Should anyone's lower cost/previously owned/older/gift panniers prove to be less than 100% waterproof, there are pannier rain covers. Multiple suppliers, styles, sizes, coverage, attachment, materials, colors, price points.
Yep. My first set of panniers were made by Robert Beckman Designs. The rain covers were made to fit the bags. The one minor inconvenience was having to remove them and put them back on if you wanted to retrieve anything. Also stopping to put them on if rain popped up unexpectedly.
On the road to Red Willow Lake in ND on July 4th, 1999. I had put on the front covers preemptively because I had thousands of dollars worth of camera equipment up front. It ended up not raining that day.
