Summer Officially Underway

This morning marks the official start to summer, though the season may have already begun in the minds of many residents and some scientists across the United States.

Summer officially begins when the sun is directly over the Tropic of Cancer, which occured at 7:28 a.m. EDT on Monday. This is called the summer solstice, and marks the longest day of the year (in terms of daylight) in the Northern Hemisphere.

In the weeks ahead, the direct rays of the sun will appear to migrate southward, reaching the equator on the first day of autumn.

Today may mark the official start to summer, but the heat has already been turned on across a large part of the nation. Today will feel very warm to downright hot from the Southwest to the East.

The summer that starts today is defined as "astronomical summer." "Solar summer" began in early May, and is the quarter of the year when the most amount of sunlight is entering the Northern Hemisphere. Astronomical summer essentially marks the midpoint of solar summer.

"Meteorological summer" is the warmest quarter of the year based on daily normal temperatures. This exact period varies slightly from place to place; but, in general, meteorological summer starts the first week in June and ends the first week in September.

At the midpoint of meteorological summer, normal temperatures reach their maximum values. For most locations, this occurs in late July or early August.

One would assume that the peak of normal temperatures coincides with the first day of astronomical summer, but that is not the case.

Even though the most amount of solar radiation is entering the Earth on the first day of astronomical summer, the heat retained by the Earth continues to exceed the heat lost until the midpoint of meteorological summer.

By Kristina Pydynowski, Senior Meteorologist