NOAA has released their latest climate report for the global climate.  In the report, available at https://www.ncdc.noaa.gov/sotc/global/201505, they note that May 2015, March-May 2015, and the year to date January through May 2015 were all the warmest on record since records began in 1880.  Precipitation amounts varied tremendously from on location to another this month.

201505 global temp  201501-201505 ytd temp 2015  201501-201505 timeline