A day of cooler temperatures on Monday will give way to scorching heat in parts of the Bay Area starting on Tuesday and continuing into Thursday as a heat dome moves into Mexico over the region before more moderate temperatures return by the end of the week.
The National Weather Service has issued a heat advisory for coastal Sonoma, the inland North Bay mountains and valleys, and the inland East Bay hills and valleys from 8 a.m. Tuesday through midnight Thursday evening. Daytime temperatures are expected to approach 100 degrees during this period.
Further inland, the Weather Service has issued an excessive heat warning for the San Joaquin Valley and lower Sierra Nevada foothills from 11 a.m. Wednesday through 8 p.m. Thursday, with dangerously warm conditions with expected high temperatures of 103 to 108 degrees.
The heat dome that brought brutally hot temperatures to Mexico in May has expanded north into the western US. In addition to California’s inland valleys, high temperatures are also forecast for Arizona, Nevada and the Pacific Northwest. A heat dome is formed when the soil warms, loses moisture and then becomes easier to heat even further, 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 Inland East and South Bays and the Inland Central Coast is moderate through Thursday, meaning there is a moderate risk of heat-related illness for sensitive populations (children , the elderly, pregnant women, people with certain medical conditions, or anyone who works outdoors without cooling or hydration). Some parts of the North Bay Valleys and far eastern Contra Costa County see a high risk of heat-related illness Tuesday for anyone without effective cooling or adequate hydration.
The Weather Service offered the following reminders for the period of extreme heat:
- Stay hydrated and drink plenty of fluids.
- Wear lightweight, light-colored clothing.
- Reduce the time you spend outside or stay in the shade.
- Never leave people or pets unattended in vehicles.
- Use sunscreen if you go to the seaside or pool.
Before the heat arrives, forecasts for the greater San Francisco Bay Area for Monday call for partly sunny skies and some clouds, with patchy fog in coastal and interior areas. Daytime highs will be mainly in the 60s to 70s on the coast and around the bay, and in the 70s to 80s inland. The lows will mainly be in the 50s.
Cooler temperatures are expected to continue through Monday with breezy winds during the day and marine layers at night.
