September is the best month to dive in Ireland, and almost nobody knows it

Every year we watch the same thing happen. The schools go back, the weather turns a bit grey, and people put the sea away for the winter — in the exact fortnight the water is at its best.

The sea runs a month behind the land

Water holds heat far better than air does, so the sea takes weeks to catch up with the seasons. Around Ireland it lags roughly a month behind, which means our warmest coastal water arrives in late August and stays high into September — not in June or July, when everyone assumes summer is happening.

So the July swimmer shivering on a bright day and the September swimmer in a grey drizzle are not in the same sea at all. The September one is in warmer water.

People quit the sea in September because the air got cold. The water did not.

The visibility improves too

Spring and early summer bring the plankton blooms that make Irish water green and murky. It is the same richness that feeds everything from mackerel to basking sharks, so it is not a fault — but it does mean you are often diving through soup in May.

By late summer the blooms have settled back and the water clears. Add a spell of calm weather with no swell stirring the bottom and you can get the best visibility of the year on this coast in September. It is not guaranteed — nothing about the Atlantic is — but the odds shift in your favour.

And there is nobody here

August in Kilkee is busy. September is not. The practical effect is that you get more of an instructor's attention, more choice of dive site, and a far better chance of getting on the water at short notice — which matters on a coast where the weather makes the decision for you.

It is also when the wildlife is at its most interesting. Trigger fish arrive on the warmest water. Mackerel are in the bay and the dolphins are following them. Basking sharks form their courtship circles off Loop Head at the end of August and into September. None of that happens in June.

The honest catch

Daylight is going, about four minutes a day by late September, so afternoon dives finish earlier than you expect. And the autumn Atlantic can put down serious swell with little notice — September gives you better water, not safer water. Check the forecast before you drive, not when you arrive.

Live sea temperature, wind, waves and tide for Kilkee are on our home page, updated continuously.

One more reason to come now

The dive and surf shop on the pier has its end-of-season deals on at the moment — wetsuits, boots, gloves and accessories. If you have been borrowing kit all summer and thinking about buying your own, this is the cheapest time of year to do it, and you still have a season's diving ahead of you to use it.

Call into us on the East Pier, or ring 085 255 2064.