Cold September in the ETR gave way to a moderately cool October. In the first decade, the weather was abnormally cold in the southern and central Russia where the decade-averaged temperature anomalies reached -2…-4° or lower, with new daily minima recorded in the Smolensk, Tambov, Tula, Oryol, Belgorod and Moscow Regions as well as in the republics of Tatarstan and Udmurtia. In the second and third decades, the temperature returned to its normal value or even slightly above it everywhere save for the south: the frosts in the Southern and North Caucasian Federal Districts at the end of the month were as cold as -4…-10° or below. In general, frosts in the ETR were not uncommon in October, but the unprecedented temperature highs were also observed: for example, in the Murmansk Region and the Komi Republic in the north of the ETR in the first half of the month, and in the north-west and centre of the ETR in the second half of October.

This is in contrast to the territories east of the Urals. There, the temperature averages fluctuated around the normal figures in the third decade but overshoot them remarkably in the second and third ones: by as much as 6-11° or more in Siberia and Yakutia. New temperature maxima were repeatedly established both in the north and the east of Siberia, and in Yakutia. During the month, cold weather prevailed in the north of the Far East, but the south of this region was overwhelmed by extreme heat in the third decade. New temperature highs were repeatedly recorded in the Amur Region and in the south of the Khabarovsk Territory where the monthly-averaged temperature anomalies reached +3-4°or more.

As a result, the monthly-averaged air temperature was higher than normal in most of the country: by 2-3° and more in the European Territory, and by 4-6° and more in the Asian Territory of Russia. Sub-normal monthly averages were measured in the north-east of the country, as well as in the south of the ETR. And as for the federal districts, the monthly-averaged temperature turned out to be lower than normal in the North Caucasian Federal District only, and was either normal or increased in all the other ones.

The monthly-averaged temperatures in most of East Asia were close to normal, with the exception of some locations where the normal values were exceeded in the south-west of China in the provinces of Yunnan and Sichuan, and in the north of Japan. In Japan, the unprecedented high temperatures were recorded in the first decade of the month: the thermometer readings rose above 30° sometimes. Conversely, the Korean Peninsula and the east of China were hit by bitter colds in the middle of the month, and new temperature minima down to -10° or below were established in these areas.

In South-East Asia and in most of the Hindustan Peninsula alike, the average temperature in October was also approximately normal, save for the state of Assam in the east of India where the normal value was exceeded by about 2°.

In most of the Near and Middle East, the monthly-averaged temperature was higher than normal, especially in the Saudi Arabia, in the Gulf countries and in the south of Iran: there, the normal values were exceeded by two or more degrees. In Iran, the previous maximum of air temperature in October was surpassed, and replaced by a new one equal to +45.6°.

The temperature in Central Asia was about normal; and in most of the region, against the background of negative anomalies that reached -1…-2° in some places. The anomalies were weakly positive in the north-west of Kazakhstan only.

The air temperature in North Africa was above-normal. The anomalies did not exceed +1° as a rule, and were higher than that in some locations only. In Morocco, the absolute maximum of temperature in the country for this month was reset to +43.5°on October 1.

In Europe, the warmth and cold co-existed during October. The air temperature in the north of the continent as well as in Spain and Portugal was higher than normal, by 2-3° or more in places. New records of heat were set in the Scandinavian countries. October in South-Eastern Europe and partially in Central Europe was colder than usual as a whole, but the negative anomalies did not exceed 1°. Extremely cold air invaded the continent from time to time: for example, the record-breaking low temperatures were observed in Belarus and in the west of Ukraine. Frosts as cold as -5° and below were recorded.

The monthly-averaged air temperature in the North American continent was above-normal everywhere with the exception of small coastal areas along the Pacific coasts of the US and Canada. In the latter country, its anomalies were as high as +4…10° or more, and this October became the warmest in the history of meteorological observations. The previous maximum of the monthly-averaged temperature in October set in 2010 was exceeded in Canada by almost 2°. As for the USA, October 2021 was the fifth or sixth warmest, while in New England in the north-east of the country, such a warm October has never been seen before.

