Ireland was on course for an average summer this year but climate change turned it into a record-breaker, scientists have found.
The unusually high night-time temperatures that put June, July and August into the record books were made 40 times more likely by the distorting impacts of the heating planet.
The average temperature, taking into account day and night over the three months, reached 16.19 degrees, beating the previous warmest in 1995, when the average was 16.11 degrees.
“It was quite a normal set-up – normal rainfall, normal sunshine – but it still led to us having the warmest summer on record,” said Paul Moore, climatologist with Met Éireann.
RM Block
The factors that fed into summer 2025’s extraordinary heat all bore the hallmarks of a changing climate.
An exceptionally dry winter and spring left soils parched so they lacked the moisture that would normally evaporate to create a cooling effect.
Recurring marine heatwaves pushed sea surface temperatures to 3 degrees above normal, meaning breezes carried warmer air onshore and the waters were less effective in absorbing heat from the land.
Multiple heat domes in Europe also meant extra warm air close to the country.
The record heat persisted despite daytime temperatures being lower than during the previous warmest summers, 1976 and 1995, which were characterised by atypical prolonged dry, sunny, hot spells.
[ August among hottest on record, continuing summer trendOpens in new window ]
“This means we have reached a point where the background warming due to climate change can transform an otherwise average season into a record warm season,” Mr Moore said.
The analysis was conducted by the ICARUS centre at Maynooth University and Met Éireann under the WASITUS (Weather Attribution Science Irish Operational User Service) project.
WASITUS seeks to explain the role climate change plays in extreme weather events by establishing the likelihood of them happening in a pre-industrial world before rapid fuel expansion drove up global temperatures.
The study found that climate change made the warm summer days nine times more likely and the warm summer nights 40 times more likely.
Put another way, instead of being a one-in-600 year event, climate change made 2025’s record summer a one-in-15 year occurrence that is set to become 300 times more likely, occurring once every two years, by the end of the century unless warming is halted.
“Mean night-time temperatures at many of the weather stations were the warmest ever found,” said Dr Claire Bergin of Maynooth University.
“That’s the concerning part. The land isn’t allowed to cool down at night-time in the way it would have been in previous summers.”
Sleepless nights resulted, which is bad for health and raises questions about how Irish homes can adapt.
“Our buildings are set to retain heat, so in terms of future planning of houses and retrofitting, there’s a need to allow not just for insulation, but ventilation too,” said Dr Bergin.
Warm air also holds more moisture, producing much heavier, intense rainfall that leads to worse flooding.
