Assessing the Global Climate in September 2018

The global land and ocean temperature departure from average for September 2018 tied with 2017 as the fourth highest for the month of September in the NOAA global temperature dataset record, which dates back to 1880. The year-to-date was also fourth warmest on record.

This monthly summary, developed by scientists at NOAA's National Centers for Environmental Information, is part of the suite of climate services NOAA provides to government, business, academia and the public to support informed decision-making.

September 2018 Temperature

• The September temperature across global land and ocean surfaces was 1.40°F above the 20th century average of 59.0°F and tied with 2017 as the fourth highest for September in the 1880-2018 record.

  • The 10 warmest September global land and ocean surface temperatures have occurred since 2003, with the last five years (2014-2018) comprising the five warmest Septembers on record. September 2015 is the record warm September at 1.67°F above average. September 2018 also marks the 42nd consecutive September and the 405th consecutive month with temperatures, at least nominally, above the 20th century average.

  • Record warm temperatures during the month were present across parts of the Atlantic and Indian Oceans and across parts of North America, South America, Europe, Africa and Asia. The area with record cold September temperatures was in southwestern Canada.

• The September globally averaged land surface temperature was 1.84°F above the 20th century average of 53.6°F. This value was the sixth highest September land temperature in the 139-year record.

  • The most notable warm land temperatures were present across southern South America, Alaska, the southwestern and eastern contiguous U.S., much of Europe, the Middle East, as well as western and eastern Russia, where temperature departures were 3.6°F above average or higher. The most notable cool temperature departure from average during September was in central and western Canada, where temperatures were 5.4°F below average or less.

  • Warmer-than-average temperatures were present across much of Europe during September 2018, giving way to the warmest September, at 3.64°F above average, since continental records began in 1910. This value surpassed the previous record set in 2016 by more than 0.20°F. September 2018 marks the first time since continental records began that Europe had a September temperature departure from average that was 3.6°F or higher.

  • South America had its second warmest September on record at 2.72°F above average. This value trails behind the record set in 2015 by 0.23°F. Africa and Asia had their third and fourth warmest Septembers, respectively. Meanwhile, North America had its smallest temperature departure from average for September in 10 years (since 2008) at 0.49°F above average.

• The September globally averaged sea surface temperature was 1.24°F above the 20th century monthly average of 61.1°F – the fourth highest global ocean temperature for September in the record. The years 2014-2018 comprise the five warmest Septembers on record, with 2015 the warmest September at 1.49°F above average.

September 2018 Sea Ice

• On September 19 and again on the 23rd, Arctic sea ice reached its annual minimum extent at 1.77 million square miles. This tied with 2008 and 2010 as the sixth smallest minimum extent in the 1979-2018 satellite record, according to the National Snow and Ice Data Center using data from NOAA and NASA. This was 629,000 square miles below the 1981-2010 average but 462,000 square miles larger than the record low set in 2012. For the entire month of September, the average Arctic sea ice extent was 656,000 square miles (26.5 percent) below the 1981-2010 average, the seventh smallest September sea ice extent on record.

• The Antarctic sea ice extent for September was 6.90 million square miles, 240,000 square miles (3.3%) below average, and the second smallest September sea ice extent since records began in 1979. Only the September Antarctic sea ice extent in 1986 was smaller at 6.83 million square miles.

Year-to-Date (January-September 2018)

• The year-to-date temperature across global land and ocean surfaces was 1.39°F above the 20th century average of 57.5°F – the fourth highest for January-September in the 139-year record. The 2018 year-to-date value was 0.43°F lower than the record high set in 2016.

• The year-to-date globally averaged land surface temperature was 2.05°F above the 20th century average of 48.7°F. This value was also the fourth highest for January-September in the record.

  • Europe had its warmest January-September since continental records began in 1910 at 3.35°F above average. This value exceeded the previous record set in 2014 by more than 0.23°F. Africa had its fifth highest year-to-date temperature, Asia and Oceania had their sixth highest on record and South America its eighth highest. North America had its lowest January-September temperature departure from average since 2013.

• The year-to-date globally averaged sea surface temperature was 1.13°F above the 20th century average of 61.1°F. This value tied with 2014 as the fourth highest for January-September in the 1880-2018 record.

For a more complete summary of climate conditions and events, see our September 2018 Global Climate Report.