UV Index
UV Index
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Today's UV index in San Francisco, United States 
will be up to 4.3, indicating a moderate level of sun exposure for the average person. Check the annual sun radiation in the city and our tips for today to make sure you're safe in the sun.
With a UV index reaching up to 4.3 in San Francisco, stay shaded during midday when the sun is strongest; wear protective clothing, a wide-brimmed hat, UV-blocking sunglasses; apply SPF 30+ sunscreen every 2 hours, even on cloudy days; and be cautious of heightened UV on bright surfaces.
The UV index in San Francisco remains relatively low throughout the year due to the city's cool, foggy climate. It rarely exceeds 6, which is considered moderate.
San Francisco has a Mediterranean climate, with cool, wet winters and dry summers. However, its coastal location and unique topography can result in microclimates, causing variable weather within the city. Fog is common, especially in the summer.
Compared to its region and neighboring countries, San Francisco is generally cooler and foggier. While much of California experiences hot, dry summers, San Francisco's summer temperatures are milder due to the marine influence. Countries like Mexico, further south, have significantly higher temperatures and less rainfall year-round.
The chart below displays the average Shortwave Radiation Sum (MJ/m²) for each month of the last year in San Francisco. It's designed to provide you with a better understanding of the yearly weather and sun exposure.