The weather in the Arctic was very warm. The average anomaly of air temperature was +4°, and +10° in the Canadian sector. In the outcome, this October became the fifth warmest in the history of meteorological observation in the region.

The average air temperature of October in the Northern Hemisphere regained (to an accuracy of 0.1°) its absolute maximum previously achieved two years ago.

In Moscow, the averaged temperature in October was +6.4°, and the anomaly was +1.3°.

The area occupied by negative SST (sea surface temperature) anomalies noticeably increased at the equatorial latitudes of the Pacific Ocean, especially in the Southern Hemisphere. The absolute values of these anomalies increased as well, and exceeded 1° in some areas of the water body. This may point to a probable eventual return of La Niña after three months of neutral phase of the Southern Oscillation.

At the tropical and temperate latitudes of the Pacific Ocean, SST anomalies were positive, and especially high along the Asian coast as well as in the central part of the Ocean. In some water areas, in quite a few of them indeed, these anomalies reached or exceeded +2-3°. Yet in the north, e.g., in the Bering Sea or in the Gulf of Alaska, the anomalies were negative again.

The SST of the Atlantic Ocean in the Northern Hemisphere was markedly higher than its normal value. In October, the Ocean was so warm only two times before, in 2003 and in 2004. The average SST anomaly remained at the level of the previous month. In the Gulf of Guinea, along the coast of North America, in the central part of the Ocean and in the North, Norwegian, Greenland and Barents Seas in its north, the anomalies were in excess of +1° – the same as in most of the Mediterranean Sea.

Precipitation in most of Russia was scarce during this October. As regards the ETR, the normal amounts were significantly exceeded in the republics of the North Caucasus only, by two or more times in places. The normal or increased values were achieved in the Krasnodar Territory, in a number of regions of Central Russia (viz., the Tver, Yaroslavl, Kostroma and Kaluga Regions) and almost everywhere in the north-west. A shortage of precipitation was observed in all other constituent entities of the Federation. In the Volga and South Federal Districts and in the south of the Central one, this shortage was quite severe: in some places, the monthly precipitation totals were as low as 10-20% of the normal amount. Heavy rains passed along the Black Sea coast of the Caucasus, bringing 60-130 mm of rainwater per day at the beginning of the month. The weather was snowy in the mountains and in the north, e.g., the depth of the snow cover reached 10 cm in the Republic of Komi and in the Murmansk Region. A new daily precipitation maximum was recorded in Saint-Petersburg.

In the Urals and in Siberia, a lot of precipitation went to the northern territories (Yamal, Taimyr and Evenkiya). The amounts were close to normal in the south of Siberia (the Altai Territory, the Altai Republic, the south of the Krasnoyarsk Territory, and the Tyumen Region), but insufficient in the rest of the territory from the Urals to the Far East.

Speaking of the Far East, the precipitation amounts were normal or somewhat increased solely in the north (in Yakutia and Kamchatka) and in the Amur Region in the south. In the rest of the territory, a notable lack of moisture was observed.

The weather in China was still rainy: the normal precipitation amounts in the east and in the centre of the country were exceeded by 2-3 or more times in some places. Heavy downpours in the province of Liaoning in the north-east of China caused mudflows and landslides. There, more than 250 mm of precipitation accumulated per day, which is in excess of twice the normal monthly figure. Heavy showers in the province of Shaanxi in the central China brought 170 mm of rainwater for a single day and led to overflowing of river banks and to flooding. Floods in Inner Mongolia resulted in the fatalities. Yet, the monthly precipitation figures were small in certain territories including the province of Jiangxi in the south and the Xinjiang Uygur Autonomous Region in the west, where no precipitation at all was observed in places. The precipitation amounts in Japan were subnormal in the south of the country and close to normal in the rest of the territory.

