Air Temperature
Extreme warmth settled in the ETR at the end of September vanished at once in the first days of the next month and set either normal or subnormal air temperatures for almost all October, with the decade-averaged temperatures 2-3° less than normal in Central Russia and the frosts as cold as -3…-5° in the south (in the Krasnodar and Stavropol Territories, the Rostov Region and the republics of the North Caucasus). But at the end of the month, the summer weather returned to introduce many new air temperature maxima in the Smolensk and Bryansk Regions in the west, in the Lipetsk and Belgorod Regions in the centre, and in the Crimea, the Kherson and Zaporozhye Regions as well as the Krasnodar and Stavropol Territories in the south. In some locations, the thermometer readings would rise above 30°. In the Crimea, no such warmth at the end of October has been seen for more than fifty years.
A completely different picture was observed beyond the Urals. In Siberia and the Far East, almost the entire month was warmer than usual, and the decade-averaged temperature anomalies exceeded +4…7°. New daily temperature maxima, higher than +20° sometimes, were recorded in Siberia, Trans-Baikal and Kolyma, in the south of the Khabarovsk Territory, and on Sakhalin.
In the Asian Territory of Russia, this October was the second warmest in history, October 2018 being the winner. On the monthly average, the temperature anomalies exceeded 2-5°. The monthly-averaged temperatures in Siberia and in the north of the Far East were ranked the second highest in the history of observations, and those in the south of the Far East reproduced the record-breaking value dated 2018. As for the ETR, the monthly-averaged temperature was close to normal, and as for Russia as a whole, October 2023 turned out to be the second warmest in the meteorological chronicle since 1891, yielding only to October 2018 already mentioned before.
Abnormally warm weather dominated all over East, South-East and South Asia. The normal monthly averages were exceeded by 2° in northern China and by 2-4 or more degrees in Mongolia. The monthly-averaged air temperatures in the rest of these regions were also above-normal, if only a bit above. The latter did not prevent this October from becoming the second warmest after 2006 in the history of meteorological observations in China, and entering the top ten warmest in India where very high temperatures up to 35-39° were still recorded at the beginning of the month. Roughly the same can be said about the countries of South-East Asia where new daily temperature maxima were recorded in Vietnam and Indonesia.
Excessive heat prevailed in Central Asia resulting in monthly-averaged air temperatures of 2-4 or more degrees higher than normal. New air temperature maxima, sometimes in excess of 30°, were reported in Kazakhstan and Kyrgyzstan.
Air temperature averages in the Near and Middle East were above-normal as well. The weather in Iran and Saudi Arabia was very hot; there, the air could heat up to +42° or above sometimes. The normal temperature values in Turkey and in the South-Caucasian countries were exceeded by about 2°.
In Europe, the heat was observed everywhere from Portugal to Ukraine: in the first decade, unprecedented high temperatures were measured in Portugal, Spain, Italy and the south of France, in the second decade, they hit the centre and south-east of the continent (Vienna, Rome, Belgrade, Budapest, Bratislava and Sofia), and in the third, they came to Belarus in the east. Scandinavia was the only area where the weather was colder than usual after early frosts. The temperatures in the north of the continent dropped to -10…-20° in mid-October. Eventually, this month was 2-4° warmer than usual in the entire European continent save for Scandinavia, yet 1-2° colder than normal in the north. It was the second warmest October in the history of Europe after the only even warmer October 2022 and, as reported for different countries, the warmest in Italy and Austria, and at the second position in the ranking list in Spain, France and Switzerland.
In North Africa, the average temperature was above-normal almost everywhere, most notably in the north of the continent where monthly-averaged anomalies reached +2° or above. The unrivalled heat settled on the Canary Islands from October 2 to October 17, with the air temperatures up to +40° in the daytime and up to +30° at night: there, such values have never been seen in October before.
As for North America, Canada did not stop to surprise with extremely high temperatures given that May, June and July of this year were deemed the hottest in its history, and August, the second hottest one. This list was extended in October when new air temperature maxima were set, for the most part, in the north of the country where the monthly-averaged air temperature was 2-8° higher than normal. The anomalies in the east (on the Labrador Peninsula) exceeded 2°.
