Portland Weather Forecast Rain returns Friday By Kristen VanDyke Published: October 26, 2015, 5:00 am Updated: February 25, 2016, 11:57 pm Related Coverage Here is your Updated Portland Weather Forecast: Was Thursday amazing or what?! PDX had the warmest day of 2016 so far with a high of 64. Hopefully everyone got out to experience it because changes arrive Friday. The day starts dry and mild. By lunch, it’s raining along the coast. Rain pushes into the Willamette Valley by mid-afternoon.