The effect of the Great Salt Lake on the frequency and geographical extent of wintertime fog is analyzed by use of fog reports, precipitation, and temperature records over a 25-yr period, during which time the size of the lake has more then doubled. Fog reports at Salt Lake City on days when precipitation other than snow grains did not occur are analyzed to find a relationship between lake size and fog frequency. While a large winter-to-winter Variability is found, there is also a strong relationship with lake size.
To analyze the geographical effect of the lake on fog, the daily range of temperature is first related to the occurrence of persistent fog; it is shown that when fog is present throughout a day the difference between the maximum and minimum temperature will be low. Analysis of the geographical distribution of these persistent fog days shows the strong effect of the lake. Also, the occurrence of persistent fog was much less when the lake was small compared to when the lake was large.