The first-half of September was a lot warmer than the second-half in Portage la Prairie, according to local weather observer Henry Romance.
From September 1st to the 15th, the daily average high was 24 while the average low was 10.3. For the second-half, the average daily high and low dipped down to 17.9 and 6.9 respectively. For the entire month, the average high was 20.0 and the average low was 8.6. 2021 was a bit warmer (22.7 and 9.9) while 2020 was a bit cooler (18.9 and 6.4).
Precipitation-wise, Portage saw 50 millimetres of rain. This is almost the same amount that fell in September for 2021 and 2020 combined. (27mm and 25mm.) Only one day saw some thunder -- one "short, faint bang" was recorded on a Monday afternoon, just before 4 p.m. The first bit of frost was recorded on the 24th.
You can see the latest weather forecast here.