October 2021 was Earth’s fourth-warmest October since global record-keeping began in 1880, 0.89 degree Celsius (1.60°F) above the 20th-century average, NOAA’s National Centers for Environmental Information, NCEI, reported November 15. NASA also reported October 2021 as the fourth-warmest October on record, 1.23 degrees Celsius (2.21°F) above the 1880-1920 period, which is its best estimate for when preindustrial temperatures occurred. Minor differences in rankings between the two agencies result from the different ways they treat data-sparse regions such as the Arctic.

As has been the case for much of 2021, the heat was focused more on land areas than ocean areas, thus affecting society more directly: October 2021 land areas had their third warmest October on record (warmest on record over Northern Hemisphere land areas), and global ocean temperatures were the fifth warmest on record, according to NOAA. Satellite-measured October temperatures of the lower atmosphere were the third-warmest in the 43-year-long record, according to Remote Sensing Solutions (RSS).

North America had its second-warmest October on record; South America had its third-warmest, Africa, its seventh warmest, and Asia, its 12th warmest. The contiguous U.S. experienced its sixth-warmest October on record, with 26 states recording a top-10 warmest October. It was also a very wet October in the U.S., ranking as the ninth wettest, and 10 states had a top-10 wettest October on record. However, at the end of October, at least moderate drought covered 48% of the contiguous U.S, the highest drought coverage for this time of year since 2012.

Figure 1. Departure of temperature from average for October 2021, the fourth warmest October for the globe since record keeping began in 1880. Record-warm October temperatures were present across parts of North America, South America, northern Africa, southern Asia, as well as across parts of the Atlantic and the Pacific oceans, and one small area of the South Indian Ocean.  (Image credit: NOAA/NCEI)

January-October ranked as Earth’s sixth warmest such period on record. According to NCEI’s annual temperature outlook, the year 2021 is virtually certain to rank among the 10 warmest years on record, and more than 95% likely to be the sixth-warmest on record. These odds are based on statistical averages and do not take into account the arrival of La Niña conditions (see below), which tend to reduce global temperature slightly.

One billion-dollar weather disaster in October; 38 so far in 2021

Earth had one billion-dollar weather disaster in October 2021, according to Aon: flooding in northern China during the first week of October that cost $1.8 billion in damage and killed 27 people. In addition, two other weather disasters earlier in the year accumulated enough damages by the end of October to exceed the $1 billion threshold, giving the Earth 38 billion-dollar weather disasters so far in 2021. The most in an entire year is 50 billion-dollar weather disasters, set in 2020.

Figure 2. Billion-dollar weather disasters in January through October 2021, according to Aon.

La Niña conditions solidly in place

La Niña conditions strengthened during October, and they are expected to persist through the Northern Hemisphere winter (90% chance) and into spring (50% chance during March-May), NOAA reported in its November monthly discussion of the state of the El Niño/Southern Oscillation, or ENSO. To be designated an official La Niña event, La Niña conditions have to be present for at least five consecutive months, with each month representing three-month average conditions. 

Over the past month, sea surface temperatures in the benchmark Niño 3.4 region of the eastern tropical Pacific (5°N-5°S, 170°W-120°W) were about 0.8 degree Celsius below average. The range for “weak” La Niña conditions is 0.5-1.0 degree Celsius below average; the range for “moderate” La Niña conditions is 1.0-1.5 degrees Celsius below average.

Figure 3. Departure of sea surface temperature from average in the benchmark Niño 3.4 region of the eastern tropical Pacific (5°N-5°S, 170°W-120°W). Temperatures ranged from 0.6-1.0 degree Celsius below average over the past month. (Image credit: Tropical Tidbits)

The NOAA and Columbia University International Research Institute for Climate and Society forecast for the December-January-February period is for a 92% chance of La Niña, 8% chance of ENSO-neutral, and a 0% chance of El Niño. At its peak, the La Niña event is expected to be at moderate strength (66% chance), with a 14% chance of reaching the “strong” threshold.

The impact of the emerging La Niña event may be boosted by an intensely negative Pacific Decadal Oscillation (PDO). The PDO is an index of sea surface temperatures across the northeast and tropical Pacific Ocean that reflects some of the circulation aspects of the El Niño-Southern Oscillation. The PDO can swing sharply from month to month, but usually it leans positive (warm) or negative (cool) for a few years at a time. Almost every month since 2017 has seen a negative PDO.

