Abnormally hot summer in the European Territory of Russia gave way to cold autumn in the first days of September. Frosts in the areas from Murmansk to Volgograd came as early as on the fifth of the month, and occurred again and again since then. The average air temperature was 2-3 or more degrees below normal in the first decade. The overall picture remained about the same later on, but the colds were spreading far and wide to occupy almost all Russia by the end of the month, save for the south of the Far East and the Arctic region. The record-breaking colds were observed in the north of the ETR, in the south of the Urals, in the north of West Siberia and in Chukotka. At the end of the month, 20-degree frosts reached Yakutia already, and the cold spells haunting the ETR came to Tyva, Khakassia, to Irkutsk, Chelyabinsk and Kurgan Regions, and to other areas of Russia as well. The Arctic territories and the south of the Far Eastern Federal District were the only regions where new maxima of air temperature were recorded.

As a result, this September became the coldest in the ETR for the past 25 years since 1996, and hence the coldest one in the 21st century. The monthly-averaged air temperature was less than normal all over Russia. Even though the weather in the Asian Territory of Russia was sometimes much colder than usual, it changed to warmth from time to time, and the monthly-averaged air temperature turned out to be close to normal both in the Asian Territory and in Russia as a whole. This temperature was less than normal in all federal districts of the ETR, close to normal in the Urals and Siberian ones as well as in the north of the Far Eastern Federal District, and higher than normal, remarkably higher indeed, in the south of the latter District. The average air temperature of September 2021 in the south of the Far East was at the third place in the list of highest historical values, yielding to September 2020 and September 1959 only.

In the east and south-east of Asia, this month was warmer than usual, notably in China and Mongolia where the monthly-averaged temperatures exceeded their normal values by 2-4° or more. This September was the hottest in the meteorological history of China, with the previous record of 2005 overridden by as much as 0.5°.

In the Hindustan Peninsula, the average September temperature was approximately normal albeit that against the background of negative anomalies in its most part.

The Middle East was occupied by heat. On the monthly average, the air in Iraq warmed up to 2-4° above the normal value. Westwards in the Near East, the temperature was generally normal, although the summer heat did not yet completely abandon this region: for example, the temperature in Israel reached 36-39° sometimes.

In the south of Central Asia, the monthly-averaged temperature anomalies were basically the same as in the Middle East, i.e., 2-4°, and the air would heat up to +40° in certain locations. But in the north of the region, namely, in Kazakhstan, the situation was entirely different: the air temperature either matched the normal figure, or was below it.

The beginning of autumn in the North African region was just as hot as summer. In the middle of the month, the heat covered the Mediterranean countries. There, the thermometer readings rose above +40° sometimes, and the monthly-averaged temperature anomalies were as high as +2…4° and more. For the second year in a row, September in this region was recognised as the hottest in the history of meteorological observations.

As regards the temperature distribution, Western and Eastern Europe looked like antipodes this month. In the West, anomalously warm weather prevailed, and the normal values of air temperatures were exceeded by two or more degrees. New daily temperature maxima were recorded in the north of France and of the UK, in Belgium and Ireland as well as in the Scandinavian countries, and a new absolute maximum for September was observed in Norway. In the East, the weather was mostly cool, with subnormal monthly-averaged air temperatures in the Baltic countries, in Finland, Belarus, Ukraine, Moldova and Romania.

Warmth in September prevailed all over the North American continent excluding Alaska and its adjacent area of Canada. The average temperatures in a large part of the US, Canada and Mexico were exceeded by 2-3° and more. The weather was extremely hot in the western United States: in California, the air in Death Valley sometimes heated above +50°. New air temperature maxima were recorded at some locations in New Mexico, Colorado and Arizona. September 2021 in the USA and Canada entered the Top Five of hottest in the history of meteorological observations.

In the Arctic, the monthly-averaged air temperature was just below the Top Five of highest for 1891-2021. This September, the normal values in the Canadian sector and in most of the Russian one were exceeded by 2-3 or more degrees, whereas the monthly averages in Chukotka and Alaska were less than normal. In the bottom line, September in the Arctic was almost 2° warmer than usual on the monthly average.

