The classic wind scale is the Beaufort Scale, intended for the sea, but also used on land. The upper limit for spraying is probably Force 3 or Force 4, with upper limits of 20 – 25 km/h or so.
Exterior painting with emulsion paintsThe temperature must be above 7 degrees, and stay above 7 until the paint is dry. If the temperature drops, and the paint freezes, then it will simply fall off the wall in time.
Rain will wash wet paint off the surface and paint won't be absorbed into a wet surface. When it is raining outside, the paint will wash away if it isn't dry. The best way to handle this is to be sure to avoid rainy days. If there is rain forecast for significant parts of the day, plan it for another time.
Paint needs an environment of at least 50 degrees in order to dry properly. It may crack sooner than later if applied in too-cold temperatures. Even if it is 60 degrees during the day, if the temperature dips below 50 degrees at night, the paint structure can be compromised.
Air that is moving helps pull away from the moisture from the paint causing it to dry faster, especially in warmer conditions.
When You Can Paint in the Rain
Interior surfaces can be painted when it is raining outside, as long as rain does not reach the inside of the house. For both exterior and interior surfaces, you can expect it to take longer for the paint to dry in the humid conditions of a rainy day than on dry, sunny days.It's always best to aim for a day that's not too hot. You'll also want to pay attention to humidity levels as well. Paint will usually dry the best when it's not overly humid. As we mentioned earlier, you'll usually find the best temperatures during the early summer and early fall, depending on where you live.
The maximum and minimum recommended temperatures for exterior paint vary depending on the type (oil or latex) and specific brand of paint used, but a general rule of thumb is that oil-based paint can be applied when the temperatures are between 40°- 90° F and latex between 50°- 85° F.
Most products require at least 4 hours of dry time before moisture can settle on the surface. The cooler the temperature the sooner you should stop painting.
Most paint brands have labels that warn users not to paint in temperatures below 35 degrees Fahrenheit. Thanks to modern advancements in paint materials, most paint manufacturers now offer acrylic latex paints that can be applied to the exterior of your home in temperatures as low as the threshold of 35 degrees.
For an oil-based paint, the best temperature to apply is between 40 and 90 degrees Fahrenheit. For latex-based paints, it's 50 to 85 degrees.
Optimal relative humidity (RH) levels for exterior painting tend to be in the 40- to 50-percent range. But these humidity levels will still not prevent you from painting altogether. They simply make the job more difficult and painstaking. It is strongly discouraged to paint when there's an RH level above 85 percent.
If the paint is exposed to excessively high humidity, the desired protective qualities of the paint may be compromised. High humidity also works against a fresh coat of paint by reintroducing water into the incompletely dried paint film. Humidity also needs to be considered when painting a wood surface.
While each and every scenario is different, spray painting is typically best done in environments with a relative humidity of 40-50%. High humidity can be equally as problematic for workers attempting to spray paint a surface. As the humidity rises, it will take longer and longer for paint to dry.
Interior Painting during Rainy WeatherInterior painting can be performed any day of the year, no matter the weather, unless your interior humidity is too great. In this case, turning on the air conditioning or a dehumidifier can make your home interior paint-worthy, even on the rainiest days.
Allow paint film to dry for at least 60 minutes prior to rain showers when temperatures are between 60°-70° F (15°-21° C) and 60-70% relative humidity. Lower temperatures, higher humidity or deep colors may increase dry time and/ or rain resistance time.
specify 10 MPH as the maximum wind speed for application. Spraying when winds exceed label restrictions is not only illegal, but can override steps taken to eliminate off-target movement (e.g. low-drift nozzles, low spray pressure, etc.).
Timing is Everything
- An overall general rule of thumb is that oil-based paint can be applied when the temperatures are between 40°- 90° F and latex paint is best applied between 50°- 85° F.
- Ideally, choose a day to paint your exterior with temperatures ranging from 60° to around 85°F with little to no wind.
Consumer Reports notes the best time to paint or stain a deck is late spring when temperatures are between 60 and 85°F and the nights are cool. You'll need four dry days for preparation, for application, and for a finish to completely dry.
Because there is less humidity, your paint will dry noticeably faster and better in the colder months, winter is the best time for painting the exterior or the home's interior. Don't wait for the hot temperature, high humidity months.
Optimal Temperature to Paint: 1.7 ºC to 37.8 ºCSince temperature varies more widely outside, that is where most issues arise. We recommend planning your painting project for temperatures ranging from 1.7 ºC to 37.8 ºC (35 ºF to 100 ºF) and when humidity is as low as possible.
For most stains, 70 degrees Fahrenheit is the optimum, with the safety range from 50 to 90 degrees Fahrenheit. Stains do vary, so check the label first. Avoid high humidity and staining on hot surfaces. All finishes, including stains and paint, have trouble drying in moist conditions.
Dries to the touch in 2 hours at 77°F (25°C) and 50% humidity. Allow at least 4 hours of dry time between coats. Dries to the touch in 4 hours at 35°F (2°C) to 45°F (7°C) and 50% humidity.
