Lake St. Peter

Where Lake St. Peter is

Lake St. Peter lies in the County of Hastings, within the Municipality of Hastings Highlands.

How deep is Lake St. Peter?

The deepest mapped contour on Lake St. Peter is 27.4 meters, and the water within that boundary descends even farther. Ontario’s bathymetry record holds 27 depth contours for Lake St. Peter.

See also Ontario's Largest and Deepest Lakes

Surveyed Depths

Ontario has surveyed the depths of several thousand of its lakes over more than half a century. Later surveys were conducted by boat with satellite positioning and produced hundreds of thousands of soundings per lake. Earlier surveys were charted by running transects across the water and drawing depth contours by hand.

Water quality

Ontario’s Lake Partner Program is a volunteer monitoring network. Participants collect water samples for phosphorus analysis and measure water clarity through the summer with a Secchi disk. Most sites are sampled for phosphorus once a year, in spring, and some several times a year between spring and fall. Phosphorus in many lakes rises through the summer, so the two kinds of average are measured on different bases.

Phosphorus is the nutrient that controls how much algae a lake can grow. A lake with little phosphorus stays clear and supports cold-water fish such as lake trout. As phosphorus rises, algae increase, the water clouds, and oxygen in the deep water falls as the algae decay. The province classifies each monitoring site by its average phosphorus:

• Oligotrophic, below 10 micrograms per litre: clear water and low algae.
• Mesotrophic, from 10 to 20: moderately productive water, with more algae and weed growth than an oligotrophic lake but rarely a bloom.
• Eutrophic, above 20: nutrient-rich water, prone to algal blooms and low oxygen at depth.

Lake St. Peter has 3 Lake Partner monitoring sites. One of them has reported phosphorus for the three or more years the province requires before a status is assigned, and is classified oligotrophic.

The longest record is held by site 5147/1 at Mid Lake, deep spot, with phosphorus sampled once a year over 10 years to 2025. Its long-term mean phosphorus concentration is 7.29 micrograms per litre, within the oligotrophic band, which extends to 10.

A Secchi disk is a white or black-and-white plate lowered on a marked line until it disappears from view. The depth at which it vanishes is the Secchi depth, a direct measure of water clarity. Clearer water gives a deeper reading.

The 59 clarity readings at site 5147/1 give a median Secchi depth of 2.8 meters.

Median Secchi depth by year at site 5147/1

See also Lake Water Quality and Blue-Green Algae in Ontario

Lake St. Peter Weather

The weather page for Lake St. Peter carries the forecast over the water, wave heights across the lake, and the modelled water temperature.

Lake St. Peter weather

Water temperature

Ontario’s aquatic resource records class Lake St. Peter as a cold-water lake.

A lake separates into layers through the summer where it is deep enough. Sunlight and wind warm and mix the upper few meters, and beneath a band of rapid cooling, the thermocline, the water stays cold. A shallow lake mixes to the bottom instead and warms through, sooner in spring and later into autumn.

No provincial monitoring station records water temperature on Lake St. Peter. The weather page for Lake St. Peter carries the LastLake model’s surface water temperature for each day of the coming week. The province’s longest in-water record is kept on eight research lakes near Dorset, sampled since 1976. A reading is taken at the surface, at one meter, at each meter to seven and then every two meters to the bottom, about every two weeks through the open-water season and about monthly under ice. The record holds 5,240 readings at a depth of one meter.

At one meter the eight lakes track one another closely. On a day when several were sampled, the warmest and the coolest lake differed by about one degree in every month of the year, and a 12 meter deep lake and a 37 meter deep lake read within 0.2 degrees of each other from June to October. The weather of the year, and not the lake, sets most of the width of the band below.

Water temperature at a depth of one meter (eight lakes near Dorset, ON)

How depth changes the temperature

The chart below is the province’s record on Harp Lake, 37 meters deep, drawn as the median temperature at each depth for each month over 49 years. In July the water at one meter is 23 degrees, at five meters 15, at seven meters 9, and from 13 meters to the bottom under 6. By October the warm layer has deepened to seven meters and cooled to 11 degrees. In February the whole column sits between 1 and 4 degrees under the ice, coldest at the top.

A shallower lake in the same record warms sooner. Heney Lake, six meters deep, reads about 1.8 degrees warmer than Harp Lake at one meter from January to May, 0.8 degrees warmer from June to August, and the same or cooler from September.

See also Lake Water Temperature in Ontario

Fish in Lake St. Peter

Ontario’s aquatic resource records name 10 fish species in Lake St. Peter. The province’s other records for the lake name one further species, rainbow trout. It appears in the records below.

