Lake St. John
44.687° N, 79.3251° W
Depth contours from the 1968 government survey. Not for navigation.
Download the depth map (SVG)Lake St. John, Ontario. 44.687° N, 79.3251° W
Maximum depth 6.1 m (1968 survey). Scale bar on the map.
Not for navigation. Depths are from government surveys and may be outdated.
borealbound.ca/lakes/on/lake-st-john/, compiled October 9, 2026
- Canadian Geographical Names Database, Natural Resources Canada. Contains information licensed under the Open Government Licence – Canada.
- HydroLAKES v1.0, Messager et al. 2016 / WWF HydroSHEDS. Licensed under CC BY 4.0.
- Census boundaries and population, 2021, Statistics Canada. Adapted from Statistics Canada. This does not constitute an endorsement by Statistics Canada.
- Aquatic Resource Area survey points, Ontario Ministry of Natural Resources. Contains information licensed under the Open Government Licence – Ontario.
- Fishing access points, Ontario Ministry of Natural Resources. Contains information licensed under the Open Government Licence – Ontario.
- Fisheries Management Zones, Ontario Ministry of Natural Resources. Contains information licensed under the Open Government Licence – Ontario.
- Lake Partner Program, Ontario Ministry of the Environment, Conservation and Parks. Contains information licensed under the Open Government Licence – Ontario.
- Bathymetry lines and survey index, Ontario Ministry of Natural Resources. Contains information licensed under the Open Government Licence – Ontario.
- City page weather forecasts and alerts, Environment and Climate Change Canada. Contains data from Environment and Climate Change Canada (ECCC Data Servers End-use Licence).
- Air Quality Health Index observations and forecasts, Environment and Climate Change Canada. Contains data from Environment and Climate Change Canada (ECCC Data Servers End-use Licence).
- Guide to Eating Ontario Fish: Advisory Database, Ontario Ministry of the Environment, Conservation and Parks. Contains information licensed under the Open Government Licence – Ontario.
Lake St. John is 6.1 m deep at its deepest point, shallower than 86% of the 2,688 surveyed lakes in Ontario. It covers 6.54 km² and lies beside Longford.
Government surveys have recorded 18 fish species here, including yellow perch, pumpkinseed and walleye.
- Maximum depth
- 6.1 msurveyed 1968
- shallower than 86% of the 2,688 surveyed lakes in Ontario
- Area
- 6.54 km²
- larger than 93% of the 18,731 lakes in Ontario
- Shoreline
- 16.1 km
- longer than 84% of the 18,731 lakes in Ontario
- Water clarity
- 2 mSecchi depth, 2025
- less clear than 86% of the 1,251 monitored lakes in Ontario
- Fish species
- 18
- more than 94% of the 2,454 surveyed lakes in Ontario
- Elevation
- 214 m
Today on the water
5.6 °C
Observed at Orillia, as of 3:00 a.m. EDT
choppy Estimated waves, next 12 hours: up to 0.3 m. Around 12 p.m., wind from the northwest: the northwest shore is sheltered, waves build toward the southeast shore.
| Time | 4 a.m. | 7 a.m. | 10 a.m. | 1 p.m. | 4 p.m. | 7 p.m. | 10 p.m. | 1 a.m. |
|---|---|---|---|---|---|---|---|---|
| Wind km/h | W 15 | W 15 | NW 20 | NW 30 | NW 30 | NW 15 | var. 5 | var. 5 |
| Gusts km/h | 50 | 50 | ||||||
| Waves (est.) m | 0.2 | 0.2 | 0.2 | 0.3 | ||||
| Temp. °C | 4 | 5 | 9 | 13 | 15 | 12 | 8 | 5 |
| Precip. % | 40 | 40 | 40 | 40 | 20 | 20 | 0 | 0 |
Tonight: Partly cloudy with 60 percent chance of showers. Risk of a thunderstorm early this evening. Wind northwest 30 km/h gusting to 50 becoming light this evening. Low plus 4.
Weather: Orillia (local forecast), as of 3:03 a.m. EDT
Sun and moon
- Civil dawn
- 6:55 a.m.
- Sunrise
- 7:25 a.m.
- Sunset
- 6:43 p.m.
- Civil dusk
- 7:12 p.m.
- Moonrise
- 6:17 a.m.
- Moonset
- 6:01 p.m.
- Moon
- Waning crescent, 1% lit
Air Quality Health Index
1 low risk
Barrie, as of 2:00 a.m. EDT
Follow this lake by email: a weekly summary of conditions.
Depth
The government depth survey from 1968 records a maximum depth of 6.1 m, drawn from 11 depth contours.
- Download the depth map (SVG)Printing this page gives the map on one sheet, with scale and sources.
Not for navigation. Depths are from government surveys and may be outdated.
Fish
Sport fish by the share of the 49 government surveys (2008–2014) that recorded them.
Forage fish and other species (9)
Forage fish
- Golden Shiner 9
- Bluntnose Minnow 3
- Emerald Shiner 2
- Blackchin Shiner 1
- Blacknose Dace 1
Other
- Brown Bullhead 20
- White Sucker 10
- Bowfin 5
- Common Carp 1
Numbers are the surveys that recorded each species.
Eating your catch
The provincial guide to eating fish (2026) sets limits for 11 species from Lake St. John. Maximum meals per month:
| Species | Length | General population | Sensitive population* | Contaminant |
|---|---|---|---|---|
| Black Crappie | 20-25 cm | 12 | 12 | PCB |
| Largemouth Bass | 30-35 cm | 12 | 4 | Mercury, PCB |
| Northern Pike | 55-60 cm | 12 | 4 | Mercury |
| Pumpkinseed | 15-20 cm | 16 | 16 | PCB |
| Rock Bass | 15-20 cm | 16 | 8 | Mercury |
| Smallmouth Bass | 35-40 cm | 4 | 4 | PCB |
| Walleye | 40-45 cm | 12 | 4 | Mercury |
| Yellow Perch | 20-25 cm | 16 | 8 | Mercury, PCB |
| Brown Bullhead | 25-30 cm | 12 | 12 | PCB |
| Common Carp | 60-65 cm | Do not eat | Do not eat | PCB |
| White Sucker | 40-45 cm | 8 | 8 | PCB |
* As defined in the guide, including children and people who are or may become pregnant. Limits are for the length the guide lists most often; they change with the size of the fish. Read the official guide
Fishing regulations: Fisheries Management Zone 16. Check seasons and limits before you fish.
Water
Clarity was measured with a Secchi disk in 16 years between 1992 and 2025; the latest annual mean is 2 m.
Getting on the water
1 listed boat launch; 1 with parking listed. marks launches on the map.
- Emergency Access
Follow this lake
Every Friday by email: the Environment Canada forecast and any weather alerts in effect.