High pressure over California resulted in very hot daytime temperatures and warm overnight low temperatures across interior Northern California. High to very high heat risk impacted the region.
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 over California resulted in very hot daytime temperatures and warm overnight low temperatures across interior Northern California. High to very high heat risk impacted the region. One daily high temperature record was broken. During the event, cooling centers were made available to the public across interior Northern California.
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 Sep 7, 1:45 AM PST, 10 hours 15 minutes earlier.
Area Forecast Discussion National Weather Service Sacramento CA 245 AM PDT Tue Sep 7 2021 .SYNOPSIS... Hot and dry weather this week with moderate heat risk during the middle of the week. Increasing chances of late day Sierra thunderstorms late in the week. && .DISCUSSION... The large area of high clouds over NorCal continues to slowly lift north as deeper moisture moving around the periphery of the high (centered over Nevada) moves up from the southeast well offshore. There is some deep convection embedded in the moisture flow evident from some enhancement on IR and occasional lightning. Active weather associated with this moisture will remain well to the west of the forecast area today as the cutoff low that's been parked off the coast finally opens and lifts out brushing the far northwest corner of the state late today. Surface pressure gradients are similar to those of 24 hours ago, and the marine layer remains very shallow with stratus mainly confined to the immediate coast. Current temperatures are very mild, ranging from the upper 60s to lower 80s through the Central Valley (around 5-10 degrees milder compared to this time early Monday). Strong high pressure will remain over NorCal through the remainder of the week. 850 mb temperatures peak in the mid to upper 20s C today through Thursday, then are forecast to drop a bit on Friday. Highs the next three days will be around 10-15 degrees above average. Smoke from wildfires burning over far northern California may work its way south tonight and Wednesday and could shave a few degrees off highs during the second half of the week. Overnight lows will remain very mild the next several nights. Widespread moderate to high heat risk (locally very high) will persist through Thursday. Strong heating over the Central Valley will result in a decent push of westerly breezes late this afternoon and this evening over the Coast Range and along the western edge of the Central Valley. This pattern may reoccur on Wednesday, but likely not quite as strong. A short-wave forecast to pass to the north on Friday may induce stronger onshore flow bringing a little cooling for Friday, and better overnight cooling for Friday night/early Saturday. A few late day thunderstorms will be possible over the northern Sierra south of Tahoe late this week (Thursday and Friday). && .EXTENDED DISCUSSION (Saturday THROUGH Tuesday)... Ensemble guidance shows upper level flow becoming more zonal over West on Saturday, breaking down the high pressure ridge. This will cause temperatures to cool a few degrees from Friday. Cluster analysis then suggests a shortwave trough may move over the PacNW and northern California on Sunday with fairly zonal flow returning for early next week. However, there is still significant uncertainty in depth and location of this wave. Overall, this shortwave will allow temperatures to keep cooling, reaching near normal by Sunday. Temperatures in the extended period are forecast in the low to mid 90s across the Valley, and 60s to 80s for the mountains and foothills. Locally breezy onshore/westerly flow may be possible as the the wave passes over the area, mainly over the mountains. -HEC && .AVIATION... Areas MVFR/IFR conditions mainly in the vicinity of wildfires with LCL MVFR conditions elsewhere due to FU/HZ. Otherwise, VFR conditions expected to predominate the next 24 hours. Locally breezy surface winds gusts 20-25 mph in the Valley and Coastal Range 21z Tuesday thru 06z Wednesday. Elsewhere, surface wind gusts under 10 kts except local southwest gusts to 20 kts in the Delta region. && .STO WATCHES/WARNINGS/ADVISORIES... Heat Advisory from noon today to 8 PM PDT Thursday for Burney Basin / Eastern Shasta County-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. &&
12 excessive heat. Local standard time, as filed.
The Burney Basin region saw high temperatures reach over 100 degrees during the event.
Lake Shasta Dam saw high temperatures reach 104 degrees during the event.
The Northern Sacramento Valley saw high temperatures reach in excess of 105 degrees, with Redding airport reaching 108 degrees during the event.
The Central Sacramento Valley region saw high temperatures reach upwards of 105 degrees during the event. On September 7th, Marysville recorded a high temperature of 106 degrees.
The Sacramento region saw high temperatures reach in excess of 105 degrees. On the 8th, downtown Sacramento reached 106 degrees.
The Delta regions saw high temperatures reach upwards of 105 degrees. Nut tree airport in Vacaville reported a high temperature of 108 degrees on the 8th.
The Northern San Joaquin Valley saw high temperatures reach over 100 degrees during the event.
The western foothills of the Sacramento Valley saw high temperatures reach upwards of 107 to 112 degrees during the event.
The north eastern foothills of the Sacramento Valley saw high temperatures reach upwards of 104 to 109 degrees during the event.
The Motherlode region saw high temperatures reach upwards of 106 to 109 degrees during the event.
Portions of the region saw high temperatures reach upwards of 100 to 104 degrees during the event.
Downieville reported a high temperature of 102 on the 7th. Generally the region saw high temperatures reach the mid to upper 90s.
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, September 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: 987032, 987033, 987034, 987035, 987036, 987037, 987038, 987039, 987040, 987041, 987042, 987043.