How to Determine Wind Speed by Observation: The Beaufort Scale

The Beaufort Scale

Wind and wind chill can be a real issue when you’re out hiking, and being able to accurately estimate wind speed without a weather forecast or an anemometer can save you from frostbite or worse. But people’s ability to do so is woefully bad and no doubt the source of many an exaggerated tale of hurricane force winds on above-treeline hikes.

However, if you’re observant and you can see the impact that the wind is having on the trees or land features around you, it is possible to estimate wind speed using the Beaufort Scale, originally devised in 1805, by a naval officer in Britain’s Royal Navy who correlated wave heights with wind speeds. It’s since been adapted for land use and is still used to report wind speeds in mountain weather forecasts in the United Kingdom.

Beaufort ForceWind Speed (mph)Seamen's TermEffects on Land
Force 0Under 1CalmCalm: smoke rises vertically
Force 11-4Light AirSmoke drift indicates wind direction; vanes do not move
Force 24-7Light BreezeWind felt on face; leave rustle; vanes begin to move
Force 38-12Gentle BreezeLeaves, small twigs in constant motion; light flags extended
Force 413-18Moderate BreezeDust, leaves and loose paper raised up; small branches move.
Force 519-24Fresh BreezeSmall trees begin to sway
Force 625-31Strong BreezeLarge branches of trees in motion; whistling heard in wires
Force 732-38Moderate GaleWhole trees in motion; resitance felt in walking against the wind
Force 839-46Fresh GaleTwigs and small branches broken off trees.
Force 947-54Strong GaleSlight structural damage occurs; slate blown from roofs.
Force 1055-63Whole GaleTrees broken
Force 1164-72StormWidespread damage
Force 1273 or higherHurricane ForceViolence and Destruction
I wish I had known about the Beaufort scales years ago when I hiked through hurricane weather my the last leg of the Long Trail. At the time, I had no idea how dangerous the high winds and rain I was hiking through were.

It was raining like hell and windy but I set off that last morning to finish my hike by the end of the day so I could get to work on Monday. Being on the trail for several days already, I had no idea what the weather forecast was and I was in a remote region without cell phone service.

I can still recall the torrential rain and wind that day and that tree branches were falling down in the forest around me. I paid it no mind, although the winds must have been blowing close to 40 mph. Had I known, I would probably have stayed in the last shelter a while longer or taken a zero day.

See Also

Wind Chill Basics for Hikers

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4 comments

  1. Thanks for the post (and so many others). For attribution, the cartoon was created by Sir George Simpson to relate the Beaufort Scale (which was devised for sea goers) to the needs of those on land. The British Meteorological Office has a factsheet on the Beaufort Scale and its predecessors which includes Simpson’s cartoon:

    https://www.metoffice.gov.uk/binaries/content/assets/mohippo/pdf/s/j/10_0425_factsheet_6_beaufort.pdf

  2. Totally in the public domain. Just sharing some history. Thanks again for your rich site.

    • Just pointing that out. I try very hard to be squeaky clean when it comes to copyright and I hope others will treat me the same.

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