The mercury rising into the 90s isn't the only reason to take a dip in Lake Michigan this weekend.

Beach closings due to high E. coli levels have been virtually non-existent along the southern shoreline this summer, making the lake even more inviting to swimmers.

The combination of offshore winds, lack of rain and plenty of sunshine have kept waters relatively bacteria-free, said Dr. Richard Whitman, the station chief and aquatic ecologist for the Lake Michigan Ecological Research Station at the Indiana Dunes National Lakeshore.

"It has been a very unusual summer," Whitman said, noting that we are moving into the "closure season," which is August and September.

The National Lakeshore, which tests water samples on a weekly basis, has yet to have any samples from its beaches exceed 235 colonies of E. coli per 100 milliliters of water, the level considered unhealthy for swimming. In fact, the majority of samples this year have tested in the single digits or teens.

Scott Hicks, supervisory biologist with the Indiana Dunes National Lakeshore, said he's kept an eye on beaches in LaPorte County and levels there are low as well.

"We've had a pretty dry period for the past two months," Hicks said. "I think it really is just a reflection on the amount of rain we've had."

Along with the weekly testing of National Lakeshore beaches, swimmers can get real-time updates on lake conditions in Miller Beach and Ogden Dunes through the U.S. Geological Survey Web site (www.glsc.usgs.gov/ProjectSAFE.php) which features the Lake Michigan Ecological Research Station's prediction system for swimming conditions, dubbed Project SAFE (Swimming Advisory Forecast Estimate).

Whitman says the system, which relies on a variety of data, including current direction, wind speed and rainfall, provides more immediate information than traditional E.coli testing, which has a 24-hour lag time for results.

"We feel confident that this approach is an effective improvement in beach monitoring and that ultimately we will be able to predict poor swimming water quality before it happens," Whitman said.

BREAKOUTS:

By the numbers

A comparison of water testing data from mid-May to the first week in July reveals lower bacteria levels this year compared to the same period in past years.

Geometric mean of number of E.coli colonies per 100 milliliters for all samples taken

2007 - 6

2006 - 12

2005 - 29

2004 - 25

Total number of exceeding samples (more than 235 E.coli colonies per 100 ml)

2007 - 0

2006 - 0

2005 - 5

* 2004 - 11

* In 2004, water was sampled five days a week, which would have contributed to a higher number of exceeding samples.

Source: Scott Hicks, supervisory biologist, Indiana Dunes National Lakeshore

To find out more

* Project S.A.F.E.'s daily monitoring data for Lake Street, Marquette Park, Wells Street and Ogden Dunes beaches can be found online at www.glsc.usgs.gov/ProjectSAFE.php.

* The Indiana Dunes National Lakeshore has a recorded message with beach closing information at (219) 926-7561, ext. 668.