Why is the coldest day of the year about 6 weks after the winter solstice?

Question

Likewise why is the hottest part of the summer always after the longest day of the year. You would think the coldest day would be Dec 21 (shortest day, sun farthest away) and the hottest day would be June 21 when the sun is closest. (Northern hemisphere for me.) Why is there a lag?

Answer 1

Good question, but only one of the other readers has gotten close. Here's the scoop. Seasonal lag (and daily lag) is a result of the amount of time between maximum solar insolation and air temperature heated by the outgoing longwave radiation. At the summer Solstice when the insolation is greatest, the earth must absorb this radiation and convert it to heat (longwave infrared radiation) which in turn heats the air. This process takes some time. What I have just explained works on a daily basis as well which is the reason why the maximum temperature of the day is around 3 or 4 p.m following the time of maximum insolation around noon.

Answer 2

Let's assume you have a line of credit with your bank account, that you have a variable income throughout the year, but a fixed expense of $10 per month. Let's look what your bank account would look like:

Month in out balance
Jan...$5 .... $10 ... $-5
Feb...$7.... $10.... $-8
Mar... $10 ... $10... $-8
Apr ... $10 ... $10... $-8
May ... $13 ... $10 ... $-5
Jun ... $15 ... $10 ... $0
Jul ... $15 ... $10 ... $5
Aug ... $13 ... $10 ... $8
Sep ... $10 ... $10 ... $8
Oct ... $10 ... $10 ... $8
Nov ... $7 ... $10 ... $7
Dec ... $5 ... $10 ... $0

Notice that when your income is lowest is not when your bank account is lowest?

Of course, this is a rough example, but it shows what is going on.

Answer 3

i'm not exactly sure, but i've always figured that it takes time for the earth to either lose or gain heat(the same is true of the summer solstice) maybe...huh....possible? I'll look back time to time to see who else can come with any other theories!