St. Louis has four real seasons, and each one affects paint. The National Weather Service office here describes the spring months of March through May as normally the wettest, counts thunderstorms on 40 to 50 days a year and 90 degree heat on about 35 to 40 days a year. Winters bring a little over 18 inches of snow in a typical season.
What is the best time of year to paint the outside of a house here?
The best months for exterior painting in St. Louis are late spring and early fall. Fall is often the steadier of the two, with mild days, lower humidity and fewer storms. Spring has good temperatures but is the wettest part of the year, so jobs get interrupted.
Summer work is fine with planning around heat and sun. Late fall works as long as the days and nights stay warm enough for the paint. Deep winter is for interiors.
Can you paint outside when it is raining or about to rain?
No. Paint needs a dry surface and several dry hours afterward. We watch the forecast and stop early when rain is coming. A covered porch ceiling or a protected entry can sometimes be done on a damp day, but open walls cannot.
It rained a few hours after painting. Is it ruined?
Usually not. If the paint had a few hours to dry before the rain, it is normally fine. Heavy rain on paint that was still wet can leave streaks, spots or washed-out areas, and those sections need to be redone once dry.
Summer thunderstorms here build fast in the afternoon. That is why we plan the most exposed walls for the morning.
How long after rain before siding can be painted?
Wait until the surface is fully dry. After rain, that is often a full dry day for wood siding and trim, and longer for brick, stucco and wood that is shaded or was soaked. Smooth siding in sun and wind can dry out within hours.
The same applies after power washing. Wood and masonry need time to dry out before primer or paint, and in humid weather that takes longer.
How cold is too cold to paint outside?
It is too cold when the air or the wall is below the minimum on the paint label. Many exterior paints set that at 50 degrees, and some are made to go on down to about 35. The temperature has to stay above the minimum for hours after the paint goes on, not only at noon.
In St. Louis that usually ends the reliable outdoor season sometime in late fall. Cold nights and heavy dew matter as much as the afternoon high.
How hot is too hot, and is direct sun a problem?
Around 90 degrees and above is too hot for most exterior paint, and direct sun makes it worse because a wall in full sun is much hotter than the air. Paint that dries too fast does not bond well and shows lap marks and blisters.
The fix is to follow the shade around the house: west and north walls in the morning, east walls in the afternoon. On the hottest days we start early.
Does humidity affect exterior paint in St. Louis?
Yes. High humidity slows drying, and St. Louis summers are humid for weeks at a time. Paint applied late in the day can still be soft when the evening dew settles, which can dull the finish or leave a sticky film on the surface.
We stop early enough for the paint to set before evening, and we allow more time between coats in muggy weather.
Can you paint inside in winter with the windows closed?
Yes. Winter is a good time for interior painting. Heated indoor air is dry, so paint dries well, and modern water-based paints have low odor, so the windows can stay closed or be opened a crack for a short time.
Winter is also when painters' calendars are less full. Cabinets, trim and whole interiors are all sensible cold-weather jobs.
Climate figures: National Weather Service, St. Louis. To plan an exterior job, call or text (314) 742-3507.