We had a blast of lake-effect snow yesterday. This happens when cold air passes over a warm lake, pulling huge volumes of moisture from the water and freezing it into snow. The air got quite a bit below freezing yesterday morning, so the northeast winds picked up a lot of vapor from the 8°C water, which it promptly dropped on the city.
Through the spring and early summer we often hear that it's "cooler by the lake." But like the idea of "global warming," that hides a lot of nuance in a simple phrase. A slightly-more-accurate telling might be that it's "less variable by the lake." And yesterday we got an example of that.
At Inner Drive Technology WHQ, which is just over 2 km from Lake Michigan, yesterday was the first day since March 2nd during which the temperature didn't get above freezing. Yesterday the temperature ranged from -3.0°C to -0.5°C, with a dip during the second round of snowfall between 8 and 10 am. On March 2nd, it ranged from -5.4°C to -0.2°C.
Contrast with Chicago's official weather station at O'Hare (23.2 km from the lake), which last had a full day below freezing on February 21st. On March 2nd it did get down to -8°C, but it got up to 3°C, after hitting 14°C on February 28th. Similarly, yesterday O'Hare was both colder (-3.9°C) and warmer (2.2°C) than IDTWHQ, warm enough for all the snow to melt just a few hours after it fell.
Today's forecast promises above-freezing temperatures everywhere in the Chicago area today, rising to 18°C by Saturday. The snow doesn't bother me, but I hope the remaining ice melts from the sidewalks today.
As threatened yesterday, we got a few rounds of lake-effect snow overnight and this morning. Since not all the leaves have fallen yet, it still looks pretty:
And of course, one member of my household really, really, really likes a fresh snowfall:
Right now we've got about 100 mm on the ground. That will melt quickly as the forecast calls for above-freezing temperatures from tomorrow morning onward, reaching possibly 18°C on Saturday. I hope so, because I've got a 20 km hike planned for the day, and I'd like it not to freeze important bits of me off.
I'll have some photos from San Francisco later today. Right now I have to shovel my walkway again, then take Cassie for a 3 km walk so I get my steps in.
I don't enjoy taking 6 am flights, of course, but they do have advantages. I left my hotel at 6:11 am and was through SFO security by 6:25. That's even faster than last year!
I'm a little less enthused about this, however:
URGENT - WINTER WEATHER MESSAGE
National Weather Service Chicago IL
224 AM CST Sun Nov 9 2025
Northern Cook-Central Cook-Southern Cook-Eastern Will-
Including the cities of Chicago, Peotone, Northbrook, Crete,
Evanston, Lemont, Park Forest, Schaumburg, Cicero, Oak Park, La
Grange, Des Plaines, Oak Forest, Oak Lawn, Calumet City, Beecher,
Palatine, and Orland Park
224 AM CST Sun Nov 9 2025
...WINTER STORM WARNING IN EFFECT FROM 9 PM THIS EVENING TO NOON CST
MONDAY...
* WHAT...Dangerous to impossible travel conditions due to intense
lake effect snow expected. Snow rates in excess of 3 inches per
hour, localized total snow accumulations of 12 to 18 inches, and
northerly wind gusts in excess of 30 mph are expected.
* WHERE...Central Cook, Eastern Will, Northern Cook, and Southern
Cook Counties.
* WHEN...From 9 PM this evening to noon CST Monday.
* IMPACTS...Snow rates in excess of 3 inches per hour will cripple
travel, including during the Monday morning commute. Strong
northerly wind gusts in excess of 30 mph will lead to greatly
reduced visibility, especially near the Lake Michigan shoreline.
Periods of thundersnow will occur, as well.
* ADDITIONAL DETAILS...Lake effect snow is often very localized,
with conditions varying from safe to dangerous across just a few
miles. Snow totals in the Winter Storm Warning area may vary
considerably from one location to the next.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Persons should consider delaying all travel while and where the lake
effect snow is ongoing.
Unfortunately for me, my work laptop is in my downtown office, and my most important meetings tomorrow are between 10 and 11:30. Because the forecast is for lake-effect snow, we have no way to predict exactly where it will hit. I've seen these things produce 30 cm of snow on one block and nothing on the next.
Right now, though, the weather looks good for aviation, and my plane appears to be here and ready to fly. We'll find out tomorrow whether I'll be able to make it to the office.
The National Weather Service Chicago office released its report on the 2024-25 winter today, the first day of meteorological spring. Highlights:
- Average temperature: -2.6°C (0.4°C below normal)
- Total snowfall: 302 mm (450 mm below normal, 10th least snowiest)
- Total precipitation: 113 mm (42 mm below normal)
They go on:
At Chicago, the average high temperature was 34.1 degrees, which is 0.5 degrees below normal. The average low temperature was 20.5 degrees, which is 1.1 degrees below normal. The mean average temperature for the season was 27.3 degrees, which is 0.8 degrees below normal. 4.43 inches of liquid precipitation were recorded, which is 1.64 inches below normal. 11.9 inches of snow were recorded, which is 17.7 inches below normal.
