Late May - Early September
Peak season in Ottawa lasts from Victoria Day (late May) until Labor Day (early September). The temperature usually ranges from 20C to 32C. Thunderstorms and high humidity are possible, particularly in the late afternoon, but smog is rare and many days are clear and sunny. Book at least a few weeks in advance, particularly on long weekends. Museums and Parliament Hill will be crowded but not unbearable. The largest crowds gather on Canada Day (July 1, www.canadascapital.gc.ca/canadaday), when parts of the downtown core are closed to traffic so revelers can enjoy free concerts and fireworks. Music festivals, particularly Bluesfest (early through mid-July, www.ottawabluesfest.ca), can also be quite crowded. Despite the heat and crowds, this is a great time of year to visit the city, because many attractions close or shorten their hours during the off and shoulder seasons. Pack lightweight clothes, an umbrella, a light jacket and sunscreen. Casual clothes will suffice for all but the fanciest restaurants.
November - April
Weather during this period is often grey, damp and cold, particularly in January and February, when temperatures can drop below -20C. Many small museums and outdoor attractions close completely, and even the large museums shorten their hours. During the week, downtown hotels are often heavily booked with meeting and convention travelers, but deals are often available on the weekends. One exception is Winterlude (the last weekend in January and the first three weekends of February, www.canadascapital.gc.ca/winterlude/). If you’re hoping to attend this popular winter festival, book your hotel several months in advance. From December through March, bring boots, a hat, gloves and a warm coat; treat your boots with a salt-resistant spray to avoid stains. In November and April, bring an insulated, water-resistant coat and umbrella.
April - Late May and Early September - End of October
The shoulder season in Ottawa lasts from roughly Easter to Victoria Day and from Labor Day to the end of October (although many places shorten their hours after Canadian Thanksgiving in early October). Many smaller attractions are open for limited hours (often weekends only); some are closed completely. However, the weather this time of year is some of Ottawa’s nicest; sunny days with temperatures between 10C and 20C are common. Crowds are smaller at major attractions, such as Parliament Hill and Gatineau Park. During the Canadian Tulip Festival (mid-May, www.tulipfestival.ca), city parks bloom with hundreds of thousands of tulips. Book your hotel room at least a month in advance. Bring a lightweight jacket and an umbrella.