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Cork boi

Yes, Leaving Cert Weather is a real thing (but only in Cork)

May and June are the sunniest months. Here’s why.

Leah Farrell / Photocall Ireland Leah Farrell / Photocall Ireland / Photocall Ireland

LEAVING CERT WEATHER is a traditional Irish phenomenon. You know: as soon as late May and early June roll around and thousands of teenagers have to spend their days indoors?

That’s when the sun comes out.

So, is this real? Or just a figment of the national imagination? Well, let’s see how the numbers stack up.

Yes, the sun really is more likely to be shining at this time of year…

Here are the average amounts of solar radiation (in joules/cm2) collected at seven Irish weather stations, over the last 30 years:

Met Eireann Met Eireann

At every one of the stations, May and June saw the most solar energy beating down on the Irish soil.

These charts of the average daily hours of sunshine also reveal that May and June are the sunniest months around the country:

Met Éireann Met Éireann

Why is this? Well, it’s partially to do with dry periods in late spring caused by continental anticyclones blocking Atlantic depressions.

But a Met Éireann spokesperson told the biggest factor in the greater hours of sunshine around this time of year is really just that the days are getting longer as our bit of the Earth tilts towards the sun. So now.

Mark Stedman / Photocall Ireland Mark Stedman / Photocall Ireland / Photocall Ireland

Is there really less rain in May and June than later in the summer?

Oh, yes. Your mother was right about this all along. As the summer moves into late June and early July, according to Met Éireann:

… the rise in pressure over the ocean and a corresponding fall in pressure over Europe results in the general wind flow at the surface becoming westerly, bringing air with a long ocean track over Ireland, so that cloud cover, humidity and rainfall increase.

But why only in Cork?

Only in the southwest of the country – as measured by rainfall readings from Valentia weather station – have May and June been the driest months on average over the last 30 years.

Nationwide, however, April is actually the driest month on average – and this is borne out by readings from Malin Head in the far north, Birr in the midlands and Shannon in the west.

You're less likely to see this in May and June jit bag jit bag

In the south east, Rosslare weather station shows the least rainfall in July. While Dublin, weirdly enough, has been driest in February.

So there isn’t necessarily less rain in May and June than earlier in the year. However, the longer days, better sunshine and generally rising temperatures at this time of year mean we probably perceive the weather as getting better – hence the Leaving Cert Weather phenomenon.

But in terms of May and June being the driest AND sunniest months? Only in Cork and the southwest. Sorry, everyone else.

More: The Leaving Cert weather came through, and people couldn’t be happier>

More: 10 Leaving Cert panics every Irish person will remember>

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