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Camping in the Boundary Waters and Quetico

Predicting Weather — Cloud Cover

You will improve your accuracy by learning about the types of clouds and how the wind affects the weather with each kind.

There are only three basic cloud formations: cirrus, stratus and cumulus.

Cirrus, From Latin, meaning "curled". These are high ice clouds in an otherwise clear sky, from 20,000 to 40,000 feet. You see them as feathery "mares' tails", long curling clouds that are the tops of thunderheads off beyond the horizon.

With cirrus clouds overhead:
If the wind is anywhere from the Northeast around through East to the South, you can expect rain in the next 24 hours.

If the wind is anywhere from the Southwest around through West to the North, good weather will remain another 24 hours.

Stratus, From Latin meaning "spread out". These are low clouds, a uniformly gray overcast from near ground level up to about 8,500 feet. They always predict unpleasant weather.

With stratus clouds overhead:
1) If the wind is from the Northeast around to the South, you can count on heavy rain in the next 24 hours.

2) If the wind direction is from any other direction, you can count on a continued overcast for the next 24 hours, with no rain or at the worst a slight drizzle.

3) If the cloud cover has a slightly billowing look, you have "strato-cumulus", clouds. This type of cloud allows you to predict immediate rain.

Cumulus, From Latin meaning "heap". These are low clouds at 1000 - 2000 feet, the heaped-up fluffy white clouds scattered in a blue sky.

With cumulus clouds overhead, it never rains, unless:
The wind shifts to the East, or,

The clouds build up into towering black clouds with winds from the West, forming the classic thunderheads sometimes shaped like an anvil (cumulo-nimbus clouds).

You can predict the weather for the next 24 hours with high accuracy if you keep these few facts in mind. There are two more cloud formations that you should know to complete you education.

Alto-cumulus. These are water and ice clouds, the "mackerel" sky, that looks like gently rolling waves in the ocean as seen from a low-flying airplane. You will see this kind of sky only a few times a year.

When you do:
With winds from the Northeast around to the South, they always mean rain within 24 hours.

With winds from any other direction, they mean just a continued steady overcast.

Alto-stratus. These produce a uniformly gray overcast, similar to stratus clouds, but higher and lighter. The sun looks as if you are seeing it through frosted glass. The weather prediction is the same as with alto-cumulus, but the precipitation will be here in ten to twenty hours, rather than in 24 hours.

So keep an eye on the wind and the clouds and amaze everyone with your uncanny meteorological predictions.

• What the Wind can tell you
• Weather Prodiction Intro
• Test your knowledge