Winter, spring, summer, fall? The weather in Chicago is too varied, too dynamic, to be described by only four seasons. After consulting with the National Weather Service, the National Climatic Weather Center, and after decades of watching Tom Skilling and listening to Chicagoans complain about the weather, we’ve identified 10 seasons in this city, one for almost every month. Here’s our scientific assessment.

Polar Vortex

Arctic air doesn’t settle over Chicago every year, but when it does, the temperature drops to 14 degrees below zero, nostrils flap shut, boiling water crystallizes, the lake steams, locks freeze, and the Hawk — the Almighty Hawk — blows beneath the hem of the most expensive Canada Goose parka. Even That Guy who runs in shorts all winter stays indoors. A polar vortex only lasts a few days, but the bragging rights about enduring a real winter last for years.

Go Away, Winter

The winter blahs usually set in after the holidays, beginning on the first day back to work after the New Year. It’s dark, it’s cold, the Bears are out of the playoffs, pitchers and catchers won’t report for another month and a half, cars are towed after two-inch snowfalls, your rich a-hole friends are in Scottsdale, the wait for a bus feels twice as long. Mike Royko suggested several strategies for enduring the long haul until spring: drinking, brooding, writing hate mail, taking hostages. Lasts until the final dingy, crusty mound of snow melts in its shadowy redoubt.

False Spring

That one day in February when the temperature is 61 degrees and runners are wearing t-shirts and shorts. Maybe the winter squeeze, a consequence of global warming, has finally shrunk the season to two months. Don’t be fooled. This season is followed by…

It’s April. Why Isn’t Spring Here?

Spring, and Chicagohenge, arrived a month ago. Yet it’s 39 degrees, and you’re standing on an L platform, pounding the heat button. The coils never glow, because the CTA insists cold weather ends March 31. April is the longest month in Chicago. The trees are greening, the plovers have returned, but…it…just…won’t…get…warm. And September is a little over four months away.

Spring!

We made it! The bathrooms are open on the beaches. Water burbles in drinking fountains. The cops drive with the windows down in their SUVs. We can sleep with our windows open. Lilacs bloom on bushes. Landscapers are grooming the lawns of the wealthy. The seats in the shade of Wrigley Field’s roof are warm enough to sit in. The only downside to spring: as the temperature rises, so does the murder rate.

Green Flag Season

My late friend Pat Kennedy, who died last year at age 80, lived almost his entire life on Eastlake Terrace. When Pat was a boy, he and his friends competed to see who would jump in the lake first each year. The bravest among them took the plunge in early April. Swimming does not officially begin on Lake Michigan until Memorial Day, when the lifeguards arrive and raise a green flag on the beach. Unless the water is infected with e. coli, in which case they raise a red flag.

It’s All Worth It For This

Summer has arrived, in its purest form. Beach volleyball! Street fairs! Farmers markets! Lollapalooza! Every day is 75 degrees and sunny. At this moment, why would anyone want to live anywhere but Chicago? The winter freeze, the spring tease — our abusive relationship with the weather is forgotten and forgiven. Unfortunately, this season lasts only three-and-a-half weeks, between the 4th of July shooting rampage and the sweatiness of August.

Is This Global Warming?

Imagine moving to Chicago on the day the Heat Wave of 1995 spiked, at 104 degrees. Imagine almost fainting as you move your furniture up two flights of stairs to an un-air-conditioned studio apartment. That heat wave has not been surpassed, but last August, the temperature reached 98 degrees, during the hottest summer in recorded history. This time, though, hundreds did not suffocate inside their homes, because the city began requiring air conditioners in apartments after the fatal heat wave. Tip: there’s no more refreshing place to escape the heat than Lake Michigan.

Why Is It Cold Again Already?

John Keats called autumn the “season of mists and mellow fruitfulness.” Apple picking. Pumpkin carving. The Chicago Marathon. Halloween in Boystown. In a poll of Americans, 45 percent named autumn as their favorite season, buffering the extreme temperatures of summer and winter. Even so, it feels like a cheat that we get only four months of temperate weather, and that the lake is only warm enough to swim in for two. Autumn ends gloomily, in what Nelson Algren called “that smoke-colored season between Thanksgiving and the season’s first true snow.”

Welcome, Winter

What makes Chicago a great weather town is variety, novelty. The weather changes monthly, and so even winter is welcome on its first arrival. The skating rinks open in Millenium Park, the golf courses are covered in snow, and are scored with the tracks of cross-country skiers. Children sled down Mount Trashmore in Evanston. The Christkindlmarket opens in Daley Plaza. Life in a four-season city requires an extensive wardrobe, so you can break out your sweaters, scarves, and overcoats. Whiskey and chili feel warmer in the belly. Last November, this magazine published a package titled “39 Reasons to Love Winter in Chicago.” Enjoy them all, while you’re still enjoying winter.