Ontario is Canada's most visited province and home to two of the country's iconic destinations: Toronto and Niagara Falls. The province spans from the Great Lakes in the south — with a climate similar to the US Midwest — to the boreal forests of the north, where Algonquin Provincial Park and the Canadian Shield define the landscape. Southern Ontario has four distinct seasons. Summers are warm and humid; falls are spectacular for colour; winters bring significant snowfall; and springs are mud-season short but beautiful. For most visitors focused on Toronto, Niagara, and the national parks, the window from May through October covers everything.
Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
| Shoulder | Shoulder | Shoulder | Good | Good | Good | Peak | Peak | Peak | Peak | Off-season | Shoulder |
Peak season — Niagara Falls, Muskoka lakes, Toronto festivals
Summer in Ontario is warm (Toronto averages 27°C in July), humid, and very busy. Niagara Falls is at maximum flow in summer and the tourist infrastructure — Maid of the Mist, Journey Behind the Falls, Skylon Tower — is fully operational. The Muskoka lakes district north of Toronto fills with cottagers from Victoria Day (late May) through Labour Day. Algonquin Provincial Park is at peak for canoe trips — book interior campsites months in advance. Toronto hosts some of its best festivals in summer: Pride (June), the Canadian National Exhibition (late August), and the Toronto International Film Festival begins in September.
Outstanding fall colours — arguably the best in Canada
Ontario's fall colour is among the finest anywhere in North America. The Algonquin Provincial Park corridor peaks in early October — the park's mix of maples, birches, and aspens produces reds, oranges, and yellows that cover hundreds of kilometres. The Algonquin fall colour webcam (available through Ontario Parks) lets you track the peak from home. The Niagara wine region in October is at its most atmospheric with harvest underway and Niagara-on-the-Lake quieter than summer. Toronto in October is excellent: comfortable temperatures, no humidity, the best restaurant season.
Niagara ice season, skating on the Rideau Canal, quieter travel
Winter in Ontario is underappreciated by visitors. The Rideau Canal in Ottawa (170 km, the world's largest naturally frozen skating rink) is one of the great winter experiences in Canada, typically open January through February. Niagara Falls in winter — when the American Falls partially freeze and ice formations build around the base — is one of the most dramatic natural scenes in Ontario. Toronto in winter is a genuine city-break destination: world-class museums, restaurants, and the indoor PATH system means you can spend days exploring without going outside in the cold.
Waterfalls, wildflowers, and Niagara blossom season
Spring in Ontario brings Niagara Falls to its highest flow of the year as winter ice melts upstream. The American and Canadian Falls thunder with maximum volume from March through June. The Niagara region's peach and cherry orchards bloom spectacularly in April and May. Wildflower season in Ontario's forests peaks in May — the trillium (Ontario's provincial flower) blankets the forest floor of Bruce Peninsula and the Niagara Escarpment. Spring migration brings millions of birds through the Point Pelee National Park corridor — one of the best birding events in North America.