A historic heat wave affected the Pacific Northwest during this interval.  It was caused by a strong upper level ridge that created dry and stable conditions over the area with strong subsidence.  Many daily, monthly, and all-time high temperature records were set over northern California.

Excessive Heat in NORTHEAST SISKIYOU AND NORTHWEST MODOC COUNTIES, CALIFORNIA
From 26-JUN-21 10:00:00 to 30-JUN-21 12:57:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Tulelake was the only station from this zone that reported observations through this event. On 06/26/21, the low temperature was 51 degrees and the high temperature was 93 degrees. On 06/27/21, the low temperature was 54 degrees and the high temperature was 91 degrees. On 06/28/21, the low temperature was 61 degrees and the high temperature was 103 degrees. On 06/29/21, the low temperature was 55 degrees and the high temperature was 103 degrees. On 06/30/21, the low temperature was 52 degrees and the high temperature was 99 degrees. Lava Beds National Monument reported sporadically through this event.  They reported a low temperature of 61 degrees on 07/26/21, a high temperature of 98 degrees on 06/29/21, and a low temperature of 61 degrees on 06/30/21.

Excessive Heat in WESTERN SISKIYOU COUNTY, CALIFORNIA
From 26-JUN-21 10:00:00 to 30-JUN-21 01:20:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

On 06/28/21, the only high temperature reported from this zone was 104 degrees at Fort Jones. On 06/30/21, the only report again came from Fort Jones, with a low of 59 degrees and a high of 103 degrees.

Excessive Heat in MODOC COUNTY, CALIFORNIA
From 26-JUN-21 10:00:00 to 30-JUN-21 12:57:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Alturas (AAT) was the only station from this zone that reported observations. On 06/26/21, the low temperature was 48 degrees and the high temperature was 96 degrees. On 06/27/21, the low temperature was 56 degrees and the high temperature was 100 degrees. On 06/28/21, the low temperature was 59 degrees and the high temperature was 105 degrees. On 06/29/21, the low temperature was 53 degrees and the high temperature was 103 degrees. On 06/30/21, the low temperature was 53 degrees and the high temperature was 98 degrees. On 06/28/21, the high temperature reading of 105 in Alturas set a high temperature record for the month of June. The old record was 102 degrees on 06/25/1961.

Excessive Heat in CENTRAL SISKIYOU COUNTY, CALIFORNIA
From 26-JUN-21 10:00:00 to 30-JUN-21 12:57:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

On 06/26/21, the reported low temperatures in this zone ranged from 57 to 61 degrees and the high temperatures ranged from 103 to 104 degrees. On 06/27/21, the reported low temperatures in this zone ranged from 63 to 68 degrees and the high temperatures ranged from 107 to 110 degrees.  On 06/28/21, the reported low temperatures in this zone ranged from 65 to 68 degrees and the high temperatures ranged from 106 to 110 degrees.  On 06/29/21, the reported low temperatures in this zone ranged from 61 to 64 degrees and the high temperatures ranged from 103 to 105 degrees.  On 06/30/21, the reported low temperatures in this zone were all 61 degrees and the high temperatures ranged from 101 to 103 degrees. On 6/27/21, Montague tied their all-time high temperatures record of 109 degrees, the other 109 degree reading occurred on 7/11/2002. This also broke the high temperature record for the month of June; the old record was 104 set on 06/20/2021.

Excessive Heat in SOUTH CENTRAL SISKIYOU COUNTY, CALIFORNIA
From 26-JUN-21 10:00:00 to 30-JUN-21 12:57:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

On 06/26/21, the reported low temperatures in this zone ranged from 55 to 58 degrees and the high temperatures ranged from 96 to 100 degrees. On 06/27/21, the reported low temperatures in this zone ranged from 62 to 63 degrees and the high temperatures ranged from 103 to 105 degrees.  On 06/28/21, the reported low temperatures in this zone ranged from 51 to 61 degrees and the high temperatures ranged from 100 to 101 degrees.  On 06/29/21, the reported low temperatures in this zone ranged from 55 to 57 degrees and the high temperatures ranged from 99 to 101 degrees.  On 06/30/21, the reported low temperatures in this zone ranged from 56 to 59 degrees and the high temperatures ranged from 96 to 98 degrees. On 06/28/21, Mount Shasta City set a record for the highest temperature in June with a reading of 103 degrees. The old record was 99 degrees, set on 06/20/2021.