The National Weather Service initiated two changes in the 1940s that could affect precipitation measurements. Stations were moved from urban sites to nearby airports where the gages are exposed to windier conditions. Moreover, at first order stations (Daggett, Kingman, Las Vegas, Tonopah, Yuma), shields were installed on the gages to reduce the influence of increased wind. Most of the stations, however, are still in urban locations. We tentatively conclude that the increase in days of precipitation is related to climate rather than measurement procedures, although this issue is under investigation.