There is only a few hours left of May here, and the NCAR reanalysis has three days of data to go. May has had fewer extremes than earlier months, but warmed toward the end. It is currently showing the same average anomaly as February, and I think that is about where it will end up. That is actually not quite as warm as last May, or as March 2015, but it continues a warm start to the year. The GISS anomaly for February was 0.8°C.