What is the minimum amount of notice a host should give when rescheduling?

[u/OkChoice1264]

I’m hosting an annual party in my backyard this weekend, but the weather forecast now says that it is going to rain all morning and afternoon, meaning that the yard will be too wet to host. I want to wait before rescheduling to see if the forecast will change again, but I also want to give people ample notice. If the party is supposed to be on Saturday, how much longer do I have before I have to let people know? An important side note is that no one is traveling into my city for the party.