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.

Excessive Heat in MOTHERLODE/CAMPTONVILLE TO GROVELAND, CALIFORNIA
From 16-JUN-21 14:00:00 to 20-JUN-21 20:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

The Motherlode region saw high temperatures reach in excess of 100 degrees with warm overnight lows.

Excessive Heat in MT SHASTA/WESTERN PLUMAS COUNTY, CALIFORNIA
From 16-JUN-21 14:00:00 to 20-JUN-21 20:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Portions of Zone 68 saw high temperatures reach the mid to upper 90s with warm overnight lows.

Excessive Heat in WEST SLOPE NORTHERN SIERRA NEVADA, CALIFORNIA
From 16-JUN-21 14:00:00 to 20-JUN-21 20:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Portions of Zone 69 saw high temperatures reach the mid to upper 90s with warm overnight lows.

Excessive Heat in CARQUINEZ STRAIT AND DELTA, CALIFORNIA
From 16-JUN-21 14:00:00 to 19-JUN-21 21:16:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

The Delta region saw high temperatures reach upwards of 110 to 111 degrees on the 17th and 18th.

Excessive Heat in SOUTHERN SACRAMENTO VALLEY, CALIFORNIA
From 16-JUN-21 14:00:00 to 19-JUN-21 21:16:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

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.

Excessive Heat in NORTHERN SAN JOAQUIN VALLEY, CALIFORNIA
From 16-JUN-21 14:00:00 to 20-JUN-21 20:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

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.

Excessive Heat in CENTRAL SACRAMENTO VALLEY, CALIFORNIA
From 16-JUN-21 14:00:00 to 20-JUN-21 20:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

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.

Excessive Heat in SHASTA LAKE/NORTH SHASTA COUNTY, CALIFORNIA
From 16-JUN-21 14:00:00 to 20-JUN-21 20:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Lake Shasta Dam saw high temperatures reach 105 to 107 degrees during the event.

Excessive Heat in NORTHERN SACRAMENTO VALLEY, CALIFORNIA
From 16-JUN-21 14:00:00 to 20-JUN-21 20:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

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.

Excessive Heat in MOUNTAINS SOUTHWESTERN SHASTA COUNTY TO WESTERN COLUSA COUNTY, CALIFORNIA
From 16-JUN-21 14:00:00 to 20-JUN-21 20:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

The western foothills of the Sacramento Valley saw high temperatures reach upwards of 109 to 110 degrees on the 17th and 18th.

Excessive Heat in NORTHEAST FOOTHILLS/SACRAMENTO VALLEY, CALIFORNIA
From 16-JUN-21 14:00:00 to 20-JUN-21 20:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

The north eastern foothills of the Sacramento Valley saw high temperatures reach in excess of 100 degrees with warm overnight lows.