Beaufort Wind Scale

  Developed in 1805 by Sir Francis Beaufort of England

  Winds WMO¹ Appearance of Wind Effects
Force Knots km/h Classification On Land On the Water
0 < 1 < 1 Calm Calm, smoke rises vertically Sea surface smooth and mirror-like
1 1–3 1–5 Light Air Smoke drift indicates wind direction, still wind vanes Scaly ripples, no foam crests
2 4–6 6-11 Light Breeze Wind felt on face, leaves rustle, vanes begin to move Small wavelets, crests glassy, no breaking
3 7–10 12-19 Gentle Breeze Leaves and small twigs constantly moving, light flags extended Large wavelets, crests begin to break, scattered whitecaps
4 11–16 20–28 Moderate Breeze Dust, leaves, and loose paper lifted, small tree branches move Small waves 0.3-1.2 meters becoming longer, numerous whitecaps
5 17–21 29–38 Fresh Breeze Small trees in leaf begin to sway Moderate waves 1.2-2.4 meters taking longer form, many whitecaps, some spray
6 22–27 39–49 Strong Breeze Larger tree branches moving, whistling in wires Larger waves 2.4-4 meters, whitecaps common, more spray
7 28–33 50–61 Near Gale or
Moderate Gale
Whole trees moving, resistance felt walking against wind Sea heaps up, waves 4-6 meters, white foam streaks off breakers
8 34–40 62–74 Gale or
Fresh Gale
Whole trees in motion, resistance felt walking against wind Moderately high (4-6 meters) waves of greater length, edges of crests begin to break into spindrift, foam blown in streaks
9 41–47 75–88 Strong Gale Slight structural damage occurs, slate blows off roofs High waves (6 meters), sea begins to roll, dense streaks of foam, spray may reduce visibility
10 48–55 89–102 Storm or
Whole Gale
Seldom experienced on land, trees broken or uprooted, "considerable structural damage" Very high waves (6-9 meters) with overhanging crests, sea white with densely blown foam, heavy rolling, lowered visibility
11 56–63 103–117 Violent Storm Very rarely experienced, accompanied by widespread damage  Exceptionally high (9-14 meters) waves, foam patches cover sea, visibility more reduced
12 64 + 118 + Hurricane Devastation occurs  Air filled with foam, waves over 14 meters, sea completely white with driving spray, visibility greatly reduced

  Note 1: WMO = World Meteorological Organization


Temperature Comfort Scale

Scale Conditions
Extreme Cold Wind Chill less than -18°C
Uncomfortably Cold Wind Chill between -18°C and -1°C
Cold Wind Chill between -1°C and 15.5°C
Comfortable Temperature between 15.5°C and 26.5°C
Warm Temperature between 26.5°C and 32°C
Uncomfortably Hot Temperature greater than 32°C and Heat Index less than 37.5°C
Extreme Hot Heat Index greater than 37.5°C
  • Wind chill - The cooling effect of any combination of temperature and wind. In Canada, wind chill is translated into a temperature that a person might feel when he or she went outside.
  • Heat index - A combination of the temperature and the relative humidity to give a temperature of what it feels like to the human body on a hot muggy day.