Weather in March can be pretty wet. There’s also a chance that it can be quite nice. And occasionally, you’ll get the soggiest day ever, and that ends up being the day where 30,000 runners and walkers take to the streets of Portland for the 38th annual Shamrock Run Portland. The weather, of course, is the one thing the race organizer cannot influence, and as a runner in Oregon, you accept the fact that you…