Be weather aware or you could be sorry.
Technical Bulletins

Weather Conditions for Coating Applications

February 15, 2023
Ensure success by being aware of the prevailing weather conditions prior to commencing a roof coating application. Understanding and assessing the weather factors such as temperature, humidity, and precipitation is crucial for optimal results.


As the change of season brings higher daytime temperatures, contractors in many parts of the country will be looking to start applying coatings. This is a great time to remind everyone of the proper weather conditions needed for a successful coating application. There are three weather factors to monitor that are critical for applying coatings: TEMPERATURE, HUMIDITY and DEW POINT.

Minimum application temperature guidelines for the substrate, product and ambient air should be followed for the coating being applied. Temperatures should hold or continue to rise during the application. Relative humidity at the jobsite location should be 85% or less. And lastly, the ambient air temperature should be 5°F or higher above the dew point unless the product is applicable for use over a wet or damp substrate.    

How to know the weather at your jobsite?

There are many apps available for both Apple and Android users that can help monitor all three weather conditions on-site.  The apps pinpoint the nearest weather station to your smart phone’s location to provide current weather dates in real time.  

Three most popular free weather apps:

·       The Weather Channel

·       Weather Underground

·       AccuWeather

Weather App Examples

As shown in the screen shots above, even though the ambient air temperature is above the minimum application temperature for some products, the humidity and dew point are not within range. Rain is also in the area. Application of a coating at this location should be delayed until conditions improve.  

Substrates should always be dry before applying coating unless the coating is applicable for use over a wet or damp surface. In most cases, coatings should be allowed to cure 24 hours before exposure to moisture. For additional information regarding coating applications, please review the individual product data sheet before using.  


Weather apps and their usefulness should be shared amongst all coating contractors and crew members. The weather plays an important role in the successful application of liquid-applied roof coating products. Download a weather app today to keep you informed of current conditions on your project site.    

If you have any questions about weather conditions for any product, please contact KARNAK Technical Services at 800.526.4236.  

The Karnak Team

Since 1933, our team at KARNAK has been dedicated to producing top-quality sustainable roofing and building solutions that protect and extend the life of building envelopes while reducing environmental impact. As a family-owned and certified woman-owned business, we pride ourselves on our commitment to quality, durability, and personalized customer service. We specialize in liquid-applied roofing systems, repair products, and comprehensive support through detailed documentation and our Q Applicator Program for contractors.

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