The oscillation outdid itself in October 2021 with a value of -3.06. That’s the lowest PDO value for any month in more than 65 years, when -3.55 was recorded in October 1955. When the PDO is negative, La Niña is more common and its impacts are often more pronounced, so the extremely negative PDO of October 2021 suggests potential dramatic consequences from the La Niña event of 2021-22.

La Niña winters in the U.S. tend to be mercurial, with sharp frontal passages and a heightening of the usual north-to-south temperature contrasts (colder-than-average conditions toward the north and warmer-than-average conditions to the south). Winter precipitation is often generous in the Pacific Northwest, where both the Seattle and Portland airports so far are already having their wettest autumn on record. Unfortunately, winter precipitation is often paltry in the Southwest, which is currently suffering one of its most intense and long-lived droughts on record.

Arctic sea ice: 8th-lowest October extent on record

Arctic sea ice extent during October 2021 was tied for eighth-lowest in the 43-year satellite record, according to the National Snow and Ice Data Center (NSIDC). Despite total ice extent’s being higher than in recent years, Arctic ice thickness and volume have been at near-record low values in recent months (see Tweet below from Zack Labe).

Antarctic sea ice extent underwent a steep decline after reaching its annual peak on September 1, when ice extent was above the ninetieth percentile for the date. Ice extent fell below the tenth percentile for much of October, and by the end of the month, was tracking at the third-lowest extent on record.

Figure 4. Global food prices averaged over the year 2021 are the highest since 1975, after adjusting for inflation. (Image credit: United National Food and Agriculture Organization)

Global food prices rise 3%, hitting a 46-year high

Global food prices in October rose 3% compared to September, and were at their highest level since September 2011 (unadjusted for inflation), the United Nations Food and Agriculture Organization (FAO) said in its monthly report on November 4. After adjusting for inflation, 2021 food prices averaged for the 10 months of 2021 were the highest since 1975.

The October increase was driven by a surge in the prices of grains and vegetable oil, with wheat prices a dominant driver. Drought in Russia and Canada contributed to the high wheat prices. However, total global production of grains in 2021 is expected to set an all-time record: 0.8% more than the previous record set in 2020. But because of higher demand (in part, from an increased amount of wheat and corn used to feed animals), the 2021 harvest was not expected to meet consumption requirements in 2021/2022, resulting in a drawdown in global grain stocks by the end of 2022 to their lowest levels since 2015/2016.

The surge in food prices this year is concerning: High wheat prices in 2011 (in the wake of export restrictions triggered by the 2010 drought in Russia) helped lead to massive civil unrest and the toppling of multiple governments (the “Arab Spring”). See this in-depth 2016 analysis, Food System Shock: Climate Change’s Greatest Threat to Civilization.

Notable global heat and cold marks for October 2021

The information below is courtesy of Maximiliano Herrera. Follow him on Twitter: @extremetemps:

– Hottest temperature in the Northern Hemisphere: 46.0°C (114.8°F) at Omidiyeh, Iran, October 2;
– Coldest temperature in the Northern Hemisphere: -50.9°C (-59.6°F) at Summit, Greenland, October 17;
– Hottest temperature in the Southern Hemisphere: 45.5°C (113.9°F) at Tete, Mozambique, October 24;
– Coldest temperature in the Southern Hemisphere: -73.7°C (-100.7°F) at Dome Fuji, Antarctica, October 2;
– Highest 2021 average temperature to date (Jan.-Oct.) in the Southern Hemisphere: 29.7°C (85.5°F) at Surabaya Airport, Indonesia; and
– Highest 2021 average temperature to date (Jan.-Oct.) in the Northern Hemisphere: 33.1°C (91.6°F) at Makkah, Saudi Arabia.

October 2021 major weather stations’ new all-time heat or cold records: one all-time heat record, no all-time cold records

Among global stations with a record of at least 40 years, one set, not just tied, an all-time heat record in October; no stations set an all-time cold record:

Cherrapunji (India) max. 32.1°C (89.8°F), October 12.

Ten all-time national/territorial heat records set or tied in 2021

As of October 31, 2021, 10 nations or territories had set or tied an all-time reliably-measured national heat record:

United Arab Emirates:  51.8°C (125.2°F) at Sweihan, June 6 (tie);
Oman: 51.6°C (124.9°F) at Joba, June 16;
Canada: 49.6°C (121.3°F) at Lytton, June 29 (record beaten 3 consecutive days);
U.S.: 54.4°C (130°F) at Death Valley Furnace Creek, California, July 9 (tie);
Morocco: 49.6°C (121.3°F) at Sidi Slimane, July 10 (tie);
Turkey: 49.1°C (120.4°F) at Cizre, July 20;
Taiwan: 40.6°C (105.1°F) at Taimali, July 25;
Tunisia: 50.3°C (122.5°F) at Kairouan, August 11;
Italy: 48.8°C (119.8°F) at Siracusa, August 11; and
Dominica: 35.8°C (96.4°F) at Canefield Airport, August 12.

