Sun on a wall is hotter than the air
A painter's thermometer isn't only the one on the porch. What matters to a coat of paint is the temperature of the surface it lands on, and a wall in direct afternoon sun can be far hotter than the air around it. Paint applied to a hot surface dries too fast. It can leave lap marks where fresh paint meets drying paint, blister when trapped moisture or solvent tries to escape, and fail to level out or bond as well as it should. For a house in Billings, working with the sun is part of doing an exterior properly.
The station figures
NOAA's engineering weather data for BILLINGS/LOGAN lists a 50-year basic wind speed of 90 mph and a 100-year rainfall rate of 2.0 inches per hour. The same NOAA station record counts 55 hours in an average year above 93°F and 543 hours above 80°F, but only 1 hour with a wet-bulb temperature above 73°F.
Those figures belong to the BILLINGS/LOGAN station and are printed in full on the cards below. Paint labels list a maximum temperature as well as a minimum, so the hot hours count when a painter plans a day.
A little history
The City of Billings says Billings was nicknamed the 'Magic City' because of its rapid growth from its founding as a railroad town in March 1882, and that the city is named for Frederick H. Billings, a former president of the Northern Pacific Railroad. It's printed here as the city states it, for background.
Following the shade
Experienced exterior painters plan their days around where the sun is. A common pattern is to start on the walls that are in shade in the morning and move around the house as the sun moves, so the crew is always painting walls that aren't in direct, hot sun. It may look as if they're jumping from side to side; that's the point. Ask the painter how they schedule the sides of your house, and whether they stop during the hottest part of the day.
Dark colors and heat
Dark colors absorb more sunlight than light ones, so a dark wall in sun runs hotter. That affects how the paint goes on and, over time, can stress some siding materials. Some product lines offer formulations designed to reflect more heat in dark colors, and some siding makers restrict how dark a color can go on their product. If you're considering a dark color, ask the painter about both.
Wind and spraying
Spraying is fast, but in gusty conditions the mist drifts onto windows, roofs, cars and neighbors' property, and dust blows onto wet paint. Many painters switch to brush and roller on windy days or protect more widely. Ask how they handle wind and what they mask.
Preparation, unchanged by weather
Heat changes timing, not preparation. The surfaces still need washing to remove dirt and chalk, scraping and sanding of loose paint, caulking of open joints, and primer on bare wood. Our exterior painting page describes the full sequence, and surface preparation explains fillers and primers.
Older paint
Under the EPA rule printed on this page, 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. Dry scraping on a hot, windy day spreads dust and chips further, so containment matters even more. If your house was built before 1978, ask whether the firm holds the RRP certification the rule describes, and how it will contain and clean up.
Questions for a Billings exterior bid
- How will the crew schedule the walls around the sun?
- What are the product's temperature limits, low and high?
- Will they spray, brush or roll, and what happens on windy days?
- What preparation does each wall get?
- If you choose a dark color, what product and siding limits apply?
- How are chips and dust contained on an older house?
The pricing guide explains how these choices affect a quote, and the sheens guide helps with finish choices.