A Long before satellites, sailors and farmers predicted the weather by watching the sky. Some of their sayings contain real science.
B A red sky in the evening often means fine weather, because the light is passing through dry, dusty air from the west. A ring around the moon can signal rain, since it is caused by ice crystals in high clouds.
C Animals may also respond to changes. Some birds fly lower before storms, possibly because falling air pressure affects the insects they feed on.
D Modern forecasting began in the nineteenth century when the telegraph allowed weather reports to be sent quickly. Today, powerful computers run models using millions of measurements.
E Even so, forecasts become less reliable the further ahead they look. Small errors grow over time, a problem described as chaos. For this reason, a forecast for next week is far less certain than one for tomorrow.