Submitted by WayneHudsonIII t3_zz4obm in askscience
Some context:
Where I live in NH, the average historical daily temp continues to drop after the Winter Solstice (December 21 this year) and doesn't level off and start getting warmer until about mid-January. Why is that?
Additionally, the average temperature climbs slower from Winter into Spring than it drops from Fall into Winter. What's going on there?
Based on my naïve understanding, I'd expect the temperature to be relatively symmetrical around the Solstice (Solstice - 1 roughly = to Solstice + 1, etc), but that's clearly not the case.
Can someone help explain this to a weather newbie?
keithatcpt t1_j2cdfjr wrote
With anything that’s warmed by a heat source, there is a “thermal lag time” where the temperature of what’s being warmed doesn’t start increasing right away. The bigger the system, the longer the lag time, and the earth is a pretty big system. Also, the energy provided by the sun generally is the same a week after the winter solstice as it is a week before, when the northern hemisphere is still cooling off on average. That’s why the coldest month tends to be January. When things start warming up in late February into March, the weather patterns tend to be windy and stormy as more energy is heating the northern hemisphere, causing evaporation from the oceans which runs into the cold air over the continents.