Wintry mix 101: How does it happen?


HOUSTON – Winter weather can be a bit tricky, especially in places that have warmer climates like San Antonio. 

In order to get any kind of wintry precipitation, a very intricate balancing act of warm and cold air has to happen. Too much warm air, and you get rain. Get enough cold air, and you get snow.

Here’s a look at what it takes to make wintry mix happen.


For rain to happen, the air that the drops travel through must remain above freezing for the entire cloud-to-ground trip.

Freezing rain

For freezing rain to happen, a small layer of below-freezing air is nestled along the ground, keeping things like trees, sidewalks, cars and bridges at 32 degrees or lower. However, there’s a large wedge of warm air just above that layer of freezing air.

As a raindrop travels from the cloud to the ground, it remains liquid until it reaches the ground, where it freezes upon contact with objects that are socked in with cold air. The creates a coating of ice that surrounds things like tree limbs and your car.


Sleet happens when there is more cold air at the surface than warm air. This means that the amount of time a raindrop spends in the above-freezing air is much lower than the time it spends in the below-freezing air.

As the raindrop falls from the cloud, it freezes long before it reaches the ground, resulting in a frozen drop of water.

A tell-tale sign that you’re getting sleet is the “pinging” sound it makes when it hits metal. You’ll usually notice it bouncing off of surfaces as well.

If the sleet falls at a fast enough rate, it can accumulate much like snow.


For snow to happen, the water must stay frozen for the entire length of the cloud-to-ground trip.

About the Author: