Met Éireann meteorologist Mark Bowe said the “warm and sunny days are gone” as remnants of ex-Hurricane Erin, which is now just a low-pressure system, will move across Ireland.
“As we head into the last week of August, which is the final month of meteorological summer, it’s certainly going to feel like something has changed,” he said.
“Those warm, sunny and humid days are, I’m afraid, gone now.
“And as we look ahead to more unsettled, blustery weather, and, of course, temperatures taking a dip as well, giving us an early taste of the autumn ahead.
“The first wave of this will be today with a cold front getting flung up and across the country as the remnants of, remember, Hurricane Erin, which is now just a regular area of low pressure, is going to move past and set a base just south of Iceland.
“Now, this front that moves over us today will be heavy at times, and you may even see the odd rumble of thunder in there as well,” Mr Bowe added.
It will be a cloudy but mostly dry start to the week this morning, with sunny spells slowly breaking through.
The skies will gradually become cloudier from the west later this afternoon as winds strengthen, and rain will spread across the country.
However, it might turn heavy at times with some thunder possible too, as temperatures will range between 19 and 23C.
Meanwhile, high seas are expected along Atlantic coasts, bringing a risk of wave overtopping.
We need your consent to load this Social Media content. We use a number of different Social Media outlets to manage extra content that can set cookies on your device and collect data about your activity.
Please review your details and accept them to load the content
But the rain will clear away this evening, leaving a clear night with just isolated showers. Mist might form overnight as winds fall light, but they will stay fresher on the coasts.
Temperatures can drop to 13 and 15C, as the night is expected to be mild.
Tomorrow will bring breezy, unsettled and a bit cooler weather than recent days, with showers drifting over the country, as well as fresh and blustery winds.
Sunny spells are expected in the afternoon, but skies will become cloudier in the evening, with temperatures ranging between 17 and 20C.