The Climate of New York state is generally humid continental, and features significant variation over the years. Winter temperatures average below freezing during January and February but near freezing along the Atlantic coastline, while summerlike conditions prevail from June to August statewide. Cold air damming east of the Appalachians leads to protracted periods of cloud cover and precipitation east of the range, primarily between the October and April months. On average, western New York is cloudier than southeast New York, much of it generated from the Great Lakes. Greenhouse gas emission is low on a per capita basis when compared to most other states due to the extensive use of mass transit, particularly across New York City. The significant urbanization within New York City has led to an urban heat island, which causes temperatures to be warmer overnight in all seasons.