While a determination on whether a new Portland ballpark will have a retractable roof has yet to be made, it is worth noting that Portland offers glorious baseball weather during the summer months – clear sunny skies, warm temperatures and low humidity. Only five MLB cities record less rainfall than Portland’s 12″ during the Major League Baseball season. In comparison, the Washington D.C. area receives over 25″ of rain from April to October.
Even during the entire eight weeks of April and May, Portland receives barely over four inches of rain, less than all but seven MLB cities during those two months. Washington D.C. gets more than seven inches of rain in April and May. New drainage technology and the lack of heavy rain in Portland during the spring would likely translate into very few rainouts in a Portland open-air ballpark.