Subnormal monthly-averaged air temperatures in Eurasia, Alaska and India as well as in part of the ocean water bodies prevented this September from taking a position among the leaders across the Northern Hemisphere, and its monthly-averaged temperature was only at the bottom of the Top Five of the highest-ranked values recorded in the history of meteorological observations on the planet since 1891.

In Moscow, the monthly-averaged air temperature was 9.9°. This is 1.1° below the normal value. In September, a negative anomaly of air temperature in the capital was last observed in 2013, and similar colds, in 1997. The frosts in the capital primed in the middle of the month.

A growth of negative SST anomalies at equatorial latitudes of the Pacific Ocean was marked both in the Northern and Southern Hemisphere. The area of these anomalies expanded since July and August, while their mean values in the El Niño area reached -0.5° again, in line with a well-known criterion of an incipient cold episode of the Southern Oscillation. Why? Was it an occasional surge, or a recovery of La Niña which terminated in spring? This should become clear in a few upcoming months. The mean SST anomaly of the Pacific Ocean in the Northern Hemisphere increased by 0.1° as compared to the previous month. Large positive anomalies were observed in the central part of the Pacific Ocean in the subtropical belt, in the south-west as well as along the Asian coast, and reached +2…3° or more in certain water areas.

Water in the Atlantic Ocean was very warm in the Northern Hemisphere: the monthly-averaged SST was above-normal everywhere, but most remarkably, at subtropical and temperate latitudes along the coasts of Europe and North America. Positive anomalies have moved far to the north and covered the Davis Strait and the Greenland Sea. The water temperature was higher than normal in marginal European seas including the North Sea, Baltic Sea and Black Sea. The average SST anomaly was 0.2° higher than in the previous month or in September 2020, amounting to the second highest value in the entire history of meteorological observations and yielding to the value recorded in September 2003 only.

Precipitation in September was normal or above-normal in the ETR with the exception of the north-western areas, and was most abundant in the central and southern ones where its normal amounts were exceeded by 1.5-2.0 times or more in many constituent territories of the Federation. At the beginning of the month already, rains flooded Astrakhan, in the middle of the month, the central and central black-earth regions as well as the Volgograd Region, and in the third decade, the Krasnodar Territory and the North Caucasus, bringing up to 60 mm of rainwater per day, or the normal monthly amount in a couple of days in some places. Rains caused mudflows, floods and landslides. In the Republic of Komi, snow fell and created a transient snow cover.

In the Urals, the monthly precipitation totals were approximately normal. The production of agricultural crops in the south of this region was adversely affected by the summer drought. In addition, the ground was covered with snow by the twenties of the month already.

Vast spaces of Siberia called for a rich variety in the distribution of precipitation. Indeed, in Western Siberia, the precipitation quantities turned out to be normal or increased, but in East Siberia, rains were sensibly in need, especially in its southern regions: for example, less than 20% of the normal monthly rainwater amount was recorded in Khakassia. Abundant rains fell in the north of Siberia with up to 70 mm of daily atmospheric moisture in some areas of the Khanty-Mansi Autonomous District. Snows in the south of the Krasnoyarsk Territory, in the Kemerovo and Irkutsk Regions as well as in the republics of Tyva, Khakassia and Altai produced a snow cover already fit for skiing.

In the Far Eastern Federal District, a lot of precipitation fell in Buryatia and in the Trans-Baikal Territory. There, the daily precipitation totals were greater than 30 mm, and the normal monthly amounts were exceeded by 1.5-2.0 times. In the rest of the territory, the figures were close to normal or lower than that. On some days, rains bringing up to 30 mm of daily rainwater flooded the Primorye and Khabarovsk Territories as well as the Sakhalin and Amur Regions. The Jewish Autonomous Region was the only area to receive insufficient precipitation in September (less than 20% of the normal amount).

The central and north-eastern regions of China were flooded with rains in amounts 2-3 times the normal ones, leading to floods and landslides, and claiming the lives of people. In the southern and western provinces, the monthly precipitation totals were sub-normal in spite of occasional heavy showers. Local meteorologists reported that September 2021 was the fourth wettest in the history of meteorological observations in China, and that such monthly precipitation totals have never been observed in the north of the country. The precipitation amounts were close to normal in Mongolia, and lower than normal in Japan and on the Korean Peninsula. On September 6, snow on Mount Fuji in Japan fell 25 days ahead of the climate.

