Dr. Jeff Masters ·

Above: The deadliest disaster of October was Tropical Depression 23W, which made landfall over central Vietnam on October 10, triggering multiple days of torrential downpours. At least 98 people were dead or missing, with 18,000 homes damaged throughout the north of the country. Image credit: Nhan Sinh/Vietnam News Agency via AP.

October 2017 was Earth's fourth warmest October since record keeping began in 1880, said NOAA's National Centers for Environmental Information (NCEI) on Friday. NOAA rated the five warmest Octobers since 1880 as being 2015, 2014, 2016, 2017, and 2003 (tied with 2017.) NASA rated October 2017 as the planet’s second warmest October on record, with the only warmer October coming in 2015. Minor differences can occur between the NASA and NOAA rankings because of their different techniques for analyzing data-sparse regions such as the Arctic.

Global ocean temperatures last month were the fourth warmest on record for any October, according to NOAA, and global land temperatures were the eleventh warmest on record. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were the warmest for any October in the 39-year record, according to the University of Alabama Huntsville (UAH) and Remote Sensing Systems (RSS).

Figure 1. Departure of temperature from average for October 2017, the fourth warmest October for the globe since record keeping began in 1880. The month was characterized by warmer-than-average conditions across much of the world's land and ocean surfaces, with record warmth scattered across the globe. The largest positive anomalies were observed across north-central Russia, Alaska, northwestern and eastern Canada, and the northeastern contiguous U.S., where temperature departures from average were +3.0°C (+5.4°F) or higher. No land or ocean areas experienced record cold October temperatures. Image credit: National Centers for Environmental Information (NCEI).

Figure 2. Departures from the 20th-century global average temperature for October, 1880-2017. The four warmest Octobers on record have all occurred in the last four years. Image credit; NOAA/NCEI.

Third-warmest year on record thus far

Each of the first ten months of 2017 have ranked among the top four warmest such months on record, giving 2017 the third highest January–October temperature in the 138-year record: 1.33°C (2.39°F) above the 20th-century average. This is behind the record year of 2016 by 0.18°C (0.33°F). This near-record warmth in 2017 is especially remarkable given the lack of an El Niño event this year. Global temperatures tend to be warmer during El Niño years, when the ocean releases more heat to the atmosphere. Given the lack of an El Niño event in 2017, it is very unlikely that we will surpass 2016 as the warmest year on record. However, 2017 is almost certain to be the planet's warmest year on record that lacks any influence from El Niño, and will be the second or third warmest year in recorded history. Earth's four warmest years of the last century-plus are likely to be 2016, 2017, 2015, and 2014.

Two billion-dollar weather disasters for October 2017

Two billion-dollar weather disasters hit the Earth last month, according to the October 2017 Catastrophe Report from insurance broker Aon Benfield: Typhoon Lan in Japan ($1 billion), and the wildfires in California ($8 billion in insured damage alone). In addition, one severe weather outbreak in the U.S. from June accumulated enough damage claims by the end of October to exceed the $1 billion threshold. Through the end of October, Earth had 24 billion-dollar weather events for the year, which is a typical number for this point in the year. The year that ended with the most billion-dollar weather disasters in records going back to 1990 was 2013, with 41; that year had 36 billion-dollar disasters by the end of October. Last year, there were 30 billion-dollar weather disasters by the end of October; 2016 ended up with 31 such disasters. Here are this year’s billion-dollar weather disasters through the end of October:

Hurricane Harvey, U.S., 8/25 – 9/2, $90 billion, 84 killed

Hurricane Irma, Caribbean/Bahamas/SE U.S., 9/5 – 9/12, $60 billion, 124 killed

Hurricane Maria, Caribbean, 9/18 – 9/21, $20+ billion, 98 killed

Wildfire, U.S. (California), 10/8 – 10/30, $8+ billion, 43 killed

Flooding, China, 6/22 – 7/5, $7.5 billion, 141 killed

Flooding, China, 7/13 – 7/17, $4.5 billion, 20 killed

Typhoon Hato, Macau/Hong Kong/China, 8/23 – 8/24, $3.5 billion, 22 killed

Severe Weather, U.S. Rockies/Plains, 5/8 – 5/11, $3.25 billion, 0 killed

Flooding, Peru, 1/1 – 4/1, $3.1 billion, 120 killed

Severe Weather, U.S. Plains/Southeast/Midwest, 3/26 – 3/28, $2.75 billion, 0 killed

Drought, China, 5/1 – 8/31, $2.5 billion, 0 killed

Tropical Cyclone Debbie, Australia, 3/27 – 4/5, $2.4 billion, 14 killed

Drought, Italy, 1/1 – 7/31, $2.3 billion, 0 killed

Severe Weather, U.S. Midwest/Plains/Southeast, 3/6 – 3/10, $2.1 billion, 0 killed

