Plant closing and notice period questions after 5 years as a customer-service rep

My employer announced that the site will close and gave us written notice. I would rather hear the honest version than the polite one. I do not know if I should start looking now or wait for severance news. What did the workforce office offer?

I stayed for the retention bonus and looked for work on the side. It cushioned the gap.

Keep everything in writing and save the confirmation numbers. It saved me later.