Due to its position between the Great Lakes and the windward side of the Allegheny Mountains, Brentwood, along with the rest of the region, receives plentiful precipitation which supports lush vegetation. Also, because it is on the windward side of the mountains, it is often cloudy, having 203 cloudy days per year. The winter is particularly cloudy, with only 28 percent sunshine in December and 23 cloudy days. In the winter, when a northwest flow establishes itself over the Great Lakes, the wind blows from Lake Erie across eastern Ohio and western Pennsylvania. That wind carries moist air from the lake, producing clouds and heavy snow squalls.