Record-breaking heat has never persisted on the planet so long.

Not only did Earth witness its hottest August on record, according to the National Oceanic and Atmospheric Administration, but it also extended its streak of record-warm months to 16. Such a lengthy period of record-setting warmth is unprecedented in 137 years of temperature observation, the NOAA said.

August’s average temperature was 1.66 degrees above the 20th century average, 0.09 degrees above the previous warmest August — set just one year ago.

Unusually warm conditions covered most of the globe. “Five of the six continents had at least a top ten warm August, with Africa and Asia observing a record high average temperature for August since continental records began in 1910,” the NOAA reported.

The summer period — encompassing June through August — was also warmest on record, 0.07 degrees warmer than the summer of 2015, the previous recordholder.

“It is plausible that this summer was the warmest in thousands of years, perhaps even longer,” climate scientist Michael Mann of Penn State University told USA Today.

As every month this year has established a new record for warmth, it follows that 2016 ranks as the warmest on record year-to-date, a substantial 0.29 degrees warmer than 2015 — the previous recordholder for the January-August period.

“[A]ll six continents had at least a top three warm January-August period, with North America, Asia, and Oceania experiencing a record high average temperature for January-August since continental records began in 1910,” the NOAA said.

The early months of 2016 recorded some of the biggest temperature departures from normal or anomalies ever observed, in large part due to a strong El Nino — during which heat from the tropical Pacific Ocean was released to the atmosphere.

But even as El Nino has waned, temperature anomalies have remain strongly positive. August’s departure from normal of 0.92 degrees tied for eighth highest in 1,640 months. “Fourteen of the 15 highest monthly temperature departures in the record have occurred since February 2015, with January 2007 among the 15 highest temperature departures,” the NOAA said.

Given the warm start to the year, NASA’s climate scientist Gavin Schmidt says there’s a 99 percent chance the year will close as the warmest on record.

First Published: September 21, 2016, 4:35 a.m.