Weather

Wind chill, heat index, dew point, and rainfall calculators.

S

Snow Day Calculator

Predict the chance of a snow day based on weather forecast and school type. A fun prediction tool.
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Wind Chill Calculator

Calculate wind chill factor using NWS formula. See frostbite risk time and danger level.
H

Heat Index Calculator

Calculate heat index from temperature and humidity. See danger level and activity recommendations.
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Moon Phase Calculator

Find the current moon phase, illumination percentage, and next full moon date.
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Sunrise & Sunset Calculator

Calculate sunrise, sunset, and day length for any US city and date.
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Frost Date Calculator

Find average first and last frost dates and growing season by USDA zone.
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Plant Hardiness Zone Calculator

Find minimum temperature, recommended plants, and planting season by USDA zone.

About Weather Calculators

These seven tools cover the seasonal and outdoor questions that shape daily plans across the United States, from a winter cold snap in Minnesota to a planting weekend in Georgia. The Wind Chill Calculator and Heat Index Calculator translate raw temperature plus wind or humidity into the "feels like" numbers the National Weather Service uses to issue cold-weather and heat advisories, so you can judge frostbite or heatstroke risk before heading out. Parents and school staff lean on the Snow Day Calculator the night before a storm to gauge the odds of a closure.

Gardeners and homeowners get the most year-round use. The Plant Hardiness Zone Calculator maps your ZIP code to the USDA growing zone printed on most seed packets, while the Frost Date Calculator estimates the average last spring and first fall freeze from NOAA station records so you know when it is safe to transplant. The Sunrise & Sunset Calculator and Moon Phase Calculator help with everything from scheduling a commute, a photo shoot, or a fishing trip to timing daylight-sensitive outdoor work.

Frequently Asked Questions

What is the difference between wind chill and heat index?
Wind chill applies in cold weather and combines air temperature with wind speed to show how fast your skin loses heat, which is what drives frostbite risk. Heat index applies in hot weather and combines temperature with relative humidity, because high humidity slows your body's ability to cool itself through sweat. The National Weather Service publishes both as "feels like" temperatures and uses them as thresholds for cold-weather and excessive-heat advisories.
How does the USDA decide plant hardiness zones, and did they change recently?
USDA hardiness zones are based on the average annual extreme minimum winter temperature at a location, divided into 10-degree Fahrenheit bands and 5-degree half-zones. The USDA released an updated Plant Hardiness Zone Map in 2023 using more weather stations and newer data, which shifted roughly half the country about a half-zone warmer. Check your zone against the current map, since older seed packets and garden books may reference the prior version.
Are frost dates a guarantee of when it is safe to plant?
No. Frost dates from NOAA station data are statistical averages, typically given as the date with a 50% chance that the last spring freeze has passed. That means a freeze after the listed date happens in about half of years, so cautious gardeners wait one to two weeks past the average last-frost date before setting out tender plants. Local microclimates, elevation, and proximity to water can shift your actual frost timing from the nearest reporting station.
Does a Snow Day Calculator actually predict school closures?
A snow day calculator estimates the probability of a closure based on factors like forecast snowfall, temperature, timing, and whether your district closes easily or rarely. It is an informal odds estimate, not an official source. Only your school district or county announces real closures, usually through its website, local news, or an alert system, so treat the calculator as a planning aid rather than a decision.
Why do sunrise, sunset, and moon times differ from what I see published?
Sunrise and sunset times depend on your exact latitude, longitude, elevation, and the local time zone, including whether daylight saving time is in effect, so a city-level figure can be off by several minutes from your backyard. The U.S. Naval Observatory is the authoritative source for these astronomical times in the United States. Moon phase timing is uniform worldwide for the moment of each phase, but the local clock time shown depends on your time zone.