I often find it difficult to explain on TV why a morning with a wind chill may be warmer than the next night when the wind will be calm, so let's go into more depth here.

What You Need To Know

  • The low temperature for a day usually occurs around sunrise

  • A clear and calm night is a perfect setup for cold air

  • Warmer air mixes down to the surface on windy nights

You may hear meteorologists say, "with a clear sky and calm wind overnight, temperatures will dip really low."

On a calm night, the most surface cooling can take place. The Earth's surface cools by radiating heat off into space.

The strongest cooling takes place right near the surface, while temperatures higher up in the sky are warmer. With a breezy wind at night, some of the warmer air mixes down towards the surface.

This happens because the wind is faster higher up in the sky since it does not have objects to run into like the winds at the surface do.

Try It at Home

If that thought is confusing, try this:

  1. Put one hand over the other a few inches apart. Your bottom hand will represent the air near the surface, while your top hand represents the warmer air higher up. 
  2. Move your bottom hand slowly and the upper hand faster, imagining how the faster air above and slower air below cause the air to spin. 
  3. This overturning motion is how warmer air from above transports downward on windy nights. 

If this still doesn’t make sense, grab oil and vinegar.

Put equal parts in a clear jar and secure tightly. Place the jar on the countertop and let it be still.

This represents a calm and clear night, with the olive oil acting as the warm air floating on top and the vinegar acting as the cold air at the bottom of the jar.

Now shake it up (this represents wind), and look at how the oil (or the warm air) mixes down.

Forecast Tip

So, it's clear (pun intended) that on a windy night, some warmer air mixes down toward the surface, preventing the temperatures from dropping as quickly as they would on a calm night.

If the wind continues to blow for the rest of the night, the official low temperature will be higher than it would have been if the wind never blew in the first place.

Juicy Details

Farmers have to know a lot about the weather to keep their crops thriving.

Believe it or not, on a calm, clear night, when frost is guaranteed, farmers use wind machines to keep produce safe. These machines can help keep temperatures several degrees warmer than the untreated areas.

In summary, a windy night is not as cold as a calm night.

Look out for part two of this three-part series.

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