Warming and drying trend with triple digit heat by late-week for the Central Valley. High Risk for heat-related illnesses for pets, livestock, and much of the population, especially with extended outdoor exposure, and for those who are heat sensitive and/or without effective cooling and/or adequate hydration. Slight chance for showers far northern California Saturday/Sunday.

Heat timeline for the week


We are seeing zonal flow over northern CA today with higher heights building into the area. This is leading to warmer temperatures and they are running generally 7-17 degrees warmer then yesterday this time. Short wave ridging builds in for tomorrow with a continued warming trend. Highs tomorrow will break the 90 degree mark for much of the lower elevations. An upper level low will be spinning over the Gulf of Alaska pushing short waves into the PacNW at times. This will bring slightly lower heights on Wednesday along with some high clouds. Cooling will be limited and highs should be similar to Tuesday.

Strong ridging then builds over the four corners region mid to late week and we will be on the western edge of this strong ridge. Extreme Forecast Index values push above 0.70 Thursday and that will be the first day of hotter temperatures.

Maximum temperatures

Warming will continue into the extended period. We will see a somewhat weak Delta Breeze the next few days but as the ridge sets up the Delta Breeze will be very limited Thursday and Friday.

Heat Risk

Extended Discussion (Friday through Monday)

Strong ridging will continue to be set up over the four corners region for the start of the extended period. This is going to keep hot temperatures in place and the peak of the heat is expected on Friday as highs push above 100 for lower elevation. Widespread high heat risk is expected for the Valley with widespread moderate heat risk for the foothills and mountains. Mild overnight lows can be expected once again Friday night.

The upper level low spinning over the Gulf of Alaska will start to slowly push south and east on Saturday. This is going to bring some cooling Saturday but it is going to be limited with widespread moderate heat risk continuing. A heat product will likely be needed for Friday and Saturday and if you have outdoor plans such as graduation, hiking or work be prepared for the heat.

Much of the lower elevations will push to near to just above the century mark and we will see widespread moderate heat risk for the Valley and Foothills. Overnight lows will be mild Thursday night and with 850mb temperatures around 23-24c the thermal belts will likely only fall into the low to mid 70s.

Clusters do differ on how quick the trough drops out of the Gulf of Alaska with some of them slowing it down. A few isolated showers will be possible over the northern mountains later Saturday into Sunday, timing will likely change depending on when the trough starts to move. Either way precip chances look very low at this point and the impact will be minimal. Increased onshore winds and the return of the Delta Breeze will develop over the weekend as the trough pushes south.