marine
layer, which rarely dissipates entirely in June, along the coast,
and a strong temperature gradient from the mild coast through the
very warm/hot valleys to the extreme heat in the desert. The all-
time high at Palm Springs is 123, but right now I am thinking they
will fall a couple degrees short of that as models show 850 MB temps
in the 31-33 deg C range near the Coachella Valley, which is not
quite as hot as the 34-36 deg C range farther east and northeast
where 850 MB temps will be within about 1 deg C of records based on
the SPC sounding climatology page. Current forecast of 121 for PSP
Tue/Wed looks good and will not change that.
Closer to the coast, the location of the sharp temperature gradient
between the coast and valleys will depend on the marine layer depth,
which should get gradually more shallow Sunday through Tuesday. Some
temps over 105 could occur in the Inland Empire at times, around 100
in the far inland parts of the San Diego County Valleys and temps
could get close to 100 over far inland Orange County, mainly
Tuesday/Wednesday. Some dense fog will occur near the coast, and
possibly could be along the immediate coast Tue/Wed, if it does not
dissipate entirely. There is hint of cooling as the upper high
weakens slightly, then low-level flow, including at 850 MB, becomes
solidly westerly and strengthens Friday/Saturday for more
substantial cooling as a trough moves south over the Northwest, as
the upper high shifts southeast, though ECMWF is has that troughing
moving east versus south, so it would have less of a cooling trend.
Most likely, temperatures late next week will lower to "just" those
of this weekend, still above the hot averages that the desert has
for late June.
&&
.AVIATION...
172000Z...Clear skies with unrestricted visibility will prevail
through this evening. However, low clouds and fog could re-develop
again along the coast tonight (moderate confidence), potentially
affecting KSAN, KCRQ, and KSNA with CIGS near 600-800 FT MSL and 3-
5SM visibility, perhaps down to 1/2-1SM briefly. Onset timing of
potential IFR looks to be 04-06Z for KSAN and KCRQ and after 09Z for
KSNA. The low clouds and fog will quickly dissipate again by around
15Z Sunday with a return to VFR at all terminals by afternoon (high
confidence).
&&
.MARINE...
Areas of fog with local visibilities 1 NM or less is forecast,
mainly during the late nights and mornings into early next week.
Otherwise, no hazardous marine weather is anticipated through
Wednesday.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning until 9 PM PDT Thursday for Apple and
Lucerne Valleys-Coachella Valley-San Diego County Deserts-
San Gorgonio Pass Near Banning.
Heat Advisory until 9 PM PDT Wednesday for Riverside County
Mountains-San Bernardino County Mountains-San Bernardino
and Riverside County Valleys-The Inland Empire-San Diego
County Mountains.
Heat Advisory from 11 AM Monday to 9 PM PDT Wednesday for Orange
County Inland Areas-San Diego County Valleys-Santa Ana
Mountains and Foothills.
PZ...NONE.
&&
PUBLIC...Maxwell
AVIATION/MARINE...GregoriaThe national radar mosaic for the moment the first event began.
3 heat, 2 excessive heat. Local standard time, as filed.
Eight people suffered heat related illnesses hiking Three Sister Trail, 2 had to be airlifted to the hospital, and a third was transported to the hospital via ambulance. The high temperature in the nearby town of Ramona was 95 degrees.
Palm Springs recorded an afternoon high of 122 degrees, just on degree shy of the all time record.
Anza Borrego State Park reported an afternoon high of 121 degrees, just one degree shy of the all-time record. Other nearby mesonets reported temperatures of 124-125 degrees.
Three Sister Hiking trail was closed on the 20th and 21st after 5 hikers suffering from heat related illnesses were rescued from the tail on the 20th. The high temperature in the nearby town of Ramona was 101 degrees.
A helicopter rescue and 3 vehicle rescues were conducted for heat related illnesses at El Capitan County Preserve. Park staff also had to do extra patrols of the area to share safety information and bottled water.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2017Every state in 2017This day in weather historyWarnings in California, June 2017
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: 708113, 708108, 708118, 708110, 708116.