What time does the fog lift in Bartlett?

Radiation fog forms overnight and typically burns off as the morning sun warms the ground — most often by mid-morning. On Tuesday, October 20, 2026, the Dense Fog Advisory for the Bartlett area ran until 10:00 AM CDT, with mostly sunny skies expected by 11 AM.

Why is it foggy in one part of Bartlett and clear in another?

Radiation fog is patchy by nature. It forms first — and sits thickest — in low-lying spots and near water, where cool, dense air pools overnight, while higher or breezier spots a few streets away can stay clear.

What does a Dense Fog Advisory mean?

The National Weather Service issues a Dense Fog Advisory when widespread fog is expected to cut visibility to a quarter-mile or less. Slow down, use low-beam headlights (never high beams), and leave extra following distance — or delay the trip until the fog lifts.

Bartlett, IL Weather — Today, Seasons & Fog Safety

Q: When is Bartlett's fog season?

Fall and winter. The National Weather Service says radiation fog is most prevalent during the fall and winter, and fall adds the perfect mix: long nights for cooling, moist ground, and warm afternoons followed by chilly dawns.

Today in Bartlett — Tuesday, October 20, 2026

NWS advisory · Until 10:00 AM CDT today

This morning: dense fog, then it burns off

A Dense Fog Advisory is in effect for the Bartlett area this morning until 10:00 AM CDT — the kind of fog that can drop visibility to a quarter-mile or less. It formed overnight after the temperature fell to about 41°F, and by mid-morning it was still hanging around at 56°F with humidity at 78% and the wind nearly calm at about 1 mph. Expect it to thin late this morning; the hourly forecast turns mostly sunny by 11 AM.

Driving this morning: low beams on, speed down, extra following distance — the full checklist is in the safety section below.

Advisory: Dense Fog Advisory, National Weather Service, until 10:00 AM CDT Tuesday, October 20, 2026

Overnight low: ~41°F · Mid-morning: 56°F, calm

Forecast · Tuesday, October 20

This afternoon: sun and the upper 60s

Once the fog clears, it's a mild fall day: sunny skies, temperatures climbing through the mid-60s around noon and topping out in the upper 60s this afternoon — a swing of nearly 30 degrees from the chilly dawn. That's several degrees warmer than the mid-October average high of about 62°F at the Elgin climate station. The evening stays clear, cooling back through the 50s after a 6:03 PM sunset.

Sunrise / sunset: 7:10 AM / 6:03 PM CDT

Source: Today's conditions and hourly forecast as observed the morning of October 20, 2026

Why Bartlett gets foggy

Most of our foggy mornings — including this one — are radiation fog, and the recipe is simple. On a clear, calm night, the ground loses the heat it soaked up during the day, radiating it straight back into space. The thin layer of air touching the ground cools with it. When that air cools to its dew point, the moisture in it can't stay invisible vapor anymore — it condenses into tiny droplets, and you get a cloud sitting on the ground. The National Weather Service notes this type of fog can be anywhere from a few feet to about a thousand feet deep, and it can cut visibility to near zero.

Four ingredients have to line up, and Bartlett had all of them last night:

Clear skies — no cloud blanket to hold the day's heat in, so the ground cools fast.
Calm or nearly calm wind — wind would stir the air and break the fog up; last night it was about 1 mph.
High pressure — the calm, clear pattern parked over the region is exactly the setup that lets the ground cool uninterrupted.
Moist air near the ground — without a deep enough layer of humid air, the temperature never reaches saturation.

Why fall is peak fog season: the Weather Service says radiation fog is most prevalent in fall and winter, and autumn stacks the deck. Nights get long — more hours of cooling before sunrise. The ground is still moist from gardens, fields, and recent weather. And the day-night temperature swing is at its biggest: a warm 68°F afternoon can be followed by a 41°F dawn, a drop of nearly 30 degrees, which is more than enough to push the air to its dew point. Because cold air is dense, it also drains downhill and pools — which is why the fog forms first and sits thickest in low-lying spots and near water, while a breezier street a few blocks away can be perfectly clear. Radiation fog is patchy like that. Then the sun comes up, warms the ground, and the fog evaporates from the bottom up — usually gone by mid-morning.

Bartlett weather by month

Bartlett doesn't have its own long-term weather station, so these are the official climate normals from the nearest one that does: Elgin, IL (Illinois climate station 112736), about ten miles northwest — close enough that its winters, summers, and rainfall pattern are effectively ours. The table below uses the station's published NOAA (NCDC) normals and snowfall averages, with temperatures rounded to the nearest degree.

