A cold front forecast to arrive over the country during the middle of the week is expected to bring about the change, according to meteorological institute DMI.
Wet weather and temperatures of around 15°C are expected by the end of the week.
“This morning we have clouds over the southwest which may bring rain. But it will otherwise clear up to bring sun most places on Monday. Day-time temperatures will be between 18 and 21 degrees,” DMI's Dan Nisvall said.
A moderate westerly and northwesterly wind is expected on the west coast, making things feel cooler in those parts.
Tuesday will see temperatures of at least around 18-21°C, according to DMI's forecast.
“In southeastern areas there will be a fair bit of sun and it looks like the temperature may reach up to 25 degrees,” Nisvall said.
“In terms of temperature, Wednesday will probably be the best day this week. But for sunshine Monday or Tuesday will probably be better,” he continued.
Wednesday night will see the arrival of a cold front from the northwest, followed by gradually colder weather and rain.
“On Thursday we will see around 18 degrees and on Friday we could be town to as low as 15 degrees. It will be almost autumn-like,” Nilsvall said, adding that the summer weather would be “taking a little break”.
“But we could still see some nice days at the end of the month and the beginning of September,” he added.