Short answer: Fall turnover happens when a lake's cooling surface water sinks and mixes with the stale bottom layer. The water often clouds up and fish scatter for a few days to a couple of weeks. To fish through it, go where the lake isn't turning: creek arms and inflows, very shallow cover, deep structure, a river, or a different lake.
It's the third week of October. Last Saturday the bass were busting shad on the points. This Saturday the water looks like weak tea, leaves hang a foot under the surface, and the cove smells faintly of rotten eggs. Same lake, same lures, almost no bites. That's probably turnover, and the fix is less about your lure than where you put the boat.
What is fall turnover?
Water is heaviest at about 39°F. In summer, warm, light water floats on top of cold, heavy water, and the lake stays in layers (Minnesota DNR). The boundary between them, the thermocline, works like a lid. The bottom layer is cut off from the air, so it can lose most or all of its oxygen while the lake is layered (IISD Experimental Lakes Area).
In fall, the surface cools, gets heavier, and sinks, pushing lighter water up. As the top and bottom temperatures even out, wind can mix the whole lake. That exchange is turnover (Minnesota DNR). In the long run it's good for the lake: it's the event that puts oxygen back into the deepest water before ice-up (IISD-ELA).
The trouble for anglers is the stretch in between. That bottom water is often low on oxygen and full of nutrients, so mixing can make water quality worse and stress fish until things settle (Virginia DWR).
What water temperature does fall turnover happen at?
There isn't one number, which is why search results disagree:
- Minnesota DNR: sinking and mixing keep going until water at all depths reaches about 39°F (MN DNR).
- Virginia DWR: on Virginia waters, turnover usually comes as the water falls into the low 60s and upper 50s (Virginia DWR).
- Wired2Fish: Shaye Baker writes that most lakes don't turn over until surface temperatures drop below 50 (Wired2Fish).
- Outdoor Canada: Gord Pyzer had turnover "well underway" in northwestern Ontario at about 55°F. He calls it "a process, not an event," and warns that waiting for 40°F means missing almost two months of the best fall fishing (Outdoor Canada).
Mixing down to about 39°F is the end of a long slide. The dirty-water stretch anglers notice depends on the lake's depth, the region, and the weather. A hard cold snap, a lot of wind, or half an inch or more of cold rain can bring it on quickly (Bassmaster, Mark Menendez). So skip the magic number. Watch your own lake's water temperature and how fast it's falling.
How can you tell if a lake has turned over?
The only sure way is to measure the temperature at the surface and at the bottom. If they're within a few degrees, the lake has turned over, says Minnesota DNR fisheries research scientist Andy Carlson (Ask the DNR, Grand Forks Herald). While it's happening, he says, clarity may drop, decaying material can hang in the water, and you may smell sulfur.
On the water, look for:
- Color: Michael Iaconelli calls it "gray-green pea soup" (Bassmaster). Baker describes a tannic, coffee- or tea-colored stain rather than mud (Wired2Fish).
- Debris: leaves and bits of dead weed floating or hanging in the water.
- Smell: sulfur, like rotten eggs.
- No bait: if you can't find baitfish in an area, the bass have probably left too (same source).
How long does fall turnover last?
It depends whether you mean the bad fishing or the whole process.
The rough patch: Virginia DWR says turnover usually clears up in about a week or two (Virginia DWR). Menendez has watched turnovers develop in Kentucky in 24 to 36 hours. He says one can last as long as four weeks, but most are over in two (Bassmaster). Gene Gilliland, then with the Oklahoma Department of Wildlife Conservation, told Bassmaster that the actual turning of a large reservoir takes two or three days at most. On small waters, after a hard rain, it can happen overnight (Bassmaster).
The full process: getting the whole lake to one temperature can take days or even months. That depends on the lake's shape and depth and on air and water temperatures (Ask the DNR).
A working rule from Chris Horton in the same Bassmaster piece: if you think the lake is turning and you're not getting bit, come back in a week.
Does every lake turn over?
No, and not all at once.
- Shallow water doesn't layer. Spots shallower than about 6 feet, like big creek arms, may not be affected at all (Virginia DWR).
- Wind and current keep water mixed. Large reservoirs or natural lakes with steady wind or regular current usually don't turn over, or not as dramatically (Gilliland, Bassmaster). Rivers stay mixed thanks to current (Wired2Fish).
- Climate matters. Lakes in places like northwestern Ontario mix twice a year, spring and fall. Some lakes in milder climates that don't freeze over may mix only once, in winter (IISD-ELA).
- Timing varies. Very few lakes turn over everywhere at the same time (Bassmaster, Iaconelli). Small, shallow ponds usually turn before larger lakes (Wired2Fish).
