High pressure ridging brought the first major heat event of the year to Northern California. Widespread moderate to high heat risk impacted the region Memorial Day weekend and into the first few days of June.
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 STO wrote it up.
High pressure ridging brought the first major heat event of the year to Northern California. Widespread moderate to high heat risk impacted the region Memorial Day weekend and into the first few days of June. Some Valley locations reached over 100 degrees for the first time this year. Temperatures generally reached upwards of 20 to 25 degrees above climatology. Several new daily high temperature records and one record monthly high temperature record were set in the area at the peak of the heatwave on the last day of May. There were three cooling centers open in Sacramento County, one in Yolo County, one in Butte County and one in San Joaquin 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 Sacramento, CA wrote its last area forecast discussion before the first event at May 31, 1:39 PM PST, 10 hours 21 minutes earlier.
Area Forecast Discussion National Weather Service Sacramento CA 239 PM PDT Mon May 31 2021 .SYNOPSIS... Well above average temperatures with dry conditions continue. Record daily highs possible on today. Temperatures lowering slightly by the weekend. && .DISCUSSION... A strong ridge of high pressure has built into NorCal and we are seeing hot temperatures this afternoon. Currently temperatures are running 5 to 15 degree warming for most location compared to yesterday this time. Today is expected to be the hottest day of this heat event with highs topping out between 102 and 108 in the Valley, 93 to 103 in the Foothills and 70s and 80s in the mountains. You will have to get south of Monterey to find a marine layer this afternoon but we should see the marine layer build back north overnight tonight. That will help to bring increased flow through the Delta and overnight lows won't be quite as hot as last night for the Delta region and the Sac region to some degree. Other areas are going to remain hot overnight and the thermal belts will likely only fall into the mid to upper 70s. The upper level ridge will remain in place tomorrow and that will bring another hot day but we will continue to see flow through the Delta and that will keep the Delta region and the Sacramento area slightly cooler then today. As we head into Wednesday and Thursday the ridge will continue to push to the east as a trough drops out of the Gulf of Alaska. This will bring a gradual cooling trend but the northern Sac Valley will still see highs break the century mark both days. The Excessive Heat Warning remains in effect into tomorrow for much of the lower elevations but the Delta and Sac area will fall off tonight with the Delta breeze developing. Whether you are in a heat product or not you should take the heat seriously and practice heat safety. -CJM && .EXTENDED DISCUSSION (Friday THROUGH Monday)... A short wave trough will be digging out the Gulf of Alaska to start the extended period but the warm air and strong ridge in place will weaken this wave and keep it to our west. This will limit the cooling we will see with this and highs will remain 5-15 degrees above average. Long wave troughing then develops over the PacNW into the second half of the weekend. Ensembles are not in good agreement with placement and timing of this trough but it should bring some continued cooling to the region. This pattern will support onshore flow and moderate Delta breezes. -CJM && .AVIATION... VFR conditions the next 24 hours. Surface wind gusts generally under 12 kts except southwesterly gusts 20-30 kts developing vicinity Carquinez Strait and west Delta after 00Z Tuesday. Local southerly gusts 10-15 kts spreading into the Sacramento area TAF sites after 03Z Tuesday. && .STO WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning until 9 PM PDT Tuesday for Carquinez Strait and Delta-Central Sacramento Valley-Motherlode-Mountains Southwestern Shasta County to Western Colusa County-Northeast Foothills/Sacramento Valley-Northern Sacramento Valley-Northern San Joaquin Valley-Shasta Lake Area / Northern Shasta County- Southern Sacramento Valley-West Slope Northern Sierra Nevada- Western Plumas County/Lassen Park. &&
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SACRAMENTO CA
1050 PM PDT MON MAY 31 2021
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0455 PM EXCESSIVE HEAT 4 N ANDERSON 40.51N 122.30W
05/31/2021 M109 F SHASTA CA ASOS
A DAILY RECORD HIGH OF 109 WAS SET FOR
REDDING AT REDDING AIRPORT, BREAKING THE OLD
RECORD OF 103 SET IN 2016, 2001, AND 1950.
THIS ALSO BROKE THE MONTHLY RECORD OF 108
FOR REDDING SET ON MAY 28, 1984 AND MAY 27,
1919.
&&
EK8 excessive heat. Local standard time, as filed.
At the peak of the heatwave on the 31st, Lake Shasta Dam saw high temperatures reach 101 degrees during the event.
At the peak of the heatwave on the 31st, Redding reached 109 breaking both the daily and monthly high temperature records. Red Bluff reached 108, setting a new daily high temperature record.
The Central Sacramento Valley region saw high temperatures in excess of 105 degrees during the event. At the peak of the heat wave on the 31st, Marysville recorded a high temperature of 106 degrees.
At the peak of the heatwave on the 31st, Downtown Sacramento hit 106 tying the daily high temperature record and Sacramento Executive Airport reached 105 setting a new daily high temperature record.
At the peak of the heat wave on the 31st, The western foothills of the Sacramento Valley saw high temperatures reach 102 to 103 degrees.
At the peak of the heat wave on the 31st, the north eastern foothills of the Sacramento Valley saw high temperatures reach mid 90s to just over 100 degrees.
At the peak of the heat wave on the 31st, the Northern San Joaquin Valley saw high temperatures reach just over 100 degrees.
At the peak of the heat wave on the 31st, the Motherlode region saw high temperatures reach in mid 90s to around 100 degrees.
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: 969434, 969435, 969437, 969438, 969440, 969442, 969443, 969444.