How this works

Windsock reads the current observation at each Bay Area field, resolves the wind against every runway that is usable for pattern work, and ranks the fields by how much margin you have against your own limits. It shows the arithmetic so you can disagree with it.

Where the numbers come from

Observations, forecasts, pilot reports and hazard advisories come from the NOAA/NWS Aviation Weather Center. That is the government's own feed, which also means no commercial service learns which airports you keep checking. This server polls it on a fixed schedule and your browser never contacts it directly.

Runway geometry, field elevation, traffic pattern direction and published pattern altitudes come from the FAA's National Airspace System Resource, cycle 2026-07-09. Nothing on this site is scraped from an airport's website.

True and magnetic

A METAR reports wind direction relative to true north. Runway numbers, and the wind a tower reads to you, are magnetic. Around the Bay the difference is a little under 13 degrees, so confusing the two puts every crosswind figure meaningfully off. Windsock computes in true, because that is the frame both the observation and the runway alignment are already in, and displays magnetic, because that is what you will hear on the radio.

Runways keep their numbers as magnetic variation drifts over decades, so a runway designated 28 may currently sit at 287 degrees magnetic. Windsock takes both the designator and the alignment from the FAA and never derives one from the other. The variation itself is computed from the current World Magnetic Model rather than taken from the FAA's own field, which for some of these airports still carries an epoch from the 1970s and is out by up to three degrees.

Gusts, and winds that will not sit still

The crosswind figure that decides a ranking is computed from the gust when one is reported, not the steady wind. If a report carries a variable range, such as 250V320, the whole arc is evaluated and the worst crosswind in it is the one shown. A wind reported only as variable gives no direction at all, so no component can be computed, and Windsock says so instead of showing a reassuring zero.

What this does not know

It does not know local noise abatement, calm wind runway conventions, or restrictions on touch and go operations. Those exist for most of these fields and they are not published anywhere a program can read reliably.

This is not a shortcut. Before building this, an automated research pass gathered a hundred and fifteen claims about local procedures at these airports and then tried to verify them. Thirteen of the twenty five it checked were wrong, including three taken from an airport association's own procedures page, and one restriction at Hayward that turned out to belong to an airport in San Diego. Seventeen of the twenty fields produced nothing that survived checking at all. So this site links to the source instead of repeating it, and it never scores a field on a rule it cannot cite.

What it assumes

Only six of these twenty fields publish a traffic pattern altitude. For the rest, Windsock assumes the standard 1000 feet above the ground and labels that assumption on the airport page every time it uses it.

Pattern altitudes are given in both feet above ground and feet above sea level, because the FAA publishes Hayward's in one datum and the national dataset publishes it in the other. Reading one as the other would put you around 600 feet high, underneath Oakland's Class C shelf.

What counts as usable

Availability for pattern work is a property of the runway, not the airport. Oakland's North Field flies patterns on 28R at 1000 feet all day; runway 12/30 at the same airport is where the airliners land, and Windsock does not count it. Moffett Federal Airfield appears because its weather is useful context for the south bay, but it is classified private use by the FAA and is never recommended.

Staleness

Every figure carries the time it was observed. If the data behind this site stops updating, the page says so and stops ranking rather than quietly serving you an old wind. An observation presented as current when it is not is worse than no observation, because you might fly on it.

The limits are yours

The defaults are deliberately tight: 10 knots of crosswind, 20 knots total, a 3000 foot ceiling and 5 statute miles. Change them on the front page to match what you and your instructor have agreed, and the address bar will carry them so you can share or bookmark that setting.

Finally

Windsock is a decision aid, not an authority and not a briefing. Every ranking links the raw report it came from, so you can read the weather yourself. Do that, and get a real briefing before you fly.