Angel Island Weather and What to Wear
The park has many sunny days each year, but Angel Island weather tends to be cooler and breezier than the surrounding cities of the San Francisco Bay Area, because it is more exposed to winds coming off the Bay and the Pacific Ocean, and is at the center of the water flows from the rising and falling tides. Fog is common in the mornings, especially during the warm summer months, which surprises many visitors from warmer areas.
In particular, even on warm days from May through October, cool mid-afternoon and early-evening breezes may catch the unwary who came to the island in shorts, T-shirts and flip-flops.
During the winter light drizzle and low clouds are common Angel Island weather patterns, even when no rain is in the forecast.
As with all of the Bay Area, the key to wearing the right clothes is to bring layers. In warm weather I’ll wear a good sweatshirt and a light windbreaker over my T-shirt, and if I get too warm I can easily fold them and put them in my pack, or simply tie them around my waist if necessary.
Why does Angel Island weather change so much over the course of a single day? Major rivers reach the Pacific Ocean by entering the northern end of San Francisco Bay. The point where the fresh water mixes with the bay and ocean saltwater changes as the tides come in and out. Angel Island lies directly on the path that the fresh water takes as it mixes with the ocean.
The narrow Raccoon Strait, located between Tiburon and Angel Island (see map below), is 160 feet (about 50 meters) deep, and is the second deepest area of San Francisco Bay. It connects to the deepest trench of all, the 313 foot (95 meters) deep main channel that runs beneath the Golden Gate Bridge. This rapid flow of cold water rushing by the island creates even more dramatic variations in Angel Island weather.
Insider Tip: When you ride the Angel Island Ferry, Mother Nature has a fun surprise that passengers often get to see. Watch the surface of the water as you start to approach the harbor at Ayala Cove on Angel Island. Often the fierce inrush or outflow of the tides in the bay and the mixing of different temperatures of water will produce areas where the surface of the water seems to be boiling or churning. It’s an amazing sight if you know when to look for it.