No, that's not a clever way to discuss the current weather patterns in Portland. Warming up prior to you work out or exercise routine and cooling down after are just as important as your activity. 

Warming up increases the temperature of your muscles for increased flexibility and mobility. It also dilates your blood vessels to increase oxygen flow throughout the body. A warm up slowly raises your heart rate and reduces stress on your heart. When you include a stretch in your warm up you increase range of motion and mobility in your joints preventing injury. Warm up for at least 5-10 minutes doing a similar activity to the one you have planned (walk before a run). 

Cooling down allows your heart rate to come down gradually and your blood vessels to contract so you don't pass out or feel sick. Including a stretch in your cool down will help the build up of lactic acid (known for soreness and stiffness) in your muscles. Hold each stretch for 15-30 seconds and don't bounce. 

Including these in your summer activities will help improve your overall health.