Field Notes / October 2026
Where to find lake trout in the Great Lakes, season by season
At a glance
| preferred temp | about 42-55 °F (6-13 °C) |
| sweet spot | about 48-50 °F (9-10 °C) |
| summer depth | often 100-200 ft |
| habit | close to bottom |
Quick answer
Lake trout are a cold-water fish. Michigan DNR puts their preferred range at 40-55 °F, and NY DEC lists 42-52 °F with an optimum of 48 °F [1][2]. In spring and late fall that water is near the surface and close to shore, often 10-30 ft deep. In summer it sinks, and the fish follow it down to 100-200 ft or more [1]. Most of the time they stay close to the bottom [2]. So the search is simple to describe: find the 48-50 °F water, then find where it touches bottom.
The problem
On the Great Lakes, the water you can see tells you almost nothing about where lake trout are. A 70 °F surface can sit on top of 45 °F water 80 ft down, and an offshore wind can flip that overnight. Most anglers set depth from habit, a fishing report or what worked last weekend.
01
Temperature is the whole game
Every season pattern for lake trout comes back to the same thing. Laboratory work by USGS found a preferred temperature of about 10 °C (50 °F) for young lake trout [3]. Adult fish use a wider band, but the agencies cluster around the same numbers: 40-55 °F from Michigan DNR, 42-52 °F from NY DEC [1][2]. The University of Minnesota notes that lake trout only do well where the water doesn't exceed about 65 °F (18 °C) [4]. Treat 48-50 °F as your target, and the edges of the band as places to check when the target is out of reach.
02
Spring: shallow and high
After ice-out the whole lake is cold, so lake trout can be anywhere in the water column, including near the top. Michigan DNR describes them in shallow areas, 10 to 30 ft deep, during the cooler months [1]. On Lake Michigan the surface is often still near 50 °F in June, and it is not unusual to see lake trout just a few feet deep in the early morning [5]. This is the one time of year when flat lines, planer boards and shallow downrigger sets catch lakers.
With PROBE →
In spring the whole column can be within a few degrees of the target. PROBE logs temperature at every depth your lure passes, so you can see whether the 48-50 °F water is at 10 ft or already sliding down to 40.
03
Summer: deep, cold and near bottom
As the surface warms, the lake stratifies. Summer surveys from 1996 to 2017 put the average thermocline at about 15-17 m (48-56 ft) in all five lakes, and a thermocline was present in nearly every survey [6]. Lake trout drop below it and follow the cold water to 100-200 ft or more [1]. They don't always wait until the water cools again: one late-September report from Lake Superior found fish holding at 160-170 ft over 200 ft of water, with a 60 °F surface, because the lake hadn't turned over yet [7].
Bottom still matters. NY DEC notes that lake trout are often found close to bottom [2], and anglers on Lake Ontario's Niagara Bar have done well keeping lures just ticking the bottom in 40-50 ft [10]. When you find 48-50 °F water, look for where it meets structure: humps, reef edges, the slope off a rocky point.
With PROBE →
Summer is where depth accuracy pays. A downrigger counter says where the cable is, not where your lure is. PROBE on the line records the lure's real depth and the temperature there, so you can confirm you are in the cold band and close to bottom. It is rated to 60 m (200 ft), which covers most Great Lakes lake trout trolling.
04
Fall: back to the reefs
Lake trout spawn mostly in October and early November, once the water falls below about 50 °F (10 °C), over boulder and cobble beds where currents keep the rocks clean of silt [4]. In the Great Lakes most spawning happens on shoals less than 6 m (20 ft) deep, though spawning has been recorded much deeper, including over 300 ft at Isle Royale [8]. Eggs are laid after dark among the cobble [1]. Rules around spawning areas vary by lake and season, so check local regulations before fishing reefs in fall.
05
Follow the food
Lake trout eat what the lake gives them. In northeastern Lake Michigan, USGS found that alewife and round goby made up 94 % of lake trout diets by weight in 2016, with goby dominating in May-June and alewife in July-October [9]. Native prey includes ciscoes and sculpin, and lakers also take smelt [1]. If your sonar shows bait schools near the cold water, fish there first.
06
Watch the wind
Wind moves water, and on the Great Lakes it moves a lot of it. A strong offshore wind pushes the warm surface layer out into the lake, and cold water from below rises to replace it. Nearshore water can drop from 75 °F to 58 °F overnight [12]. When that happens, the cold band can move shallower and closer to shore. Check the temperature profile before you assume yesterday's depth still works.
Find the 48-50 °F water, and know your lure is in it.
See how PROBE works →PROBE
How PROBE helps
Lake trout fishing is a temperature search with a depth problem attached. PROBE solves both on the same line: it logs temperature at every depth your lure passes, records the lure's real running depth on every pass, and saves the depth, temperature, GPS position and weather of every strike. Trolling mode records your route and boat speed alongside lure depth. After a few trips you have your own map of where 48-50 °F water sits on your lake, season by season.
Field log /
Late July, Lake Michigan, rocky bottom in 120 ft
| Surface temp | 71 °F (22 °C) |
| 48-50 °F found at | 95-110 ft |
| Bottom depth | 120 ft |
| Lure depth (PROBE) | 104 ft, with 115 ft of downrigger cable out |
| Boat speed | 1.9 mph (GPS) |
| Strikes | 3 lake trout, at 101, 105 and 108 ft |
The counter said 115 ft; the lure actually ran at 104. All three fish came in 49 °F water, within 20 ft of the bottom.
Field rule
Lake trout rule: find the 48-50 °F water, then find where it meets bottom.
A note on the fishery
Lake trout are a restoration success story in parts of the Great Lakes. In 2024 the Great Lakes Fishery Commission's Lake Superior Committee declared lake trout fully recovered in most of Lake Superior, with natural reproduction at or above pre-1938 levels [11]. Regulations still vary by lake and management unit, and they change. Check your state or provincial rules before you go.
FAQ
Frequently asked questions
What water temperature do lake trout prefer?
Michigan DNR gives 40-55 °F and NY DEC gives 42-52 °F with an optimum of 48 °F. About 48-50 °F (9-10 °C) is a good target.
How deep are lake trout in the Great Lakes in summer?
They follow the cold water down, often to 100-200 ft or more, and are usually close to the bottom.
When do lake trout spawn in the Great Lakes?
Mostly in October and early November, when the water falls below about 50 °F, over rocky reefs and shoals.
Your own lake trout map, built one pass at a time.
Get PROBE →Sources
- Michigan DNR, "Lake trout"
- NY DEC, "Trolling for Lake Ontario Trout and Salmon"
- USGS, "Optimum temperature for growth and preferred temperatures of age-0 lake trout"
- University of Minnesota, "Lake trout"
- MidWest Outdoors, "Go High and Fast for Lake Trout"
- Limnology & Oceanography (2020), summer physical variables for the Great Lakes, 1996-2017
- Angling Edge, "Deep water lake trout trolling tactics on Lake Superior"
- Wildlife Management Institute, "Deepest Lake Trout Spawning in the Great Lakes Documented at Over 300 Feet"
- USGS, "Shifting diets of Lake Trout in northeastern Lake Michigan"
- Lakeland Boating, "Dredging up lake trout"
- Great Lakes Fishery Commission, Lake Superior Committee, lake trout restoration (2024)
- Spectrum News 1, "Upwelling and its impact on Lake Michigan"