Please help what are fun things to do?

My friend and I are 13 years old and we are super bored we don't want to use electronics or anything similar. We have at least 3 acres to do stuff on a barn, and a lake. Sadly it's too cold to swim in the lake. but, it's not snowing, it's only a little chilly. We can go outside no problem. We kind of live in the middle of no where so we can't go to the mall, but there's a party store close by.