A station named Imperial
The weather figures on this page are not El Centro's own. They come from the NOAA station named Imperial. In an average year at Imperial, NOAA counts about 893 hours with the wet-bulb temperature above 73°F and about 1,930 hours above 67°F.
A wet-bulb temperature is what a thermometer reads with a wet wick around its bulb. Evaporation cools the wick, so the reading drops further below the ordinary air temperature when the air is dry and stays closer to it when the air is moist. A count of hours above a given wet-bulb tells you how often the station's air was both warm and carrying a lot of moisture. It's an engineering figure, but it translates directly into how paint behaves.
How damp, warm air changes the work
Most house paint today is water-based. The film forms as the water leaves, so anything that slows evaporation slows the whole process: the time before the surface can be touched, before it can take a second coat, and before it can face weather or washing. When the wet-bulb is high, a painter may see:
- a second coat that drags or lifts the first because the first is still soft underneath;
- surfactant leaching, a sticky, tan or glossy streak that appears when moisture reaches a fresh film too soon;
- longer waits before tape can come off cleanly;
- more dust and insects stuck in a film that stays tacky.
None of this means paint can't go on. It means the product's recoat time is a minimum, not a promise, and an honest schedule allows for the conditions on the day.
Planning the job around it
A few habits make a real difference:
- Watch the forecast for dew, not just rain. A wall that is dry at noon can be wet by evening; exterior painting usually stops early enough for the film to set first.
- Ventilate indoor work. Moving air through a room speeds drying more than raising the temperature does. Box fans in windows, pointing out, pull moist air away from fresh walls.
- Ask for recoat by touch, not by the clock. A good painter checks that the previous coat is firm before rolling the next.
- Leave doors and cabinet fronts to cure. Enamel on surfaces that get handled needs longer than walls before it is used hard.
Our interior painting page and exterior painting page describe each job in more detail.
Older paint and the federal lead rule
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.
Sanding, scraping and heat-stripping all disturb paint. If your house was built before 1978, raise this early. You can ask the painter whether the firm holds RRP certification; that's the single credential question this page suggests. Then ask how they would contain dust, protect floors and soil, and clean up at the end of each day.
Preparation, room by room
In an occupied home, the order of operations matters as much as the paint:
- Move or cover furniture, then mask floors and fixtures.
- Fill holes and cracks, sand flat, and wipe down the dust.
- Spot-prime patches and stains so they don't show through.
- Cut in edges, then roll walls, then paint trim and doors.
Our guide to drywall repair and surface preparation explains why patches flash through a finish coat, and the sheens guide helps you match finish to room.
A short list for the walk-through
- Which product will you use, and what are its recoat and cure times?
- How do you decide a coat is ready for the next one?
- When will you stop exterior work each day?
- How will you handle older paint if the house predates 1978?
- What do you need me to move or clear?
Compare proposals with our pricing guide in hand.