Literally every other Willamette Valley location was cooler than normal in May. And Cottage Grove is the closest reliable one with a long term record.
Corvallis ran below their long term mean in March. Two other stations south of the valley mentioned by Omegaraptor, Medford and Roseburg, saw below normal months as recently as March. And yet EUG hasn't managed one in over a year...the overall stats around them say they are the outlier.