Published Friday 13 October 2023
The First Frost of Autumn 2023 was observed yesterday, Thursday 12 October 2023 at one of the primary stations, Mount Dillon, Co Roscommon when the minimum air temperature fell to -1.2 °C (6.6 °C below its 1991-2020 Long Term Average (LTA)).
Climatologist, Dr Sandra Spillane says that the “First Frost is the first air frost observed in Autumn, that is when the daily minimum air temperature falls below zero degrees Celsius at a meteorological or climatological station”. As one moves inland, away from the coasts, the occurrence of air frost increases” Frosts can of course be a hazard to crops and plants. Frosts in Autumn are less of a hazard to crops than those in late spring, although they sometimes cause damage.
Many times, air frost occurs when skies are clear and winds light, allowing for cooling at night. Air frost can occur in any month, in Ireland. However, it is rare in the months of June, July and August. We know of only one occurrence of air frost in July when -0.3°C was observed at Mostrim, Co Longford on Monday 8 July 1889. There have been two instances of the First Frost occurring in an August, the last being Mount Dillon observed -0.6°C on Monday 30 August 2010 and the other is the August national minimum air temperature record of -2.7°C observed at Rathdrum, Co Wicklow on Sunday 30 August 1964.
In 1972, air frost in early September caused widespread defoliation of the potato crop. The first frost of 1972 occurred on Friday 8 September 1972, with the lowest air temperature being -3.5 °C observed at Clonsast, Co Offaly and 17 other stations were below zero degrees also.
There is a weather saying, “the First Frost and the Last Frost are usually preceded by a temperature very much above the mean” (source: Irish Examiner of Saturday 23 March 1889), so do keep an eye on the weather forecast for your area on our National Weather Forecast pages.
- The First Frost of Autumn 2023 was observed yesterday, Thursday 12 October 2023 at one of the primary stations, Mount Dillon, Co Roscommon when the minimum air temperature fell to -1.2 °C (6.6 °C below its 1991-2020 Long Term Average (LTA)).
- The Last Frost of Spring 2023 was observed on Tuesday 25 April 2023. Air temperatures fell were below zero degrees at around half of the primary (SYNOPTIC) stations and day’s lowest temperature was -3.4 °C which occurred at Mount Dillon, Co Roscommon (6.7°C below its LTA).
- Therefore in 2023 we had 169 days frost-free consecutive days. The year with the longest number of frost-free consecutive days was 80 years ago, in 1943, when there 244 days (and also the latest First Frost and second earliest Last Frost).
- The lowest minimum air temperature of 2023 so far is -7.2 °C at Lullymore Nature Centre, Co Kildare on Tuesday 17 January 2023.
- It has been 303 days since the last Ice Day, which was observed on Wednesday 14 December 2022 at Ballyhaise, Co Cavan when the air temperature was -0.2 °C (10.9 °C below its LTA). Ice Days occur when the daily maximum temperature falls below zero degrees Celsius.
Figure 1. Daily minimum air temperatures < 0.0 °C in 2023
Figure 2. Visible satellite image on morning of Thursday 12 October 2023 showing area of clear skies, ideal conditions for air frost
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