What a Wind Advisory actually means
It is the alert for a day that will feel worse than the forecast number suggests. The sustained and gust thresholds behind it, the step up to a High Wind Warning, and the short list of things that blow away.
A Wind Advisory is issued by your local National Weather Service office when sustained winds of roughly 31 to 39 mph for an hour or more, and/or gusts of 46 to 57 mph, are expected. It is the tier below a High Wind Warning, and it describes a day of broken branches, scattered power outages, trucks swaying on the interstate and trash cans in the neighbor's yard, not a day of structural damage. About 254,000 Americans a month search the phrase, mostly on the morning it appears. Every US city page here shows the live NWS alerts for that location alongside the hourly wind forecast, so you can see when the gusts peak.
Sustained versus gust, because the numbers are not the same thing
Wind forecasts and advisories always quote two figures. Sustained wind is the average over a two-minute period, measured at 10 meters (33 feet) above open ground. A gust is a peak lasting a few seconds. In gusty conditions the gust is typically 1.4 to 1.6 times the sustained speed, and it is the gust that snaps the branch. A forecast of "20 mph, gusting 40" is a Wind Advisory kind of day even though 20 mph on its own is nothing. When you read the hourly wind on a city page, look at the gust column first.
The ladder: advisory, watch, warning
- Wind Advisory: sustained 31 to 39 mph and/or gusts 46 to 57 mph. Criteria vary by office; some Western and Plains offices, where wind is routine, set the bar higher, and some coastal and mountain zones have their own thresholds.
- High Wind Watch: a High Wind Warning is possible in the next 12 to 48 hours.
- High Wind Warning: sustained 40 mph or more for an hour, and/or gusts of 58 mph or more. Note that 58 mph is the same figure that makes a thunderstorm severe; it is the speed at which wind starts taking down healthy trees and pieces of roofs. See Severe Thunderstorm Warning vs Watch for the storm version of the same threshold.
Three related products often appear on the same day. A Lake Wind Advisory covers inland lakes where waves become dangerous for small boats. A Gale Warning is the marine equivalent, for sustained winds of 34 to 47 knots offshore. And on dry, windy days a Red Flag Warning may accompany the advisory, because wind is the ingredient that turns a grass fire into a wildfire; Red Flag Warning explained covers that.
What a 45 mph gust actually does
- Trees: dead limbs and shallow-rooted or leaf-heavy trees drop branches. Fully leafed trees in early autumn catch far more wind than bare ones in January, so the same gust does more damage in October.
- Power: most outages during an advisory are branches on lines, not poles down. Charge phones before the peak hours.
- Driving: high-profile vehicles, RVs and anything towing a trailer are the risk. Crosswinds on bridges and open stretches are worse than the average number suggests. Slow down and keep both hands on the wheel.
- Loose objects: patio umbrellas, trampolines, empty bins, inflatable decorations. Take them down the evening before; that is the whole reason the advisory is issued a day ahead.
- Flying and water: small aircraft and small boats stay put. Airline delays are more likely from crosswinds at the destination than from the wind at home.
Reading the wind forecast the day before
Wind is one of the variables where the forecast models disagree most, especially on the timing of the peak and on whether gusts will "mix down" from higher altitudes on a sunny afternoon. On our city pages, Denver and Oklahoma City are good examples, the NWS blend, the American GFS and the European model show their hourly wind side by side. If they agree on a 2 PM peak, plan around it. If they split, secure things early. Our accuracy scoreboard shows which model has been most reliable in your city, and wind chill vs feels like explains why the same 35 mph day feels brutal in January and merely annoying in May.
Advisories, watches and warnings share one grammar across every hazard. If the terms still feel interchangeable, start with watch vs warning, and what the difference means, and make sure the alerts reach you with how to get weather alerts on your phone.