This map displays the observed dew point spread at a given point in time. The dew point is the temperature at which the air would be fully saturated (100% RH) and capable of forming dew (or frost, if it's cold enough). In the summertime, dew points are a useful measure of humidity (much more so than Relative Humidity). Dew points below 50 are dry, dew points between 50 and 65 are sticky but not unbearable and anything above 65 is very humid.