September begins Tuesday, which often marks the start of San Francisco’s warmest and sunniest stretch of weather. But the atmosphere will not follow the traditional script this year.
The Bay Area will be locked in a deep, drizzle-filled marine layer this week, keeping temperatures as much as 15 degrees below normal. An early-season cold front may even bring a chance of significant rain to parts of Northern California on Thursday, but it will probably fall apart before reaching the Bay Area.
Here’s what to expect this week:
Significant early-week cooldown
Widespread fog and low clouds Monday morning will be the precursor to a cool day. High temperatures will be as much as 10 degrees lower than Sunday — in the low 60s at the coast, the mid-60s to low 70s along the bay shoreline and the 70s inland. Napa, Concord and Livermore may rival their coolest day since May, with highs 10 to 15 degrees below normal.
A weak low-pressure system will bring a chance of drizzle to the Bay Area on Tuesday. Wet roads are most likely in the morning and evening along the coast and in the hills, including in San Francisco. Precipitation amounts are expected to be less than a tenth of an inch. High temperatures will be similar to Monday.
Fizzling cold front possible late week
Wednesday will probably be the best chance this week to see fleeting sunshine in San Francisco as the Bay Area gets a brief break between low-pressure systems…