A record of Washington D.C. dew point temperatures from the 1840s

Digitization of historical data through the Climate Data Modernization Program made a number of long-term climatic data records available for analysis. One such dataset is that of Washington D.C., where hourly weather observations have been taken since the 1840s. The earliest periods of data are infrequent, but it remains a near-continuous record. Temperature observations, including dew points are part of this record. Dew point temperatures are frequently used as a measure of human comfort, and observations from Washington D.C. provide an indication of how they have changed since the mid 1800s. Changes to observation practices, instrumentation and station location throughout the record provide challenges for assessing long-term patterns in dew point temperatures.