Determination of the 1%, 2.5%, and 5% occurrences of extreme dew-point temperatures and mean coincident dry-bulb temperatures

The ASHRAE Research Project RP-754 was carried out to find the outdoor design occurrences of extreme dew-point temperature and the corresponding mean coincident dry-bulb temperature for a large number of locations in North America. Thirty years of data were used for 239 U.S. locations, and the last 30 years of hourly data available were used for 143 Canadian locations. In this paper, tables are given that present the 1%, 2.5% and 5% extreme summertime occurrence of dew-point temperatures and corresponding values of humidity ratios and the mean coincident dry-bulb (MCDB) temperature for the period of record. A map showing the general geographical trends for the spatial distribution of the design dew-point value is also presented.