Where the rain falls in the year
NOAA's normals for the Santa Rosa station average 31.53 inches of precipitation a year, 18.64 inches of it in December through February, with about 8.9 days a year of an inch or more. The same normals average 25.8 days a year with a high of 90°F or more, including 2.4 days at 100°F or more, and 14.9 nights at or below 32°F.
The part of that record most useful to a painter is the split: the station's normals put 18.64 of those inches in December through February. That makes the calendar a real factor in deciding when exterior work goes ahead, and when it makes more sense to work indoors.
Wet wood doesn't hold paint
Rain on siding and trim isn't just a delay on the day. Wood soaks up water through bare ends, cracks and failed paint, and it gives that water up slowly. Paint put over damp wood can blister or peel as the moisture tries to leave through the new film.
Before an exterior repaint, a careful painter will:
- wait for a dry spell long enough for siding and trim to dry through, not just on the face;
- check suspect boards with a moisture meter, especially at the bottom courses and around windows;
- prime bare end grain, which drinks water fastest;
- re-caulk open joints so the next storm can't get behind the new paint.
Ask how they decide wood is dry enough, and what reading they look for.
Cold nights and a fresh film
Paint labels set a minimum temperature for application and for the hours after it. A coat that goes on at midday can still be caught by a cold night before it has formed properly. The 14.9 nights at or below 32°F in the station's normals are a reminder that the overnight low matters as much as the daytime high. Painters working in the cooler parts of the year often start later, stop earlier, and keep an eye on the low in the forecast.
Using the wet months well
When outside work is off the table, the inside of a house is not. Interior painting has its own conditions to watch:
- Rooms need airflow to dry; on damp days a fan and a cracked window still help.
- Bathrooms and laundry rooms take longest and need a finish that stands up to moisture.
- Ceilings, stairwells and hallways are easier to schedule when nothing else is happening in the house.
Our interior painting page and the sheens guide cover the choices for each room.
When the old paint is the issue
Under EPA's Renovation, Repair and Painting Rule, anyone paid to do work that disturbs paint in homes, childcare facilities and preschools built before 1978 must hold RRP certification, firms included, even sole proprietorships, and their workers must be trained in lead-safe work practices.
Scraping peeling exterior paint is one of the most common ways old paint gets disturbed. If your home was built before 1978, put this on the table at the first visit: you can ask whether the firm holds RRP certification, and how the crew will contain chips and dust on the ground and keep them off garden beds.
The exterior season, step by step
- Book the painter early enough to inspect and quote before the weeks you hope to paint in.
- Plan repairs to rotten trim first; paint is not a patch.
- Wash, let dry, scrape and sand, then prime.
- Paint the topcoats once the surfaces and forecast both allow.
- Walk the job together at the end and list touch-ups in writing.
The exterior painting page explains each step, and our pricing guide covers why prep-heavy jobs cost more.