This was supposed to be a bang-up summer for outdoor activity, with the economy wobbly and many Americans opting to stick closer to home. National parks still are predicting a jump in attendance this year.

But the wildfires whipping through the nation’s forests have begun to hurt sales at some recreation businesses, casting a cloud that could persist through the summer and fall.

Known World Guide Service Inc. in Velarde, N.M., which arranges hiking and river rafting trips, said its revenue is down 70 percent this year. BSR Sport in Glenwood, Colo., which sells bicycles and other sporting gear, is having its worst year ever. Outdoor equipment store Mountain Miser Ltd. in Englewood, Colo., has seen sales slide 6 percent so far this year, and owner David Goodman expects they’ll fall further.

“I don’t think anybody’s going to be setting any records this year,” he said.

Although it’s too soon to determine the overall economic effect of the fires, the Outdoor Industry Assn. said sales are likely to suffer further if the fires keep raging, prompting vacationers to change plans.

Weaker sales in areas near the fires, and the worries they are causing elsewhere, are particularly disappointing because they’re coming at the peak of a key selling season for outdoor equipment companies.

Kent, Wash.-based Recreational Equipment Inc. generates about 25 percent of its annual sales from mid-May through mid-July, spokesman Mike Foley said. And REI’s second-largest concentration of stores is in Colorado, where some of the season’s worst fires have raged.

“It’s an important couple of weeks for us,” Foley said.

Farther from the fires, some retailers are wary, partly because scant rainfall has left many of the West’s most inviting areas vulnerable.

“What concerns us is it is so early in the season,” said John Mead, president of San Diego-based Adventure 16 Inc. Sales have been flat so far this year for the company’s five stores, all located in Southern California.

“We’re hoping for the best,” Mead said, “and preparing for the worst.