What Is A January Thaw?
Is there always a January Thaw? Find out if this is more lore than fact.
Quick Reference
- What: A brief warm-up of about a week in late January, when temperatures average around 10 degrees F above the previous week.
- When: Roughly January 23 is the coldest day of the year in much of the Northern Hemisphere. The thaw lands shortly after.
- How often: Slightly more than 50% of years. Recognized as a “singularity” in weather lingo.
- Cousin pattern: Indian Summer, the same kind of singularity in mid-October.
- Companion read: Our December weather lore and historic blizzards.
“January thaw,” like Indian Summer, is more than just another piece of weather lore. Annual averages really do show a slight temperature increase, and subsequent dip, during the final week of January. Historically, January 23 is the coldest day of the year in much of the Northern Hemisphere. Almost exactly six months later sits July 24, the warmest day of the year, on average. Between those two dates, average daily temperatures show a fairly predictable rate of increase. While there may be deviations from that pattern during any given year, the model holds true when looked at over a period of several years.
A “Singularity” in the Annual Curve
Though predictable, the climb from cold weather to warm and back again is not completely smooth. Small “blips” in the overall pattern reveal noticeable fluctuations that can be observed from year to year. These blips are called singularities in weather lingo. Indian Summer, a period of unseasonably warm weather that usually appears in mid-October, is one such blip. The January Thaw is another.
During the January Thaw, which usually lasts for about a week, temperatures rise an average of 10 degrees F higher than the previous week, then drop back down in time for February’s arrival. Though it is called a “thaw,” the January Thaw does not necessarily melt away snow and ice during its stay. In areas where winter weather is exceptionally cold, temperatures during the thaw may not even rise above freezing. More temperate regions, however, may even experience what could be described as a “false spring.”
Though they are a verified weather phenomenon, January Thaws do not happen every year. In order for a singularity like the January Thaw to be recognized, it only has to appear slightly more than 50 percent of the time.
When Each Region Feels It
| Region | Typical thaw window | Average rise |
|---|---|---|
| Northern New England | Jan 20-27 | 8-10 F (often still below freezing) |
| Mid-Atlantic / Ohio Valley | Jan 22-28 | 10-12 F (above freezing common) |
| Upper Midwest | Jan 23-30 | 8-12 F |
| Southeast | Jan 20-25 | 12-15 F (often “false spring”) |
The National Weather Service tracks daily temperature climatology for every U.S. station, so you can see whether your town has hit the thaw curve in any given year.
That is the beauty of weather. Though predictable to some degree, it always keeps us on our toes.
Frequently Asked Questions
What is a January thaw?
A brief warm-up of about a week in late January, when daily temperatures average roughly 10 degrees F above the previous week. It is recognized as a “singularity” in the long-term temperature curve, like Indian Summer in October.
Does a January thaw happen every year?
No. To be classified as a singularity, the pattern only has to occur slightly more than 50% of the time. Some winters skip the thaw entirely.
When is the coldest day of the year?
January 23, on average, in much of the Northern Hemisphere. The opposite point on the calendar is July 24, the warmest day on average.
Does a January thaw actually melt the snow?
Sometimes. In colder regions like northern New England, temperatures may not even rise above freezing during the thaw, so snow stays put. In milder regions the thaw can produce a “false spring” with significant melt.
What is a weather singularity?
A small but recurring “blip” in the long-term temperature pattern that appears around the same calendar date in most years. Indian Summer and the January Thaw are the two best-known U.S. examples.
How long does it last?
Usually about a week. Temperatures climb in the days leading up, peak somewhere around January 25, and drop back down by the end of the month.
Where can I check whether my area had one?
The National Weather Service publishes daily temperature climatology for every U.S. station. Pull up the late-January chart and look for the dip-and-bump pattern in the average curve.
Tell Us
Did your town get a thaw last January? Tell us in the comments. For more winter pattern reads, see our historic blizzards and December weather lore.
Jaime McLeod
Jaime McLeod is a longtime journalist who has written for a wide variety of newspapers, magazines, and websites, including MTV.com. She enjoys the outdoors, growing and eating organic food, and is interested in all aspects of natural wellness.
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- Jaime McLeod
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- Jaime McLeod
We in So Cal just had about a week of beach weather, which is now ending. This is our “January thaw.”
Interesting 🙂 We could use a lot of January “thaw” around here. LOL Hee hee