For the start of the Eugene Marathon look for morning clouds with temperatures in the upper 30’s to near 40. The sun will start peeking out maybe in the morning but definitely  by the afternoon (the race will be over by then except possibly for the slower walkers) when the high temperature hits 66. Bad weather for the marathon would be bright sunshine with no clouds in the sky and very warm temperatures or overcast and very chilly with rain and wind. None of that will be happening, so get out and enjoy the day whether you are in the marathon, watching the marathon or doing something else altogether different.