San Mateo County, CA: Current UV Index and Hourly Forecast

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As of 12:52 PM PDT on July 9, 2026, all 33 cities in San Mateo County, CA in our database have a UV Index reading of Very High. The city with the highest UV Index reading right now is Portola Valley, CA with a reading of 9.9.

Over the next 24 hours, the highest UV Index reading in San Mateo County, CA is expected to be 10.7 in Portola Valley between 1:00 PM - 2:00 PM PDT today.

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Current UV Index in Cities in San Mateo County, CA

• Atherton - 9.6
• Baywood Park - 9.6
• Belmont - 9.6
• Brisbane - 8.3
• Broadmoor - 8.3
• Burlingame - 9.6
• Colma - 8.3
• Daly City - 8.3
• East Palo Alto - 9.6
• El Granada - 8.2
• Emerald Lake Hills - 9.6
• Foster City - 9.6
• Half Moon Bay - 8.2
• Highlands - 9.6
• Hillsborough - 9.6
• La Honda - 9.9
• Ladera - 9.6
• Loma Mar - 9.9
• Menlo Park - 9.6
• Millbrae - 8.2
• Montara - 8.2
• Moss Beach - 8.2
• North Fair Oaks - 9.6
• Pacifica - 8.2
• Pescadero - 9.9
• Portola Valley - 9.9
• Redwood City - 9.6
• San Bruno - 8.3
• San Carlos - 9.6
• San Mateo - 9.6
• South San Francisco - 8.3
• West Menlo Park - 9.6
• Woodside - 9.6