To read a marine forecast on a Canadian lake, start with the wind speed in knots, the direction the wind blows from, and any warning in the first two days, because those elements decide whether a trip is reasonable. Environment and Climate Change Canada issues the Great Lakes Regular Forecast at 3:00 a.m., 10:30 a.m. and 6:30 p.m. local time, and a Strong Wind Warning begins at 20 knots, about 37 km/h. The sections below explain each part and how to use it before you leave the dock.
Where do I find the official forecast for my lake?
Environment and Climate Change Canada (ECCC) publishes the official marine forecasts for the Great Lakes. Its Regular Forecast covers the current day and the next day, with detailed wind information and a general description of the weather, so it is the product to check first. If your lake is one of the smaller Ontario waters, use the Recreational Boating Marine Forecast instead. ECCC issues it only from May 1 to November 30, at 5:00 a.m., 11:30 a.m. and 5:00 p.m., and it covers Lake Simcoe, Lake Nipissing, the North Channel of Lake Huron, Lake Nipigon and Lake of the Woods.
For a lake outside these products, the official sources consulted do not specify a dedicated marine bulletin for it. Use the forecast for the nearest area on the Canada.ca weather website instead, and read it with the local caution described in the wind section below.
What do the forecast sections mean?
A marine forecast covers five days, but the level of detail changes across that span. The first 48 hours carry the most information, including warnings, watches and wave heights. The following three days receive a more general outlook, although wind speed and direction are still given for all five days. Read the first two days closely for the decisions you need to make today, and use the rest to judge whether a planned weekend outing is realistic.
Two supporting products add context. The technical marine synopsis describes the position, intensity and movement of the main low-pressure systems, high-pressure systems and fronts affecting the region during the forecast period, which helps explain why the wind is changing. A Marine Weather Statement is a bulletin issued outside the regular schedule for conditions that are not severe but could still be hazardous. It is written in plain language and can flag significant features expected in the three-to-five-day outlook.
How do you read wind speed and direction?
Wind speed in marine forecasts is given in knots. One knot equals 1.852 km/h, so the conversion is knots × 1.852 = km/h. A forecast of 20 knots is therefore about 37 km/h, and 34 knots is about 63 km/h. The figure is the average wind expected over open water. It does not tell you how strong individual gusts will be, so keep a margin below the number you consider manageable.
Direction is the direction the wind blows from, not the direction it is heading. ECCC references it to true north rather than magnetic north. A forecast for a northwest wind therefore means air moving from the northwest, which pushes waves toward the southeast shore. Before you compare a compass bearing with the forecast, convert it to true north, because the difference between the two norths varies by location.
Near shore, the wind may differ from the forecast. ECCC states that wind conditions close to shore may vary from the forecast winds because of coastal terrain. Bluffs, headlands, valleys and wooded shorelines can funnel, block or accelerate the wind. Expect the wind to shift as you round a point, and treat the open-water figure as a guide to the lake, not a promise for the bay you are leaving.
Why do wave heights matter?
The Wave Height Forecast, issued at the same times as the Regular Forecast and covering the current and next day, gives significant wave height in metres, measured from trough to crest. Significant wave height is the average of the highest one-third of waves, not the maximum. Some individual waves in a group will therefore be noticeably higher than the published value, so the figure does not mean every wave stays below it.
Use the wave height as a planning measure for how your boat will behave, not as a comfort threshold. Compare it with the limits stated in your boat’s manufacturer documentation, which describe the conditions the boat was designed or rated for. Keep in mind that the Recreational Boating Marine Forecast does not include wave heights. The official sources consulted do not specify where wave heights for those smaller Ontario waters are published, so check the Canada.ca marine pages before you go out.
What do the wind warnings mean?
For the Great Lakes, ECCC uses four wind warning levels, based on the forecast wind speed in knots:
- Strong Wind Warning: 20 to 33 knots, issued from May 1 to November 30.
- Gale Warning: 34 to 47 knots.
- Storm Warning: 48 to 63 knots.
- Hurricane Force Wind Warning: 64 knots or more.
Wind, gale, storm and hurricane-force warnings are part of the Regular Forecast and are not issued as separate bulletins. Read the whole Regular Forecast, not only its opening line, because a warning can appear within the body text. Localized warnings and watches, by contrast, are issued as separate bulletins, so check for them as well.
When are forecasts issued and updated?
For the Great Lakes, the Regular Forecast and the Wave Height Forecast are issued at 3:00 a.m., 10:30 a.m. and 6:30 p.m. local time, using Eastern Daylight Time or Eastern Standard Time depending on the season. The Extended Forecast is issued at 3:00 a.m. and 6:30 p.m. The Recreational Boating Marine Forecast follows its own schedule of 5:00 a.m., 11:30 a.m. and 5:00 p.m. during its season.
Use the issue time printed on each bulletin. A forecast issued at 3:00 a.m. may be out of date by midday, because a newer issue can replace it. Before you leave, check the most recent issue, and check again before you commit to a longer route or a return trip.
How do you decide whether to go out?
Start from the most recent Regular Forecast for today and tomorrow, and read the wind speed, wind direction, warnings and wave height together rather than one at a time. Then apply these checks:
- If a Strong Wind Warning or a higher level applies to your area, postpone the trip. A warning means the forecast has identified conditions serious enough to name, so plan around the postponement, not around the warning.
- Compare the wind and waves with what your boat and crew can handle. Use the manufacturer documentation for your boat’s stated limits and your own experience, and remember that the wind figure is an average.
- Check the trend. If the next issue or the Extended Forecast shows wind building through the period you intend to be on the water, shorten the trip or choose another day.
- Set a turnaround point before you leave. Agree with everyone aboard on the signs that mean you return, such as a wind shift, a fast build of cloud, a rise in wind or a sudden drop in temperature.
- File a trip plan with someone on shore, including your route, your expected return time and what they should do if you are overdue.
Once you are underway, keep watching. If conditions worsen faster than the forecast suggested, head for the nearest sheltered water while it is still safe to do so, and remember that the wind near the shore can differ from the open-water figure you planned around.
Frequently asked questions
Does a Hurricane Force Wind Warning mean a hurricane is coming?
No. The category is defined by a forecast wind speed of 64 knots or more. ECCC states that it does not mean an actual hurricane is expected or occurring. Treat it as a severe wind warning and stay off the water.
What is freezing spray, and when should I check for it?
Freezing spray is sea spray that freezes on a boat’s surfaces and adds weight to the vessel. ECCC issues a freezing spray warning when ice build-up of 0.7 cm per hour or more is expected. The warning appears within the Regular Forecast, so check it in cold weather, even on a calm day.
