Say winter's over and people cheer, but mention it's the end of summer and people shriek: "Don't say that!"

With Labor Day come and gone and the first official day of fall only two weeks away, the end-of-summertime blues are setting in for sun worshippers. But why does the end of summer lovin' provoke such a strong reaction?

Experts say decreased activity, less sunlight and a sense that some fun-in-the-sun time was wasted all make the end of summer more depressing than the conclusion of the other three seasons.

"Sometimes there's that feeling of letdown, like you planned on going sailing and biking, and lo and behold, you haven't gotten your camping gear out once," said Dr. Kathy HoganBruen (search), a Washington, D.C.-based clinical psychologist.

It seems like everyone has a tale of winter's-coming woe. New York City Board of Education employee Iris Rachnowitz, 53, told FOXNews.com she didn't get to the beach once this summer.

"Now I have to go back to work. I'll have to get my son up for school. I need a vacation from the vacation," she said.

Her friend, New York City resident Marlene Yuzik, mourns September every year.

"My son goes back to school and I get melancholy. I like having him around. Now I have to worry about the friends he hangs out with," said Yuzik, 50. "And I'm a year older."

Jennifer, a 30-year-old Arlington, Va., resident who works in politics and chose not to reveal her last name, said the fact that it's an election year meant no lazy days by the pool this summer.

"I spent a good part of summer working. No vacation, no beach. But even if it weren't an election year, I hate when summer ends," she said. "It gets darker, colder, you're less motivated. It's just depressing."

HoganBruen said that with lighter workloads, the promise of vacation time and the kids being out of school, many Americans have unreasonable expectations of summer fun.

"People have the image of people in bathing suits, going to Martha's Vineyard. People in magazines and catalogues seem to have all the leisure time in the world. This is not realistic," she said. "On weekends we still have errands, responsibilities. There's a sense of disappointment when you didn't accomplish what you wanted, even if it's leisure time."

Dr. Robert Thayer, a psychology professor at Cal State Long Beach and author of "Calm Energy: How People Regulate Mood With Food and Exercise (search)," said he thinks summer activities like volleyball and swimming, in contrast with the hibernation that winter inspires, have a lot to do with the buzz-kill when the season changes.

"The link between physical activity and mood is very strong – exercise stimulates energy and vigor," he said.

Thayer added that about 10 to 15 percent of the population suffers from a clinical disorder triggered by shorter days and less light.

"As the seasons change and light diminishes, we move into possible SAD (seasonal affective disorder) (search)," he said. People without this disorder are also known to get the blues without enough exposure to the sun.

On the bright side, experts say there are ways to combat the winter blahs. Thayer advises joining a gym and beginning a regular exercise program. And HoganBruen recommends looking forward to next summer.

"Plan ahead for next year, whether it means saving money, doing research, finding a companion," she said.

HoganBruen added that people should also try to look forward to the fresh start of fall.

"The same type of person who romanticizes summer might also be equally enticed by the L.L. Bean catalogue showing people rolling in leaves," she said. "Just because Labor Day has passed doesn't mean the nice weather is over. September-October is still a great time to go camping, biking, to play tennis. Go outside, get exposure to sunlight."

Rachnowitz agreed that autumn brings its own gifts.

"I like it when the leaves change," she said.