Reference tables
Computed live from the same formulas as the calculator. The wind chill table matches the chart published by Environment and Climate Change Canada within one degree.
| Wind (km/h) \ Air (°C) | 0 | −5 | −10 | −15 | −20 | −25 | −30 | −35 | −40 | −45 | −50 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 10 | −3 | −9 | −15 | −21 | −27 | −33 | −39 | −45 | −51 | −57 | −63 |
| 20 | −5 | −12 | −18 | −24 | −30 | −37 | −43 | −49 | −56 | −62 | −68 |
| 30 | −6 | −13 | −20 | −26 | −33 | −39 | −46 | −52 | −59 | −65 | −72 |
| 40 | −7 | −14 | −21 | −27 | −34 | −41 | −48 | −54 | −61 | −68 | −74 |
| 50 | −8 | −15 | −22 | −29 | −35 | −42 | −49 | −56 | −63 | −69 | −76 |
| 60 | −9 | −16 | −23 | −30 | −36 | −43 | −50 | −57 | −64 | −71 | −78 |
| Air (°C) \ RH | 100 % | 90 % | 80 % | 70 % | 60 % | 50 % | 40 % |
|---|---|---|---|---|---|---|---|
| 24 | 35 | 34 | 32 | 30 | 29 | 27 | 25 |
| 26 | 39 | 38 | 36 | 34 | 32 | 30 | 28 |
| 28 | 44 | 42 | 40 | 37 | 35 | 33 | 31 |
| 30 | 49 | 46 | 44 | 41 | 39 | 37 | 34 |
| 32 | 54 | 51 | 48 | 45 | 43 | 40 | 37 |
| 34 | 59 | 56 | 53 | 50 | 47 | 44 | 41 |
| 36 | 65 | 61 | 58 | 54 | 51 | 48 | 44 |
What the numbers mean
Both scales follow the Government of Canada’s published levels.
- 0 to −9 — Low risk. Little frostbite risk for most people.
- −10 to −27 — Moderate risk. Dress warmly; cover exposed skin on longer outings.
- −28 to −39 — High risk. Exposed skin can freeze in about 10 to 30 minutes.
- −40 to −47 — Very high risk. Exposed skin can freeze in about 5 to 10 minutes.
- −48 to −54 — Severe risk. Exposed skin can freeze in about 2 to 5 minutes.
- −55 or colder — Extreme risk. Danger: outdoor conditions are hazardous. Exposed skin can freeze in under 2 minutes.
- 20 to 29 — Little discomfort
- 30 to 39 — Some discomfort
- 40 to 45 — Great discomfort; avoid exertion
- Above 45 — Dangerous; heat stroke possible
How the calculation works
Wind chill is expressed in temperature-like units: it is how cold exposed skin feels, not a real temperature. Humidex combines air temperature and humidity into one “feels like” number.
WC = 13.12 + 0.6215·T
− 11.37·V^0.16
+ 0.3965·T·V^0.16T in °C, V = wind in km/h (10 m). −20 °C at 30 km/h → −33H = T + 0.5555·(e − 10)
e = 6.11·exp[5417.753·(1/273.16 − 1/(Td+273.16))]T air °C, Td dew point °C, e in hPa. 30 °C with a 15 °C dew point → 34When you give relative humidity, the calculator takes e as RH × the saturation vapour pressure at the air temperature, using the same exponential. Because Environment Canada’s published chart may use a slightly different humidity conversion, a value can differ from its chart by 1.
Frequently asked questions
Is wind chill a real temperature?
No. It is a cooling effect on exposed skin expressed in temperature-like units. If it is −10 °C with a wind chill of −20, your face feels as cold as on a calm day at −20 °C, but objects such as your car do not drop below −10 °C.
Does wind chill apply above 0 °C?
Environment Canada reports wind chill only at 0 °C or colder because that is when frostbite becomes a concern. The formula works up to +5 °C with a wind of at least 5 km/h, and this calculator shows the value up to that point.
What is a good rule for frostbite risk?
Risk rises quickly below a wind chill of about −27. From −28 exposed skin can freeze in 10 to 30 minutes; from −40, in under 10 minutes. Cover skin, and check on others in the cold.
Why does the humidex need humidity?
Sweat evaporates more slowly in humid air, so the same temperature feels hotter. Humidex adds a vapour-pressure term to the air temperature to capture that effect.
What humidex is dangerous?
Environment Canada rates humidex above 45 as dangerous, with heat stroke possible, and says to avoid exertion from 40 to 45. People who are older, very young, ill or working outdoors are at higher risk at lower values.
Are the results the same as the weather forecast?
They use the same published formulas, but a forecast uses measured wind and dew point at specific times and places. Treat this as a calculator, not an alert, and follow local weather warnings.
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How we check it
Automated tests compare the wind chill function with the official chart on Canada.ca cell by cell (6 wind speeds × 11 temperatures). 65 of 66 cells match exactly and the remaining cell (−30 °C at 30 km/h: we give −46, the chart shows −45) is within one degree. The three published worked examples (−15/20 → −24, −20/30 → −33, −30/40 → −48) match exactly.
Humidex is compared with the official temperature × relative-humidity chart (112 cells, 21–34 °C, 65–100 %): all within one degree. Dew-point results also match the widely published example (30 °C with a 15 °C dew point = 34). The frostbite and discomfort bands are tested at every boundary.
Limits: we did not run Environment Canada’s own calculator. The wind chill formula is the published 2001 formula, not copied from a government page. Real conditions such as sun, shelter and clothing change how cold or hot it feels.