Regina is best visited between June and September. Summer brings long warm days, a prairie sky that seems impossibly large, and enough sunlight to justify the city's claim to be among the sunniest in Canada. Temperatures regularly reach 30°C in July and August, and the evenings are warm enough to sit outside well into the night. The Roughriders season runs through football season, adding a civic energy that the city lacks in the offseason.
May and September are excellent transitional months: cool mornings, clear days, and without the full summer heat. The Wascana Park waterfowl are particularly active in May during nesting season. September brings the Cathedral Arts Festival.
Winter is challenging. Regina is one of the coldest major cities in Canada — temperatures of -30°C or colder are not unusual in January and February, and the wind across the flat prairie adds considerably to the perceived temperature. The city is well-equipped for winter life (heated underground connections between downtown buildings, good public spaces), but visitors who arrive unprepared will be miserable. If you must go in winter, dress in proper layers, and do not underestimate what -30°C with wind feels like.