Met Office rules out September heatwave as unsettled weather follows record UK summer

Met Office rules out a September heatwave

If you were banking on one more burst of 30°C heat, stand down. The Met Office has ruled out another UK heatwave to kick off September, pouring cold water on talk of an “Indian Summer.” The early-month outlook points to a mix of sunshine, showers, and a fair bit of cloud—more low 20s than searing highs.

Met Office meteorologist Craig Snell summed it up plainly: the current forecast shows “nothing like what we have seen during the summer months.” Between 4 and 13 September, forecasters expect changeable and unsettled conditions across most of the country. That means spells of rain sweeping in from the Atlantic, some brighter gaps between fronts, and temperatures that feel warm when the sun is out, but not extreme. For the south, think 20–24°C on the better days; further north, mid to high teens are more likely.

This is a sharp shift from the summer pattern, when high pressure parked over or near the UK for long stretches, locking in sunshine and heat. September is shaping up differently. Low pressure systems are set to take turns in charge, nudging the jet stream back into a more typical late-summer position and driving in bands of rain and scattered showers.

What about those whispers of 30°C in early September? Forecasters have pushed back on that. The ingredients just aren’t there for a sustained hot spell. You might catch a day that edges a little higher in the southeast if the cloud breaks just right, but the setup doesn’t support a run of very hot days.

It’s also worth clearing up what counts as a heatwave. The Met Office defines it by location-specific thresholds—usually between 25°C and 28°C—met or exceeded for at least three consecutive days. That’s why a warm day or two doesn’t qualify. With Atlantic fronts and cooler nights returning, most places won’t hit those thresholds three days in a row.

There’s confusion over “Indian Summer” too. It’s not an official term in UK meteorology. People use it loosely for a warm, calm spell in autumn. Could the UK still see a short, mild window later in September? It’s never off the table in this country, but it’s not what the current forecasts are pointing to in the first half of the month.

The bigger picture here is remarkable. Provisional Met Office numbers show summer 2025 will “almost certainly” be the UK’s warmest on record. From 1 June to 25 August, the mean temperature stands at 16.13°C—1.54°C above the long-term average. That would top 2018’s record of 15.76°C and push the fabled summer of 1976 outside the top five in a dataset going back to 1884. This summer also logged four official heatwaves and stretches of relentless sunshine.

So yes, the mood music in September will feel different. After months of high pressure and heat, the weather is tilting back to something closer to normal for early autumn—cooler nights, more cloud around, and a bit of wind tossed in with the rain. In the sunnier breaks, it will still feel pleasant. Early September sun is strong enough to push the mercury into the low 20s in the south. But it won’t be a rerun of August’s peak heat.

Why the pattern is changing

Through summer, the UK often sat on the warm side of the jet stream, with high pressure keeping rain-bearing systems at bay. As we move into September, that balance flips. The jet stream is sliding back across the Atlantic in a way that helps low pressure systems track towards the British Isles. Those systems bring showers, longer spells of rain, and a breeze—especially along western coasts and hills.

In simple terms, the atmosphere is no longer set up to trap heat over the UK. Instead, it’s primed to swap air masses more often. That’s why the forecast keeps using words like “changeable” and “unsettled.” It’s a back-and-forth pattern: a band of rain, then a clearer slot; a fresh breeze, then a calmer day; a touch cool, then a milder afternoon when the sun breaks through.

Here’s how that’s likely to play out region by region in early to mid-September:

• Scotland and Northern Ireland: Frequent showers, some longer spells of rain, and breezy at times. Daytime highs mostly 15–18°C, a little higher in any brighter interludes in the east.
• Northern England: A mix of cloud, showers, and the odd sunny day. Highs around 17–20°C. Nights turning cooler under clearer skies.
• Wales and the Midlands: On-and-off rain bands followed by drier windows. Highs 19–22°C, feeling warmer in any sunshine but cooler in the wind and rain.
• South West: Changeable, with showers or longer rain at times and a noticeable breeze on coasts. Temperatures broadly near 19–22°C.
• South and South East: The best chance of brighter spells. Highs 21–24°C on the warmer days, though cloud and patchy rain still move through.
• Coasts and hills: Breezier with lower feels-like temperatures and more frequent showers when fronts pass.

