Widespread major to extreme HeatRisk from Tuesday into next weekend. Critical fire weather conditions are also anticipated in the Sacramento Valley and adjacent foothills tonight through Wednesday.

Excessive Heat Warning

Key Points

  • Long-duration, major heat event expected this week impacting holiday outdoor events.
  • Excessive Heat Warning remains in effect for the Valley, Delta and foothills from Tuesday morning through Saturday evening.
  • Red Flag Warning is in effect for much of the Sacramento Valley and adjacent elevations below 3000 feet tonight through Wednesday evening.

Discussion

Clear skies cover the region as very strong ridging over the eastern Pacific edges closer. Another short-wave trough will slide over the ridge later today before shifting east. This will help to moderate the rise in temperatures across the region today as warming of only up to 5 degrees is expected compared to Sunday. Behind the wave, northerly surface gradient is forecast to tighten overnight tonight resulting in locally breezy north wind across western portions of the Sacramento Valley. The breezes will last into Tuesday afternoon before weakening, then another bout of northerly breezes is expected Tuesday night and Wednesday (though not quite as strong).

Heat and Fire weather concerns

Combined with very low humidity, the result will be areas of critical fire weather conditions and a Red Flag Warning remains in effect for late tonight into Wednesday.

Red Flag Warning tonight through Wednesday

Long duration heatwave will result in widespread major to extreme heat risk across much of NorCal beginning Tuesday and lasting into at least the weekend. Highs of 105 to 115 will be possible through much of the valley and foothills during the week with overnight lows only mainly in the 70s.

This level of HeatRisk is very dangerous to anyone without proper hydration or adequate cooling. Strongly consider canceling outdoor activities. An Excessive Heat Warning remains in effect for the Valley, Delta and foothills from Tuesday morning through Saturday evening.

HeatRisk_Tue-Sat

Extended Discussion (Friday through Monday)

597 DM upper high progged off the CA coast Friday continues the heat across interior NorCal. High progged to shift inland Saturday/Sunday over CA as EC bumps heights up to 600 DM. High then drifts into the Great Basin Monday. NBM forecasting max temps from 107 to 117 Friday into Saturday, then a slight trend down Sunday into Monday but remaining 5 to 15 degrees above normal.

Overnight low temperatures forecast from the upper 60s near the Delta to mid 80s in the thermal belts of the foothills.