SUMMER BEGINS TODAY

It's been hot for weeks. Temperatures have danced around 90 degrees with high humidity to match. This isn't the kind of weather people associate with spring.

But it should be.

Today is officially the first day of summer. Those prior hot days technically were as much a part of spring as rain and early May flowers.

Doesn't it seem strange that summer doesn't officially begin until weeks after the streets begin to sizzle?

Who decides when the first day of summer is anyway?

"It's astronomical," says Al Robertson, a weather expert and professor of health and leisure at Southeast Missouri State University.

"The first day of summer is determined by the alignment of the sun and the earth," he said.

Chris Jones, a meteorologist with the National Weather Service in Paducah, Ky., said that the seasons and the temperatures sometimes don't have anything to do with each other.

"Theoretically, today it could have been 65 degrees and you would have been calling me saying 'It's summer and why is it not hot yet?'" he said. "It just so happens that it's been really hot lately."

The latter parts of spring tend to be warmer. And by summer's end the hot temperatures have cooled off as well.

"Weather runs in cycles," Robertson said. "The warmest time of year is next month, not right now. Two weeks ago people were wondering when summer would show up."

There's usually a month lag after a season begins before the weather begins to catch up. Robertson said it takes that long for the sun to fully heat the atmosphere.

There is a reason that June 21 is the first full day of summer, whatever the temperature.

The summer solstice began Thursday about 9:45 p.m. That means the sun has reached its most northerly point, directly over the Tropic of Cancer.

In the Northern Hemisphere, this is the longest day of the year and the beginning of summer.

But these won't be the hottest days of the summer, as everyone is aware.

Both Jones and Robertson said it takes over a month to heat up the atmosphere. That's why the dog days of summer aren't until July and August.

Shortly, the sun's strongest rays no longer will be exactly over the Tropic of Cancer. They will be heading back toward the equator and will be doing so all summer.

The days will progressively grow shorter as the summer concludes.

"Two weeks from now, you won't see that lightness at 9 p.m. that you saw last night," Robertson said.

The last official day of summer is Sept. 20.

The first day of fall is the autumnal equinox, which is when the sun's strongest rays are again over the equator.