Where do fish go during and after turnover?
During: they scatter. Iaconelli says deep fish tend to suspend and shallow fish tuck tight to cover (Bassmaster). Menendez says baitfish spread out, both sideways and down, looking for water with enough oxygen. Bass bite in a few places: the top foot or two, where wind and plants add oxygen; very deep water the turnover doesn't reach, in some reservoirs; and spots where runoff tumbles in (Bassmaster).
After: they have more room. Once oxygen is the same from top to bottom, fish can use depths that were off-limits all summer. Walleye, northern pike, muskellunge, and cisco tagged with depth sensors used deeper water after turnover (Ask the DNR). As Gilliland puts it, "what was deep in the summer isn't deep in the fall" (Bassmaster).
How do you fish the fall turnover?
- Run to better water. Iaconelli's first move is to leave. If he's near the dam, he runs up the lake. If the upper lake looks bad, he heads toward the dam (Bassmaster).
- Find inflows and current. Creeks with fresh inflow stay more stable (Virginia DWR), and current adds oxygen (Wired2Fish). Skip the muddy ones, though. Menendez says nothing is tougher on a bass than cold, muddy water (Bassmaster).
- Go very shallow. Baker fishes water shallower than 2 or 3 feet. He throws topwaters until the water reaches the low 50s, then squarebills, lipless cranks, spinnerbaits, and vibrating jigs (Wired2Fish). Virginia DWR's go-to is a wacky-rigged soft stickbait pitched to shallow targets.
- Or go deep. Baker finds turnover hits hardest from about 4 to 15 feet. He works deep brush and rock with jigs, Ned rigs, shaky heads, and drop shots (same source).
- Fish slow and tight to cover. Pitch to wood with a slow, gentle fall, or skip a stickbait under docks (Bassmaster, Iaconelli).
- Follow the bait. Schools of baitfish are easier to find than single bass, and they leave turned-over water too (Wired2Fish).
- Switch waters. If a pond is turning, the big lake nearby may not be yet, and the reverse. Rivers and creeks are a solid backup (same source).
Can fall turnover cause a fish kill?
Yes, mostly in ponds. A heavy, cold rain or a long stretch of high wind can mix a pond fast enough to drop oxygen too low for fish. A severe mixing event can kill nearly every fish larger than an inch or two in one night. An early warning sign is fish at the surface at sunrise, "gasping for air" (Mississippi State University Extension). Older, deeper ponds sheltered from the wind get hit harder. Shallow ponds in windy spots, 6 to 8 feet deep at most, are less likely to have turnover kills (Kentucky State University Cooperative Extension). After a kill, MSU Extension suggests having a fisheries biologist look at what's left of the fish population.
Stay safe on cold water
Fall water is colder than the air makes it feel. The National Weather Service says cold shock can be as dangerous in 50-60°F water as in 35°F water, and that wearing a life jacket significantly improves your odds of surviving (NWS). Wear it, and tell someone where you're going if you head up a remote creek.
How to plan a trip during turnover season
- Watch the water temperature trend over the past week, not just today's reading.
- Read recent reports for words like "dirty," "stained," or "turned over."
- Pick a backup: a river, a pond, or a creek arm with an inflow.
- Check the forecast for cold rain and hard wind, which can bring turnover on fast.
- Log it. Date, water temperature, and what bit. Next October, your notes will beat any rule of thumb.
MyFishNavigator can't tell you whether a lake has turned over. That takes a top-to-bottom temperature reading. It helps with the rest of the planning. Set a pin and it builds one expert briefing for that spot and date. When a freshwater gauge is in range, the briefing includes a live water temperature and how it compares with the normal for that date. It also pulls in recent local reports, and when those reports mention murky or stained water, the briefing says so first and adjusts the spots and tackle. Pin the creek arm or the river below the dam too, and compare. On Pro, depth contours on the trip map, where state depth data is available, help you find shallow flats and deep breaks. You can start free with 10 trip briefings a month, no credit card required.
Fall turnover FAQ
Is fishing good during fall turnover?
Usually not in the water that's turning, for a few days to a couple of weeks (Virginia DWR). But turnover rarely hits a whole lake at once, so moving can save the day.
Does lake turnover happen in spring too?
Yes. After the ice melts, surface water warms toward 39°F, sinks, and mixes with the water below (Minnesota DNR).
What does lake turnover smell like?
Like sulfur or rotten eggs, from decaying material brought up off the bottom (Ask the DNR; Wired2Fish).
Do fish go deeper after fall turnover?
Many can. Once oxygen evens out, tagged walleye, pike, muskies, and cisco have been tracked using deeper water (Ask the DNR).