In most of the US, the monthly-averaged temperatures were close to normal except for the north-east and partially the south-west, where the normal values were exceeded by about 2°. In New England, the average temperature was the second highest in the history of meteorological observations in Maine and the third highest in the history of those in Vermont and New Hampshire. The weather in Mexico and in the countries of Central America was warmer than usual.
The average air temperature in the Arctic was 2° higher than normal. This October was the fifth warmest in the history of meteorological observations. Subnormal temperature conditions were formed in Alaska and Scandinavia only.
Regarding the Northern Hemisphere, October 2023 was the warmest since 1891. In the last three years, each subsequent October has been declared the warmest in the meteorological ranking list.
In Moscow, the average temperature in October was +5.5° corresponding to an anomaly of -0.3°. The last cold October in the capital (i.e., the one with subnormal monthly-averaged temperature) was observed six years ago in 2017.
Sea Surface Temperature
El Niño continued at the eastern equatorial latitudes of the Pacific Ocean. The area occupied by large positive SST anomalies did not noticeably change since the previous month. The average SST anomaly was approximately +1.5° within this water area and +2° or higher in locations closer to the equator. The average SST anomaly calculated for the Pacific Ocean in the Northern Hemisphere reproduced its record-breaking value established in October 2020. High anomalies became less common than in the previous month when they reached +3…4° compared to only 2° now. In addition, almost no negative anomalies were present, whereas in September, they occupied a noticeable area in the tropical zone.
As for the Atlantic Ocean in the Northern Hemisphere, the average SST anomaly reached its absolute maximum again. This was observed for the tenth month in succession, i.e., each month in 2023. The average SST anomaly exceeded +1° for the fifth time in a row. Negative anomalies took place off the US coast only, as in September, while high positive ones (in excess of +2…3°) were still observed in the north of the Barents Sea.
In Russia, this October was marked by abundant precipitation: its monthly totals in the ETR were subnormal in the south only, and either reached or exceeded the normal values elsewhere. The latter was most notable in the North-West, Central and Volga Federal Districts where they were exceeded by 1.5-2.0 or more times, and new maxima of daily precipitation totals were established.
In the Urals and to the east of them, precipitation was also excessive in most constituent entities of the Federation, and was only deficient in the Republics of Khakassia and Buryatia, in the Irkutsk and Arkhangelsk Regions, in the Primorye Territory as well as on the Sakhalin and Kuril Islands. In locations of abundant precipitation, its rate sometimes reached 90 mm of rainwater per day.
The weather in most of East Asia was dry: normal or above-normal precipitation was only observed in the south-west of this region, in the north-west of China, and partly in Japan.
Ample precipitation came to the countries of South-East Asia where the summer monsoon was still in place. The normal precipitation amounts in some areas were exceeded by 1.5-3.0 times. Heavy rains in Thailand and Myanmar led to floods in the first half of the month. Record-breaking precipitation quantities were measured in certain locations.
In India, the summer monsoon was over, and the weather was dry. During the month, rains fell just in some places in the north and east of the country.
A lot of precipitation was received by the countries of Central Asia where the normal monthly figures were exceeded by 1.5-2.5 times.
The weather in the Near and Middle East was mostly dry.
The same can be said about North Africa where precipitation was basically observed in the south along the coast of the Atlantic Ocean and the Gulf of Guinea.
Precipitation in Europe favoured the west, centre and east of the continent, but was scarce in the south where almost half of Greece was seized by the drought. On the other hand, torrential downpours that hit Great Britain several times in October caused massive floods in the country, showers at the end of the month inundated Milan in northern Italy, and heavy rains in Ukraine deluged a number of settlements.
In Canada, the weather was dry, whereas in the USA, heavy rains passed across the north of the country, but the weather in the south was also mostly dry. Drought that was observed in Central America was appraised by the experts as the most severe one in the last half of the century.
In Moscow, 126 mm of precipitation fell in October. This is the eighth result in the meteorological chronicle of the capital since 1891. The monthly-averaged precipitation anomaly amounted to 180%.