Start with the station's own numbers
The figures below belong to the station NOAA names Beale AFB/Marysville, and the fact gives the distance: in an average year at Beale AFB/Marysville, about 12 miles from Yuba City, NOAA counts about 43 hours with the wet-bulb temperature above 73°F and about 557 hours above 67°F. The same station's data list about 10 freeze-thaw cycles in an average year and a 100-year rainfall rate of 1.5 inches per hour.
None of those is a forecast, and none describes a particular wall. They are a record of how often the station's air was both warm and damp, and how often it swung across freezing. Each one connects to something a painter has to manage on the job.
Why wet-bulb hours matter to wet paint
A wet-bulb reading folds heat and moisture into one number. The higher it runs, the less room the air has to take on more water. Latex and acrylic paint dry by giving water up to the air, so on a damp, warm day the film stays soft for longer before it can be handled, recoated or rained on.
What that means in practice:
- A painter may space coats further apart than the can's minimum when the air is heavy.
- Fresh exterior paint needs time to set before evening dew settles on it; a late-afternoon finish on a shaded wall is the classic way to end up with streaks or a dull, blotchy surface.
- Interior rooms with poor airflow, such as bathrooms, closets and laundry rooms, dry slowest. Fans and an open window help more than turning up the heat.
The point is not that Yuba City is humid or dry. It is that the station counts a known number of these hours, and a careful painter watches the conditions on the day rather than painting by the calendar.
Freeze-thaw and the joints around the paint
A freeze-thaw cycle is a swing from above freezing to below and back. Whatever the count, each swing moves water trapped in cracks and gaps. On a painted exterior, the weak points are the joints: where trim meets siding, around window and door frames, and along the bottom edge of boards near the ground.
Before new paint goes on, those joints should be opened up where the old caulk has split, cleaned out and refilled with a sealant the painter can paint over. Paint stretched across a cracked joint will crack again along the same line.
Splitting the work: inside, outside, or both
Many owners ask for interior and exterior work at once. It's often smarter to plan them as two linked jobs:
- Exterior first when the weather on the day suits it, because the outside work is the part that depends on dry surfaces and a steady temperature.
- Interior can fill days when the exterior can't proceed, such as after rain or when walls are still wet from washing.
- Cabinets and trim are often done last, so dust from other work doesn't settle into fresh enamel.
Ask the painter how they'd sequence the job and what they do on days when outside work has to stop. See our exterior painting page and interior painting page for what each job involves.
Preparation decides whether the finish lasts
On most houses the real work is getting the surface ready. Expect to talk about:
- Washing off dirt and chalky residue so the new coat can grip.
- Scraping loose paint back to a firm edge and sanding the step so it doesn't telegraph through.
- Priming bare wood, patched spots and stains.
- Repairing soft or split trim before it is painted over.
Our guide to drywall repair and surface preparation covers the indoor side of this.
The C-33 classification
California's Contractors State License Board issues a C-33 Painting and Decorating Contractor classification. If you want to know whether the painter holds it, ask them directly. That is the one credential question we suggest putting on your list; the classification's own CSLB page linked below explains it.
Before you sign
- Which walls and rooms are included, and which are not?
- How many coats, and which products, on each surface?
- What happens if a coat can't dry before rain or dew?
- How will joints and gaps be sealed before painting?
- Who protects floors, plants and furniture, and who cleans up?
A clear written proposal answers all of these. Our pricing guide explains why two proposals for the same house can differ.