Summer in Ann Arbor is the 4th coldest on record

The average temperature for June was down 0.8 degrees; average temps were down 4.6 degrees in July, according to National Weather Service data.

Kahlbaum cited two possible explanations for the cooler temps. Some scientists believe El Nino in the Pacific Ocean is the cause, he said - a view shared by U-M's Dr. Frank Marsik and the National Oceanic and Atmospheric Administration. Marsik said El Nino has caused the jet stream to dip lower than usual over the eastern United States, which allows cool Canadian air to dominate. Conversely, the upper dip of the jet stream has gone way up on the west coast, causing unusually high temps in the Pacific Northwest this summer.

Rob Deedler with the National Weather Service offered a different reason, saying the North Atlantic Oscillation is the cause. NAO is a weather trough that hovers over eastern Canada. When it's a negative NAO, as Deedler says it is this year, that allows cooler Canadian air to flow into the eastern U.S. When the NAO is positive, above average temperatures generally occur.

"What it boils down to is the position of the jet stream," Kahlbaum said.

The cooler months have had a varying impact on businesses whose peak season is summer.

Attendance at the Buhr Park Pool in Ann Arbor is "indeed down," said Gail LaVictoire, facility supervisor. On exceptionally rainy or cool days, the city doesn't even open the pool. The benefit is less payroll expense for lifeguards, which saves the city money, LaVictoire said.

Fuller Pool, on the other hand, stays open all summer, rain or shine. Facility supervisor Dan McGuire said traffic has been steady for lap swimmers, but low for families.

Walt Korican, a longtime salesman at Big George's Home Appliance Mart, said the cooler temperatures have hurt air conditioner sales. While apartment-sized units have been selling reasonably well, he said sales of window models are way down. Korican attributes much of the slump to this summer's weather, but said newer homes with central air have also taken a bite out of sales.

Derek Wagoner, who works at the Dairy Queen on Packard Street, said cool weather has slowed business somewhat. He said sales were better in June when the weather first warmed up, and also noted part of the recent slowdown could be due to the approaching school year.

"Right now it's been slow," he said.

Despite the weather, the boating business appears to be faring well this summer. Jay Preston of Nicholson's Powersports in Scio Township, which sells wave runners, said business is steady. Tammy Hoak of Wilson Marine in Brighton agreed, but added her company does a lot of out-of-state business, where the weather and the bad economy aren't such factors.

"Actually, (the weather) hasn't affected anything," Hoak said.

It's been a mixed bag for gardeners this summer.

Mark Hodesh, owner of Downtown Home and Garden in Ann Arbor, said the weather has been excellent for the gardening business. Cooler temperatures have encouraged more gardening, he said. On the downside, the weather has delayed the ripening of some vegetables, namely tomatoes, which are a month behind schedule, he said.

"It's a slow year for tomatoes," Hodesh said. "Lots of them on the vine still, not turning red."

So what does the cool summer portend for the coming winter? If it's any consolation, meteorologists who believe the Atlantic Ocean is responsible for this summer's weather predict a wet but mild winter.

Photos by Lon Horwedel, AnnArbor.com: Fuller Park Pool lifeguards Shannon Martin, left, and Melissah Lang bundle up in parkas as they watch over lap swimmers at the pool Sunday.

David Wak is a freelance writer for AnnArbor.com. Reach our news desk at news@annarbor.com or 734-623-2530.