Weather Calculators
Air Quality Index Calculator
Convert a PM2.5 concentration reading into its EPA Air Quality Index value and health category using the official breakpoint table.
Barometric Pressure Calculator
Convert between sea-level pressure and pressure at altitude, or find the sea-level equivalent of a station pressure reading, using the standard barometric formula.
Dew Point Calculator
Calculate dew point in Celsius and Fahrenheit from air temperature and relative humidity using the Magnus formula approximation.
Heat Index Calculator
Calculate the heat index feels-like temperature from air temperature and relative humidity using NOAA's official Rothfusz regression formula.
Humidity Calculator
Calculate relative humidity from air temperature and dew point, or directly from actual and saturation vapor pressure readings, using the Magnus approximation.
Rainfall Accumulation Calculator
Add up a list of comma-separated rainfall readings into a total accumulation and average per period, in inches or millimeters.
Snow Day Calculator
Get a fun weighted snow day probability score from expected snowfall, temperature, wind speed, and day of the week. For entertainment only.
Storm Surge Calculator
Estimate storm surge height from central pressure and sustained wind speed using a simplified inverse barometer and wind setup model, for educational use.
UV Index Calculator
Convert a UV Index reading into its EPA exposure category, protection recommendation, and approximate time for unprotected skin to begin burning.
Wind Chill Calculator
Calculate wind chill temperature from air temperature and wind speed using the National Weather Service's official formula, valid at or below 50 degrees F.
What "Feels Like" Temperature Actually Measures
Weather reports routinely show a "feels like" temperature that differs from the actual air temperature, and that number isn't a vague impression — heat index and wind chill are both calculated from specific formulas combining temperature with humidity or wind speed to estimate how the human body actually perceives conditions. Ten calculators here cover the meteorological formulas behind these everyday weather numbers.
Popular Weather Calculators
Ten tools span temperature perception, moisture, and severe weather:
- Heat Index Calculator — combines air temperature and humidity to estimate perceived heat.
- Wind Chill Calculator — combines air temperature and wind speed to estimate perceived cold.
- Dew Point Calculator — calculates the temperature at which air becomes saturated with moisture, a key humidity comfort indicator.
- UV Index Calculator — estimates UV radiation intensity based on location, time, and atmospheric conditions.
- Rainfall Accumulation Calculator — totals expected or measured rainfall over a period.
Why Dew Point Is a Better Humidity Comfort Measure Than Relative Humidity
Relative humidity is deceptive as a comfort measure because it's relative to air temperature — 70% relative humidity feels very different at 60°F than at 90°F, since warmer air holds more moisture at the same relative percentage. Dew point, by contrast, is an absolute measure of moisture in the air, which is why meteorologists consider it a far more reliable comfort indicator: a dew point above roughly 65°F starts to feel humid and muggy regardless of the actual air temperature, while relative humidity alone can't tell you that consistently across different temperatures.
Frequently Asked Questions
Why do heat index and wind chill only apply above or below certain temperatures?
Heat index calculations are only meaningful and validated at higher temperatures where heat stress is a real risk, and wind chill similarly only applies at colder temperatures where wind-driven heat loss matters, which is why both have defined temperature ranges of applicability.
Does UV index depend only on time of year?
No — altitude, cloud cover, latitude, and time of day all affect UV index in addition to season, which is why the same date can show very different UV index values in different locations.
Explore More
Interested in the atmospheric science behind these numbers? See the Environmental Calculators, or check flight-relevant weather math in the Aviation Calculators.