News Photo by Julie Riddle A customer, headed out for an afternoon of fishing, picks up a container of worms from bait shop owner Kurt Herriman at Clem’s Bait and Tackle in Alpena on Friday.

ALPENA — High temperatures in the waters of Lake Huron may — or may not — make for good fishing at this week’s Michigan Brown Trout Festival.

Higher-than-average temperatures in early July have raised the temperatures of the Great Lakes above normal for this time of year.

Hitting an above-average temperature around June 20, Lake Huron cooled slightly and then, in the middle of a stretch of hot days, jumped to about 72 degrees around July 7 — the earliest in the year the lake has reached that temperature, and almost 10 degrees above average.

On Monday, the surface temperature on Lake Huron was about 68 degrees.

On average, the lake only reaches about 69 degrees, not reached until the beginning to middle of August.

Water temperatures affect where fish can be found, important in Alpena all summer but of particular note during the Brown Trout Festival now underway.

Warm water drives some fish deeper, explained Kurt Herriman, owner of Clem’s Bait and Tackle in Alpena and a 30-year veteran of fishing the Great Lakes.

Some species, including the bigger fish in the sights of those angling for a Brown Trout Tourney prize, can’t tolerate warm water and will dive deeper, farther from the boats and fishermen above them.

Dave Fielder works at the Michigan Department of Natural Resource’s Alpena Fisheries Research Station. He said the warmer the surface is, the deeper the water’s thermocline drops. He explained the thermocline is where the warm water transitions to cold. He said most of the fish that people will target during the tournament will be below the thermocline line and fishermen will need to adapt to that.

“They will have to use downriggers and fish deeper, or fish further offshore to get to the brown trout, lake trout, and salmon. I would say they would have to go at least 75 foot down or more, ” Fielder said. “Fish like walleye and bass are more tolerant to warm water and can be caught in shallower water above the thermocline.”

In spring and later in the year, the water is more predictable, but, in summer, water temperature can vary from day to day and from location to location. Brisk winds, such as those that blew through Alpena last week, push away warm water near the surface, allowing cooler underlayers of water to rise.

Variations in temperature don’t necessarily mean good fishing or bad fishing if you understand the patterns of fish — something Herriman said comes only with experience.

While some fishermen carefully check temperatures and will set up shop over a spot that is to their thermometer’s liking, other fishermen believe in hovering wherever bait fish are, knowing eventually the bigger fish will need to come for a meal, regardless of the temperature.

Temperatures for the week of the tournament are expected to be in the mid to upper 80s, with a mild wind with no more than 15 to 20 mile-per-hour gusts, possibly making for record-breaking high water temperatures.

Julie Riddle can be reached at 989-358-5693, jriddle@thealpenanews.com or on Twitter @jriddleX.