READING THE DATA · 3 MIN READ

Wind, direction, and gusts

A north wind blows toward the south. Get that backwards and every wind report you read means the opposite of what you think.

Wind is always reported by where it comes from. A north wind arrives from the north and travels southward. This convention is centuries old and comes from sailing, where what mattered was the direction weather was arriving from.

In coded reports it appears as degrees: 090 is due east, 180 due south, 270 due west, 360 (or 000 for calm) is north. So 12010KT means wind from 120 degrees, east-southeast, at 10 knots.

Sustained versus gusts

The main number is a sustained average, usually over two minutes at airport stations. Gusts are the punches: brief peaks that exceed the sustained speed by a meaningful margin. A report of 10 knots gusting 22 describes a very different afternoon than a steady 16, even though the averages are similar.

Gusts are what knock over patio umbrellas, spoil drone flights, and make a beach day miserable. If you're planning anything sensitive to wind, the gust number is the one to plan around.

What speeds feel like

Under 8 mphCalm. Smoke drifts, leaves barely move.
8–15 mphBreezy. Flags extend, hair misbehaves.
15–25 mphWindy. Small trees sway, umbrellas struggle.
25–35 mphStrong. Walking takes effort, driving high-profile vehicles is work.
Above 35 mphDamaging territory. Branches come down.

A shift is information

A sudden change in wind direction usually means an air mass boundary just crossed your location, a front, a sea breeze, or the outflow racing ahead of a thunderstorm. When a direction shift arrives with a temperature drop and a pressure change, something real just happened, and the station felt it before you did.

One conversion worth memorizing: aviation reports wind in knots, and one knot is about 1.15 mph. A 30-knot wind is roughly 35 mph.

See it on your own sky
Fat Tail shows these numbers measured by the airport sensor nearest you, and explains each one when you tap it. Free forever, coming soon to iOS.
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