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Hi there,
I have always found this an interesting question too. Wayne's
answer is on the right track, but implies that this is a coastal
phenomenon. A very good explanation for why it is generally true that the
coldest days of winter occur well after the days begin to lengthen was
published in Colombo's Canadian Global Almanac, 1997. I obtained
permission from the publishers to reprint it in the Halifax Field
Naturalist in 1998. They told me at the time that it written by David
Phillips of Environment Canada, the well-known weather expert. I still had
it in my computer files, so I have pasted it in below.
Cheers,
Patricia L. Chalmers
in Halifax (but a Winnipeg native, who is enjoying these brisk
sunny days. If only we had some snow!)
_________________________________________________________________
Why isn't the shortest day of the year the coldest day of winter?
There are at least three good reasons why the shortest day of the
year, which falls on December 21st, isn't usually the coldest. First, the
ground and particularly water bodies absorb and hold heat, in much the same
way barbecue coals retain heat long after the barbecue is extinguished. It
requires many weeks of cold weather before that stored heat is lost.
Secondly, regions in the far north of Canada receive no direct
heat from the sun until early February. As a result, pools of arctic air
that accumulate over the country get progressively colder until the north's
long winter night is over. Thirdly, as the winter advances, the snow cover
usually increases in depth. Snow is one of the best insulators in the
world - it can stop the upward flow of heat from the earth below as readily
as it can reflect the incoming heat from the sun back into the
air. Accordingly, winds originating over snow and ice-covered terrain tend
to be colder in January and February (when the snowfields have had a chance
to get established) than they are in December.
So that is why the coldest day of the year often occurs in early
February, on average, a month and a half after the shortest day of the
year.
Colombo's Canadian Global Almanac,
1997
_________________________________________________________________________________
At 02:19 AM 08/02/2007 -0400, Wayne Neily wrote:
>Hello Andy,
>
> The short answer is the proximity of the ocean, which retains heat much
> better than the land, and results in the delay of the coldest weather in
> the fall (and the arrival of warmer weather in the spring) in areas with
> coastal climates.
>
> Likely someone will be able to give you a more complete answer and
> perhaps some additional factors.
>
>Wayne Neily
>Tremont, Nova Scotia
>
>
>"In nature's infinite book of secrecy
>A little I can read." - William Shakespeare, 1607.
>
>
>From: "Andy Moir/Chris Callaghan" <andyandchris@ns.sympatico.ca>
>Reply-To: naturens@chebucto.ns.ca
>To: <NatureNS@chebucto.ns.ca>
>Subject: Re: [NatureNS] The Depths of Winter
>Date: Wed, 7 Feb 2007 17:38:49 -0400
>I am curious why the low point for temperatures would come in February. I
>would have thought it would come when the days are shortest, in late
>December. What other factors are at play, other than length of day, that
>make late January and early February the coldest part of the winter?
>Andy Moir
>Freeport (or Freezeport, lately)
--=====================_1997057500==_.ALT
Content-Type: text/html; charset="us-ascii"
<html>
Hi there,<br><br>
<x-tab> </x-tab>I have
always found this an interesting question too. Wayne's answer is on
the right track, but implies that this is a coastal phenomenon. A
very good explanation for why it is generally true that the coldest days
of winter occur well after the days begin to lengthen was published in
Colombo's <u>Canadian Global Almanac</u>, 1997. I obtained
permission from the publishers to reprint it in the <u>Halifax Field
Naturalist</u> in 1998. They told me at the time that it written by
David Phillips of Environment Canada, the well-known weather
expert. I still had it in my computer files, so I have pasted it in
below.<br><br>
<x-tab> </x-tab>Cheers,<br><br>
<x-tab> </x-tab>Patricia
L. Chalmers<br>
<x-tab> </x-tab>in Halifax
(but a Winnipeg native, who is enjoying these brisk sunny days. If
only we had some snow!)<br><br>
_________________________________________________________________<br>
Why isn't the shortest day of the year the coldest day of
winter?<br><br>
There are at least three good
reasons why the shortest day of the year, which falls on December 21st,
isn't usually the coldest. First, the ground and particularly water
bodies absorb and hold heat, in much the same way barbecue coals retain
heat long after the barbecue is extinguished. It requires many
weeks of cold weather before that stored heat is lost.<br>
Secondly, regions in the far
north of Canada receive no direct heat from the sun until early
February. As a result, pools of arctic air that accumulate over the
country get progressively colder until the north's long winter night is
over. Thirdly, as the winter advances, the snow cover usually
increases in depth. Snow is one of the best insulators in the world
- it can stop the upward flow of heat from the earth below as readily as
it can reflect the incoming heat from the sun back into the air.
Accordingly, winds originating over snow and ice-covered terrain tend to
be colder in January and February (when the snowfields have had a chance
to get established) than they are in December.<br>
So that is why the coldest day
of the year often occurs in early February, on average, a month and a
half after the shortest day of the year. <br><br>
&am