Cloud cover on a winter night - expect warmer weather because clouds prevent heat radiation that would lower the temperature on a clear night.
Cumulus towers (cumulus castellanus) - possibility of showers later in the day.
Clouds going in different directions (e.g one layer going west, another layer going north) - bad weather coming, probably hail.
Cumulonimbus clouds early in the day and developing throughout the day -greater chances of severe weather.
Mammatus cloud (formed by sinking air) - thunderstorm is dissipating (not forming).
Cirrus clouds high in the sky like long streamers - bad weather within the next 36 hours.
Altocumulus clouds like mackerel scales - bad weather within the next 36 hours. The old sailor's saying for these types of clouds is "Mares tails and mackerel scales, tall ships carry short sails." Another is "Mackerel skies and mare's tails, sailors furl their sails." Mackerel skies and mares tails formations sometimes appear in the same sky. When that happens, rain is sure to follow the next day.
LOOK FOR A RAINBOW IN THE WEST
Most major storm fronts travel west to east, and a rainbow in the west means moisture, which can mean rain is on its way.
On the other hand, a rainbow in the east around sunset means that the rain is on its way out and you can look forward to sunny days.
Remember: Rainbow in the morning, need for a warning.
LOOK AT THE MOON AT NIGHT
If it is reddish or pale, dust is in the air. But if the moon is bright and sharply focused, it's probably because low pressure has cleared out the dust, and low pressure means rain.
Also, a ring around the moon (caused by light shining through cirrostratus clouds associated with warm fronts and moisture) can indicate that rain will probably fall within the next three days. Remember: Circle around the moon, rain or snow soon.
Detect which direction the wind is blowing.
Easterly winds can indicate an approaching storm front, westerly winds the opposite.
Strong winds indicate high pressure differences, which can be a sign of advancing storm fronts.
Deciduous trees show the undersides of their leaves during unusual winds, supposedly, because they grow in a way that keeps them right-side up during typical prevalent winds.
If you see a red sky during sunset (when you're looking to the west), there is a high pressure system with dry air that is stirring dust particles in the air, causing the sky to look red. Since prevailing front movements and jet streams weather usually move from west to east, the dry air is heading towards you.
A red sky in the morning (in the East, where the sun rises) means that the dry air has already moved past you, and what follows behind it (on its way towards you) is a low pressure system that carries moisture.
Take a deep breath. Close your eyes and smell the air.
Plants release their waste in a low pressure atmosphere, generating a smell like compost and indicating an upcoming rain.
Swamps will release gasses just before a storm because of the lower pressure, which leads to unpleasant smells.
A proverb says "Flowers smell best just before a rain." Scents are stronger in moist air, associated with rainy weather.
Many people can feel humidity, especially in their hair (it curls up and gets frizzy).
You can also look at the leaves of oak or maple trees. These leaves tend to curl in high humidity, which tends to precede a heavy rain.
Pine cone scales remain closed if the humidity is high, but open in dry air.
Under humid conditions, wood swells (look out for those sticky doors) and salt clumps (is that shaker working well?)
If birds are flying high in the sky, there will probably be fair weather. (Falling air pressure caused by an imminent storm causes discomfort in birds' ears, so they fly low to alleviate it. Large numbers of birds roosting on power lines indicates swiftly falling air pressure.)
Seagulls tend to stop flying and take refuge at the coast if a storm is coming.
Animals, especially birds, get quiet immediately before it rains.
Cows will typically lie down before a thunderstorm. They also tend to stay close together if bad weather's on the way.
Ants build their hills with very steep sides just before a rain.
Cats tend to clean behind their ears before rain.
Turtles often search for higher ground when a large amount of rain is expected. you will often see them in the road during this period (1 to 2 days before the rain.
A very old wives tale says if birds feed in a storm it will rain for a long time, if they dont it will clear soon.
Observe animals! They are more likely to react to changes in air pressure than we are.
Make a campfire. The smoke should rise steadily. Smoke that swirls and descends is caused by low pressure (i.e rain on the way).
Check the grass for dew at sunrise.
If the grass is dry, this indicates clouds or strong breezes, which can mean rain. If there's dew, it probably won't rain that day.