Two weather warnings were in place on Sunday, as heavy rain hit Ireland.
Met Éireann put in place a status yellow rainfall warning for Cork and Waterford until 6pm on Sunday. The forecaster said these areas could expect outbreaks of heavy rain and rainfall accumulations of 25 to 40mm during this period.
It also issued a status yellow rainfall warning for Leinster, valid from 6pm on Sunday to 6am on Monday. The forecaster said the province can expect thundery downpours during this period. These downpours will push northward, with rainfall totals of 25-40mm possible in some areas.
Cork City Council has announced that is cancelling events planned for St John’s Eve, or Bonna Night, as a result of the weather.
Highest temperatures on Sunday will be between 14 to 17 degrees Celsius generally, but will reach 18 or 19 degrees in parts of Ulster.
The weather will turn increasingly mild and humid over the coming days and it will also become increasingly unsettled as a warm front moves across continental Europe from the Sahara.
Met Éireann said while there will be some spells of lovely sunshine at times this week and temperatures towards the middle of the week will hit the mid-20s or higher, there will also be heavy showers and thunderstorms.
The rise in temperatures is being driven by the arrival of a potentially record-breaking heatwave forecast to grip much of continental Europe next week, with temperatures in cities from Spain to Germany expected to exceed 32 degrees and climb to more than 38 degrees in the hottest areas.
It is being driven by a combination of a storm stalled over the Atlantic and high pressure over central Europe that is expected to pull very hot air from Africa northward, leading to the expected heatwave over a large portion of western and central Europe.
In France, temperatures of between 35 degrees and 40 degrees are expected across most of the country, except Brittany, from Monday, Météo-France said, and were unlikely to fall below 20 degrees overnight.
“Even though it will be shortlived, this heatwave could be remarkable for its momentum and intensity,” the forecaster said.
Cities from Madrid to Berlin, including Paris, Brussels and Frankfurt, are likely to experience a "multi-day heatwave" in the first half of the week, with similar temperatures of 32 degrees or above expected further east later, in Bucharest, Vienna, Budapest, Belgrade and Sofia.
London, which has also had an indifferent summer so far temperature-wise, is likely to see a number of days next week when temperatures reach 30 degrees.
Long-range weather forecasts show summer temperatures throughout July and August are now expected to be higher than normal, rivalling those of 2018, which according to the European Environment Agency was one of the three warmest years on record on the continent.
Hazy sunshine
In Ireland, Monday will see a mix of hazy sunshine and a few heavy, possibly thundery downpours.
It will feel warm and humid, with highest temperatures ranging from 18 to 22 degrees.
Tuesday will be dry and bright at first with hazy sunshine. However, there will be the risk of isolated thunderstorms, particularly in inland parts of Munster and south Leinster.
From Wednesday, temperatures will rise into the mid-20s, and locally up to 26 or 27 degrees.
Night-time temperatures may be in the mid-teens and it will feel warm and humid.
Temperatures could reach as high as 27 degrees in Ireland on Thursday, making it the hottest day of the year so far.
People who suffer from asthma and hay fever have been warned to safeguard against potential attacks, with the pollen count expected to rise.
Ireland has the highest mortality rates from asthma in western Europe, with 63 deaths in 2016.
The Asthma Society of Ireland (ASI), which issued the warning ahead of the anticipated arrival of fine weather this week, said more than 300,000 people suffer from both asthma and hay fever together.
It warns that with the arrival of peak grass pollen season, a high risk is expected during dry sunny days. – Additional reporting: Agencies