Globally October 2017 was the second warmest October since reliable measurements began in 1880, 0.90C warmer than the 1951-1980 mean. October temperature was +1.18C relative to the 1880-1920 base period, which provides our best estimate of pre-industrial global temperature. The warmest October was 2015 at +1.08C relative to the 1951-1980 mean. 2016 was the 3rd warmest at +0.89C. The 2017 January to October 10-month mean is second highest, behind 2016, compared to the first 10 months of other years.
Although a weak La Nina is present, the global mean temperature in October stayed relatively high; polar regions were especially warm. 2017 will likely to be the second warmest year in the record.