A year on a BC trout lake, season by season

A BC trout lake runs on a calendar, and the calendar is set by water temperature rather than by the date. The same week in May can be the best fishing of the year on a low valley lake and the week the ice is still going off a plateau lake an hour's drive up the hill. Once you know the stages, and roughly where a lake sits on them, most trips plan themselves.

Ice-off

The ice goes off a lake from the edges in. A dark ring of open water opens along the shore first, then the sheet rots, greys and finally goes in a day or two of wind. Trout have spent the winter under the ice in cold, dim water with little to eat, and they come to the warming margins hungry. The weeks just after ice-off are some of the best of the year, and the shallows matter more than the depth. Stay off ice that is rotting or pulling away from the shore; the open ring is the angler's water.

Spring turnover

Fresh water is heaviest at about 4 degrees. As the surface warms to that point it sinks, and for a few days the lake mixes from top to bottom. The water can turn murky, bottom debris comes up, and some lakes briefly smell of sulphur. Fishing is often slow while it happens. It does not last: once the lake has mixed it is cold and full of oxygen from surface to bottom, and the insects start to move.

The chironomid weeks

Late spring into early summer belongs to the chironomid, a small midge whose larvae live in the mud and whose pupae rise to the surface to hatch in enormous numbers. On many interior lakes it is the most important trout food of the year. Mayflies, damselflies and the first sedges follow as the water warms. This is the season when the shoals, the flat shelves a few metres deep, hold most of the fish. The guide to chironomids covers how to fish it.

Summer and the thermocline

By July a lake of any depth has layered: warm water on top, cold water on the bottom, and a narrow band between them where the temperature drops fast. Rainbow trout feed best in water in the low to middle teens and are stressed as it climbs past about 20 degrees, so in the heat of the day they sit deep, along the drop-offs and in that band. Mornings and evenings still bring them up. A shallow lake with no cold layer can go quiet for weeks, which is when a deep lake or a higher one is the better drive. In warm water, land a fish quickly and keep it wet if it is going back.

Fall turnover and the second season

As nights cool, the surface layer chills until it matches the deep water and the lake mixes again. For a week or two the fishing can be patchy. Then the whole lake is cool and oxygenated, the trout spread back into the shallows, and they feed hard ahead of winter on leeches, scuds, water boatmen and minnows. Fall is the quiet favourite of many BC stillwater anglers: fewer people, bigger fish on the move, and lakes that fish all day.

Freeze-up and winter

Once the water cools far enough, a calm cold night skins the lake over and it stays capped until spring. Some lakes are open to ice fishing and some are closed, and each lake's page says what the regulations on file allow. This site never says whether ice will hold a person. Its winter model only estimates whether a lake has likely frozen. Ask locally and check the ice yourself.

Elevation moves every date

Air cools by roughly six and a half degrees for every kilometre you climb. A lake at 1,400 m sits in air several degrees colder than a lake at 400 m through the whole year, so its ice goes off later, often by weeks, its chironomid weeks come later, and it stays cool into summer when the valley lakes are too warm. Coastal lakes on Vancouver Island and in the Lower Mainland sit low and in mild air, and many barely freeze. The interior plateaus of the Thompson-Nicola, the Okanagan and the Cariboo put many lakes above 1,000 m. The table below counts it.

How high the lakes sit, by region
Region	Lakes with an elevation on file	Middle elevation	At or above 1,200 m
Vancouver Island	136	179 m	0
Lower Mainland	72	158 m	0
Thompson-Nicola	120	1,106 m	43
Kootenays	73	953 m	15
Cariboo	153	1,008 m	23
Skeena	51	851 m	5
Omineca	79	824 m	3
Peace	33	965 m	10
Okanagan	94	1,132 m	40

Counted from the 811 lakes in the atlas that carry an elevation. The middle elevation is the median: half the region's lakes sit above it and half below. A lake with no elevation on file is left out rather than guessed.

Using the calendar

In spring, start low and follow the ice-off uphill week by week. The lake that was frozen last weekend may be the best water this weekend.
In a summer heat wave, climb. A higher lake or a deeper one keeps its fish feeding when a low shallow lake does not.
In fall, work back down. The high lakes cool, turn over and freeze first, and the valley lakes fish on after them.
Whatever the season, the seven-day forecast on each lake's own coordinate tells you which day of the week to go.

Open the map: 1,842 BC lakes, each with a 7-day forecast and a score