High pressure originating from the Desert Southwest built westward into California resulting in very hot daytime temperatures across the region and warm overnight low temperatures, particularly in the thermal belts. High to very high heat risk impacted the region with a four day heatwave.
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 originating from the Desert Southwest built westward into California resulting in very hot daytime temperatures across the region and warm overnight low temperatures, particularly in the thermal belts. High to very high heat risk impacted the region with a four day heatwave. Several daily high temperature records were either tied or broken on the 18th. During the event, cooling centers were made available to the public across interior Northern California. A list of the cooling centers available are as follows: five cooling centers in Sacramento County, one in Butte County, seven in Calaveras County, one in Placer County, two in San Joaquin County, two in Tuolumne County, two in Yolo County, and Solano County had two libraries available for cooling.
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 Jun 16, 1:40 PM PST, 20 minutes earlier.
Area Forecast Discussion National Weather Service Sacramento CA 240 PM PDT Wed Jun 16 2021 .SYNOPSIS... Widespread triple digit heat expected for the lower elevations into the weekend. High to very high heat risk is expected with well above normal temperatures. && .DISCUSSION... High clouds continue to streaming in from the south with otherwise quiet conditions being observed. High pressure over the Four Corners will remain the dominant feature and expand even more into our region. Today marks the start of interior Northern California's heat wave, with Valley highs ranging from the upper 90s to near 105. The mountains and foothills will see increased temperatures too, with their highs generally in the 80s and 90s. With the higher daytime temperatures, and limited opportunities to cool off at night, overnight lows are forecast to range from the mid 60s to low 70s for the Valley, the upper 60s to the mid 70s for the foothills, and the 50s to the upper 60s for the mountains. With that being said, it still looks like the hottest days will be tomorrow and Friday when highs through most of the Valley will be around 110 degrees. Additionally, overnight lows will remain mild beginning tonight with upper 60s to around 80 common in the Valley and foothill/mountain thermal belts. The result will be widespread high to very high heat risk. Heat safety precautions should be taken! The ridge is expected to hold over the weekend; however, guidance has suggested it may weaken a bit. Temperatures will still remain elevated for most areas, with triple digit heat continuing for the Valley. The immediate Delta area may see some Delta influence which could put temperatures closer to upper 90s to near 100 there. Another feature to keep an eye on the next few days is the rapid spread of high-level moisture westward from Baja and northern Mexico around the southern periphery of the expanding high. IR and WR vapor imagery has been showing occasional cloud enhancement. Models indicate some of this moisture will brush the southeast corner of the forecast area later Thursday into Friday. Think there is a slight chance for at least some cumulus to form on our side, and perhaps even an isolated shower over Tuolumne and Alpine county. Any thunderstorms that do develop, should stay east of the crest and outside of our CWA. && .EXTENDED DISCUSSION (Sunday THROUGH Wednesday)... Strong upper ridging responsible for our heat wave weakens Sunday and shifts into the Great Basin early next week as upper low develops off the CA coast. This will result in a cooling trend through the extended forecast period. Triple digit heat continues through much of the Central Valley Sunday, then 90s are forecast Monday with triple digit heat lingering in the Northern Sacramento Valley. Highs by midweek return to near normal with 80s to 90s for the interior with 60s to lower 80s for the mountains and foothills. && .AVIATION... VFR conditions over the next 24 hours. Locally gusty north winds 15 to 20 mph down the Sacramento Valley 06-18z Thursday, light winds elsewhere. && .STO WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning until 9 PM PDT Saturday 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. &&
11 excessive heat. Local standard time, as filed.
The Delta region saw high temperatures reach upwards of 110 to 111 degrees on the 17th and 18th.
The Sacramento region saw high temperatures reach upwards of 109 to 110 degrees on the 17th and 18th. On the 18th, several daily high temperature records were broken, Sacramento city at 110, Sacramento Executive Airport at 109 and Vacaville at 109 degrees.
Lake Shasta Dam saw high temperatures reach 105 to 107 degrees during the event.
The Northern Sacramento Valley saw high temperatures reach in excess of 110 degrees during the event. On June 18th, Redding and Red Bluff tied daily record high temperatures of 110 and 111 degrees respectively.
The Central Sacramento Valley region saw high temperatures reach upwards of 110 degrees during the event. On June 18th, Marysville recorded a high temperature of 110 degrees.
The Northern San Joaquin Valley saw high temperatures reach over 105 degrees during the event. On June 18th, Stockton tied the daily high temperature record of 108 and Modesto recorded a record daily high temperature of 107 degrees.
The western foothills of the Sacramento Valley saw high temperatures reach upwards of 109 to 110 degrees on the 17th and 18th.
The north eastern foothills of the Sacramento Valley saw high temperatures reach in excess of 100 degrees with warm overnight lows.
The Motherlode region saw high temperatures reach in excess of 100 degrees with warm overnight lows.
Portions of Zone 68 saw high temperatures reach the mid to upper 90s with warm overnight lows.
Portions of Zone 69 saw high temperatures reach the mid to upper 90s with warm overnight lows.
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: 969621, 969624, 969628, 969630, 969632, 969638, 969644, 969649, 969651, 969653, 969655.