Heat dome bringing triple-digit temperatures to Bay Area; heat advisory issued
A day of cooler temperatures Monday will give way to scorching heat in parts of the Bay Area beginning Tuesday and lasting into Thursday as a heat dome baking Mexico moves over the region before more moderate temperatures return toward the end of the week.
The National Weather Service has issued a Heat Advisory for the Sonoma coastal range, North Bay interior mountains and valleys, and the East Bay hills and interior valleys in effect from 8 a.m. Tuesday to midnight Thursday night. Daytime temperatures are expected to approach 100 degrees during the period.
Farther inland, the Weather Service issued an Excessive Heat Warning for the San Joaquin Valley and lower Sierra Nevada foothills from 11 a.m. Wednesday to 8 p.m. Thursday with dangerously hot conditions with high temperatures of 103 to 108 degrees expected.
The heat dome that has brought brutally hot temperatures to Mexico in May has expanded north into the western U.S. Aside from California's interior valleys, high temperatures are also forecast for Arizona, Nevada and the Pacific Northwest. A heat dome is formed when the ground is warmed, loses moisture, and is then easier to heat even more, with the atmosphere trapping the hot air like a lid on a boiling pot.
The Weather Service said the heat risk for the inland North Bay, the East and South Bays, and the inland Central Coast through Thursday is moderate, meaning there's a moderate risk of heat-related illnesses for sensitive populations (children, the elderly, pregnant women, those with certain medical conditions, or anyone working outside without cooling or hydration). Some areas of the North Bay valleys and far eastern Contra Costa county on Tuesday, are seeing a major risk for heat-related illnesses for anyone without effective cooling or adequate hydration.
The Weather Service offered the following reminders for the period of excessive heat:
- Stay hydrated and drink plenty of fluids.
- Wear lightweight, light-colored clothing.
- Reduce time spent outdoors or stay in the shade.
- Never leave people or pets unattended in vehicles.
- Use sunscreen if going to the coast or the pool.
Before the heat arrives, the forecast for the greater San Francisco Bay Area for Monday calls for partly sunny skies and some clouds, with patchy fog in coastal and interior areas. Daytime highs will be mostly in the 60s to 70s on the coast and around the bay, and in the 70s to 80s inland. Overnight lows will be mostly in the 50s.
Cooler temps are expected to persist through Monday with breezy daytime winds and marine layer stratus overnight.