Summer makes my cycle shorter?

So I've been tracking my period for the past three years via an app. I have PCOS so I have quite long cycles but I am quite in tune with my body and know when to expect them, and although the cycles are long they are quite regular and tend to be within 1 - 3 days of the apps prediction.

A week ago, my period came weeks early with NO symptoms - completely blind sided me. I logged the period in the app and when I did this I took a brief look back at other logged periods and noticed a trend - my cycles are shorted during the summer? Who knows, this might be a complete coincidence; but this extra early period follows the pattern that the last three summers have too!

Have you guys ever noticed this, or even know why this happens? Or am I just imagining it lol.