It is possible to make some generalizations about the weather in Banff National Park. July is the warmest, with average highs of 22°C in the Town of Banff. January is the coldest month with average lows of -15°C, though the mercury can drop into the minus thirties. The relative dryness of the air in Banff, however, makes even extreme temperatures more bearable.
In winter, visitors must be especially careful of wind chill. A temperature of -20°C on the thermometer may feel like -30°C with the wind chill. Regardless of the season, the temperature will fall about 1°C for every 200m of elevation gain.
The length of the day in Banff varies greatly throughout the year. Daylight can last as little as eight hours in December. At the end of June, the sun rises at 5:30 am and sets at 10:00 pm.
The tables below give more detailed information about temperatures, precipitation and sunlight for the Town of Banff and the village of Lake Louise.
An element of the weather in Banff National Park that one can always count on is the snow. In the alpine and sub-alpine zones (above and just below the treeline), there is more precipitation in the form of snow in the winter than in the summer. In the montane (the valleys), there is more precipitation in the form of rain in the summer than in the winter.
The mountains of the Continental Divide are well suited to collecting snow from the clouds that pass over. The divide includes the Main Ranges of the Rocky Mountains, along the western side of the Park. Lake Louise is set in the Main Ranges along the divide. Even though the village of Lake Louise is only 130m higher than, and 55km away from Banff, it receives 76cm of snow in December while Banff gets only 44cm. A drive along the Icefields Parkway from Lake Louise to Jasper allows visitors to view many of the glaciers along the Continental Divide that are fed by this high snowfall.
Throughout the park, whether you are in the Rockies' Main Ranges or its more easterly Front Ranges, on the hiking trails or on the highways, you should treat the snow with respect. The town of Banff receives appreciable amounts of snow through into the spring, and the snow returns in late autumn. From November to March, make sure your car is winterized, and that you have snow tires, chains, proper clothing, and emergency candles. The mountain passes of the hiking trails may not be clear until the end of June. Never assume that because the trail or road is clear at your feet that it will be clear at your destination.
Avalanches are a particular snow hazard in mountainous areas such as Banff National Park. Traveling through the backcountry of Banff immediately after a heavy snowfall can be beautiful, but it can also be very dangerous. In the day or so following such a snowfall, the snow has not had time to settle, and is very unstable prime avalanche time. In early spring, there is the danger of climax avalanches. When the snow has accumulated to maximum depths and is beginning to melt, the whole depth of a snowpack may come down in an avalanche.
Educate yourself about the dangers of avalanches. Find out about the latest avalanche conditions before skiing or hiking in areas and conditions of avalanche risk. Reports are available by calling the Canadian Avalanche Centre at 1-800-667-1105 or the Banff Warden Service at 762-1460 (recorded message) .
Likely the most reliable characteristic of the weather in Banff National Park is its variability. The weather at one point in the park may be quite different from that of other points relatively near by. At one specific location the weather can vary considerably from year to year, and from day to day, so be prepared! Even if it is warm and sunny at the trailhead, take rain gear and a sweater. You might need them by the time you reach your destination.
The weather can also change dramatically throughout the day. The dryness of the air causes temperatures to vary considerably from night to day. The temperature on a summer night can drop to a few degrees above freezing even if daytime temperatures climbed into the upper twenties.
Vacationing in such a variable climate means thinking ahead. If you plan to ski, hike or drive in (or into) circumstances where the weather could be a danger, be sure to get the most up-to-date condition reports possible. The Visitor Centres in Banff National Park can provide you with current conditions. The Weather Office in Banff has an up-to-date recorded message that gives the daily forecast, and any advisories or warnings for Banff and the other mountain parks. Their number is (403) 762-2088.
There are certain constants that continually affect Banff National Park's weather: the Park's latitude, the Pacific air from the west, the mountains that surround and fill the Park (particularly those of the Continental Divide), and the occasional spurt of continental air from the east.
Like any place, the Park's global latitude accounts indirectly for some of its weather patterns. In winter, the sun stays up for only a short while and hits the ground fairly obliquely, providing relatively little heat and keeping temperatures low. In summer, the sun stays in the sky for a relatively long period of time, but its rays hit the ground at a fairly oblique angle, diminishing its warming power.
The prevailing westerly winds are perhaps the most influential factor in Banff's weather. These winds bring moist Pacific air from the ocean, across British Columbia toward Banff National Park. As this moist air is forced up over mountain peaks, it cools. The cool temperature causes the moisture in the air to condense and precipitate out. As the air descends on the downwind side of the mountain, it warms and stops precipitating.
The last great hurdle that the moist Pacific air has before entering Alberta is the mountains of the Continental Divide. This formidable barrier pushes the air to new heights, lower temperatures, and wrings a great deal of the remaining moisture out of the air. As the now dryer air descends and warms, it flows through the less contiguous Front Ranges, depositing much less precipitation.
On occasion the wind will come from the east, pushing continental air up over the mountains. In this case, the normal situation is reversed, and precipitation is deposited on the Front Ranges. This upslope weather happens in the early summer, and also gives Banff the occasional mid-winter cold spurt.
Climate, more than any other factor, determines what will exist in an ecosystem. The climate is the primary determinant of what types and amounts of vegetation will exist in an area. The types and amounts of vegetation determine the types and numbers of herbivorous and omnivorous animals. At the top of the ladder are the carnivores, dependent on all below them. So the answer to the above question is, "Climate influences everything in Banff National Park!"
Wildlife habitat is sculpted by the weather. During the winter some animals, like bears, can hibernate. Others animals, like voles, adapt by traveling through tunnels in the snow. Still others, like bighorn sheep, are dependent on the grass that hides beneath the snow. In the winter, they must make their way down toward the montane valleys or to the few windswept slopes to find food. Their long term populations are determined by the numbers that their winter habitat will support.
Humans in Banff National Park have habits similar to those of the wildlife, and we respond to the changes in weather in a similar way. In winter, we may choose to hibernate in our own way. Those that do not, stay pretty much to the montane valleys, perhaps traveling to the few high mountain slopes where the conditions are right for skiing. In the summer we again range high up into the mountains to hike, ride horses, bike, climb.
Visitors to Banff National Park must remain aware of the effect that climate has on all the animals (humans included) in the Park. Make sure that you are informed, and prepared to enjoy and endure all of the kinds of weather that you will encounter. Please be sensitive to Banff's wildlife and to their efforts to respond to the park's climatic cycles. Remember that humans share Banff's valleys and mountains with the park's wildlife and vegetation.