How likely is it that -30°F will be reached at the airport in the remainder of winter? Based on the last 40 years of historical data, more than 70% of years reach -30°F on or after February 5, and the odds don't drop below 50% until February 22. Even in March it's not too uncommon - in fact, 4 of the last 5 years have seen -30°F or colder in March. However, the medium-range forecast is quite warm (see below), and of course the ongoing El Niño and positive PDO phase suggest that warmth will continue to dominate.
The chart below shows how the January-March standard deviation of daily mean temperature anomalies (departure from normal) varies with an index of El Niño/La Niña behavior. The standard deviation is quite noticeably reduced when the ENSO index is above +1, so there's little doubt that the El Niño episode is contributing to the lack of variability in Fairbanks this winter.
Fairbanks winter temperature variance is similarly affected by the PDO phase (which is of course correlated with ENSO), and if we create a combined index of PDO+ENSO behavior, the overall correlation with the variance is slightly greater than for ENSO alone.
Here's a chart showing how the ENSO/PDO effects on temperature variance change through the year; each column represents the correlation coefficient for a three-month period. Interestingly the variance reduction for El Niño is slightly greater in late winter than early winter, which probably reflects the fact that El Niño's impacts on the atmospheric circulation reach their peak in late winter. The opposite effect is observed in late summer and autumn, with temperature variance being somewhat enhanced during El Niño conditions and reduced during La Niña.