So I believe most people would agree that January is generally the coldest month of the year for most of the northern hemisphere. I live in the US, and believe it or not, but almost everywhere West of the Great Plains gets their coldest weather in December instead of January.
Mid- to late-January is statistically the coldest. Temps start to warm up a little in February.
Jan. and Feb. are pretty close around here. Last I saw, Jan. was a little colder with average temps starting to rise late Feb.
February in SC, in general, is when we get the coldest, wintery-est weather.
The coldest week in Wisconsin tends to be in late January, but occasionally it’s in early or even mid February. Never in December — I’m surprised the OP finds that to be the case in the “Western US.” Could he/she be more specific? That phrase covers MANY different physical zones over a large area.
January.
March is however our snowiest month making the winter drag on a bit.
Early January is the coldest around here, and if we are going to get a freeze(we usually don’t) this will be the month for it. But December is a close second, and it’s not unheard of to have a freeze. In fact the coldest temperature on record was in Dec. 1989(14F in Galveston, 7F in Houston). February is so much warmer that I usually plant my tomatoes in the second week.
I’m going to pick January for Chicago and that’s without me looking at weather data. I think January because not only is it cold all month, but it seems we get the most extreme cold blasts then, dragging down the average.
My birthday is near MLK day and it always seems to be the most miserable day of the year, although I’m sure that’s confirmation bias.
I googled it, and it’s January. I would’ve guessed February though. It just seems more desolate and colder.
Yeah, it seems to me the longest slog of the year is from the day after the Super Bowl (early February) until St Patrick’s Day. Plus, annoying Valentine’s Day commercials.
January. Average highs in the upper-50’s, average lows in the mid-40’s F. Brrrr.
January is coldest by average but sometimes February has the longer stretches of sub-zero days.
Maximum, minimum are pretty misleading things on their own.
Let’s say a place has a maximum of 14C (57F) and minimum of -2C (28F).
Another place has a maximum of 9C (48F) and a minimum of 6C (43F).
Despite the numbers, the second place will feel much colder.
As best I can tell, it’s pretty much a tie between December and January in Denver. Depends on the year. Just based on living here, it seems like January has longer cold spells, but it could be that from here winter just goes on and on and on
Ha! I just went by my gut instinct and said December. According to Google, I was right – the coldest month in Southern California is December.
The coldest month in my part of western Canada statistically is January although in '19 we had the coldest February in 80 years. The long range forecast is much the same for '20 as we’ve had a relatively easy winter so far.
I just checked our monthly averages and the average low is the same for January and December but the average high for January is one degree colder so I went with January. 44/11 F.
And your summer temps are only ten degrees higher. That does indeed qualify for Brrrr 
In the past it was January but it seems that recently winter is arriving earlier but not lasting as long as it used to. The previous two winters it felt like winter started around Thanksgiving and that it was over by New Year’s Day. We even had snow in December of 2017 :). This winter seems to be shaping up to be similar to the other recent ones. It feels like spring is starting here in south Texas and that the coldest days were from late November to mid December.
January, Arkansas. But our heaviest snow storms tend to be in Feb-March.