Month	Avg high	Avg low	Precip.	Snowfall
January	28°F	11°F	1.68″	10.7″
February	33°F	16°F	1.38″	7.4″
March	44°F	26°F	2.23″	4.2″
April	58°F	36°F	3.91″	0.9″
May	69°F	47°F	3.84″	0.0″
June	79°F	57°F	4.31″	0.0″
July	83°F	62°F	3.93″	0.0″
August	81°F	60°F	4.43″	0.0″
September	74°F	51°F	3.63″	0.0″
October	62°F	40°F	2.66″	0.0″
November	46°F	29°F	3.12″	1.7″
December	33°F	17°F	2.10″	8.5″
Year	—	—	37.22″	33.4″

The year in one paragraph: January is the coldest month (average high 28°F, low 11°F) and July the warmest (83°F / 62°F). Rain is spread across the year at about 37 inches, with the wettest stretch running April through August — thunderstorm season — while winter's moisture mostly arrives as snow, about 33 inches a year, concentrated in December through February. Frost dates frame the garden calendar: at Elgin, the median last spring freeze falls on April 26 and the median first fall freeze on October 11 — so by late October, nights at or below freezing are routine, which is part of why mornings like today's happen.

Source: Illinois State Water Survey historical climate summary for station 112736 (Elgin, IL), publishing NOAA/NCDC climate normals (1971–2000) and 1971–2000 snowfall averages.

Fog & severe-weather safety

NWS guidance

Driving in dense fog

The National Weather Service's checklist for fog like this morning's:

Slow down and allow extra time to reach your destination.
Use low-beam headlights — that switches your taillights on too, so drivers behind you can see you. Use fog lights if you have them.
Never use high beams. They glare off the fog and make it harder to see the road ahead.
Leave plenty of distance from the vehicle ahead, to account for sudden stops.
Follow the lines on the road to be sure you're staying in your lane.
If visibility drops to near zero, turn on your hazard lights and pull into a safe place — a parking lot, not the shoulder — and stop. If there's nowhere to pull in, get as far off the road as possible, hazards on, lights otherwise off, emergency brake set, and your foot off the brake pedal so your tail lights don't draw another driver toward you.

Source: National Weather Service, "Driving in Fog" safety guidance

Official alerts

Where to get official alerts

Bartlett's watches and warnings — fog advisories like today's, plus thunderstorm and tornado warnings in season — come from the National Weather Service Chicago office. Skip the rumor mill and go straight to the source:

Official NWS forecast for Bartlett, IL: forecast.weather.gov — Bartlett point forecast, updated around the clock with any active advisories at the top of the page. The same office's fog safety pages live at weather.gov/safety/fog-driving.

A Dense Fog Advisory — the alert in effect this morning — is issued when widespread fog is expected to bring visibility down to a quarter-mile or less. When you see one for the morning commute, the safest trip is a delayed one: radiation fog usually lifts by mid-morning.

Source: National Weather Service (Chicago forecast office, weather.gov/lot)

Weather questions, answered

What time does the fog lift?

Usually by mid-morning. Radiation fog forms overnight and burns off as the sun warms the ground, evaporating from the bottom up. Today's advisory runs until 10:00 AM, with mostly sunny skies expected by 11 AM — a textbook timeline.

When is Bartlett's fog season?

Fall and winter, with fall the classic season here: long nights, moist ground, warm afternoons, and chilly dawns are the exact recipe. Fog can happen any month, but September through November is when the foggy-morning commute shows up most.

Why is it foggy in one part of town and clear in another?

Because radiation fog is patchy. It forms first — and hangs on longest — in low-lying areas and near water, where cool, dense air pools overnight. Two streets can have completely different visibility, which is why conditions on your route can change without warning.

What does a Dense Fog Advisory actually mean?

It's the Weather Service saying widespread fog is expected to cut visibility to a quarter-mile or less — the point where driving at normal speeds stops being safe. Slow down, low beams on, extra following distance, or wait it out.

More Bartlett essentials

Foggy-morning drive ahead? Check the Bartlett construction & road alerts before you leave — fog plus a work zone is the combination that actually snarls a commute — and the Bartlett events calendar if you're planning the day once the sun comes out. Or head back to the Bartlett Guide home page for everything else around town.

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