Severe Weather, U.S. Midwest, 6/11, $2.0 billion, 0 killed

Severe Weather, U.S. Midwest/Plains/Southeast/MS Valley, 4/28 – 5/01, $2.0 billion, 20 killed

Drought, Somalia, Ethiopia, Kenya, 1/1 – 3/31, $1.9 billion, hundreds killed

Severe Weather, U.S. South, 2/27 - 3/2, $1.9 billion, 4 killed

Severe Weather, U.S. South, 1/18 - 1/23, $1.3 billion, 21 killed

Typhoon Lan, Japan/Philippines, 10/18 – 10/23, $1.0 billion, 17 killed

Tropical Storm Nanmadol, Japan, 7/4 – 7/6, $1.0 billion, 37 killed

Severe Weather, U.S. Plains/Midwest/Northeast, 6/27 – 6/30, $1.0 billion, 0 killed

Winter Weather, U.S. Plains/Midwest/Southeast/Northeast, 3/13 – 3/15, $1.0 billion, 11 killed

Severe Weather, U.S. Plains/Rockies, 6/12 – 6/14, $1.0 billion, 0 killed

October Billion-Dollar Disaster 1. Dry “diablo” winds fanned a massive wildfire outbreak of over 20 fires in portions of California during early October, which killed 43 people and injured 185. This death toll surpasses the Griffith Fire in Los Angeles on October 3, 1933 (29 killed) as the deadliest fire event in California history, and makes it the deadliest U.S. wildfire event in 99 years. The last deadlier U.S. wildfire was the Cloquet, Minnesota fire of October 12, 1918, which killed over 400 people. CalFire reported that more than 8,560 structures were destroyed in the October 2017 fires. Insured damage was expected to reach $8 billion, with overall economic losses even higher. This is the costliest wildfire event for insured damage in world history, beating the $3.0 billion cost (2017 dollars) of the 1991 Oakland, California fire. Above: firefighters assess the scene as a house burns in the Napa wine region of California on October 9, 2017. Image credit: Josh Edelson/AFP/Getty Images.

October Billion-Dollar Disaster 2. Super Typhoon Lan peaked as a top-end Category 4 typhoon with 155 mph winds east of the Philippines before weakening and hitting Japan as a Category 2 storm with 105 mph winds. Lan's torrential rains triggered flooding and landslides that killed nine in the Philippines and eight in Japan. Lan damaged 6,200 homes in Japan and 1,100 in the Philippines, causing $1 billion in damage. Above: Super Typhoon Lan at peak intensity as seen by the VIIRS instrument on the Suomi satellite on October 21, 2017.

October Billion-Dollar Disaster 3. A severe weather outbreak on June 12 – 14 centered over Wyoming and Nebraska unleashed 31 tornadoes, including four EF2s. Nobody was killed. Initial damage estimates in June were less than $1 billion, but by the end of October, damage was estimated at $1 billion. Above: WU depiction of NOAA/SPC severe weather outlook for Monday, June 12, 2017; the red area corresponds to a moderate risk, the second-highest of SPC's five risk categories.

La Niña is back

In its November 9 monthly advisory, NOAA’s Climate Prediction Center (CPC) issued a La Niña advisory, declaring that La Niña conditions were now in place in both the atmosphere and ocean. NOAA gave odds of around 65-75% that La Niña conditions would extend at least through the upcoming Northern Hemisphere winter of 2017-18. Sea surface temperatures (SSTs) in the benchmark Niño 3.4 region (in the equatorial Pacific) were about 0.8°C below average over the past week; SSTs of 0.5°C or more below average in this region are required to be classified as weak La Niña conditions, with the 3-month average SSTs holding at these levels for five consecutive months (with an accompanying La Niña-like atmospheric response). See our post last Thursday for more details.

Figure 3. Sea surface temperatures (SSTs) in the benchmark Niño 3.4 region (in the equatorial Pacific) were oscillating around 0.7°C below average for the first half of November, below the 0.5°C below average threshold for weak La Niña conditions. Image credit: Levi Cowan, tropicaltidbits.com.

Arctic sea ice extent the fifth lowest on record for October

Arctic sea ice extent during October 2017 was the fifth lowest in the 38-year satellite record, according to the National Snow and Ice Data Center (NSIDC). Sea ice surrounding Antarctica reached its yearly maximum extent on October 12, and had the second lowest maximum extent on record, behind 1986.

Notable global heat and cold marks set for October 2017

Hottest temperature in the Northern Hemisphere: 45.7°C (114.3°F) at Hermosillo, Mexico, 24 October

Coldest temperature in the Northern Hemisphere: -45.2°C (-49.4°F) at Summit, Greenland, 28 October

Hottest temperature in the Southern Hemisphere: 45.3°C (113.5°F) at Tete, Mozambique, 27 October

Coldest temperature in the Southern Hemisphere: -68.8°C (-91.8°F) at Concordia, Antarctica, 1 October

(Courtesy of Maximiliano Herrera.)

