Minneapolis - St. Paul, Minnesota -

Summer's coming. Grab a sweater.

Sunday and Monday may be in the 80s, but some forecasters say don't be fooled.

Across Minnesota and the Dakotas, temperatures could be below normal through the end of August, according to the federal Climate Prediction Center. The outlook for "meteorological summer" -- June, July and August -- prompted one Accuweather forecaster to predict a "year without summer."

"That's how the dice are loaded," said the Climate Prediction Center's senior meteorologist, Ed O'Lenic.

So far, the trend toward a cool summer has been emphatic, with furnaces blasting through the first days of June across the state. The average daily temperature for the first 11 days of June in the Twin Cities was 7.2 degrees below normal.

As of Friday, lilacs hadn't bloomed yet at Wolf Ridge Environmental Learning Center near Finland, Minn. They're usually out June 6.

Of course it's all about averages, and the Twin Cities has already seen two days with highs in the 90s, even though they were in May, which isn't summer in anybody's book. The 97-degree reading on May 19 even stands a good chance of remaining the highest temperature of the year.

Looking on the bright side

"Year without summer? That's a bit harsh," said Chuck Lennon, spokesman for the state Department of Tourism.

Cool temperatures might make lake swimming less appealing, Lennon said, but otherwise shouldn't have much effect on the traditional Minnesota summer pastimes. Despite the generally cool spring so far, state parks campsite occupancy has been running generally higher than last year, according to the DNR.

"Hiking you might stay a bit cooler," Lennon added. "You can ski in a wet suit. Everything else is [climate] controlled."

We've been through this before. Minnesotans experienced some unusually cool summers in the early 1990s. June through August in 1992 was the second-coolest such stretch in more than a century, with an average daily temperature in the Twin Cities 4.5 degrees below the 117-year normal.

But three years ago, the Twin Cities' summer was the fourth warmest on the books, 4 degrees above normal.

This year, the Climate Prediction Center is calling for a summer-long average daily temperature ranging from 0.1 to 0.6 degrees below normal across the region.

Daily temperatures were predicted to rebound toward normal this week. Even Accuweather is predicting a high of 85 for the summer solstice, June 21. But the cold early start to the month could drag the averages down, leaving the center's predicted pattern intact.

The center's long-range outlooks are based on a collection of factors including soil temperatures, climate histories and other international outlooks. They also frequently rely on temperature fluctuations in the equatorial Pacific known as El Niño and La Niña, but that has entered a neutral phase in recent months after being in the cool or La Niña phase from late 2007 through early 2008.

Not everyone agrees

Different forecasters evaluate trends differently, of course.

Telvent DTN, a Burnsville firm that does short- and long-term forecasting for energy, agriculture and other industries, is calling for a cool start to summer, a warm middle and an average end, said Jeff Johnson, chief science officer.

"Average it all out over those three months and our forecast is close to average," Johnson said, adding that summers in the Upper Midwest tend to turn out close to average.

Roseville meteorologist Frank Watson, who makes some seasonal forecasts more than a year in advance, arrived at the same result by a different route. Watson is stubbornly sticking with a forecast of a warmer-than-normal June, followed by a warm July and a cooler-than-normal August.

If the cool summer predictions win out, one benefit could be less air-conditioning.

"People are not going to be using as much," said Xcel Energy spokeswoman Mary Sandok.