Late July/early August in the NWT, flew into the field and it was 70 degrees and sunny. The next day was in the 60's but we were in and out of rain gear several times, and the day ended with a major thunderstorm with winds that substantially challenged the tents.
Rest of the trip was overnight lows in the high 30's/low 40's, highs in the 50's, mostly cloudy, scattered rain storms with the sun occasionally peaking out. The last 3 days in the field we were completely socked in with rain and fog and spent most of the time glassing when we could in rain gear. Once we got back to base camp on day 10, it was sunny and t-shirt weather again.
Basically, I saw every type of weather except for snow over 10 days, and wore everything from a t-shirt to rain gear to down puffy.