On Your Mark, Get Set...

Try this mathematical equation to predict when your favourite fishing lake will freeze.

It happened this past weekend in Northwestern Ontario, and in many other areas across Northern Ontario. No, not the Santa Claus parade. Many of the small and moderate size lakes froze over, making ice anglers light-headed with anticipation.

So giddy, in fact, that I've been fielding email messages from ice anglers to the south of us who are biting their lips in eagerness. The hard water brigade wants to know if the ice is safe enough yet to venture out on, and if it is not, when do I think it will be.

young male ice angler holding walleye

If you're wondering how soon it will be before the ice on your favourite Northern Ontario walleye lake is good enough to walk on, check out Gord Pyzer's formula in this blog.

In a word, the answer is "no," the ice is definitely not thick enough yet to walk on. The good news, however, is that by monitoring the air temperature and wind speed in your home area, you can use a very simple and cool—sorry, pun intended—mathematical formula to predict when your favourite Northern Ontario lake will be safe to fish.

angler with ice auger

Many of the small and moderate size lakes in Northern Ontario have started freezing over, making ice anglers giddy with anticipation.

Here is how you can do it—or better yet, if you have kids at home who are chomping at the bit to go ice fishing, how you can put them up to the arithmetic challenge.

Start by taking the average temperature (in degrees Fahrenheit) over the past 24 hours. Let’s say that the daytime high yesterday was 30° F and the nighttime temperature last evening was 20° F. This means the average temperature was 25° F. Now, subtract the average temperature (25° F) from the freezing point of water (32° F) and we get 7°... or more importantly, seven freezing degree days (FDDs).

That was simple, right?

Now, everything kicks into gear when your favourite lake first develops a thin coating of ice. From this stage on, the ice will typically increase in thickness at the rate of one inch per 15 freezing-degree days (FDDS). So, if we go back to our example, this means that if there were seven FDDs over the last 24 hours, the lake added about half an inch of ice.

young ice angler holding trout

Of course, we know that ice builds up more quickly when there is a slight to moderate breeze, no snow on the surface, and clear skies. Snow, in fact, acts like a thermal blanket and serves to keep the frost from penetrating the surface of the lake and the ice. As a result, deep snow cover will slow down the ice formation process significantly.

ice angler holding lake trout

Small and moderate size stocked trout lakes usually offers the best early-season bets for the eager ice angler.

Indeed, as I've mentioned in the past, this is why lakes in the high Arctic don't freeze into a solid block of ice. At some point, the snow and thick ice act as a down jacket to stop the water from freezing any further.

Over the past couple of winters, I have found this formula to be an extremely accurate way to keep track of how much and how fast the ice is forming and building up on my favourite walleye, trout, crappie and yellow perch lakes. And I've been able to keep even more detailed diaries using the following chart developed by my buddy Bob Dostie, who has incorporated information and data that he obtained from the U.S. Army Corps of Engineers.

ice thickness chart

So, forget the Santa Claus parade—the good news is that many of the lakes across Northern Ontario are now finally covered with ice. And if you keep track of the high and low temperature each day, you can accurately determine how fast it is building up.

angler with ice angler

With that in mind, charge the battery in your snowmachine, add gas line antifreeze to the fuel tank, gather up your ice fishing gear from the rafters in the garage, and start sharpening your hooks. The hard water ice fishing season is about to begin across Northern Ontario.

About Gord Pyzer

Gord Pyzer is the fishing editor of Outdoor Canada magazine and field editor of In-Fisherman magazine. He is the co-host of the Real Fishing Radio Show and host of Fish Talk With The Doc.

Recommended Articles

5 Tips for your Fly-in DIY Adventure

Imagine fishing on a secluded pristine remote lake.

Weighting for Panfish

Ice fishing for Ontario Panfish

Shallow Water Walleye

Learn Tips and Techniques From The Extreme Angler

Big Boat Portaging

Fishing on Lady Evelyn Lake in Northeastern Ontario

Prime Time for Ontario Panfish

The best time to ice fish for crappies and panfish is when the predator activity is low

Family Friendly Fishing Getaways in Northern Ontario

Fish TV rediscovers 2 fishing lodges for bass and walleye.

Into the Bear's Den: Bass Fishing on the French River

They say don’t poke the bear unless you are prepared to get bit!

A Multispecies Mecca: Lake of the Woods

From Lake Trout to Pike and everything in between, Lake of the Woods is calling

Bivins’ Bounce Crappies

This technique is a must for crappie fishing

Bobber Down

You’ll double your hook-up ratio and find yourself constantly yelling, "Bobber down!"

The Ultimate Social Distancing Getaway

Lots of wilderness, space, and fresh air in Ontario.

Spring is in the Air

4 tips and recommendations to help prepare anglers for open water fishing season

Top 5 Musky Destinations in Ontario

The Musky Hunter shows you where to land the best musky in Ontario waters.

Crawford’s Diamond in the Rough

A year-round resort for the true die-hard angler on Lake of the Woods

Making Memories

Killarney Mountain Lodge serves as a backdrop for a meaningful outing between friends

Three Surefire Solutions for Catching Canadian Muskies

Ontario, Canada is a dream destination for all musky anglers

Cranking Up The Heat in Northern Ontario

Tips for Using Crankbaits When Fishing Bass

The Spin on Early Season Walleye

Depending on where you are walleye fishing in Ontario, the conditions range from early spring to near summer-like.

Who Let the Dawgs Out

Fishing Muskie on the Ottawa River

Become a World-class Fishing Guide

Misconceptions, behind-the-scenes intel, and key tips from a professional guide.