Weather
Free weather calculators: wind speed converter, feels-like temperature, heat index, dew point, cloud base altitude, and more tools.
Practical weather maths: what the conditions feel like, what they do to people and property, and when to call something off. 21 calculators. The atmospheric physics side lives under Meteorology; this section is the applied half.
Heat index and wind chill both answer “what does this actually feel like”, and both have limits people ignore. Heat index assumes shade and a light breeze. Full sun adds as much as 8C to the apparent temperature, so a reading that says 38C is closer to 46C standing in it. Wind chill only applies below 10C and above about 5 km/h wind, and outside those bounds the formula returns numbers that mean nothing.
Snow load is the one with real consequences. Fresh dry powder runs about 100 kg per cubic metre, old settled snow can reach 400, and wet snow or an ice layer more again. A roof carrying 60 cm of powder and a roof carrying 60 cm of settled wet snow are not remotely the same problem, which is why the page asks about snow type rather than depth alone.
Where a scale is official, the page uses the official thresholds: Saffir-Simpson for hurricanes, Enhanced Fujita for tornadoes, and the national AQI breakpoints for air quality rather than a generic version.
Hurricane Category Calculator (Saffir-Simpson Scale)
Determine the hurricane category from wind speed using the Saffir-Simpson Hurricane Wind Scale. See expected damage, storm surge, and safety guidance.
Tornado Scale Calculator (Enhanced Fujita Scale)
Determine the EF rating of a tornado from estimated wind speed. See damage descriptions, frequency statistics, and historical comparisons.
Frost Point Calculator
Calculate the frost point temperature from air temperature and relative humidity. Find out whether frost will form on surfaces overnight.
Evapotranspiration Calculator
Estimate daily evapotranspiration (ET) for your garden or farm. Calculate how much water plants lose to heat, wind, and humidity each day.
Growing Degree Days (GDD) Calculator
Calculate growing degree days (GDD = ((Tmax + Tmin)/2) - base) for crops from daily high and low temps. Returns cumulative GDD for planting timing.
Roof Snow Load Calculator
Calculate snow weight on your roof in psf from snowfall depth and snow type. Compares load against typical residential limits to assess structural safety.
Wildfire Risk Calculator
Calculate wildfire risk level based on humidity, wind speed, drought duration, vegetation type, and temperature. Get a Low to Extreme risk rating.
Air Quality Index Calculator
Calculate Air Quality Index (AQI) from PM2.5, PM10, and ozone. Returns AQI category from Good (0-50) to Hazardous (301+) with health guidance for each level.
Outdoor Event Weather Risk Calculator
Assess weather risk for outdoor events from temperature, rain, wind, and humidity. Returns a risk score from low to extreme for weddings, sports, and festivals.
Heat Index Calculator
Calculate the heat index (feels-like temperature) from air temperature and humidity. Includes danger thresholds from Caution to Extreme Danger in F and C.
UV Exposure Time Calculator
Calculate safe sun exposure from UV index and Fitzpatrick skin type (I-VI). Returns time to sunburn without protection and with SPF 30 and SPF 50.
Wind Chill Calculator
Calculate wind chill in °F or °C from air temperature and wind speed. Returns NWS formula result and frostbite risk time at 30-minute intervals.
Barometric Pressure, Altitude and Weather
Convert pressure units, estimate your altitude from a barometer reading, and read the forecast from a three-hour pressure trend. Includes worked examples.
Dew Point Calculator
Dew point, comfort band and fog risk from air temperature and humidity. Shows the spread, cloud base height and grams of water per cubic metre.
Humidity Comfort Index Calculator
Check if your indoor or outdoor humidity is in the comfort zone. Get health and comfort recommendations based on relative humidity.
Lightning Distance Calculator
Calculate lightning strike distance in miles and km by counting seconds between flash and thunder. Returns distance and 30-30 rule shelter guidance.
Rainfall Volume Calculator
Calculate total water volume from rainfall on a given area. Useful for rainwater harvesting, irrigation, and drainage planning.
Snowfall Accumulation Calculator
Estimate snowfall accumulation from precipitation amounts and air temperature. Convert snow depth to snow water equivalent using typical snow density ratios.
Carbon Offset Cost Calculator
Work out annual carbon offset cost from tonnes of CO2 and the market price per tonne, or build the tonnage from driving, flying, electricity and beef.
Feels Like Temperature Calculator
Calculate feels-like temperature using heat index or wind chill from actual temperature, humidity, and wind speed. Covers both Fahrenheit and Celsius input.
Wind Speed Converter
Convert wind speed between Beaufort scale, mph, km/h, knots, and m/s. Includes Beaufort reference from calm to hurricane force with land and sea descriptions.