Question about TS Hanna

I have been watching the weather and it now seems that TS Hanna may be affecting our area this weekend.  When is a decision made about whether we will swim or not? How will we be notified?  Is there an alternative date in these type of extreme cases?  A tropical storm going through here, even the night before, would really agitate the river.  Just getting a little nervous, because I really want for the swim to happen, but I want to make sure it is safe since it is my first time.  Thanks for your reassurances and information ahead of time.