Daily and top ten monthly records established for Chicago this past winter...
- December: None
- January: None
- February: None
The following top ten seasonal records were set for Chicago this past winter:
** 10th least snowiest winter on record with 11.9 inches of snow.
In other words, an average winter for the cold but a very mild winter for the snow. Nothing too extreme, nothing too nice, nothing too awful.
NCDC predicts a fairly average spring, starting with a fairly normal storm bearing down on us this week. Because it wouldn't be early March without a reminder that our weather doesn't get consistently nice until June.
We've got a classic weather event rolling through Chicago right now:
What makes it atypical is the low pressure over northeast Minnesota (980 mB) and the tight pressure gradient around it. So while the temperature at IDTWHQ has gone up 7.2°C (13°F) in five hours—2°C in the last hour alone—we've also got a bit of wind. O'Hare reports southwest winds at 16 kts with peak one-minute winds of 39 kts, which qualifies as a fresh gale.
But you see that blue line curving through Minnesota, South Dakota, and Wyoming? That cold front will slide through Chicago overnight, bringing us below freezing for a couple of days.
For what it's worth, the normal temperature range for March 1st is -3.1°C to 4.9°C. We should get that entire range between 8pm and 3am tonight.
So this isn't really that unusual for Chicago. March has the most variable weather of any month here. That's why we dress in layers.
First, the temperature at Inner Drive Technology WHQ has gotten up to 10.5°C for the first time since 3:33 pm on Monday December 9th. If it goes up just 0.1°C more, that will make today the warmest day since Monday November 25th. Fingers crossed.
Second, the National Geospatial-Intelligence Agency returned to DNS this morning. Someone at the Department of Defense must have noticed that the government's maps had vanished and was able to get the DNS entries restored. In consequence, I have downloaded everything through Romania, imported everything through Comoros (except China; that's importing right now), and the automatic indexer has captured 274,194 new places for a total gazetteer size of 2,668,565 places. That will rise dramatically later today; there are 2.05 million records for China, of which the import tool has already saved 1 million.
Updates as conditions warrant.
Update: As of 2:29 pm the temperature hit 10.6°C for the first time since 1:49 pm on Monday November 25th. Today is officially the warmest day of the 2024-25 winter season!
Garmin periodically challenges its users to get active. About once a month they put out a distance challenge for walkers. This month, the challenge was to do a 4.8 km walk this weekend. Cassie and I just did that, as it turns out Jimmy's Pizza Cafe is conveniently 2.6 km away. It helps that we haven't had temperatures this warm (4.0°C) since just after 1pm on the 3rd.
Butters, however, did not like getting left behind. According to my security camera, she spent 18 minutes crying by the front door, took a quick stroll around my lower level, then went back to cry by the front door for another 10 minutes before going upstairs to cry in the living room. She gave up for a while, then returned to the front door for another 15 minutes, alternately crying and sitting quietly. I haven't watched the whole 54 minutes but I'd bet she was quiescent for less than 10.
I am sorry for my neighbors. Fortunately, the neighbor to the north is out of town. And frankly, the neighbors to the south have a 3-year-old boy who makes far more noise in the aggregate than any dogs I've ever owned (or looked after).
Tomorrow I'll go back to complaining about world events. Right now, I'm taking both dogs and my friend Kat's new book to Spiteful Brewing.
Butters, possibly traumatized by Cassie and me leaving her alone for almost half an hour yesterday, has decided to stake out my office:
Incidentally, this is what Cassie and I walked past in the local park yesterday:
We've had progressively warmer days since the temperature bottomed out Monday morning. We might even get above freezing today! I hope so, because I need a 5 km walk to meet a Garmin challenge this weekend. (Cassie will help with that; Butters, not so much.)
My friends have gone to a tropical beach for the week, which means I get a second dog for a few days. She has been here many times before (most recently on Saturday), so she knows the drill. Still, five minutes after her people left, Butters seemed resigned to never seeing them again:
By the time I woke up this morning, however, she seemed to have settled in just fine:
Walking the two of them together in this cold doesn't actually work, however. Butters hates cold weather; Cassie loves it. So Cassie wound up dragging Butters for half of this morning's walk, making all three of us miserable. After lunch I'll walk them again...separately.
The temperature at Inner Drive Technology WHQ has gone up all day, just surpassing yesterday's afternoon high of -11.3°C:
Of course, yesterday's actual high was -10.3°C, at midnight, and we won't hit that again until tomorrow. But by Friday we'll be able to walk outside without losing extremities, and by Sunday it'll even be above freezing. And then, in 10 days: spring!
There is one advantage to Arctic air over Chicago, though: the air is really clear.
