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September 2021 Provisionally Warmest on Record

Mean temperatures across Ireland were above their long-term averages, with September temperature records broken at several stations.  Phoenix Park in Dublin also had its warmest September in 122 years.

Mean temperatures for Ireland were 2.1°C above their long-term averages (LTA 1981-2010) for the month, with an even higher value for the monthly minimum average temperature of 3.0°C. The mean maximum temperature for September was 0.8°C above LTA. In general, the temperatures observed were around that observed in August 2021 and in some areas, even warmer.

Munster and Leinster had their warmest September on record, with mean temperatures of 15.6°C and 15.1°C respectively. Connacht had its joint highest, matching 2006, with 14.7°C. While Ulster had its second highest 14.3°C, its highest was in 2006 with 14.4°C.

This warm weather is partly due to the warm nights experienced during September in all areas, with cloudy weather and high pressure dominating. Ireland, and each province, recorded their warmest minimum monthly temperatures:

  • – Munster was 11.8°C (2.4°C above its LTA)
  • – Connacht was 11.6°C (2.4°C above its LTA)
  • – Leinster was 11.3°C (2.4°C above its LTA, joint 1st with 2006)
  • – Ulster was 10.8°C (2.2°C above its LTA).

The Met Office have given a value of 10.7°C for Northern Ireland – its highest average minimum September temperature on record.

Individual stations also observed record warm weather:

  • – Shannon Airport, Co Clare (1.5°C above its LTA) also recorded its warmest September on record (length 71 years).
  • – The highest daily temperature was 27.9°C at both Shannon Airport, Co Clare (10.2°C above its LTA), its highest daily maximum temperature for September on record (length 75 years).

While in the long-series dataset (observations recorded between 09 UTC on the day to 09 UTC the next day and over 24 hours):

  • – Phoenix Park, Co Dublin had its warmest September in 122 years with a month’s average of 15.8°C (2.4°C above its LTA), the previous warmest was in 2006.
  • – Malin Head, Co Donegal experienced its second warmest September in 122 years, with a monthly average temperature of 14.6°C (1.4°C above its LTA) – its warmest September was in 2006.

Dr Sandra Spillane, Climatologist at Met Éireann said: “September 2021 has been a notably warm and dry month across the island of Ireland, with mean temperatures well above average and below average rainfall.  Much of September was characterised by periods of high pressure which often brings dry and settled weather, before conditions turned more Autumnal towards the end of the month as low pressure moved across Ireland.”

The latest climate projections for Ireland signal a warming trend across all seasons into the future.  More details on September 2021 in our Monthly Statement.

Temperature Graphs for September 2021 - click image for link and chose 'Temp Graph'

Temperature Graphs for September 2021 – click image for link and chose ‘Temp Graph’

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