People Staying In Rv Parked On My Property (ca)

There is a nice RV parked on our property. It’s a largely unused portion of our land but it is the only flat area in the neighborhood. I don’t generally mind when folks park there for a few hours or construction vehicles use the space, but these folks but been there about 36 hours and we have big rain storms this week.
I spoke with the guy in the RV today and he seems ok, he is a friend of a neighbor. The neighbor owns the RV. The friend is visiting for the whole week through Thanksgiving. Thus far they don’t seem problematic.
Is there any legal risk with allowing them to stay? The items I have considered are: - tenancy laws if they’re on property for more than 72(?) hours - a tree falling on the trailer becomes our liability - they could dump sewage in the creek just behind the RV
I don’t really want to ruin someone Thanksgiving, but also don’t want to make a dumb decision.
TIA!
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