Great Lake Effects

The Great Lakes influence the weather and climate of nearby land regions at all

times of the year. Much of this lake effect is determined by the relative temperatures

of surface lake water compared to the surface air temperatures over those land areas.

The graph below shows the average monthly temperature of the surface water of

Lake Erie and the surface air temperature at Buffalo, New York.

In an average year, four lake-effect seasons are experienced. When surface lake

temperatures are colder than surface air temperatures, a stable season occurs.

The cooler lake waters suppress cloud development and reduce the strength of

rainstorms. As a result, late spring and early summer in the Buffalo region tends to be

very sunny.

A season of lake-effect rains follows. August is usually a time of heavy nighttime

rains, and much of the rainy season is marked by heavy, localized rainstorms downwind

from the lake. Gradually, during late October, lake-effect rains are replaced by snows.

Generally, the longer the time the wind travels over the lake, the heavier the lake effect

becomes in Buffalo.

Finally, conditions stabilize again, as the relatively shallow Lake Erie freezes over,

usually near the end of January. Very few lake-effect storms occur during this time

period.


The passage states, “The cooler lake waters suppress cloud development…” because the water cools the

air above its surface. Explain why this cool air above the lake surface reduces the amount of cloud

development.