George Weiner, in Bel Air, asks: "Why was BWI chosen as the 'official' site for collection weather data? Since that data is taken from a very small, specific place in time, of what value is it?" The airport became Baltimore's official weather station in 1950. It was moved from the Customs House downtown out of concern about unrepresentative conditions on an urban rooftop. NWS instruments are now in a grassy area of the airport. Long surface data records can reveal important changes over time.

> Read Frank Roylance's blog on MarylandWeather.com