A detailed study of urban bias in surface temperatures of China's northern plains is described. Temperatures of climatological surface stations were examined using a statistical rank-score procedure that allows screening of the data without knowledge of the station history information. Time series found to exhibit large potential discontinuities (i.e., those introduced as a result of nonclimatic factors such as observation schedule changes, instrument replacements, and station moves) were excluded from further analysis. In addition to the usual total population statistics, census area classifications and population densities were used to distinguish between 21 urban and 8 rural stations. Location-related biases associated with latitude and longitude positions were first removed from all station data, however, using ordinary least-squares regression techniques. Finally, a systematic sampling strategy was employed to estimate magnitudes and trends of urban bias in annual and seasonal mean temperatu... Abstract A detailed study of urban bias in surface temperatures of China's northern plains is described. Temperatures of climatological surface stations were examined using a statistical rank-score procedure that allows screening of the data without knowledge of the station history information. Time series found to exhibit large potential discontinuities (i.e., those introduced as a result of nonclimatic factors such as observation schedule changes, instrument replacements, and station moves) were excluded from further analysis. In addition to the usual total population statistics, census area classifications and population densities were used to distinguish between 21 urban and 8 rural stations. Location-related biases associated with latitude and longitude positions were first removed from all station data, however, using ordinary least-squares regression techniques. Finally, a systematic sampling strategy was employed to estimate magnitudes and trends of urban bias in annual and seasonal mean temperatu...