The information is given in whole inches above or below chart datum. However, Lake Erie's maximum wind occurred in July, NNW at 87 knots. Gales, however, are encountered less than 1 percent of the time from May through September. These directions are also favored during other seasons along with northwesterlies and northeasterlies. The shallowness and orientation of Lake Erie make it susceptible to SW and NE winds, which can quickly raise dangerous seas and, if persistent, create a dangerous surge problem at both ends of the lake.
Rough seas are most frequent in autumn and in the E half of the lake.
Poor visibility is mainly a spring and autumn navigational problem. Over open water, spring is the most prevalent fog season. Vibilities of less than 0.5 mile occur up to 5 percent of the time. Visiblities of 2 miles or less ocur 5 to 10 percent of he time during most of the navigation season. The shoreline is susceptible to both autumn radiation fogs and early spring advection fogs.