The short answer
Summer and early fall give the most reliable weather for exterior painting in Portland. Roughly late June through September is the main painting season. In a dry year, good days can stretch into early October. Spring can work too, but only in a real dry stretch, and those are hard to count on.
A sunny afternoon isn't enough on its own. Three things decide whether paint will last: the temperature, moisture on and in the siding, and enough dry time for the paint to cure.
Paint goes on in an afternoon. It needs dry days to become a finish.
Temperature: read the can
Every exterior paint lists a minimum temperature on the label, for both the air and the surface. Some products are made for cooler weather. Others need it warmer. What matters is that it stays above that minimum while the paint dries, including the evening after you paint.
Hot sun causes trouble too. Paint on a wall in direct summer sun can dry too fast, which can leave lap marks and weak adhesion. Painters often follow the shade around the house for this reason.
Dew is the hidden problem
On cool fall evenings, siding can drop below the dew point and get wet even when it hasn't rained. If fresh paint gets hit by dew before it sets, you can see surfactant leaching: sticky, streaky, tan or glossy runs on the surface. It can often be washed off, but it's better avoided.
That's why fall painting days are shorter. A crew may wait for the morning dew to dry off the north and shaded sides, then stop early enough that the paint can set before evening. If you want to paint in the fall, plan around those shorter windows.
Wet siding needs time
After a long wet season, siding holds water deep in the wood. Paint over damp wood and it can blister or peel. A careful painter will wait for several dry days and may check the boards with a moisture meter before priming. Rain in the forecast within a day or so of painting is a reason to wait.
Exterior paint prep is most of the job
The weather gets the attention, but prep decides how long the paint lasts. A good job usually includes:
- Washing the house gently and letting it dry fully
- Scrape and sand loose or peeling paint, feathering the edges
- Repairing or replacing soft and rotted boards before any paint goes on
- Spot-priming knots and stains, and taking care to prime bare wood
- Caulking open joints around trim, while leaving the bottom edges of lap siding open so it can breathe and drain
- Covering plants, walks, windows and fixtures
If a quote skips most of this list, ask why. Paint can only hold on as well as the surface under it.
What if it's already October?
You may still have a few good days. Smaller jobs fit best: a front door, trim touch-ups, one weathered side of the house. A full repaint of the siding this late is a gamble. It is often smarter to do the repairs now, book the painting for next summer, and move your painting projects indoors for the winter.
Questions to ask your house painters
- What product will you use, and what is its minimum temperature?
- How do you handle rain or dew in the forecast?
- What prep is included, and what costs extra?
- How many coats, and on which surfaces?
- Will you repair soft wood before painting, or paint around it?
Plan early
Good painters fill their summer calendars early. If you'd like to paint a house exterior next year, spring is a fine time to get an estimate and a spot on the schedule.
Triple SSS Construction paints homes around Portland, Gresham and the east side. We'll walk the house with you, point out repairs that should come first, and plan the work around the weather. Call (503) 781-2093 any time.
Exterior Painting
