How Cold Is Too Cold to Clean Windows Outside

Freezing is the practical line. Above about 35 degrees, exterior glass cleans normally. Between 32 and 35 it gets slow and fussy. Below freezing the water starts setting up on the pane before anybody can pull it off, and a half frozen film dries worse than the dirt that was there to begin with. Around the Twin Cities that puts the last good week for outside windows somewhere in late October or November, and which week it is depends on the weather rather than the calendar.

Why the cold ruins the job

Cleaning a window is two steps. Wet the glass, then get every bit of that water back off it. Cold weather does not bother the first step at all. It wrecks the second one.

Near freezing, water turns thick and slow and squeegee rubber stiffens up, so a pull that would normally leave nothing behind leaves a haze along the edge instead. A few degrees colder and the film begins to crystallize while it is still sitting on the pane. Once that starts there is no saving the pass. You rewet it and try again, and the second attempt is colder than the first.

Hoses are the other half of it. Water standing in a hose, in a pole, or in a filter freezes from the outside in, and when a line goes solid the day is over whether the glass is finished or not.

Where the line actually falls in Minnesota

The air temperature is only part of it. What matters is how cold the glass is, and glass can sit well below whatever your phone says.

• Upper 30s with sun on the wall: normal work, no trouble
• 32 to 35 degrees: workable but slow, and much better on the south and west walls that have had sun on them
• Below 32 degrees: exterior glass work stops being worth doing
• Below the mid 20s: nobody should be running water on a house at all

North side glass in the shade can be ten degrees under the air reading, and a stiff wind pulls heat off a wet pane faster than still air at the same temperature. A sunny 34 degree afternoon on the front of a south facing house is a workable day. A gray 34 degree morning on the north side is not.

Hot water is not the workaround

It sounds obvious and it is a bad idea. Hot water on very cold glass puts the surface under thermal stress, and a pane that already has a chip, a scratch, or a nick along its edge can crack from it. The edge is the weakest part of a piece of glass, and it is also where the water lands first as it runs down.

The other problem is that it does not even help. Hot water gives up its heat in seconds against a cold pane and steams the whole time it is doing it, so you end up right back where you started with fog in the way. Lukewarm is as far as that idea goes.

What still makes sense once it is too cold outside

More than people think, and most of it is the half that gets skipped.

Interior glass is usually the dirtier side by midwinter. Cooking film, dust out of the forced air, dog noses, woodsmoke, and the handprints that collect once everybody is inside for five months. Sills and tracks are in the same category, and a sill with no grit and no old grime sitting in it gives mildew much less to work with once the windows start sweating, which they will. That is covered in why you get condensation on windows in winter.

Storm windows are a now or April decision. The haze on an old storm is almost always on the two faces nobody can reach, and once the panel is shut for the season it stays that way until spring. See how to clean storm windows before winter.

Gutters also run later in the year than glass does. The oaks around here keep dropping into November, and a trough can be emptied in cold weather as long as it is not iced in. Gutter cleaning starts at $120, and gutter cleaning in St. Paul is usually the last outdoor job on the calendar before the snow.

Planning the last exterior cleaning of the year

If the outside of the glass has not been washed since spring, the honest advice is to deal with it in the next couple of weeks rather than in a month. Once the plows and the road salt start, a film builds on the street side windows and it sits there until April. That is a long stretch of looking out through it, with the sun low enough all winter to light up every streak on the way in.

Nobody can promise a warm week in November. What I can tell you on the phone is whether the stretch coming up looks like it will cooperate, and if it does not, there is no sense paying for exterior work that is going to fight back. Window cleaning starts at $99 and we work in St. Paul and the metro around it. You can request a quote or book a free 10-minute consultation.