Over the Fourth of July holiday, more than 1 million Wisconsin residents and visitors typically enjoy the state's abundant lakes and rivers to boat, fish, swim and paddle around, according to the Department of Natural Resources.

But following widespread flooding in June across southern Wisconsin, the agency said, people need to exercise more care than usual.

Beaches and other recreational waters can become polluted by sewage and other contaminants. Debris is washed into waters and high currents can become a danger. Emergency slow-no-wake rules are still in effect on many southern waters, including the Madison chain of lakes as well as Cherokee Marsh.

The added organic material delivered during the flooding creates conditions ripe for another water quality concern, the growth of excessive blue-green algae, which can produce toxins harmful to people and animals. People should look for the telltale blue-green scum near the water's surface before swimming or allowing animals to drink. The state's beach health Web site www.wibeaches.us offers the most up-to-date source of information on the status of beaches regularly monitored

The good news, DNR officials announced in its weekly outdoors report, is that even in the south, lake and river conditions vary greatly, and fully three-quarters of Wisconsin's more than 15,000 lakes are in northern Wisconsin, which didn't suffer the flooding. So there are still plenty of great opportunities to get out and enjoy Wisconsin's lakes and rivers this holiday.

Recreational safety specialists regard the Fourth of July weekend as the busiest boating weekend of the year in a state that had more than 617,000 motorized boats registered in 2007, and several hundred thousand more nonmotorized boats on the water, including canoes and kayaks. Year-in and year-out, they say, failure to wear life jackets and operating a boat while intoxicated, or being on a boat operated by an intoxicated person, are leading causes for boating fatalities.

Water levels are dropping on southern and central Wisconsin lakes and rivers following the flooding in mid-June, but many river systems in particular remain above normal levels. Most lakes and flowages in the north have normal to low water levels.

Fishing success has shown steady improvement in the north in the last week with some nice catches of walleye, bass and panfish reported. The mayfly hatches have subsided on all but the largest lakes and this seems to have spurred on the bite on many waters.

Largemouth and smallmouth bass success have greatly improved as most of the fish are through nesting and quickly recovering from the stress of spawning. Some bluegill were still on their spawning beds early in the week but all should be finished up in the next week or so.

Water temperatures out on Lake Michigan are just about perfect for trout and salmon fishing from the surface on down. In recent days the surface water temperatures have warmed into the mid and at times upper 50s. Boat anglers trolling on Lake Michigan had many good trips that produced some large catches of chinook salmon, some steelhead and a few lake trout.

The Mississippi River remains about 2 feet above normal heights with a recent large decline in the past few days. Most boat landings are now useable. Fishing activity has resumed and there are recent reports of good catches of bluegills in many areas and fishing for sauger and walleye picked up a little late in the week.

All the emergency slow-no-wake restrictions on the lakes in Jefferson County have been lifted. The rivers and streams still have the slow-no-wake restrictions in effect. All of the boat landings on the Rock and Crawfish Rivers are still flooded so anglers are hitting the lakes instead. Anglers are having good luck catching bass on Rock Lake using an assortment of baits ranging from leeches to spinner baits. Some bluegill were also being caught out in the lake suspended at the thermocline. Anglers drifting and using plastic, pieces of crawlers or waxworms are having the best luck. Several of the roads in Jefferson County have reopened fortunately now that the holiday season is approaching.

* Many bird species have begun fledging young and some early nesters like cardinals and song sparrows are onto their second broods.

* Fireflies and a variety of dragonflies and damselflies are out in abundance. Plants in bloom include blue flag, hawkweed, ox eye daisy, yarrow, harebell, spiderwort, and butterfly weed. Blackberry and raspberry canes have begun producing fruit in the south.

* The first positive tests for West Nile Virus for 2008 in Wisconsin were reported this week in a bird from Eau Claire County and a horse in Chippewa County. Significant mosquito hatches are being reported statewide, and anyone spending time out of doors this holiday weekend is encouraged to take proper steps to minimize mosquito bites. Information on West Nile Virus is available on the DNR Web site.

A 3-minute audio version of this report can be heard by calling 608-266-2277.