We are lucky in Portland to have Forest Park within our city limits so we can hike anytime. We are surrounded by scenic places such as the Gorge and the Cascades where we can hike for much of the year. There are many hiking books with trails and tips available. Remember that when you hike you need to take water, food, appropriate clothing and some safety gear depending on where and how long you plan to be out. Mall walking and treadmills are what walkers use to stay warm and dry in the winter.
Some malls have specific walk hours and some are open early just for walking.
Most mall walkers are seniors and many have infirmities making the mall an inappropriate place to do speed work. A number of Anchorage Team in Training walkers did 14 miles in the mall preparing for the Honolulu marathon. Not my favorite, but a good choice in sub 20 degree weather. Treadmills are a good substitute for outdoor walking especially in the dark and wet. You do, however, need to spend some time on the road if you are preparing for a road event.