How much sunlight does SF get?

[BayAreaHillbilly]

Originally Posted by vdy1985

Definitions of percent possible sunshine on the Web:
the ratio of measured bright sunshine to the total possible bright sunshine in a given time period such as an hour or a day, expressed as a percent.
rredc.nrel.gov/solar/glossary/gloss_p.html

This is how I understand it: This means that if a spring day has 10 hours of sunlight, and the day is foggy for most of it except for 3 hours of sunshine, you would get a 30% number. If it was sunny for all 10 hours you would get 100% sunshine. Both examples could be considered "sunny days" but it doesn't give as clear a representation as sunshine %.

Given that SF has foggy neighborhoods that would drag down its % sunshine, 66% sunshine combining the city overall is pretty darn good. Unless of course these stats are based on only one section of the city, ie. Hunters Point which is very sunny. I'm assuming it is averaging it, though I could be wrong. On second though, maybe I am wrong, it would be pretty hard to collect so much data by using individual neighborhoods. It may be safe to assume the number comes from an "average sunlight" neighborhood. So not Bayview or Sunset. Probably Downtown? Which is mostly Bay side, so more sunny.

When I lived in SF, I near the ball park, so it was generally sunny. The thing that got to me was the chilliness due to the winds, even in the summer.

Regardless, here is some stats for comparision:

% sunshine
Phoenix 85%
Sacramento 78%
Eureka 51%
Denver 69%
Chicago 54%
LA 73%
SF 66%

The main SF City weather station is located in the Duboce Triangle (used to be near Mission Dolores). That may be where the data are taken, if so, probably a reasonably "average" location versus the opposite extremes of HP/Bayview/Potrero vs The Richmond/The Sunset.

[creative36]

Awesome. I may have to move to San Fran. I like the fog and the wind. I hate sunny hot places. Any one that complains about the cold is female or weak.

[mysticaltyger]

Originally Posted by skyway31

Cities on or near the coast in California are very difficult to characterize based on sunshine with statistics. San Francisco being a classic example of this. It is utterly worthless to have a discussion about sunshine in SF as a whole because you HAVE to state which neighboorhood your're speaking about. If you're talking about an area on the western side of the city, that area is going to have a lot more fog/grey than an eastern city neighborhood. People from other areas have a very tough time grasping the idea that it's not the same in a city or area as a whole.

I already did this in a previous post.

The sun shines 58% of the time on the foggy side of town and 66% in the sunniest part of town.

Even 58% sunshine isn't bad.

[ambient]

I live in the Marina and work in SOMA. I've been here for about eight months, and I have to say that it's fairly sunny. If you're not from here, the thing to keep in mind is that this is a real micro-climate area - the weather is not only different here from South Bay or East Bay, it's even different from one neighborhood to the next. Is it sunny or foggy? It depends on where you are and when you're there.

Early in the morning or late in the evening in the Marina, it may be foggy; during the day, it may be perfectly sunny. During the day in SOMA, it may be nice and sunny; drive over towards the Sunset area, and you can just see the fog bank sitting there a couple of blocks ahead of you. In certain parts of the city, you'll find yourself really wishing you had remembered to bring your coat, especially when the sun dips and the wind picks up a bit; in other parts, you're peeling off your sweater to cool down. It keeps things fairly interesting...

[mysticaltyger]

Originally Posted by skyway31

The same thing applies to L.A. as well. If L.A.'s sunshine numbers are from downtown or Hollywood, they are going to make L.A. look much better. For the folks that live on the coast, it is significantly different. It's possible(I can't confirm as I've never lived in SF) that the only difference between sunshine in L.A. and SF is that a MUCH larger percentage of the L.A. where people live/work/visit is much further inland than SF. If you're in SF, you're never more than 7 miles from the shoreline. So much of the L.A. people live/work/visit is greater than 7 miles inland (i.e. away from the coastal stratus).

That's somewhat true. The LA sunshine reading is taken in the sunnier downtown area. I don't think they have a sunshine meter at the LA Airport, which is near the coast. But if it's like other parts of coastal SoCal, the sun shines about 68% of the time in coastal LA and 73% of the time downtown. I would imagine the San Fernando Valley is probably even sunnier than downtown LA.

I base the coastal sunshine reading on what they get at the San Diego Airport, which is only a few miles from the beach.