The national lakeshore's weather is greatly affected by Lake Michigan and can change quickly. Summers are warm and humid with high temperatures generally in the mid-80s (30c) and low temperatures in the mid-60s (18c). There are about 15 days per year above 90 (32c).Warm periods are occasionally interrupted by frontal action descending from Canada. This generally brings days of pleasant, dry weather. Sunshine is abundant in summer. Highs in winter are usually in the low to mid 30s (0c) with low temperatures in the low 20s (-5c). There are about 15 days per year below 0 (-18c). Winters tend to be cloudy except for periods of extreme cold when skies are clear.