Beach forecast for Playa San Mateo

How we rate a beach day

We rate every beach hour from 0 to 10 with simple, fixed rules:

• Adds: sunshine (up to 3 points, fewer with more clouds), warmth (up to 4, from the feels-like temperature; ideal between 81 °F and 91 °F), a calm sea (1), water at 70 °F or warmer (1; from 64 °F, half) and low or mid tide (1: more sand). Anything without data is left out and the rest is scaled to 10.
• Takes away: cold (feels-like below 64 °F, 1 to 4 points), rain (half a point if likely, up to 6 if it rains; thunderstorms, 8), wind from force 4, about 12 mph (1 to 6 points; half a point more if offshore, which blows inflatables out to sea, or onshore, which churns the water), waves (1 to swim with care, 4 if dangerous, 1 more for high rip current risk), very high UV (half a point; extreme, 1), water below 59 °F (1) and spring high tides (1: little sand left).
• Swimming: calm, use care (waves from 2.6 ft, or long swell) or dangerous (from 6.6 ft, or 4.9 ft with a long period), based on how much of the wave reaches this shore given the way it faces. In the U.S., today's and tomorrow's rip current risk comes from the National Weather Service surf zone forecast when it issues one; otherwise we estimate it from the waves.
• Best windows: runs of 2 to 5 hours rated 4 or more and close to the best hour, at least one hour apart.
• Day rating: the average of the best window; a 2-hour window keeps 85% of it and a 3-hour window 95%.

Today, in the best window: sun 3 of 3, warmth 1 of 4, calm sea 0 of 1, water 0 of 1 and tide 1 of 1; minus waves 2; short window: the rating keeps 85%.

It's a guide, not a guarantee: weather changes and every beach is different. Always follow the lifeguard's flags.