As one might expect, freezing rain or rain at temperatures close to freezing is rather common at this time of year in Fairbanks, although it requires an unusually warm airmass aloft. This morning's sounding from Fairbanks (shown below) revealed above-freezing temperatures from about 2000-4500 feet elevation, but sub-freezing conditions existed closer to the ground. This means that rain falling out of the warm cloud layer aloft was chilled to or below freezing before reaching the ground, and so ice formed readily on ground-level surfaces in locations where the air was at or below freezing.
The history of hourly observations since 1950 (see chart below) shows that October has the highest frequency of freezing or near-freezing rain, with the phenomenon occurring in nearly 40% of all years. The frequency peaks in mid-October, so today's event is right on schedule for this kind of thing.
The chart below shows that the distribution of October cold rain events has been fairly even through the years, although today's event is the first since 2006. It seems freezing rain has taken a preference for deep winter in recent years.