One all-time national/territorial cold record set or tied in 2021

As of October 31, 2021, one nation or territory had set or tied an all-time national cold record:

United Arab Emirates (for places at low elevations): -2.0°C (28.4°F) at Raknah, January 9.

Eighty-seven monthly national/territorial heat records beaten or tied as of October 31

In addition to the all-time national/territorial records listed above, 87 nations or territories have set monthly all-time heat records, for a total of 96 monthly all-time records. Six nations or territories have set all-time monthly cold records (including the all-time cold record set in the United Arab Emirates).

– January (10): Mexico, Bangladesh, Nigeria, Japan, Malta, Tunisia, Turkey, Russia, Georgia, Spain;
– February (12): Iraq, Uzbekistan, Mongolia, South Korea, Liechtenstein, Slovenia, Croatia, Slovakia, Poland, Sweden, Pakistan, Northern Mariana Islands;
– March (14): Northern Mariana Islands, Qatar, Saudi Arabia, Bahrain, Kuwait, Pakistan, Oman, Jersey, Guernsey, Germany, Netherlands, Luxembourg, Belgium, US Virgin Islands;
– April (4): South Africa, Northern Mariana Islands, Hong Kong, Tajikistan;
– May (8): Northern Mariana Islands, Taiwan, Russia, Qatar, Turkmenistan, Uzbekistan, Dominica, Saba;
– June (8): Cocos Islands, Congo Brazzaville, Mexico, Belarus, Estonia, Malta, Tunisia, Botswana;
– July (1): Cocos Islands;
– August (10): Qatar, Mexico, Morocco, Spain, Andorra, Iceland, Gabon, Botswana, Kenya, Philippines;
–  September (9): Hong Kong, Norway, Saba, Central African Republic, Maldives, Botswana, Dominica, Angola, Kenya; and
– October (11): Iran, Morocco, China, South Korea, Taiwan, Botswana, Bangladesh, Antigua and Barbuda, French Southern and Antarctic Lands, Peru, Malaysia.

Five monthly national/territorial cold records beaten or tied as of October 31

– April (2): Slovenia, Switzerland;
– June (2): Saba, Paraguay; and
– July (1): Namibia

Hemispherical and continental temperature records in 2021

– Highest minimum temperature ever recorded in April in the Southern Hemisphere: 31.7°C (89.1°F), at Vioolsdrif, South Africa, April 13;
– Highest minimum temperature ever recorded in May in Europe: 29.4°C (84.9°F), at Zymbragou, Greece, May 2;
– Highest minimum temperature ever recorded in June in North America: 40.3°C (104.5°F), at Stovepipe Wells, U.S., June 18;
– Highest reliable temperature on Earth: 54.4°C (130°F) at Death Valley Furnace Creek, California (U.S.), July 9 (129.9°F measured there in August 2020 was also rounded to 54.4°C);
– Highest minimum temperature ever recorded in North America and the highest minimum temperature in the world in July: 42.0°C (107.6°F) at Stovepipe Wells, California (U.S.), July 11;
– Highest minimum temperature recorded in July in Europe: 34.3°C (93.7°F), Kalymnos, Greece, July 31;
– Highest minimum temperature recorded in August in Europe: 35.2°C (95.4°F), Plakias, Greece, August 3;
– Highest temperature ever recorded in Europe: 48.8°C (119.8°F), Siracusa, August 11; and
– Highest minimum temperature ever recorded globally in September: 38.9°C (102.0°F) at Badwater Basin (Death Valley), California (U.S.), September 9.

Editor’s note: This post was updated on November 16 to include Malaysia in the list of all-time October national records.

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Jeff Masters

Jeff Masters, Ph.D., worked as a hurricane scientist with the NOAA Hurricane Hunters from 1986-1990. After a near-fatal flight into category 5 Hurricane Hugo, he left the Hurricane Hunters to pursue a...

Bob Henson

Bob Henson is a meteorologist and journalist based in Boulder, Colorado. He has written on weather and climate for the National Center for Atmospheric Research, Weather Underground, and many freelance...