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How Accurate Are Weather Forecasts?

We provide weather forecasts for millions of locations around the world. How reliable are they?

Two women walking under umbrella during heavy rain.

Weather forecasts can be wrong.

There is no guarantee for getting caught out in the rain, even if the forecast says it differently.

©iStockphoto.com/ablokhin

Our Weather City Pages give you today's and tomorrow's weather, an hour-by-hour forecast, a 14-day forecast, searchable past weather, and climate information for a location.

Are 14-Day Forecasts Accurate?

Modern weather predictions are a combination of computer-based models and human experience. As a rule of thumb, the closer a weather forecast is in time, the more accurate it is. Long-term predictions have a larger margin of error because there are more unknown variables.

This means that our short- and medium-range forecasts are the most accurate. Long-range forecasts predicting the weather for more than 7 days in advance should be seen as a rough guide, as the accuracy of weather predictions falls considerably around the one-week mark.

If you notice a weather forecast that is repeatedly incorrect, please let us know.

Weather Station Limitations

Past, current, or predicted temperature values displayed in a weather report may not always represent the warmest or coldest temperature for a location on a particular day.

This is due to practical limitations:

  • Time: If the temperature is recorded at 13:00 (1:00 pm) and again at 14:00 (2:00 pm) but the temperature peaks at 13:30 (1:30 pm), the readings for the maximum temperature will be a little too low.
  • Frequency: Some weather stations do not report as frequently as others. Some stations transmit their readings every 30 minutes or every hour while others may do so every 2 or 3 hours. Also, some stations are not consistent with the times in which they provide their reports.
  • Location: In some cases, weather stations are quite far away from the city, so weather conditions may differ there.

Where Does the Weather Data Come From?

CustomWeather provides the weather data on timeanddate.com. They use weather stations at airports, stations run by the World Meterological Association (WMO), and MADIS weather stations which are typically a community effort.

What Is Weather?

Weather is defined as the state of the atmosphere with respect to heat or cold, wetness or dryness, calm or storm, clearness, or cloudiness. It includes temperature, pressure, humidity, clouds, wind, precipitation, and fog.

While weather relates to mostly temperature and precipitation on a day-to-day basis, climate is the term for average atmospheric conditions over longer periods of time.

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