Guide to Long Range Weather Forecast Canada

Isopleth Map

Although long-range forecasts are inherently uncertain, there are a lot of factors that can affect their accuracy.  Natural variability in the atmosphere and unpredictable events like sudden changes in sea surface temperatures and atmospheric circulation patterns are among them.

Meteorologists and climatologists evaluate past forecasts and compare them with actual weather conditions to assess the reliability of ECCC long-range forecasts.  Known as verification, it helps identify areas where forecast models need to be adjusted or improved.

Although ECCC long-range forecasts can be useful for predicting weather and climate conditions, they're not infallible and actual conditions may differ from what's predicted.  To get a better idea of what to expect in the coming days and weeks, it's always a good idea to check out multiple sources of information, including local weather reports.

Why and How?  The other maps in this section show you how these forecasts have held up over time.  Currently it's impossible to predict daily highs and lows more than a week or two in advance, and many scientists say it'll never be possible.    Complications like the butterfly effect limit weather forecasting.

There's another section on this Environment Canada website that gives climate normals (a summary of average conditions).  Here's a weather almanac Canada consultants and forecasters use.  El Niño or La Niña is one of the biggest indicators of long-term weather.  You can explore the effects of these large scale meteorological and oceanographic trends at the bottom of the ECCC webpage.

Here's what else you can try: First, go to dryday.com and enter your location for a 30-day weather forecast (probability of precipitation), then go to weatherspark.com and enter your location for climate comparisons.  Finally, let us know what you think.

The following organizations and institutions produce long-range weather forecasts:  

- A long-range forecast is produced by the National Oceanic and Atmospheric Administration (NOAA) using computer models, satellite data, and historical weather patterns.  Also, they take El Niño or La Niña into account.

- Weather forecasts are produced by the European Centre for Medium-Range Weather Forecasts (ECMWF), an international organization.  Their forecasts are based on computer models, satellite data, and ground-based observations.

- In the United Kingdom, the Met Office uses a similar approach to NOAA and the ECMWF, combining computer models with satellite data and observational data.  Weather forecasting company AccuWeather uses its own proprietary models and data sources to produce long-range forecasts.

Depending on the region or type of weather, different organizations make "best" long-range forecasts.  All of the organizations listed above have a good track record for long-range forecasts.