An aerial view of the Missisquoi River delta (Quebec Ministry of Environment photo).
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Click here to view enlarged map as 740 KB PDF file. The climate in the Lake Champlain Basin varies geographically and is affected by four main factors: the location of the Basin near the eastern edge of the continent; air masses traversing the area from other regions; the mountains to the east and west; and the moderating influence of the Lake itself. When the prevailing westerly winds reach the mountains to pass over them, the air is cooled often causing rain in summer and snow in winter.

The Average Annual Precipitation Map [740 KB] shows the effect mountains in the Basin have on precipitation. Higher elevations in the Basin receive greater amounts of precipitation. For example, the average annual precipitation in the mountains exceeds 50 inches (127 centimeters) compared with about 30 inches (76 centimeters) in the valley.

Click to enlarge! Basin weather varies dramatically by season. Click on the thumbnail satellite images on this page to enlarge them. These images, courtesy of NASA, show just how different the weather can be from month to month. Can you guess what season it is in each photo? Find the Lake--why is it blue in one image and not in the other?

The growing season also varies in different parts of the Basin, from only 105 days in the higher elevation regions to 150 days along the Lake. The longer growing season, coupled with fertile soils, makes the lowlands a rich agricultural area. The north facing slopes of the mountains have the shortest growing seasons along with the lowest temperatures.

Click to enlarge! The Lake also influences the climate. Summer sunshine warms the surface layer of the Lake. During the fall and early winter, as the water releases this heat, temperatures in the Champlain Valley are moderated. Conversely, in the spring, warmer air and increased sunshine melts the snow and lake ice but the Lake takes longer to warm than the surrounding land. Breezes off the Lake keep the shoreline areas chilly, extending cool conditions well into May.

Learn More... Lake Champlain Basin Program, 2004
Design: Nicole L. Ballinger (LCBP) | Maps: Northern Cartographic and LCBP