Everyone knows about rain, snow, sleet, and hail, but don’t forget about their lesser-known cousin: freezing rain. This rare and fascinating type of precipitation occurs when liquid rain hits a cold surface and rapidly freezes, creating a slick (and often very pretty) layer of ice.
Here’s everything you need to know about this stunning yet hazardous weather phenomenon.
How does freezing rain form?
Freezing rain occurs when snowflakes or ice pellets pass through a warm air layer during their descent, melting into liquid droplets. If these droplets then travel through a shallow layer of subfreezing air near the surface, they become supercooled. Upon contact with surfaces at or below freezing temperatures, the supercooled droplets freeze instantly, forming a layer of ice.
An infographic showing how warm air can influence different forms of precipitation, including freezing rain.
Difference between sleet and freezing rain
The many forms of precipitation are ultimately decided by the temperature of the air it contacts as it falls. Almost all precipitation starts as snow in the high clouds. If temperatures remain cold all the way down, it falls as snow. If it passes through a thin layer of warm air, it typically becomes sleet.
In the case of frozen rain, it starts off cold, passes through a warm layer, then another cold, and finally hits a cold surface. These are fairly precise conditions, hence why you don’t see it too often in many parts of the world.
Due to specific atmospheric patterns and weather systems, frozen rain is relatively common in parts of North America. This typically occurs when a layer of very cold air is trapped in the lowest levels of the atmosphere beneath a warm front. Natural features like valleys near large bodies of water are especially prone to this phenomenon, as they help lock in the cold air while warmer, moisture-laden air flows above.
Beautiful but deadly: an ice-caked street in Salem after a freezing rain ice storm.
Image credit: Bob Pool/Shutterstock.com
For instance, the Appalachian Mountains and low-lying valleys can trap cold air, while warm, moist air flows over it, creating ideal conditions for freezing rain. Another key factor is cold air damming, where easterly winds from the Atlantic hold cold air against the mountains while warm air moves above it.
Freezing rain can transform the world into a spectacular winter wonderland, coating trees, cars, and lamp posts in icicles and a shimmering layer of ice. However, it can also pose a danger. Roads become treacherously slick, making travel risky, while the weight of accumulating ice can snap tree branches and bring down power lines, leading to outages and hazards. The coating of hard ice can also pose a real problem for planes, helicopters, and other aircraft wanting to land.
In early spring 2025, parts of eastern North America were hit with an especially bad bout of freezing rain. On March 30, thousands of people living around the Great Lakes were left without power after a spring storm doused the region with freezing rain, while similar conditions were reported north of the border in Atlantic Canada.
Weather events like this are typical of the colder months, so it’s tempting to say this will be the last freezing rain downpour of early 2025 – but never say never.
Source Link: Freezing Rain: The Rare Weather Dousing North America Is Shaped By Unusual Forces
