Met Éireann has said temperatures are set to reach the low to mid 20s over the next few days, unusual for the month of June.
Today started cloudy with drizzly conditionsin many parts of the country, though some have been seeing good sunshine since.
Meterologist David Rogers said a mini-heatwave from tomorrow was not set in stone for everyone.
"Tomorrow it will be a rather cloudy start for most parts of the country, with little bits of mist and hill drizzle early in the morning. The cloud should lift during the day," he said.
"There's a better chance of more widespread sunshine tomorrow, but it's not completely cast iron that everywhere will get a lot of sunshine tomorrow."