So, what are the risks?
First of all here in the Denver Metro Area of Colorado between the months of November and March we rarely have a 4-7 day stretch where the temperature doesn't fall under 35 degrees. That means that even if during the day the ambient air temperature is as high as 60-70 degrees at night it may fall well below the 35 degree limit. We know that water freezes at 32 degrees Fahrenheit and all of the 100% Acrylic House Paints are water-based. When the temperature is below 35 the curing process for the paint is arrested. This means it is going to take longer for the paint to fully cure. If we get a deep freeze before the paint has ample time to dry with extended cold days below freezing the paint film could completely freeze, crack and peel once it thaws.
The most common cold weather problem Is called "Surfactant Leaching" (see picture below). This a very unsightly appearance on the surface of the paint. It looks like streaks running down the surface of the film. It is usually caused when paint has been applied in nice warm sunny days with cold nights and after a few days or even up to a week a wet and cold rain - snow storm comes and the humidity reaches 100% and every thing gets wet and freezes.
I think it is important to look for a weather window that will be an unusually long warm spell up to 70 during the day and not below freezing at night 4-7 days in a row and then hoping that a very wet cold storm doesn't appear for another week or two. This will give the paint a little more time to cure and avoid any of the above mentioned problems.
Painters paint exteriors in winter for many different reasons. Finishing a new house to completion, selling a house, insurance settlements, and ultimately because money is tied up and can't be paid until the paint job is completed. If you have to paint during the winter months it is important to look for the weather opportunities and plan accordingly. Consider the possibility of waiting until warmer weather will prevail. Discuss any of your concerns with your painter and plan around the weather forecast.
I hope this was helpful. Stay warm, and have safe and happy holidays.
Jay - Founder of Adirondack Painting.