Precipitation in South-East Asia was abundant: the normal amounts were exceeded by two or more times in some locations of Indochina, and by 3-4 or more times in Indonesia. At the beginning of October, rains on the islands of Borneo and Sulawesi caused massive floods and casualties. In the middle of the month, Vietnam was inundated. In some places, up to 300-400 mm of rainwater fell per day. New daily precipitation maxima were recorded. Due to floods and landslides, schools were closed and highway traffic circulation was disrupted.

A lot of rains fell in India again, so that the normal precipitation totals were overshot by two or more times. In West Bengal, downpours caused devastating floods in the first days of October. The daily precipitation amounts exceeded 300 mm, i.e., almost four times the normal monthly figure. More than 2.5 million people were affected, and the fatalities were reported. In the middle of the month, continuous rains caused severe floods in the south-east of the country. Snow fell in the mountains. In Nepal, rains fell for three days in succession, causing floods and landslides that killed 88 people.

The weather in the Near and Middle East was mostly dry, but heavy rains did occur in certain locations. At the beginning of the month, downpours induced by the Shihan tropical storm hit Oman and Yemen, bringing up to 300 mm of daily rainwater to the former country. This was three times the normal annual amount. The same storm brought torrential rains to the south-east of Iran. In the last days of the month, bizarre rains in Iraqi Kurdistan brought more than half of the normal monthly rainfall amount per day.

October was dry in most of Central Asia. The normal precipitation amounts went only to the east of Kazakhstan and Kyrgyzstan.

Almost no rains fell in the north of Africa. Heavy downpours came to the countries of West Africa only, and were especially intense in the west of the continent. More than 100 mm of rainwater fell in Côte d'Ivoire in twelve hours, with 60 mm of this figure poured just in half an hour. The normal precipitation quantities were exceeded by 1.5-2.0 or more times everywhere from Senegal to the countries of the Gulf of Guinea.

In Europe, heavy rains fell in many countries this October. In the south of the continent (in the Balkan countries, in Greece, in the south of Italy and France, and in Spain), the normal precipitation figures were exceeded by 1.5-2.5 times. In southern Italy and in Sicily, rains with an intensity of 40-70 mm per day caused catastrophic floods. The city of Catania was flooded with 600 mm of rainwater, i.e., the normal annual quantity. Torrential rains led to floods in the south of France. In Marseille, more than 100 mm of precipitation – almost three times the normal monthly amount – fell for a single day. The entire Côte d'Azur was flooded. In the Italian province of Liguria, 750 mm of precipitation fell in twelve hours to set up a new European record, and 500 mm in six hours, which was also a new record-breaking achievement. The motor and railway traffic circulation was almost completely paralysed. Heavy rains took place in the north of the continent as well: there, the normal monthly totals were exceeded by 1.5-2.0 times. The streets of London sank under the water after the torrential rains. From 130 to 370 mm of precipitation accumulated per day in Scotland. Many residents found themselves in distress. Heavy rains pelted in the Baltic States and Scandinavia, bringing up to half the normal monthly amounts per day in some places. New maximum precipitation totals were set in a number of European countries. But the areas of very scarce precipitation were also vast, comprising the countries of Eastern Europe and partly Central Europe.

The United States were flooded with rains. The normal monthly amounts were exceeded by 1.5-3.0 or more times almost everywhere. This October entered the Top Ten of the wettest in the history of observations. At last, rains came to California, where up to 250 mm of rainwater accumulated in some regions in October after a prolonged drought from March to September when the minimum precipitation total in history was recorded. In the territory of California and Nevada, October 2021 was the second wettest in the meteorological chronicle. In the states of Utah and Wyoming, snow fell, a blizzard rose, and snow banks up to 45 cm high were formed in some places. In Canada, almost no precipitation was received in the provinces of Yukon, British Columbia and Saskatchewan in the west of the country, and close to the normal amount in the rest of the territory. The precipitation quantities were normal or increased in the central part of Mexico where vast areas went under water after torrential rains, and were scarce in the rest of the country.

In Moscow, 42 mm of precipitation fell in October: this is 71% of the normal monthly amount. The normal annual total has already been reached in the capital.