Humans have been trying to predict the weather since long before any mechanical equipment came into use. Written passages confirm that weather forecasts were already being made over a thousand years ago, using all kinds of natural elements. Mountaineers, wilderness guides, and sailors still rely partly on natural observation to predict changes in the weather rather accurately.
Watching the sky has always being a popular way to predict the weather. Clouds change noticeably when a storm is approaching, so they are generally an accurate sign of what's to come. For example, dark clouds announce rain, while low white cottony clouds foretell fair weather. In general, dark clouds are always a sign of bad weather, but how bad depends on the thickness of the clouds and the presence of wind. Tornadoes, hail, and electric storms are all preceded by the appearance of dark clouds.
Looking at other elements in the sky can also help forecast the weather. Examples include a halo around the moon to announce rain, and a morning summer fog to predict fair weather. Fog in winter can often announce rain.
Observing the behavior of animals is another popular way to predict the weather. Horses often get agitated when a tornado is approaching, for example. In certain countries, such as China and Japan, animals are used to predict earthquakes, as their behavior is seen as a better way to predict them than any equipment currently available. Other animal behavior has not been studied but is still part of weather lore, like squirrels collecting an unusually large amount of food as a sign of an upcoming harsh winter.
Listening to the human body can also help you predict the weather. Approaching storms can cause sensitivity to pain and worsen symptoms of arthritis and gout. Back pain, tooth sensitivity, and migraines can all be aggravated by an approaching low pressure front.