Every time i quit/force quit inside a volcano, it resets the season to Day 60 and the start of Dry Season. This happened twice to me. Once during mild season (Day 78) and during early hurricane season (Day 106).
I entered the volcano to gather some elephant cacti and some gold. My booty bag burned from a random lightning....in both instances. Pressed Cmd+Q (on Mac) to quit. When i log back in, I'm reliving Dry Season again.
The days remaining seem to change for both day resets though. The first time my Day reset, I had 13 days remaining in Dry season. The second time it reset, I had 12 days remaining in Dry Season. I'm using a mod for showing more status so i noticed this the second time it happened.
It also messed around with my day counter. In the volcano it reset to Day 60, but when I exit the volcano, it continues on with the day i had before i entered the Volcano (Day 107)...but STILL Dry Season.
However, maps, items, and stats remain the same. Previously Foraged / Dugged Up / Mined items in Volcano aren't reset. Only the season and the days changes.
Quit without saving inside the volcano. May have to have a previous save inside the volcano during dry season to trigger.