October 2021 was characterized by lower than normal sea surface pressure over Scandinavia, Iceland, Great Britain and Ireland, as well as over the central and eastern Mediterranean region. Above normal sea surface pressure was present everywhere else across the EFAS domain. Monthly precipitation totals were above the long-term mean in the northwest and northern Europe as well as the northern central Mediterranean region. Sums below the long-term mean were observed mainly in the eastern and southern parts of the EFAS domain. Monthly mean air temperature values were below the long-term mean in the central parts and above the long-term mean over the remaining parts of the EFAS domain.

At the beginning of October, the Iceland low and Azores high were around their typical positions. Another high-pressure system was located over eastern Europe and an upper-level low-pressure system over the eastern Black Sea. While the high-pressure system over eastern Europe was stable and extended to the southeast in the first decade of October, the Azores high shrunk and finally dissipated. The trough associated with the Iceland low expanded to the western Mediterranean region and swung eastward. Several heavy precipitation events were associated with this trough. A low-pressure system developed over the Ligurian Sea and moved south-eastward. It brought heavy rains to Greece and neighbouring countries for several days. While the high-pressure system over east Europe dissipated, another high-pressure system moved to Great Britain and Ireland and a low-pressure system moved to northern Scandinavia. An upper-level trough expanded from this low-pressure system to the central Mediterranean region, and later a low-pressure system was cut-off there. This system was associated with heavy rainfall events in southern Italy, southern Balkans and western Turkey. At the same time, another low-pressure system arrived in Scandinavia. In the next days, the high-pressure system located over Great Britain and Ireland moved towards central, and later, southern Europe. A low-pressure system moved from the Atlantic to Scandinavia. It got intensified and brought strong winds to northern, central and eastern Europe while moving to the Kara Sea. A high-pressure system moved from the Azores over central to eastern Europe and transformed into a ridge reaching out to the Azores High. During the same days, a quasi-stationary low-pressure system developed over the central Mediterranean Region and intensified to a medicane (named Apollo or Gloria depending on the country). It brought high precipitation amounts over this region. In the last days of October, the ridge disappeared, and a high-pressure system remained just over east Europe. A low-pressure system moved from Iceland to Great Britain and Ireland.

The highest precipitation amounts were observed over the central Mediterranean region, east of the Black Sea and at the west coasts of Scandinavia, the Iberian Peninsula, Great Britain and Ireland (Figure 1). No or almost no precipitation fell in many parts of east Europe and Anatolia as well as the south-western and south-eastern parts of the EFAS domain. Monthly precipitation totals above the long-term mean occurred mainly over Scandinavia, Great Britain and Ireland, the Balkans, Sicily, and over some parts of the southern coast of the Mediterranean Sea (Figure 2). Monthly totals below the long-term mean were reported mainly over central and east Europe, Anatolia as well as over the south-western and south-eastern parts of the EFAS domain.

The monthly mean air temperature ranged from -9.5°C to 32.4°C with the highest values in the southern parts of the EFAS domain. The lowest temperature values were reported in the northern and mountainous parts (Figure 3). Air temperature anomalies ranged from -4.3°C to 9.6°C (Figure 4). Monthly mean air temperature values below the long-term mean occurred in south and southeast Europe, and in some regions in Northern Africa, while positive air temperature anomalies appeared in the other parts of the EFAS domain.