From sunny skies to sudden snowstorms, the weather can change quickly. But how do meteorologists know what’s coming?
While weather forecasts aren’t always perfect, scientists use observations, technology, and an understanding of Earth’s atmosphere to predict conditions days in advance.
Long before satellites and computer models, people looked to the natural world for clues about upcoming weather. Changes in animal behavior, cloud formations, and even the positions of celestial objects were once used to anticipate storms or seasonal shifts. Some of these observations have scientific explanations, while others have little connection to what actually happens in the atmosphere.
So, how do scientists predict the weather, and why do forecasts sometimes get it wrong?
Reading the atmosphere
Weather begins with the movement of air, heat, and moisture through Earth’s atmosphere. Differences in temperature and air pressure help drive winds and influence where clouds and precipitation form.
Meteorologists measure these conditions using weather stations, radar, satellites, and weather balloons. Weather stations record local conditions, and radars detect precipitation and track its movement. Satellites provide a broader view of cloud systems and developing storms. Meanwhile, weather balloons collect information about temperature, humidity, and wind at different altitudes.
Scientists combine these observations with computer models that use mathematical equations to simulate how the atmosphere may change. By comparing multiple models and analyzing current conditions, meteorologists can estimate everything from tomorrow’s temperature to the likelihood of a major winter storm.
Looking to nature for clues
Before modern forecasting tools existed, people relied on patterns in the natural world to anticipate changes in the weather. Some traditional sayings, such as “red sky at night, sailor’s delight,” even have a basis in atmospheric science.
In regions where weather systems generally move from west to east, a red sunset can sometimes indicate clearer conditions approaching. Animals have also long been associated with weather forecasting. Birds may respond to changes in air pressure, while insects often change their activity levels in response to temperature and humidity.
Beyond observations on Earth, people also looked to the sky for answers. A historical forecasting practice known as astrometeorology attempted to predict weather conditions, including storms and rainfall, by studying the positions and movements of stars, planets, and other celestial objects.
Although these methods are not supported by modern forecasting science, celestial phenomena do influence conditions on Earth. The Sun provides the energy that drives weather, while Earth's axial tilt changes the amount and intensity of sunlight different regions receive throughout the year, producing the seasons. The Moon's gravitational pull creates ocean tides, but lunar phases and planetary positions are not reliable predictors of everyday weather.
From traditional predictions to the Farmers’ Almanac
The practice of using natural patterns and celestial observations to anticipate weather continued long after the development of early scientific forecasting methods. One well-known example is the Farmers’ Almanac, first published in 1818.
Known for its long-range predictions, the Farmers’ Almanac uses a proprietary formula said to incorporate sunspot activity, lunar cycles, and planetary positions to forecast weather months in advance. Its predictions often describe seasonal conditions, such as particularly snowy winters or unusually hot summers.
While modern meteorologists use atmospheric observations and computer models to develop forecasts, the Farmers’ Almanac draws on a longstanding tradition of studying natural and celestial patterns. These different approaches reflect the many ways people have sought to understand and anticipate changing weather conditions.
Why aren’t weather forecasts always accurate?
Even with advanced technology, predicting the weather remains challenging. Earth’s atmosphere is constantly changing, and small differences in current conditions can lead to much larger differences in future outcomes.
This is why a forecast for tomorrow is generally more reliable than one for two weeks from now. As predictions extend further into the future, uncertainty increases. Meteorologists account for this by running multiple simulations with slightly different starting conditions. Known as ensemble forecasting, this approach helps scientists evaluate a range of possible outcomes rather than relying on a single prediction.
Long-range forecasts can identify broader patterns, such as whether a season is more likely to be warmer or wetter than average. However, predicting the exact weather on a particular day months in advance remains beyond the capabilities of current forecasting science.
The science behind the forecast
From centuries-old weather traditions to sophisticated computer models, our methods for predicting the weather have changed dramatically. While scientists may never be able to forecast every storm with perfect accuracy, continued research is helping us better understand Earth’s atmosphere.
The next time you check the forecast before heading outside, consider the science behind those familiar weather symbols. Each prediction represents countless observations and calculations working together to help us understand what the skies may bring.
The next time you check the weather forecast, consider the science behind those familiar symbols and the many forces shaping conditions here on Earth. To explore how our planet fits into the larger Solar System, visit the Museum’s Nathan and Fannye Shafran Planetarium and discover more about the celestial objects and movements that influence our world.
