Saint Helena, CA Weather

Key Messages

Updated at 1231 AM PDT Fri Oct 23 2026

- Gusty offshore flow across the North Bay Interior Mountains tonight through Saturday morning

- Below normal temperatures today, increase to near normal for the weekend

- Coastal Flooding due to full moon and thermal expansion this weekend through at least the middle of next week

Short Term

Issued at 1231 AM PDT Fri Oct 23 2026 (Today and tonight)

The first rainfall event of the new water year is winding down, after bringing widespread beneficial wetting rainfall across our entire forecast area. Pockets of scattered light rain across the Central Coast remains possible through sunrise this morning. Lingering clouds and moisture will help keep temperatures below normal today before warming to near normal for the weekend. A developing burst of offshore flow will produce gusty winds across the North Bay Interior Mountains this evening through the morning hours Saturday as a relatively weak and progressive 'inside slider' trough passes south through the Central Valley today. A much drier airmass will build in behind the trough with PWATs falling from around 0.75" during the day today, to below 0.50" after sunset. The strongest wind gusts will occur above 2500ft, up to 45 MPH with little vertical gradient forcing to help translate stronger winds to lower lying areas.

Long Term

Issued at 1231 AM PDT Fri Oct 23 2026 (Saturday through Thursday)

The weekend will see a return of temperatures to near normal for this time of year and bright sunny skies due to the drier airmass. Progressive low amplitude ridging this weekend will give way to an upper level low dropping south out of the PNW for the beginning of next week. Overall, consensus in the synoptic patter begins to diverge from there, but either way temperatures appear to remain right around normal with some pleasant Fall days through the extended forecast. Minor coastal flooding due to lunar phase and thermal expansion is possible at normal trouble spots.

Aviation

(12Z TAFS) Issued at 417 AM PDT Fri Oct 23 2026

MVFR-IFR most sites with the exception of STS where fog and LIFR conditions have developed. Expect MVFR CIGs to persist through late morning with guidance showing clearing between 17-20Z. Persistent cloud cover should prevent fog from reaching APC this morning with moderate confidence that CIGs will stay on the IFR/MVFR border. Moderate to high confidence in VFR conditions this afternoon through the end of the TAF period as a much drier air mass moves in in the wake of the departing upper level low. Winds return to a more typical pattern with breezy onshore winds during the afternoon/evening and lighter, variable to offshore winds overnight.

Vicinity of SFO...MVFR CIGs persist through late morning with VFR conditions/clear skies expected this afternoon through the end of the TAF period. Moderate onshore winds peaking around 15 knots are expected this afternoon before winds weaken overnight and gradually become more easterly.

SFO Bridge Approach...Patchy cloud cover may linger over the southern SF Bay longer than over the SFO terminal this morning. Guidance suggests it could take longer for cloud cover to clear across the South Bay/Southern SF Bay as additional rounds of low level clouds push in from the interior.

Monterey Bay Terminals...MVFR through late morning. Moderate confidence that CIGs will clear around 19Z with VFR conditions to prevail through the remainder of the day. Onshore winds to around 10-12 knots expected during the afternoon with lighter, variable to offshore winds expected overnight.