When does San Francisco need sun protection?

Whenever the UV index is 3 or above. In San Francisco that is typically from May through September, and any clear spring or fall day UV reaches 3. The EPA Sun Safety action steps apply at the same threshold used worldwide.

Does San Francisco need sun protection in winter?

Not every day. Midwinter middays in San Francisco often sit below UV 3, but clear late-winter and early-spring days cross the threshold before summer fully arrives. Check the live index.

Does the water make UV worse in San Francisco?

It can. Sand and water reflect ultraviolet, so skin that is not covered (including under the chin and on the tops of feet) picks up extra dose on top of the direct sun. The live UV index on this page is the sky reading; reflection is on top of that.

UV index in San Francisco today

San Francisco's famous fog hides a subtler truth: when the sky clears, midsummer UV still climbs into the very high band. Cool air off the Pacific does not reduce the index, and open waterfront paths have little natural shade.

Live reading · data by Open-Meteo · reference monitoring by ARPANSA

Today and tomorrow in San Francisco

Peak UV, temperature and conditions for San Francisco. Tomorrow’s peak is the number to plan around if you’re heading out in the middle of the day.

Weather conditions right now

Cloud and rain cut heat more than they cut UV. A partly cloudy beach day in San Francisco can still sit at protection levels. Why you burn on cloudy days.

When San Francisco needs sun protection

Sun protection is typically needed from April through October in San Francisco, and on any clear day the UV index reaches 3 or above.

The threshold, per SunSmart and ARPANSA: whenever UV reaches 3 or above, Slip on covering clothing, Slop on SPF 50+ sunscreen, Slap on a hat, Seek shade and Slide on sunglasses. Read the full sun safety guide.

Where the UV adds up in San Francisco

Long, happy hours outdoors are where exposure quietly accumulates. Local favourites where the five S’s earn their keep:

Crissy Field and the Presidio
Ocean Beach
Golden Gate Park
Embarcadero and Ferry Building walks

The UV scale at a glance

0–2Low
3–5Moderate
6–7High
8–10Very high
11+Extreme

Frequently asked questions

When does San Francisco need sun protection?: Whenever the UV index is 3 or above. In San Francisco that is typically from May through September, and any clear spring or fall day UV reaches 3. The EPA Sun Safety action steps apply at the same threshold used worldwide.
Does San Francisco need sun protection in winter?: Not every day. Midwinter middays in San Francisco often sit below UV 3, but clear late-winter and early-spring days cross the threshold before summer fully arrives. Check the live index.
Does the water make UV worse in San Francisco?: It can. Sand and water reflect ultraviolet, so skin that is not covered (including under the chin and on the tops of feet) picks up extra dose on top of the direct sun. The live UV index on this page is the sky reading; reflection is on top of that.