Major weather stations that set (not tied) new all-time heat or cold records in October 2017

So far in 2017, 173 major weather stations have set records for the all-time highest temperature ever measured, and 17 have set records for the all-time lowest temperature ever measured. Here are the records for October 2017:

Poxoreu (Brazil) max. 43.0°C, 13 October

Brasilia Airport (Brazil) max. 36.5°C, October

Nova Xavantina (Brazil) max. 43.9°C, 16 October

Carolina (Brazil) max. 40.9°C, 22 October

Colinas (Brazil) max. 40.9°C, 24 October

(Courtesy of Maximiliano Herrera.)

No all-time national heat records set or tied in October 2017

No all-time national heat or cold records were set or tied in October 2017. As of November 18, fourteen nations have set or tied all-time national heat records in 2017, and two have set or tied all-time cold records. National all-time monthly temperature records so far in 2017 have numbered 52 for maximum temperature, and 2 for minimum temperature. Most nations do not maintain official databases of extreme temperature records, so the national temperature records reported here are in many cases not official. I use as my source for international weather records researcher Maximiliano Herrera, one of the world's top climatologists, who maintains a comprehensive list of extreme temperature records for every nation in the world on his website. If you reproduce this list of extremes, please cite Maximiliano Herrera as the primary source of the weather records.

All-time national heat records set or tied in 2017:

Comoros: 96.8°F (36.0°C) at Hahaya International Airport, 15 November

Macau: 102.2°F (39.0°C) at Ka Ho, Coloane Island, 22 August (tie)

Hong Kong: 102.2°F (39.0°C) at Wetland Park, 22 August

San Marino: 104.5°F (40.3°C), at Serravalle, 3 and 9 August

Vatican City: 105.3°F (40.7°C) at Roma Macao AWS, 2 August (tie)

United Arab Emirates: 125.2°F (51.8°C), at Mezaira, 30 July

Spain: 117.1°F (47.3°C), at Montoro AEMET, 13 July

Iran: 128.7°F (53.7°C), at Ahwaz, 29 June

Oman: 123.4°F (50.8°C), at Qurayyat on 30 May and at Joba on 31 May (tie)

Pakistan: 128.3°F (53.5°C), at Turbat on 28 May (tie)

Guinea: 113°F (45.0°C), at Koundara, 29 March (tie)

Ghana: 110.8°F (43.8°C), at Navrongo, 26 March

Chile: 113°F (45.0°C), at Cauquenes, 26 January

Cocos Islands (Australia): 91.0°F (32.8°C), at Cocos Island Airport, 23 February (tie with 8 April 2015 and 11 April 1998)

All-time national cold records set in 2017:

United Arab Emirates: 22.3°F (-5.4°C) at Jabel Jais, 3 February

Qatar: 34.7°F (1.5°C) at Abu Samra, 5 February

National monthly maximum temperature records tied or beaten in 2017 (52):

Jan: Comoros, Uganda, Singapore, Mexico

Feb: Iceland

Mar: Kenya, Indonesia, Spain, Chile, Cook Islands

Apr: Ghana, Wallis and Futuna, Honduras, Samoa, Uganda, Pakistan, Cabo Verde, UAE

May: Greece, Iran, Norway, Austria

June: Mexico, Oman, Iraq, Turkey, Albania, Portugal, UAE

July: Cyprus, Comoros, Mayotte, Saudi Arabia, Indonesia, Niger

August: Iran, UAE, Trinidad and Tobago, USA, French Guiana

September: Syria, Saudi Arabia, Iceland

October: Portugal, Hong Kong, Comoros, Brazil

November: Kyrgystan, Uzbekistan, Tajikistan, Cabo Verde, China

National monthly minimum temperature records set in 2017 (2):

Jan: St. Eustatius

July: Greenland

Other records set in 2017:

World record of highest minimum temperature for March: 35.6°C at Yelimane, Mali, 31 March

Asian record of highest temperature ever recorded in April: 50.0°C at Larkana, Pakistan, 19 April

World record of highest temperature ever recorded in May (tied): 53.5°C at Turbat, Pakistan, 28 May

Asian record of highest temperature ever recorded in June: 53.7°C at Ahwaz, Iran, 29 June

Northern Hemisphere record of lowest temperature ever recorded in July: -33.0°C at Summit, Greenland, 4 July

Have a great weekend, everyone! I'll be keeping an eye on the tropics over the weekend, but right now there are no areas of unusual concern to discuss. Threre are still several more weeks we need to be vigilant in the Atlantic, though.