CHICAGO (TheStreet) -- It's an eternal mid-year stage of the business cycle: As heat and humidity rise, motivation and revenue drop.

Unless you're running an ice-cream stand or construction business, summer tends to be a slow time for many businesses. Which means months of low sales, inefficient employees and trickling revenue.

These days, owners can't afford to write off a few lost months. The key to making summer count? Either diversify to bring in new hot-weather business, or use your slow time more productively, laying the foundation for a blockbuster fall.

For a lesson in how to expand your product lineup, look at

McDonald's

(MCD) - Get Report

, which rolled out snack items such as frappes, smoothies and wraps to draw customers beyond traditional mealtimes. The company credited the new offerings with a 5% uptick in same-store sales from April to May.

You don't have to be a global powerhouse to follow that model. Consider the gourmet food company

North Aire Market

, based in Shakopee, Minn. The business was built on the Maggie and Mary's line of dried soup mixes (the most popular of which, Creamy Wild Rice, won first place at the International Fancy Food Show in New York).

The downside was that soup sales collapse come summertime. So the company gradually expanded its offerings, and its products now include cold beverage mixes in flavors such as English Toffee Freezie and Key Lime Smoothie. Soup might remain its signature product, but North Aire Market found a way to make sales year-round.

If changing your product lineup isn't an option, owners and employees can still find ways to stay busy and challenged.

"While many businesses experience a slowdown during the summer, it doesn't mean it has to be a non-productive period," says Cher Murphy of the public-relations firm Cher Murphy PR, which has worked with many small businesses. "Quite to the contrary, you should be thinking of it differently. Consider these months the most opportune time to focus on all the things you've been needing to do, but were too busy to tackle."

Such housekeeping projects might include some literal cleaning: Set aside a day or week to clear desks, organize supply closets and clean out e-mail folders. It can also include strategic planning for the fall or holiday season: Think about where you want to be by the end of the year and lay out the steps that will get you there. Include your employees in the process to keep them motivated and invested in your mission.

You can also take this time to re-evaluate your promotions and marketing plans.

"Get up to speed on social media tools and plan how they can be effective in reaching your target market," says Murphy. (Spending hours experimenting with Facebook or Twitter might have seemed like an indulgent waste of time during your busy season, but it's a perfect summer project.) Murphy also suggests writing press releases in advance, even if you don't plan to send them out until months down the road.

Summer can also be great time to focus on networking. Schedules tend to be more flexible, making it easier for business owners to fit in meetings with potential customers, suppliers and community leaders.

While you want to keep your employees productive, remember that they need a chance to slow down, too. Build goodwill by offering more flexible schedules, relaxing the dress code or closing up early on Friday afternoons. And don't forget to schedule your own vacation. Everyone deserves a break, even you.

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Elizabeth Blackwell is a freelance writer based in Chicago. She is the author of Frommer's Chicago guidebook, and writes for the Wall Street Journal, Chicago, and other national magazines.