Global temperature records show that June became the 14th month in a row to reach new highs, US scientists have said.
The global average temperature across land and sea surfaces in June was 0.9C (1.6F) above normal for the 20th century, the US government's National Oceanic and Atmospheric Administration (Noaa) said.
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It was the hottest June in records dating back to 1880, and the 14th consecutive month that a monthly global temperature record was broken - the longest such streak since records began, the scientists said.
It is also the 40th June in a row to see temperatures beating - at least nominally - the 20th century average.
The last time the global temperature across land and sea surfaces for June was below average was in 1976.
June was the 378th consecutive month with temperatures above 20th century averages, with no below-average month since December 1984.
The UK saw average temperatures for the month of 13.9C (57F), some 0.9C (1.6F) above the average for 1981 to 2010, mostly due to extremely warm night time temperatures, Noaa said.
The average minimum temperature for the UK was the joint warmest in records going back to 1910, the data showed.
The record highs have happened in the face of a powerful El Nino climate phenomenon in the Pacific that pushes up global temperatures and warming caused by greenhouse gas emissions from human activity.
Scientists from Nasa's Goddard Institute for Space Studies (Giss) said January to June was the planet's warmest half-year on record, with an average temperature of 1.3C (2.4F) warmer than the late 19th century.
Five of the first six months of the year also set records for the smallest monthly extent of sea ice in the Arctic.
Walt Meier, a sea ice scientist at Nasa Goddard, said: "It has been a record year so far for global temperatures, but the record high temperatures in the Arctic over the past six months have been even more extreme.
"This warmth as well as unusual weather patterns have led to the record low sea ice extents so far this year."
While records are being broken in 2016, Nasa scientists said it was more significant that global temperatures and Arctic sea ice were continuing their "decades-long" trends of change.
The changes are ultimately driven by rising concentrations of carbon dioxide and other greenhouse gases in the atmosphere, they said.