Summer 1990 started off quite terrible in June with the wettest June in places in 8 years at the time (since 1982) and for others since 1958. It was a cool month and the coldest June since 1985 at this time but June 1991, a year after, was to be even colder.
July 1990 featured some heavy downpours early and late in the month including a daily rainfall of 32.0mm at Dublin Airport on the 4th and 28.2mm at Cork Airport on the 29th. However, after a relatively dull start in parts, it became very sunny through the month with many days having at least 10 hours of sunshine for stations. It was the second consecutive very sunny July following July 1989 which had broken records for sunshine at some stations. July 1990 was Rosslare's sunniest July on record with an average of 9.3 hours of sunshine per day and a monthly sunshine total of 289.5 hours. We have not seen a monthly sunshine total as high as this since. Three closest times we have:
August 1995 - 283.9 hours at Rosslare
July 2006 - 283 hours at Rosslare
July 2013 - 280.0 hours at Sherkin Island
With the sunshine came lots of 20°C+ days. 20°C was reached somewhere in Ireland everyday from the 10th onwards (inclusive) bar the 15th. The highest temperature was 27.7°C at Valentia Observatory on the 13th. The first week of the month in contrast with some heavy downpours had temperatures for the month around two degrees below normal.
July 1990 is very forgotten by people without a doubt. You barely ever see it being spoken about yet it was very sunny.
The warm weather was to continue into the first 2-3 days of August 1990 with it intensifying further for a time in the east, especially in Dublin.
Apart from the extreme west where some rain was recorded including 5mm in Belmullet, Ireland laid under an anticyclone on the 1st August bringing plenty of sunshine to places and very warm conditions with temperatures reaching 24-25°C in a light southerly flow. In the extreme west, winds were quite gusty though. Temperatures did not drop much overnight getting only down to 14-17°C generally so a very uncomfortable night. The 2nd was a very similar day to the 1st but temperatures rose even further reaching record breaking highs in Dublin.
The 2nd August 1990 was the hottest day of the 20th century in Dublin and remains the hottest day on record in the county. The Botanic Gardens, Glasnevin, Co. Dublin recorded an afternoon maximum temperature of 31.0°C on the 2nd whilst 30.6°C was recorded at the Ordnance Survey office in Phoenix Park, the highest recorded there since its records began in 1881. Casement Aerodrome got up to 29.5°C, the hottest August day here since 1975 and Dublin Airport got up to 28.7°C, its hottest day on record. Dublin Airport's temperature here was more than a degree higher than its previous record of 27.6°C on 13th July 1983. To remind you, with these soaring temperatures (and yes actual soaring temperatures) it was complete blue skies.
A cold front pushed eastwards on the 3rd introducing much cooler conditions ending a long period of warm, settled weather for the majority of places since the 10th July. Much of August 1990 provided humid and dry conditions afterwards but not all that sunny. In fact, it became the dullest August on record in parts of the west including at Belmullet which had only 58.8 hours of sunshine all month, 38% of its average August sunshine! This was following a very sunny July of course. There continued to be many days above 20°C for parts regardless of the dull conditions resulting in the warmest August since 1984. The Irish Mean Temperature (IMT) for August 1990 was 16.7°C (+1.3°C above the 1981-2010 average) whilst the IMT for August 1984 was 16.9°C. July 1990's IMT did not stand out that much but it was a warm month with 16.1°C (+0.7°C above the 1981-2010 average) in comparison to an IMT of 17.8°C in July 1989 which had been Ireland's warmest month on record at this time beating July 1983 by 0.2°C.
Ireland was not alone in the record breaking heat as was the UK. Before August 1990, the UK temperature record was 36.7°C at Raunds and Canterbury on August 9th 1911 so the record stood for 79 years! It was beaten in August 1990 with Cheltenham recording a maximum temperature of 37.1°C on the 3rd. In contrast to the 1911 record, this record were to stand only for 13 years being beaten again in August 2003. Wales' record was set too with 35.2°C at Hawarden Bridge on the 2nd. Unlike August 2003, the heat was far more widespread in August 1990. The Central England Temperature (CET) for August 1990 was 18.0c which is the 9th hottest August on record in the series up to 2017. In comparison, the hottest August is 1995 with a CET of 19.2°C.
Examples of maximum temperature recordings in the UK in early August 1990:
Manchester Airport
2nd Aug: 34.0°C
3rd Aug: 33.9°C
Birimingham Airport
1st Aug: 31.0°C
2nd Aug: 33.5°C
3rd Aug: 35.0°C
Heathrow
1st Aug: 32.5°C
2nd Aug: 34.0°C
3rd Aug: 36.5°C
4th Aug: 34.4°C
Rhyl
2nd Aug: 33.5°C
3rd Aug: 30.9°C
Blackpool Airport
2nd Aug: 33.5°C
Pershore
1st Aug: 30.6°C
2nd Aug: 34.1°C
3rd Aug: 35.6°C
It was so hot in the UK that the tarmac was melting and the gritters were out on the roads.
Brighton did not get below 23.9°C on the night of August 3rd/4th 1990 which is the hottest night in the UK on record for any month.
Sea temperatures around Ireland at the beginning of August 1990 were between 15°C in the west to 18°C on the southeast coasts. These kinds of temperatures are more typical for the French coasts, not the Irish waters!
Seeing the synoptic for midday on August 2nd 1990, it's no surprise why it was so hot:
Sea surface temperature (SST) anomalies for August 1990:
http://news.bbc.co.uk/onthisday/hi/dates/stories/august/3/newsid_2527000/2527311.stm
https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/joc.3370120603
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