A mixed bag forecast means we could be set for either 40 days of sunshine or 40 days of rain, according to the folklore surrounding an Anglo-Saxon saint.
Met Éireann said today is set to be a mix of cloud and mist with patchy drizzle, mainly in the north and east of the country.
But, if the legend is true, the long dry spells developing as the day progresses bode well for some good weather ahead, particularly in the south and southeast.
Folklore has it that the weather through the end of July and August is determined by the whim of a medieval saint who is celebrated on 15 July.
St Swithin was a ninth century Anglo-Saxon bishop of Winchester and, according to legend, was tutor to a young King Alfred the Great.
He is best known for a proverb that predicts 40 days of rain or sun, depending on what weather is like on his special day.
Little is known about the saint, but he is said to have requested he be buried outside Winchester Cathedral so his grave would be exposed to both the footsteps of worshippers and the elements.
But in the 10th century, after some priests moved his tomb inside, a great storm hit, which was taken as a sign of St Swithin's displeasure.
It sparked the proverb: "St Swithin's Day if thou dost rain, for forty days it will remain, St Swithin's Day if thou be fair, for forty days will rain na mair."
Well, as legend would have it ...whatever the weather has in store for us today, is how it will remain for 40 days and 40 nights. Yep; #StSwithinsDay folks! So, let's see shall we...Audrey has the latest #rteweather #folklore #saints #weather pic.twitter.com/TU9jjR2DwY— RTE Weather (@WeatherRTE) July 15, 2020
Additional reporting PA