Greetings from Southern Oregon,
The most commonly recommended time to travel the Rogue-Umpqua Scenic Byway is June through October, mainly to ensure clear roads, fair weather and more daylight hours. Volumes of water running in the falls largely depend on wintertime precipitation. We’re off to a good start for this year, considering the flood warnings throughout Southern Oregon several weeks ago. And Crater Lake started seeing enough snow in October to close some roads.
You could plan your trip in mid- to late spring, but mountain travel in this region could still be unpredictable then. If I were planning the trip for myself, I would check the National Weather Service’s precipitation records for this region throughout the winter to confirm they were average or above, obtain extended weather forecasts for the period that I wanted to visit and verify favorable road conditions on ODOT’s website, www.tripcheck.com.
Here’s a story from the Mail Tribune newspaper on the Rogue-Umpqua waterfalls that may help: http://www.mailtribune.com/apps/pbcs.dll/article?AID=/20080313/LIFE/803130301&cid=sitesearch