Previous studies of changes in visibility over a period of years have indicated either a general trend toward better horizontal visibilities or no change. In this study, visibility, relative humidity, wind direction, and other related data from three National Weather Service Offices (Akron, Ohio; Lexington, Ky.; Memphis, Tenn.) are used to determine changes in daylight visibilities during the summer seasons of 1962–69. Analyses of the data indicate that the percent of restricted visibility was greater during the period 1966–69 than during the period 1962–65 both before and after adjustment for the effects of location, time of day, humidity, and wind.




Ohio State Climatologist, National Weather Service, NOAA, Columbus, Ohio


Eastern Region Headquarters, National Weather Service, NOAA, Garden City, N.Y.


National Weather Service Office, NOAA, Akron, Ohio


Ohio Agricultural Research and Development Center, Wooster, Ohio