peakwinter
/piːkˈwɪntə/ noun
the coldest week of the winter
Icy winds.
A blast from the east.
The sky is a featureless white.
Snow swirls in intermittent flakes.
Ponds, pools and puddles freeze over.
Add another layer before you head out.
Mind you don't slip, slide and fall.
Soup, stew, hot chocolate.
Whack up the heating.
No sign of a thaw. Peakwinter
Yes I know the weather's not as bad as it could be, and some of you have it a lot worse, and come on there's hardly any snow in that photo, and you call this cold we had proper cold when I was young. But there's always one week that's colder than all the others, no matter what the year, and that's what I'm defining as peakwinter.
Peakwinter's not always snowy. It is this year for those of us in the east of the UK but cold can spread without wintry precipitation, sometimes under a clear blue sky.
Peakwinter's not always cold. It is this year but some years it never gets really chilly. Peakwinter is a relative concept so some years are properly freezing while others are fairly mild.
Peakwinter doesn't always start on a Sunday or a Monday. This year it coincides with a calendar week, or looks like it will, but any seven-day period with any starting date will do.
Peakwinter's always the coldest part of the annual cycle but varies considerably year on year. Duration is constant but timing and severity differ. It's the worst week of the year for being homeless, a bird in search of nourishment or a tenant with a coin-operated meter. But some years it's worse than others.
Peakwinter's not always obvious at the time. If the cold snap comes in January you won't yet know if February will be worse. If it's not especially cold you might not realise that this is as bad as it's going to get. Peakwinter often slips by unnoticed.
So far this winter, the coldest seven-day period was in early January.
Jan 4
Jan 5
Jan 6
Jan 7
Jan 8
Jan 9
Jan 10
Average 3°C
5°C
4°C
5°C
3°C
1°C
3°C
4°C
n.b. These are maximum daily temperatures. Data is for Hampstead.
But this week, if the forecast is to be believed, is due to be much colder.
Feb 7
Feb 8
Feb 9
Feb 10
Feb 11
Feb 12
Feb 13
Average 1°C
3°C
-1°C
0°C
2°C
0°C
1°C
1°C
n.b. I'll come back and update this as the week progresses.
Peakwinter in 2019/2020 was a lot milder.
Jan 18
Jan 19
Jan 20
Jan 21
Jan 22
Jan 23
Jan 24
Average 7°C
7°C
7°C
6°C
6°C
8°C
8°C
7°C
It barely seems credible, given we're currently in the grips of a deep freeze, that the coldest week last winter still hit 7°C. But that's how weather works - far more variable than any changes in underlying climate.
I've gone back and worked out the average peakwinter temperatures for the last 12 years (and the months in which they occurred).
2009/10
2010/11
2011/12
2012/13
2013/14
2014/15
2015/16
2016/17
2017/18
2018/19
2019/20
2020/21
Jan
Nov
Jan
Jan
Jan
Feb
Jan
Jan
Feb
Jan
Nov
Feb
1°C
1°C
2°C
1°C
7°C
4°C
4°C
5°C
1°C
5°C
7°C
1°C
Four of the last twelve winters had a week as cold as the one we're currently enduring. No week has been colder overall. Four winters peaked with a middly low around 4 or 5°C. Two winters never had a week colder than 7°C (possibly the winters you spent the least on heating).
Over the last 12 years there have been 12 days when the temperature in Hampstead failed to get above freezing, including yesterday, but never enough in a row to drag the peakwinter average down to 0°C or below. There have also been 250 sub-zero nights over the same period, but that's not what we're measuring here.
Peakwinter normally occurs in January, which is also midwinter. It can be as early as November, which has happened twice recently. February's not uncommon, but things have invariably warmed up by March.
For balance, here's another new word.
peaksummer
/piːkˈsʌmə/ noun
the hottest week of the summer
Last year boasted this sweltering peaksummer week.
Aug 6
Aug 7
Aug 8
Aug 9
Aug 10
Aug 11
Aug 12
Average 33°C
29°C
35°C
32°C
32°C
34°C
33°C
34°C
No other peaksummer in the last 12 years can touch it.
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
Jun
Jun
Sep
Jul
Jul
Jul
Jul
Jul
Jun
Aug
Jul
Aug
27°C
28°C
26°C
26°C
29°C
27°C
27°C
28°C
29°C
30°C
29°C
33°C
Peaksummer normally hits the high twenties but more recently has hovered closer to thirty. This may be related to climate change or may be a statistical blip.
Peaksummer normally occurs in July, or one month either side. 2011's peaksummer in September, which dribbled into October, was a true outlier.
Peaksummer is a long way off at present, at least four months, and likely to be thirty degrees warmer. But it is something to look forward to as we endure peakwinter this week.
