Portugal experienced its hottest September this year since records started in 1931, the Portuguese Institute for Sea and Atmosphere (IPMA) said on Wednesday.

It said the average air temperature was 23.4 degrees Celsius, some 2.9 degrees Celsius higher than the average for 1991-2020, "making this month of September the hottest since 1931," the IPMA said in a statement.

"The maximum air temperature reached 31.03 degrees Celsius, about 4.21 degrees Celsius above the norm, which is again the highest of a historic series," it added.

Portugal was hit by two hot spells during the month, according to the agency, which said September was the fifth driest for rainfall since 2000.

The country recorded its highest temperature for the month of May this year, reaching 40.3 degrees Celsius. 

The IPMA said last week that it had been the third warmest summer on record.