Torrential rains flooded South-East Asia where the normal monthly rainwater amounts were exceeded by 1.5-2.0 or more times. Showers in Thailand, Vietnam, Malaysia, Indonesia and Philippines caused massive floods, destroyed houses and deluged agricultural lands. The fatalities were reported. In Vietnam, a natural disaster resulted after Jolina, a strong tropical cyclone that poured more than 900 mm of rainwater (three times the normal amount) for a time interval from September 10 to September 13. The rainfall season in the south of Malaysia and in Indonesia started a month before its climatic due date.

Monsoon showers kept on torturing the countries of the Hindustan Peninsula. In India, more than 1100 mm of rainwater accumulated for a summer monsoon season that was not yet complete by mid-September. This was one of the highest achievements ever recorded in history. Indian meteorologists claimed that the participation totals collected for this season were highest since 1944. Showers in the states of Gujarat and West Bengal brought up to 500 mm of precipitation per day. Likewise, mountainous Nepal was not spared from September rains that brought 120 mm of atmospheric moisture for some eight hours. Heavy showers, floods and landslides pounced upon Pakistan and its north-eastern regions in particular. Casualties where reported here and there.

The weather in the Near and Middle East was dry, with no precipitation at all in many regions. Yet, occasional heavy showers did occur in the south of the Arabian Peninsula, and brought up to 2-3 normal monthly precipitation amounts to this arid region.

In most of Central Asia, the weather was also dry everywhere with the exception of the north Kazakhstan where the monthly precipitation totals were normal or slightly increased.

No precipitation was observed in the Mediterranean countries of Africa excluding its narrow coastal strip. But a lot of heavy rains came to Nigeria and the Gulf of Guinea countries to the south of Sahara and caused numerous floods in these areas. Floods after heavy rains were also observed in Sudan where the Nile overflowed its banks and the water flows caused harm to tens of thousands of people. The citizens of Cameroon saw snow for the first time in life in their near-equatorial African country.

Central Europe received scarce precipitation this September, in contrast to the west and east of the continent. The monthly precipitation figures in Spain and Portugal or in the south of France were 1.5-3.0 or more times greater than normal. The south-west of France was hit by the record-breaking heavy rains of intensity as high as 50-100 mm per hour. Judging by the statistical data, such precipitation rates are observed once in a hundred years in this region. Up to 200 mm of daily rainwater accumulated in some areas of Spain and Portugal to result in severe floods that inundated highways and railroads, paralysed the traffic and destroyed 50 to 100% of harvests in grape, persimmon and citric plants. Heavy downpours bringing up to 50 mm of rainwater per day took place in the south of England and changed the streets of London into rivers. Showers flooded the north of Italy where the airport of Milan disappeared under water. As of Eastern Europe, the normal monthly precipitation amounts were exceeded by 1.5-2.5 times in Ukraine and Belarus where the intensity of rains reached 30-50 mm per day. Pelting rains caused floods in Slovenia. The first snow fell in Finland and created a snow cover up to 10 cm deep.

In the US, most precipitation went to the eastern and north-western regions of the country where the averages either reached or exceeded the normal values, by 2.0-2.5 or more times in some places. Heavy showers in the middle of September came along the Atlantic coast and caused floods. Highways turned into rivers, and New York was flooded with water. The tropical storm nicknamed Nicolas hit the coasts of Texas and Nevada. Heavy rains accompanied these outbreaks. On the other hand, the weather in the central regions was generally dry in September. In Alaska, snow was observed for the first time.

In Canada, rains were abundant in the Peninsula of Labrador, and in the northern regions of the country, with the normal amounts exceeded by 2.0-2.5 times. Hurricane Larry flooded Newfoundland, pouring up to twice the monthly rainwater amount per day in some places,

Mexico alongside the other Central American countries suffered from rains this month. The showers in mid-September flooded the central regions of Mexico. More than 30 thousand of people were affected, and some of them died. No such damages due to rains have been seen in Mexico over more than forty years. In Central America, heavy rains caused most trouble to the citizens of Guatemala and Honduras.

In Moscow, the monthly precipitation total was 84 mm, amounting to a 129% anomaly. For the past nine months, 95 percents of the normal annual precipitation amount have already been collected.