As time progresses, there is increasing demand for meteorological data where forecasts are most needed – such as in urban areas where people live and work. Although urban observing systems do not always subscribe to conventional sighting guidelines, one of the major advantages of using data from such systems is that they provide information indicative of local exposures and are therefore highly useful for weather and climate applications.

Extensive examinations of data obtained from the AWS/WeatherBug network shows that the nocturnal heat island effect is readily quantified using such data. The methodology involves examination of day-night differences of temperatures within and surrounding the urban areas of interest. The case of Washington, D.C., is presented as an example, so that direct comparisons can be made against the results of examinations of micrometeorological data collected there by the NOAA DCNet program.

The nocturnal heat island of Washington is shown to be spatially complex, and to have average features that correspond closely to classical expectations. The methodologies employed are readily applicable elsewhere, and can be used to quantify the heat islands of all major US cities.