Pavement Temperatures and Effects: How to get Pavement Temperatures
There are many methods available to determine pavement temperatures. A handheld sensor provides a more accurate reading, while the weather forecast, local transportation department activities, and your state's road and weather information system also all provide valuable data. Using a rough estimate may be the easiest way to guide your decision-making.
The table below shows rough estimates of what the pavement temperature may be at night or in cloudy conditions compared to the air temperature. In sunny, warmer conditions, pavement temperatures will likely be closer to or warmer than air temperatures.
Rough Estimates of Pavement Temperature at Night or in Cloudy Conditions
Air Temperature (°F) | Likely Pavement Temperature (°F) | Risk of Rain Freezing on Pavement | Notes |
|---|---|---|---|
38–35°F | 33–30°F | Possible | Pavement temperature can cool below freezing even with above-freezing air. |
35–33°F | 32–28°F | Likely | Common range for surprise black ice; it often happens on clear, calm nights. |
33–32°F | ≤ 28°F | Very likely | Wind cooling can depress pavement 5–18°F below expected values. |
32–28°F | ≤ 26°F | Almost certain | Sub-freezing pavement will freeze any rainfall on contact. |
Below 28°F | < 25°F | Instant freezing | Freezing rain converts to glaze ice immediately upon contact. |
Learn more about these other methods for determining pavement temperatures:
Pavement temperature sensors
A digital handheld infrared temperature sensor can be used to measure pavement temperature more accurately. The sensors can be purchased for about $50 or less at auto parts stores or big box stores. Be sure to select a sensor that can read temperatures below 15°F Fahrenheit. If the temperature reading keeps changing, it is not acclimated to the cold yet. Give it enough time for the temperature reading to stabilize. Point the sensor at your sidewalk and driveway to get a pavement reading.
Watch your local transportation department's response
You can learn a lot about an approaching storm by paying attention to what local transportation departments are doing. If you see lines on the pavement, it usually means a storm is forecast and roads are being anti-iced.
You can also look at the color of the deicer being used. White material is typically regular road salt (sodium chloride), while green or other colored products are often treated salt designed to work better in colder temperatures. Sand use, if deicers are usually used, also can indicate cold pavement temperatures.
Pavement temperature trend
In addition to pavement temperature, it is important to consider the temperature trend. Check the weather forecast to see the predicted weather conditions and temperature. If it is sunny, the pavement will warm up. If air temperatures are rising, the pavement temperature will likely rise slowly too. The trend can help determine if a deicer is needed or melting will occur on its own or if rain or meltwater will freeze on the pavement as temperatures drop. If it will be warming to above freezing, you may not need to use salt. After a snowstorm, temperatures often drop quickly. Be prepared for colder pavement and try to remove snow as soon as possible before it gets too cold for deicers to work well.
State RWIS system
Most state departments of transportation manage Road and Weather Information Systems (RWIS) throughout the state. The stations are located next to highways and have sensors embedded in the pavement to collect surface and subsurface information. Above ground instruments monitor air temperature, wind, and other parameters. Many states allow access to some of the information. For example, Minnesota has a 511MN website that has camera views and weather and pavement condition information from RWIS stations. Air and surface temperature (aka pavement temperature) in addition to humidity, road conditions, precipitation and much more information can be viewed.
The 511MN information is also available as a mobile app. Check your state transportation department’s website to see if they offer pavement temperatures and other winter condition information. These sites won’t provide the pavement temperature where you are, but can help you decide if the pavement temperature is likely to be lower or higher than air temperature.
