There are all sorts of folklore terms for weather quirks and regional patterns, but the January Thaw and Indian Summer are pieces of weather folklore that are rooted in actual weather data.
For the middle latitudes, particularly the northern half of the country, the lowest temperature of the year is around January 23, and the hottest temperature falls around July 24. Between those two dates, temperatures more or less rise or fall fairly evenly, with two notable warm snaps in January and October.
These annual temperature quirks (or “singularities”) are predictable enough to have earned their status among the folklore seasons. The warm temperatures that occur in late January are known as the January Thaw, while the warming in middle of October is called an Indian Summer.
During both the January Thaw and Indian Summer, temperatures are usually around 10° F warmer than the usual expected seasonal temperatures with the warming trend lasting about a week. In some areas, those 10 degrees are the difference between freezing and not freezing, creating an unseasonable thaw. In other areas, temperatures may just be a little warmer than usual.
While these two seasonal variations can’t be completely relied upon, they statistically happen more than 50% of the time. For a gardener, the January Thaw and Indian Summer provide some unique opportunities, so take advantage of these warm snaps to:
- Repair Damage from Frost Heaving: The temperature change and associated freeze-thaw cycles can cause plants to be pushed out of the ground. Go out on a warm day and make sure everything’s still firmly planted, and add extra mulch to anything affected by frost heaving.
- January Lawn & Garden To-Do List (article)
- October Lawn & Garden To-Do List (article)
- What Is a January Thaw? (farmersalmanac.com)