Istanbul recorded its third-highest daily rainfall since measurements began at the Kandilli Observatory in 1911, according to the Boğaziçi University Kandilli Observatory and Earthquake Research Institute, as authorities warned that the risk of heavy rain, flooding and flash floods could continue across parts of the Marmara and Western Black Sea regions.

The institute's Meteorology Laboratory said 129.6 millimetres of rain fell at the Kandilli Observatory station on October 15, making it the third-highest daily rainfall recorded at the station between 1911 and 2026.

One of the wettest days on record

According to the observatory's historical records, the highest daily rainfall was 165.8 millimetres on 20 July 1951, followed by 131.3 millimetres on 3 October 1942.

The 129.6-millimetre rainfall recorded on Thursday therefore ranks third overall and the second-highest daily rainfall ever recorded in October at the observatory.

The institute also reported that 174.3 millimetres of rain fell between 1 and 15 October, with nearly 74 per cent of that total recorded on a single day.

Researchers noted that the observatory's meteorological archive, which dates back to 1911, remains one of Türkiye's most important long-term climate datasets for analysing extreme weather events and climate trends.

Heavy rain to shift eastward

The observatory said the severe rainfall and gale-force winds affecting Istanbul are expected to weaken from Thursday evening, although moderate rainfall is likely to continue for some time.

Meteorologists forecast that the weather system will gradually move eastward, bringing heavy rain to Kocaeli, Sakarya, Düzce, Bolu and parts of the Western Black Sea, including Zonguldak, Bartın and Karabük.

Rain is expected to continue across much of Marmara, the Black Sea region, northern Central Anatolia, and parts of southern and eastern Türkiye on Friday. Forecasters warned that rainfall could intensify again during the afternoon around Çatalca in Istanbul and Kırklareli.

Flood risk remains

On Saturday, rainy conditions are expected to persist across Marmara, the Aegean, the Mediterranean and Central Anatolia.

The observatory warned that parts of eastern Marmara, western Black Sea provinces and inland areas of the Aegean could experience heavy rainfall capable of triggering flash floods and urban flooding. Meteorologists said rainfall expected in parts of the Western Black Sea on Saturday night could exceed the intensity of the storm that affected Istanbul on Thursday.

Rainfall is forecast to ease on Sunday, while lighter showers may continue early next week along Istanbul's northern coastline and parts of the Western Black Sea.(ILKHA)