Seasonal Lag - Seasonal Lag On Earth

Seasonal Lag On Earth

Earth's seasonal lag is largely caused by the presence of large amounts of water, which has a high latent heat of freezing and of condensation. Its length varies between different climates, with extremes ranging from as little as 15–20 days (for polar regions in summer) to as much as 2½ months (for low-latitude ocean areas). Interestingly, in many locations, it is not "seasonally symmetric", that is, the time between the winter solstice and coldest time is not the same as between the summer solstice and hottest time. In low and middle latitudes, the summer lag is longer, while in polar areas the winter lag is longer. In mid-latitude continental climates, it is approximately 20–25 days in winter and 25–35 days in summer.

San Francisco, for example, has a long seasonal lag of almost three months in the summer, with typical temperatures peaking in mid-September, and October as its second-warmest month . This is unusual for a location 38° north of the equator, but is caused by the water in the Bay Area surrounding the city on three sides. Many areas along North America's west coast have very small winter lag and are characterized by a much more gradual spring warming and rapid autumn cooling.