you switch from heat to a/c in the same day. sunday the temp was in the 50's all day, and down into the 40's at night. so when we got home sunday evening i got a fire going and burned through the night. yesterday it was almost 90. last night we ran the a/c in our bedroom to cool it down and cut the humidity a bit. it's funny, someone sent me one of those "you know you live in the north country if..." emails a few weeks and one of them was "you switch from heat to a/c in the same day. i didnt actually think it was possible!