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791-acre lake in Thunder Bay District, Ontario. The lake tops out around 13 ft. The depth data here comes from the Ontario MNRF survey of 1979, a decades-old survey (a transect sounding survey). Every species below gets its seasonal read from the same numbers driving the chart.
On the chart, Thornbury Lake draws 794 acres inside 10.5 miles of shoreline, broken up by an island. An index of 2.7 puts the bank firmly in maze territory: point after pocket after cove, every one a casting target. There is no deep basin to speak of — the entire surface is under ~15 ft, prime weed water end to end. Tip to tip the water measures near 2.6 mi with a 1.1-mi widest point. You'll find it in Thunder Bay District. Closest neighbour on DepthScout: Harvey Lake, 4 mi southeast of here.
Spring lake whitefish on Thornbury Lake hold shallow, usually 4 to 13 ft. Depth-wise the year is flat: 4 to 13 ft in summer, 4 to 13 ft once it turns cold. Put Deep basin first on the milk run — a deep basin near 13 ft that grades prime for summer. The feeding windows run early morning. The summer box starts with a blade bait vertical or a small jigging spoon.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 4 to 13 ft | midday & dawn | Break off the point (4 ft) | Small jig + waxworm, Blade bait (small) |
| Summer | 4 to 13 ft | dawn | Deep basin (13 ft) | Blade bait vertical, Small jigging spoon |
| Fall | 3 to 13 ft | dusk | Break off the point (4 ft) | Small spoon (gold), Jig + plastic larva |
| Winter | 4 to 13 ft | midday & dawn | Deep basin (13 ft) | Jigging spoon + bead chain, Tungsten jig + waxie |
When the water first warms, walleye slide up into 3 to 13 ft. There's no big seasonal slide here — summer means 4 to 13 ft, winter 4 to 13 ft. If you only fish one area, make it Break off the point: a drop-off around 4 ft that scores prime in fall. In summer the feeding windows fall in the evening and early morning. Keep a crawler harness on bottom bouncer or a deep crankbait (trolled) rigged through the warm months.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 13 ft | dusk & dawn | Break off the point (4 ft) | 1/8 oz jig + minnow, Hair jig |
| Summer | 4 to 13 ft | dusk & dawn | Break off the point (4 ft) | Crawler harness on bottom bouncer, Deep crankbait (trolled) |
| Fall | 4 to 13 ft | dusk & night | Break off the point (4 ft) | Jigging rap, Jig + big minnow |
| Winter | 4 to 13 ft | dusk & dawn | Deep basin (13 ft) | Jigging spoon + minnow head, Rattle bait |
The spring pattern is a shallow one: northern pike in 2 to 8 ft. Midsummer fish sit out in 4 to 13 ft before dropping to 4 to 13 ft for winter. The spot to know is Shallow bay flat, a weed flat in about 2 ft of water that rates prime for northern pike in spring. Plan around early morning and the evening in the warm months. Summer baits: a bucktail or a weedless spoon over cabbage gets it done.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 8 ft | midday & dawn | Shallow bay flat (2 ft) | #5 inline spinner, Spoon (red/white) |
| Summer | 4 to 13 ft | dawn & dusk | Break off the point (4 ft) | Bucktail, Weedless spoon over cabbage |
| Fall | 4 to 13 ft | midday & dawn | Break off the point (4 ft) | Big rubber (Bull Dawg style), Husky-style jerkbait |
| Winter | 4 to 13 ft | midday | Shallow bay flat (2 ft) | Tip-ups, Large jigging spoon |
The chart marks 6 structure features on Thornbury Lake; the deepest is Deep basin at about 13 ft.
Season dates, license requirements, and size and bag limits for Ontario waters are set by the Ontario fishing regulations (FMZ summary) — and special regulations can apply to Thornbury Lake specifically, so confirm the current rules before you fish.
Check the official Ontario fishing regulations →
Thornbury Lake is about 13 ft (4 m) deep at its deepest point. The depth data here comes from the Ontario MNRF survey of 1979, a decades-old survey (a transect sounding survey).
Anglers target lake whitefish, walleye, northern pike on Thornbury Lake.
Deep basin is the top-rated area: a deep basin in about 13 ft of water that rates prime for lake whitefish in summer. The map above holds the full rated-spot list for every species and season.
For lake whitefish, the summer bite is best in early morning. Each species page section below lists the seasonal windows, and the map shows a live NOW badge when you're inside one.
Fishing on Thornbury Lake is regulated by the Ontario fishing regulations (FMZ summary). Check the official Ontario regulations for current license requirements, season dates, and size and bag limits — special regulations can apply to this specific water.
Harvey Lake 4 mi · Volks Lake 5 mi · Brandon Lake 8 mi · Makokibatan Lake 14 mi · Whitefish Lake 19 mi · Crayon Lake 22 mi · Kayedon Lake 22 mi · Abazotikichuan Lake 23 mi · Harrogate Lake 23 mi · Opichuan Lake 24 mi · Tennant Lake 25 mi · Kellow Lake 26 mi
See how Thornbury Lake stacks up: best walleye lakes in Ontario · best northern pike lakes in Ontario · best lake whitefish lakes in Ontario
More water nearby: Thunder Bay District fishing maps (662 charts). Browse all Ontario fishing maps or see every water on DepthScout. Bathymetry credit: state fisheries survey programs. How we build these maps. Fish here with a sonar unit that logs? Send us your depth data and we'll improve this chart, credited to you. For fishing guidance only, never navigation.