A September to remember: why the skies stayed blue
For several days, Northern Ireland enjoyed the kind of early autumn weather that makes you double-take at the calendar: crisp mornings, long sunny spells, and gentle, dry afternoons. It was the meteorological sweet spot—warm in the sun, jacket weather in the shade. If you felt like it was something special, you weren’t imagining it. This was the kind of settled pattern we typically associate with late spring, not the school run in September. For many, it was the best spell of the year.
What happened? A resilient dome of high pressure sat to the west and south-west—think of the Azores High flexing north—nudging the jet stream further up and over the region. That kept Atlantic systems at bay. Light winds, sinking air, and clear skies did the rest. Daytime temperatures pushed into the high teens and low 20s Celsius in places, especially inland, while nights cooled rapidly under clear skies. It was classic early-autumn: big temperature swings, low humidity, and those long, golden evenings.
The pattern created a few telltale signs. Radiation fog formed in river valleys and low-lying spots around dawn, then burned off by mid-morning. With less cloud cover, UV levels were modest, so you could sit out without the fierce bite of midsummer sun. Coastal areas—think the Causeway Coast and the Ards Peninsula—stayed a touch cooler with onshore breezes, while sheltered spots in counties Armagh and Tyrone warmed up quickly.
Sea surface temperatures, still relatively mild from summer, helped keep coastal nights from getting too chilly, while inland valleys—parts of Fermanagh and the Bann basin—saw the coolest dawns. The air mass was dry, so showers struggled to get going. On satellite and radar, Northern Ireland often looked like a hole in the weather—cloud and drizzle skirting by to the north and south.
Is this rare? Not exactly, but the timing matters. Late-season spells like this have become more frequent across the UK and Ireland over the past two decades. Rising background temperatures load the dice towards milder months, even if the day-to-day weather still swings around. In recent years, September has produced some of the most pleasant stretches of the year—not heatwave territory, but that near-perfect blend of light and warmth.
Forecasters call this a “blocking” pattern. It doesn’t take much to break it—a deeper Atlantic low or a shift in the jet stream can flip the script. But while it holds, it’s a gift for outdoor work and last-minute getaways. If you booked a midweek break at Portrush or a Mournes hike on a whim, you nailed the window.
- Afternoons often reached the high teens to around 20°C inland; cooler along exposed coasts.
- Clear nights brought chilly starts, with fog pockets in valleys and near loughs.
- Winds stayed light and variable, often turning onshore near the coast in the afternoon.
- Rainfall was scarce, with most places staying dry for days at a time.
How it played out on the ground—from beaches to farms
On the North Coast, beaches at Portstewart and Portrush felt like a quiet encore after summer—ice cream vans back on the prom, cafes pouring flat whites onto pavement tables, paddle boarders making the most of calm seas. Inland, the trails in the Sperrins and the Mournes were busy but not crowded. Those who know the hills waited for the first clear, cool mornings to get crisp views and fewer midges.
Urban life changed gear too. Belfast’s lunchtime crowds shifted outside, from City Hall benches to the Cathedral Quarter. Cycle commutes ticked up as roads stayed dry and winds light. Sunset walkers took laps around the Lagan Towpath and the Ormeau Embankment, leaning into that slow-burn golden light you only really get in September.
For farmers, this was a valuable work window. Dry ground meant machinery could get onto fields without damage. Many took the opportunity to tidy hedges, lift late potatoes, reseed small patches, and square away hay and straw. The dry spell also helped reduce the risk of soil compaction after a mixed summer. Livestock benefited from steady grass growth in the warmth, though some upland spots saw grassland dry faster than expected, nudging farmers to monitor grazing pressure.
Small businesses felt it too. Coastal B&Bs reported late bookings. Garden centres moved autumn plants and bulbs earlier than planned, with customers keen to plant while the soil was warm. Contractors pushed ahead with repairs and outdoor projects, from repointing to roof work, which depend on a run of dry days to finish well.
Energy demand dipped during the day as the sun did part of the heating job, and solar panels contributed steadily in the clear conditions. Nights were cooler, so households still flicked the heat on for an hour or two in the morning. It wasn’t summer-level savings, but it was a welcome softening of bills in that awkward shoulder season between seasons.
Transport ran smoother than usual. With winds light and seas calm, ferry crossings were generally kinder, and flights were less vulnerable to weather disruption. Roadworks could progress without rain delays—good news for crews and anyone stuck behind temporary traffic lights.
Wildlife gave away the season even as the days felt summery. Swallows and house martins gathered on wires, ready to head south. Spiders were busy in hedgerows, their webs beading up with dew at dawn. Along lough shores—Lough Neagh and Strangford Lough in particular—migrating waders took advantage of exposed mudflats in the dry spell. It was a quiet but confident handover from summer to autumn.
There were some caveats. Prolonged dryness, even in September, lifts wildfire risk in heather and gorse uplands. Local fire services typically ask walkers to be cautious with disposable barbecues and cigarettes during spells like this. Rivers and small streams can dip a little after several dry days, so angling conditions change quickly.
If you’re wondering how unusual this all is, the short answer is the flavour of it—settled, dry, pleasantly warm—isn’t unheard of. But the frequency is the story. Climate records across the British Isles show a steady rise in average temperatures since the late 20th century, and that shift makes late warmth more likely, not just in July and August but into September. The UK’s exceptionally warm September in recent years put a marker down: the shoulder months are changing character.
So what next? Forecast models suggest the high will weaken as Atlantic systems probe back in. Expect a more typical pattern to return: thicker cloud, patchy rain or showers from the west, and a livelier breeze. Temperatures are likely to ease back towards the seasonal mid-teens by day, with fewer of those big daytime jumps and a cloudier feel. No immediate sign of a deep autumnal storm, but the door reopens to changeable weather—the usual give-and-take with the Atlantic.
For planners, here’s the takeaway. Use dry spells like this to get outdoor work done early, because autumn’s mood swings return fast. Gardeners can plant perennials and spring bulbs while soil is warm. Walkers should keep an eye on morning fog in valleys and carry layers for those sharp temperature swings. And yes, keep sunglasses in the car—you’ll need them in that low, blinding late-afternoon sun on west-facing roads.
For everyone else, take the win. September won’t always behave like this, and nobody gets fined for sneaking one more evening walk by the coast. From Carrickfergus to Coleraine, from Enniskillen to Newry, the mood music was simple: blue skies on borrowed time, borrowed very happily. If you were looking for a phrase to sum it up, “Northern Ireland weather at its best” isn’t far off.
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