Interestingly, there is a pressure anomaly that corresponds with the temperature anomaly. The pressure of the spot is about 30 hPa lower that the surrounding region indicating a localized low pressure cell, suggesting that something on the surface is heating the atmosphere sufficiently to cause this.
By taking co-ordinates around the edge of the spot, east-west and north and south, and doing a bit of math, the average diameter of the spot is 215 km.
Taking the co-ordinates from your comment (65.5857 N, 117.02636 E) and looking at Google Earth, there is an Alrosa diamond mine at co-ordinates 65° 01’ 11” N, 117° 05’ 04” E (65.01972 N, 117.08444 E) that Google Earth does not list the name of.
Given the isolated nature of this mine my speculation is this mine is associated with the anomalous spot you noticed.