Minneapolis weather in September

Minneapolis's forum calls September a local favorite — not too hot, not too cold, good for biking and hiking — while flagging it as one of the harder months to predict, with unseasonably warm or genuinely cool stretches both common. By the third week, regulars say nights and mornings often sit in the 50s, worth a light jacket.

Regulars describe a real air-mass swing that defines this month: a hot, humid flow from the south can feel almost tropical, then switch quickly to cool, dry air from the northwest - genuinely two different summers within the same week. Our row backs the warm, humid average sitting between those extremes, 26.7C reading as a hot 28C at 70 percent humidity, over 17C nights, with a real 139.1mm of rain across 10.1 days. Regulars are specific that rain here usually arrives as a brief thunderstorm line marking one of those air-mass changes rather than settling into a multi-day soak, and that mosquitoes become a real presence through this muggier stretch of summer. Visitors from a hotter, more humid climate consistently find the overall summer here comfortable by comparison. The record: 10.8 hours of sun, a 15.5 kph wind and AQI 49.

Summer here is two air masses taking turns, and regulars describe the swap: almost tropical air from the south, then a quick change to cool dry air from the north-west, with the heat at its worst from mid-July into early August. Our row averages 28.4C reading as 30C over 18.3C nights at 67 percent humidity, with 86.7mm of rain across 7.9 days and 12.5 hours of sun. On the other summer question they are calmer than visitors expect: mosquitoes drop off considerably by July, they depend on how wet the spring was, and wind and open water keep them down - which is an argument for the lakes rather than against them. The record: a dew point of 16.1C and AQI 58.

Regulars are blunt that May here is a tossup rather than a forecast: mid-month can be in the sixties and seventies by day or in the forties and fifties, and early May can still turn cold and snowy. Our row averages 20.6C over 9.8C with 0.1cm of snow - a trace, which is what a small chance of a late flurry looks like averaged over thirty years. Their advice is layers plus a light jacket, so a warm afternoon does not overheat you and the evening does not catch you out. The lakes in the uptown chain - Bde Maka Ska, Isles and Harriet - rent kayaks and canoes and are walkable all the way round, and mid-May is when the trees finally go green. Rain is 106.6mm across 9 days. The record: humidity 63 percent, 10.4 hours of sun inside 14.9 of daylight, and AQI 49.

June arrives just after the first hatch of black flies and mosquitoes, which regulars date to around Memorial Day weekend, so the bugs are a real part of the month - along with ticks. How bad depends on how wet it has been, and our row's 105.4mm is the wet side of that. Their working rules are the useful part: mosquitoes do not fly well in wind and do not like bright sun, so daylight hours in the open are usually fine, and a breeze off one of the lakes does the job on its own. Dusk and early morning are when the spray earns its place. On heat, June is before the peak - they put that at mid-July into early August - though summer here swings between almost tropical air from the south and cool dry air from the northwest inside a day. The record: 26.7C over 16.1C, 12.1 hours of sun and AQI 59.