As summer approaches and temperatures rise, office dwellers tend to get a little antsy. In fact, a growing number of employees are calling in sick and skipping work during the warm-weather months, new research shows.

Of 1,077 full-time employees polled, 39 percent said they've called in sick to take a day off in the past, and 30 percent said they planned to do so again this summer, according to the "Summer Absenteeism" survey conducted by Harris Interactive.

Among employees who faked sick days, most said they used their time off to go to the beach or go shopping. Not surprisingly, the most popular days to skip work were Monday and Friday, the survey found.

In addition to wanting to enjoy the weather, respondents also said they called in sick whenever they needed a mental-health day or had limited time off due to a demanding workload.

"In my experience, employees really value time off more than they value those extra couple of bucks," said Scott Demorest, co-founder of ACME Business Consulting, a Portland, Ore.-based firm.

Demorest said that as long as client requirements are met, he doesn't mind if an employee wants to spend a day at the beach every now and then, but conceded that as a business owner, summer absenteeism can be difficult to monitor. "The way we address this issue is we give them a bank of hours for paid time off," he said. "It can be for vacation or sick time, but you can use it as you want."

According to Jim Kizielewicz, vice president of Kronos, a Chelmsford, Mass.-based workforce-management company that sponsored the survey, as soon as one employee misuses a sick day, it sets a precedent for other employees to do the same. Unscheduled absences can also have a negative impact on co-workers and productivity.

The survey also asked respondents for their suggestions regarding time off. Most respondents were in favor of creating "summer Fridays" at their workplace, a benefit that would allow all employees to take a half or full day off at the end of the week.

Other suggestions included compressed work weeks and providing employees with a bank of paid time off to use at their discretion.

The younger generations of employees are demanding more flexibility in the workplace, Kizielewicz said, and employers need to learn how to adapt. "The workplace is in the midst of a revolution. What worked yesterday, like sick-time benefits, won't work with Generation Y," he says. "Today, best-practice organizations are providing employees with flexibility and rewarding them based on results."