The “Dead of Winter” is an old saying that refers to the coldest part of the winter season. This annual chilly period, statistically, begins today.
While actual daily weather varies, historical average temperatures in most of North America reach their lowest point of the year between January 10th and February 10th. This cold period does not begin on the winter solstice, the day we receive the least amount of solar energy, because of a phenomenon known as seasonal temperature lag.
Air temperature depends on both the amount of heat received from the sun and the amount of heat lost or absorbed by the oceans and continents. From the start of winter through mid-February, both the oceans and land are losing more heat than they gain.
These few cold weeks are the climatological opposite of the “Dog Days of Summer.”