Expert: Dave Dombek - 12/29/2006

Question
Why are the seasons on either side of a solstice not equal, in terms of length
and temperature? For example - the part of winter in November and
December is usually shorter and warmer than its corresponding part in
January, February, and March.

Or, why are the seasons not mirrored on either side of a solstice; why is
March not like September?

(I'm at a latitude of 51 degrees North.)

Answer
Hana,

That is a good question! Basically, the reason for what you described is something we call "seasonal lag". It takes a long time for the atmosphere too cool down in the fall and early winter, just like it takes a long time for it to warm up in the spring and early summer.
A good example of this would be putting a pot of water on the stove and turning up the burner to high. That water would eventually come to a boil, but not right away, especially if it started off cold. That is the same with the atmosphere. The "burner" of the atmosphere, the sun, is on a high setting in late April, May, and June, but it is still warming up during that time. By late summer, the burner is being turned down gradually, then at a more rapid pace during the fall. By late October and November, the sun is getting fairly weak and low in the sky, but it can still be warm at times then...or at least comfortable. The same goes with that pot of water. After it is boiling, and you turn the burner down to low, it doesn't just cool down instantly. It takes a LONG time.
So, because of seasonal lag, the temperature curve DOES NOT follow the solar curve.

I hope this helped!

Sincerely,

Dave Dombek
Expert Senior Meteorologist
AccuWeather.com