Why the wasp season here has a hard stop
Everything about wasp control in Chicago runs on one seasonal fact: the colony is annual and the end date is not negotiable. The University of Minnesota describes Upper Midwest nests dying when freezing temperatures in the mid to upper twenties kill the old queen and the workers, and it identifies queens as the only members of the colony that survive winter. Average winter lows around 19 degrees clear that bar with room to spare. That gives you a usable calendar. April and May are queen months, when a nest is a comb of a few cells and one wasp. June and July are growth, when the colony is working but manageable. August and September are peak, with the University of Minnesota putting nests at up to about 5,000 wasps. The practical takeaway is about cost and risk, not biology. The identical nest handled in May takes minutes and no protective gear. Handled in September it takes a suit, a night visit, and a wider safety zone. If you spot a starter comb in spring, deal with it then rather than deciding it is too small to bother with.
The wasps you meet on a Chicago block
Four species show up in the Illinois data, and knowing which one you have changes the plan more than anything else on this page. Native paper wasps build the classic open comb on a stalk, often under a porch ceiling or a garage overhang, with cells you can count from the ground. The European paper wasp does the same but favors enclosed metal: downspouts, pipe ends, hollow rails, and hose reels. Both stay small and both sting mainly when the comb is touched. Bald-faced hornets are the ones that make people call the same day. Penn State reports their range across most of the contiguous states, and their nest is a fully enclosed gray envelope with a single entrance near the bottom. Disturb it and a large number of workers respond together. European hornets, per Penn State established throughout the eastern United States, hide their comb in hollow trees, wall voids, and attic spaces. You often never find the nest, only the hornets at a window after dark and the stripped bark on shrubs where they have been chewing.
Back porches, garages, and the spots wasps prefer
wasps want the same thing a queen wanted in April: a covered, dry, undisturbed corner nobody visits in early spring. Chicago's building stock is full of them. Wood back porches are the classic case. The underside of a stair landing, the top corner where the framing meets the house, and the hollow inside a porch column all give shelter from the roughly 38 inches of rain the city gets a year. A comb tucked into a stair landing sits directly above where people carry groceries. Detached garages are second. The gable end, the overhang above the service door, and the gap where the roof sheathing meets the wall all attract nests, and the garage gets used just infrequently enough in spring that nobody notices the building. The third group is the house itself: soffit vents without screen, the gap behind a loose piece of trim, and the space behind a shutter. These are the nests that get expensive, because the comb is out of sight and the colony can chew inward as it grows. The fix is the same for all three: look in April, and close the openings after the freeze.
What a first visit should include
A good visit starts with watching rather than spraying. The technician should walk the whole property, not just the nest you reported, because a house that suited one queen often suited two. Expect them to check the porch framing, the garage gable, the soffit line, the parkway tree, and any gap in trim. For an exposed comb the work is quick: an aerosol at dusk, then removal. For a hidden nest the tool changes to a dust placed at the entry, applied after dark when the workers are inside. Dust travels to the comb on the wasps themselves, which is the point, because you cannot spray what you cannot see. Ask what happens next. Will they come back to take the nest down, or is that on you. Will the opening be sealed, and is that included or a separate charge. What is the plan if traffic is still heavy in a week. Given how many Chicago nests sit in porch and soffit voids, the sealing conversation is the one that determines whether you are making this call again next August.
What actually moves the price
Two quotes for the same nest can differ mostly because they cover different work. Read for scope before you compare numbers. Access is usually the biggest single factor. A comb on a first floor porch rail and a hornet nest on a third floor gable are the same species of problem and a completely different amount of ladder, gear, and time. If the nest is over a walkway or a shared stairway, add setup for keeping people clear during the work. Concealment is the second. Killing a colony at a soffit gap is straightforward. Opening the soffit to pull out a large comb, then closing it back up, is carpentry, and it should be priced and described as such rather than assumed. Timing is the third. A September colony of several thousand wasps needs a night visit and full protective equipment. The same job in June is daylight work. Ask for the scope in writing, covering how many nests, whether the paper gets removed, whether openings get sealed, and what the follow up is. That single page is what makes two quotes comparable.