Native San Diegans - so spoiled. People go to the beach all year round here.

The weather people have their catch phrases in California when it is gray in May or June they say - May gray, June gloom - but... Southern California weather is not consistent, you will have hot sunny days any time of the year, but also a marine layer (hence the gloom and gray) any time of year. Rain is very rare in May since it is past the rainy season, but the marine layer can be present particularly if you are near the coast. So pay attention to the weather before you leave. It will not be cold (by east coast standards) but may be cool. If you are planning on beach days you may be disappointed on some days but if you are going to see the sights, just bring a light jacket and long pants for the cool days and you will be fine. There is no humidity here, so even on the brightest sunniest days you will generally not feel too hot.