From my experience, San Diego's most predictable period in which a charter is least likely to be cancelled, is July - October. I've probably been on 20+ local charters and I've had only two cancelled. The warmest top water temps tend to occur in late summer/early fall (appx 70 degrees). However, temps at depth are consistently low 50s all year round (except this year which is an El Nino year).
San Diego's strong points include:
- One of the healthiest giant kelp beds in the world (Point Loma)
- Other giant kelp beds up and down the coastline, including La Jolla Cove
- Wreck Alley which includes sites such as The Yukon, The Ruby E, and NOS Tower
- La Jolla Shores, which is very diver friendly w. a grassy park right in front. There's a long stretch of instructor friendly "shallows" which is mostly just sand, but then opens up into a deep, deep canyon that constantly provides new creature subjects for those who dive it often.
- Los Coronados Islands (technically in Mexico) offer fun shallow dives w. better-than-usual visibility for the area. Lots of friendly sea lions here.
All that said, I don't think any local diver would ever argue that the crown jewel(s) of So Cal diving are the Channel Islands. If you want to experience the best of So Cal diving, this is where you need to go.
BTW - my personal favorite local operation is Waterhorse Charters.
Waterhorse is is great in San diego, and the Coronado's which they do frequently are fantastic dives with usually great visibility!
As as for the Crown Jewels, I'd have to say the Oil Riggs, are fantastic, usually great visibility, great growth and palagics....the other crown jewel I'd say is Farnsworth bank, purple hydro choral is awesome.
as for diving So. Ca. , in anything less than a 7mm.....NFW , if I'm doing one shore dive my 7mm is fine, any more than that , or a multi dive boat, and im diving dry thanks. We are a pretty dry climate the surface interval on a So. Ca. Dive boat can be damn chilly regardless of the year!
id also add that while summer might be a good time to not have a charter cancelled, winter is the best time to truly get spectacular visibility!