Excessive Heat Warning from 11 AM Friday to 11 PM PDT Sunday. Hot and dry conditions will continue through the weekend with the region’s first widespread heatwave of the season. Peak heat expected Saturday, then will gradually moderate for the Independence Day holiday into late next week.
The trough which brought below normal temperatures and mountain thunderstorms has shifted eastward into the Great Basin, with a return to dry weather for the foreseeable future. In its wake, a broad upper- level ridge will establish residence over the Golden State, prompting the first significant, widespread heat of the season for the region. At 2 pm, temperatures were 5 1o 10 degrees warmer than the same time yesterday, for the Valley. Red Bluff has already reached 104.
Highs today will range from the low/mid-90s in the Delta, upper-90s to low-100s for the Sacramento Metro and northern San Joaquin County, and low/mid-100s for the central and northern Sacramento Valley. This primarily equates to widespread moderate heat risk with isolated pockets of high heat risk for this afternoon.
For Friday, we’ll add a few/several degrees from Thursday’s highs with overwhelming majority of Valley real estate forecast to exceed the triple digits. Some locations in the central and northern Sacramento Valley — far from the “cooling” influence of the Delta — will flirt with the 110 deg F mark.
For comparison, normal July 1 max temperatures range from 93 deg F for Downtown Sacramento to 97 deg F for Redding.
Saturday is likely to be the hottest day for many communities, followed by a few degrees of cooling for Sunday. Overnight lows will remain quite elevated in the 70s for the central and northern Sacramento Valley as well as foothill thermal belts within the inversion. Heat risk for Friday- Sunday will be major for the hottest locations in the Valley, including Redding, Red Bluff, and Chico.
Consequently, an Excessive Heat Warning is in effect Friday-Sunday for the Sacramento Valley and Sierra foothill locations north of Yolo County, plus the majority of the San Joaquin Valley east of I-5 or along/south of Stockton.
Please take the necessarily precautions to protect yourself from this upcoming heatwave with ample hydration, shade, air conditioning, and sunscreen.
Exercise abundant caution around area waterways as they are still running EXTREMELY cold, fast, and higher than usual for this time year as a result of the continued summer snowmelt above ~ 8000 feet. The air may be hot, but the water is cold and dangerous!
Extended Discussion (Monday through Thursday)
The overall weather patterns impacting the forecast area remain much the same as before for Monday to Thursday, with a trough replacing the current ridge sometime Monday evening or Tuesday morning. The trough will weaken over California mid-week, then rebuild over Wednesday & Thursday. The pressures associated with the upper level trough aren’t really anomalous, so conditions will remain warm throughout the end of the week. There will however be a chance for isolated thunderstorms in the Sierra, south of Lake Tahoe, starting Monday; though with the lack of precipitable water in the area, they may not appear at all. Temperatures will remain high throughout the extended forecast period, with the northern Sacramento Valley seeing at least a 50% chance of temperatures above 100 degrees through the end of the week, and much of the rest of the Valley seeing at least a 50% chance of surpassing 90 degrees. The city of Sacramento will likely see some temperatures dipping down into the high 80s towards the end of the extended forecast period though, due to onshore flow from the upper level trough. As before, it remains important to practice both heat safety and cold water safety. While river temperatures will likely rise a bit due to higher air temperatures this weekend, they will more than likely remain at dangerous levels for swimmers looking for a break from the heat.