The immediate setup fits that story. The Met Office outlook points to further showers and longer periods of rain crossing the UK, with southern areas seeing some of the heaviest pulses mixed in with dry breaks. Where the rain clears and the sun appears, it will feel mild to warm for early September. But the overall theme looks like a clear step away from the summer’s stable, hot pattern.

All of this comes on the heels of an extraordinary few months. Four heatwaves is a lot in one summer. The temperatures were high, but so was the persistence—week after week of strong sunshine, dry ground, and warm nights that didn’t allow much cooling. For infrastructure, that meant rail speed restrictions, melting road surfaces in places, and fatigue for anyone working outdoors. For households, it meant fans running, windows thrown open at midnight, and sleep getting harder during the hottest bursts.

The environment has felt it too. Many people have spotted what ecologists call “false autumn.” That’s when stressed plants mimic seasonal change before the calendar says it’s time. Leaves brown early and drop, berries ripen ahead of schedule, and hedgerows take on a September look in August. It’s a survival move. Heat and dryness push trees and shrubs to conserve water by shedding leaves sooner or by setting seed earlier than usual.

Walk through a park and you might see horse chestnut leaves crisping at the edges or birch carpets forming underfoot weeks ahead of normal. Hedgerows heavy with blackberries and hawthorn berries may look picture-perfect, but the timing tells a story of stress. Wildlife will adapt—birds and small mammals will take advantage of early fruit—but the shift scrambles the usual ordering of food supplies. If later autumn turns wet and windy, some of that fruit can rot early, narrowing the window for feeding.

None of this means a cold snap is waiting in the wings. False autumn is about stress, not an early winter. But it’s a clear sign that the summer was exceptional. The provisional mean temperature—16.13°C up to 25 August—isn’t a blip. It’s a big jump above the long-term average and enough to dethrone 2018 as the UK’s warmest summer on record.

So what should you expect if you’re planning the school run, commuting, or heading to outdoor events in early to mid-September? Pack for variety. A lightweight waterproof and a layer for cooler mornings will do more work than sunglasses alone. Ground conditions will vary too—after downpours, city drains can struggle for an hour or two, while rural paths will switch from dusty to slick in a day. Wind gusts will be noticeable near showers, especially along western coasts.

On the temperature front, nights will start to feel fresher. That helps with sleep but takes the edge off daytime warmth. In the southeast, you’ll still get that late-summer feel on brighter days, but the heat won’t stick around. In the north and west, the mix of cloud and showers keeps daytime highs modest and evenings cool enough for a jacket.

Is there any chance the pattern flips later in September? Forecast confidence naturally drops as you push further out in time. A short, drier spell can appear between Atlantic systems, and if the sun gets a clear run, it will feel pleasant. But that’s not the same as a heatwave, and it’s not what the early-to-mid-month guidance is flagging.

One more point on that “Indian Summer” chatter. In popular use, people mean a warm, settled spell sometime in autumn. It can happen in the UK, but meteorologists don’t treat it as a forecast term or a promise. The signal you’d look for is a sustained ridge of high pressure taking hold over the UK or just to the east. Right now, the signal leans the other way.

If you’re a gardener, the change brings a mixed bag. Rain will ease watering pressure and perk up lawns that went straw-yellow in August. But bursts of heavy rain after a dry spell can run off baked ground before it sinks in. Mulch helps, and so does steady, slow watering for shrubs and young trees. For allotments, cooler nights reduce heat stress but slow ripening for late tomatoes and peppers.

For runners, cyclists, and anyone getting outside, early September is actually a sweet spot: cooler air for effort, fewer heat warnings, and enough daylight in the evenings to squeeze in miles after work. The flip side is slipperier surfaces after showers and gusty crosswinds on exposed routes.

Transport-wise, unsettled doesn’t usually mean widespread disruption. But local downpours can hit visibility and spray on faster roads. If a deeper low crosses the country, expect a day of delays here and there—particularly on ferries and high routes in the west—before things settle again behind the front.

All told, we’re heading into a familiar British mix after a summer that was anything but. The headline is simple: no fresh heatwave on the cards for early September, no promised “Indian Summer,” and a return to the stop-start rhythm of showers, brighter spells, and modest temperatures. In the sunshine it will feel nice, even warm at times. But the run of exceptional heat has ended, and the weather is moving on.