High temperatures will continue for the rest of the week, as a status yellow weather warning has come into effect since 1pm for the entire country.
The weather alert remains in place until Friday morning, with Met Eireann forecasting daytime highs of 27 to 30 degrees while at night it's not expected to fall below 17 to 20 degrees.
Even hotter temperatures are expected in Roscommon, south Leitrim, Longford, Westmeath, Cavan and Monaghan with a status orange weather alert in these areas, and temperatures of over 30 degrees in places.
Meanwhile, the HSE has issued advice to help prevent heat exhaustion and heat stroke.
People are advised to ensure central heating is off, stay out of the sun between 11am and 3pm, stay hydrated, and keep drinks in the fridge.
Babies and children, people over 65, and people with underlying conditions are most vulnerable.
People are advised to seek medical help if they experience any signs of dehydration such as dizziness, drowsiness, or a racing heart.