Popular species in the province’s records

• Lake Trouttrout and whitefish
• Brook Trouttrout and whitefish
• Yellow Perchperch
• Smallmouth Basssunfish
• Largemouth Basssunfish
• Rock Basssunfish
• Pumpkinseedsunfish

Spawning areas

Ontario maps 10 fish spawning records within the Lake St. Peter outline, for two different species, and all of them are mapped below.

By number of records

By area mapped

• Lake Trout7 areas0.5 ha
• Smallmouth Bass3 areas0.2 ha

The federal Fisheries Act prohibits the harmful alteration, disruption or destruction of fish habitat without an authorization, so a dock, dredging, infill or shoreline work at a mapped spawning area is reviewed on that basis.

Stocking history

Ontario’s stocking records for Lake St. Peter run from 1946 to 2014 and hold 80 releases. Lake Trout account for most of the fish: 101,690 released in 40 of the years between 1946 and 2014. The last recorded release was 1,105 lake trout yearlings in 2014.

The province’s record of stocking for recreational fishing, kept from 2016, lists no release into Lake St. Peter.

Eating the fish

The 2026 Guide to Eating Ontario Fish carries consumption advice for one species taken from Lake St. Peter, tested for contaminants at a sampling location in McClure Twp., Hastings Co. Each figure below is the most meals a month the guide advises for a fish of that length. Where mercury sets the advice, the figure falls as the fish gets longer, because mercury accumulates over a fish’s life. Where the guide has no result yet for certain contaminants at a location, it sets a precautionary limit of 16 meals a month. A zero means the guide advises no meals of that fish at that size.

General population: adultsSensitive population: children under fifteen, women who are or may become pregnant

Fisheries Management Zone 15

Lake St. Peter lies in Fisheries Management Zone 15. Ontario sets its fishing seasons and catch limits by zone. The province describes it as a zone of many natural lake trout and brook trout lakes, with a well-developed road network and moderate angling effort.

Fisheries management zones around Lake St. Peter

Where a row reads zone-wide, the zone’s own season or limit above applies. Lake Trout: Only one line may be used when angling through the ice.

See also Fishing Seasons in Ontario, Zone by Zone and Fish Stocking in Ontario Lakes

Lake St. Peter Ice Fishing

An ice hut on Lake St. Peter must be removed by March 31. The province sets dates for ice hut removal as a safety measure to ensure huts are removed before thawing occurs. One date applies to an entire fisheries management zone (FMZ). Lake St. Peter lies within FMZ 15.

An ice hut must also be removed before the ice breaks up, whether or not that date has passed. The deadline clears huts from the ice ahead of the thaw and does not close the fishing season.

Registration is required in FMZ 15 for an ice hut built of anything other than fabric, and for a fabric tent covering seven square meters or more. Registration is free, and the number is displayed on the outside of the hut.

Ice In / Out Date

No ice record is kept on Lake St. Peter. The province’s nearest long record covers eight lakes near Dorset, about 72 kilometers away. It holds a date for every winter since 1975, observed by eye and from cameras set on the shore.

On those eight lakes the median date of complete ice cover is December 7 and the median date of complete ice loss is April 20, a median season of 134 days.

The date the ice forms has moved later through the record: a November 26 average across 1971 to 1980, and December 11 across 2011 to 2020. The date it leaves has moved by less than a day each decade over the same period. The two charts below are drawn to one scale of 26 days, so they can be read against each other.

Ice in date (eight lakes near Dorset, ON)

Ice out date (eight lakes near Dorset, ON)

Ice conditions

No public record reports the thickness or the condition of the ice on Lake St. Peter on any given day. Ontario publishes ice safety guidance for anyone going out on the ice, at ontario.ca.

See also Lake Ice in Ontario and When the Lakes Will Freeze This Winter

Islands and names

Lake St. Peter contains one island in the Ontario Hydro Network’s outline, of 0.3 hectare.

Official names

Ontario’s geographic names register lists 3 official names on the water and its islands: 1 island. The register records the origin of one name: Summer Island, “The owners of the island spend their summers there.”

Nearby lakes

• Papineau Lake16 km away
• Bark Lake20 km away
• Baptiste Lake21 km away
• Kamaniskeg Lake29 km away

All lakes

Questions about Lake St. Peter

• How deep is Lake St. Peter?

  Its deepest charted contour is 27.4 meters, and the water within it is deeper.

• How big is Lake St. Peter?

  Its surface covers 2.4 square kilometers, with 16 kilometers of shoreline and 1 island.

• What fish are in Lake St. Peter?

  Ontario’s aquatic resource records name ten species, among them lake trout, smallmouth bass, largemouth bass, yellow perch and brook trout. The lake’s spawning, consumption and stocking records also name rainbow trout.

• Is the water clear?

  The one monitoring site with a phosphorus status is classified oligotrophic, the clearest of the province’s three bands.