Met Office Deep Dive: Record heat, flying ants, and a changeable outlook

Author: Press Office

As we step into July, the weather continues to be a major talking point across the UK and Europe.

This week’s Met Office Deep Dive explores the extraordinary heat that closed out June, the unusual radar signatures caused by flying ants, and what the forecast holds as we move further into summer. From record-breaking temperatures to unsettled conditions ahead, here’s everything you need to know.

A record-breaking June

June 2025 has officially gone down in the record books. England recorded its warmest June on record, while the UK as a whole experienced its second warmest, just behind June 2023. This follows a record-breaking spring and continues a trend of increasingly warm conditions linked to our changing climate.

Minimum temperatures were particularly notable, with several tropical nights recorded, where temperatures do not fall below 20°C. Heathrow and other localised spots experienced this phenomenon, contributing to a muggy and uncomfortable feel overnight. These warm nights, combined with daytime highs reaching into the mid-30s across the southeast, made for a sweltering end to the month.

Flying ants on the radar

One of the more unusual observations this week came not from the skies, but from the ground, or rather, just above it. Swarms of flying ants were picked up on radar, appearing as strange, flashing echoes particularly northwest of London. These were initially mistaken for showers, but closer inspection revealed their true identity.

Radar works by emitting electromagnetic beams that reflect off small particles like raindrops. Flying ants, being similar in size to raindrops, can also reflect these beams, creating radar signatures that resemble precipitation. This phenomenon, often seen during “Flying Ant Day,” is a fascinating example of how biological activity can intersect with meteorological technology.

The heat across Europe

The UK wasn’t alone in experiencing extreme heat. Across continental Europe, temperatures soared, with Portugal reaching 46.6°C, breaking its national June record. Spain followed closely with 46°C, also setting a new June benchmark. Paris saw such intense heat that the Eiffel Tower was closed, and water was distributed on public transport to help people cope.

Widespread extreme heat warnings have been issued in Europe, including red alerts across parts of France. Schools were closed in some areas due to the dangerous conditions. The heat also triggered intense thunderstorms, particularly in Switzerland, where the combination of high temperatures and atmospheric instability led to dramatic weather events.

READ MOREEngland’s warmest June on record and the UK’s second warmest since 1884

Why is it so hot?

The persistent heat in Europe is being driven by a large area of high pressure, currently centred over eastern Europe. This system is causing air to descend and compress, intensifying the heat day by day. As the high drifts eastward, it drags the heat with it, while allowing the Azores High to build in from the southwest, bringing more settled conditions to southern parts of the UK.

Sea surface temperatures are also playing a role. Across the Mediterranean, sea temperatures are in the mid to high 20s, well above average for this time of year. This warms the air above, which then moves inland, further fuelling the heatwave.

Forecasting the heat: Partial thicknesses

One of the tools used by Met Office meteorologists to forecast heat is “partial thickness.” This refers to the vertical distance between two pressure levels in the atmosphere, typically 1000 hPa and 500 hPa. Warmer air expands, increasing this thickness, while cooler air contracts it.

By analysing these thickness levels, forecasters can identify where the warmest air masses are located. For example, values around 143 decametres often correlate with surface temperatures of 35°C. This week, the highest thicknesses were observed over southeastern England on Monday and Tuesday, aligning with the peak of the heat.

A fresher feel ahead

As we move into the first week of July, a shift in the weather pattern is underway. High pressure to the southwest is introducing a more westerly flow, bringing in fresher air. While it won’t be cold, temperatures will drop to more comfortable levels, particularly in the southeast.

Daytime highs will remain in the mid-20s across southern England, while Scotland, Northern Ireland, and northern England will see temperatures in the mid to high teens. Dew point temperatures, a measure of atmospheric moisture, will also fall, reducing the muggy feel that has dominated recent nights.

A changeable outlook

Despite the fresher air, the return of a westerly flow also means a return to more unsettled conditions. The classic northwest–southeast split is expected to re-establish itself, with the northwest seeing more cloud, rain, and showers, particularly towards the end of the week.

By Thursday and Friday, frontal systems will begin to move in from the Atlantic, bringing rain and stronger winds to Scotland and Northern Ireland. Meanwhile, the southern half of the UK will remain largely dry and settled, though not as hot as earlier in the week.

READ MOREWhat is humidity and how does it affect human health?

Weekend weather: Silverstone and Wimbledon

Looking ahead to the weekend, the weather is expected to turn more unsettled. At Silverstone, Sunday’s forecast includes heavy rain, the possibility of thunder, and blustery winds, far from ideal racing conditions. This marks a stark contrast to the dry, bright, and warm weather earlier in the week.

Wimbledon will fare slightly better. Wednesday may see a few showers, but Thursday and Friday are expected to be dry, bright, and warm, ideal for tennis. Saturday, however, brings a higher risk of showers, with longer spells of rain likely on Sunday.

Looking further ahead

The outlook for mid-July remains uncertain, but there are hints of a return to more settled conditions. The 14-day forecast suggests the possibility of warmer, drier weather returning, though this will depend on the positioning of high-pressure systems and the persistence of the westerly flow.

Climate change continues to be a key factor in the increasing frequency and intensity of heatwaves. The records broken this June are part of a broader trend, with long-standing temperature benchmarks being surpassed more regularly.

Word of the week: ‘Swallocking’

To close this week’s Deep Dive, we leave you with a new addition to your weather vocabulary: “swallocking.” This term describes hot, humid, sultry weather, exactly the kind of conditions many of us have experienced recently. It’s a fitting word for the sticky, oppressive heat that has defined the end of June and the start of July.

Keep up to date with weather warnings, and you can find the latest forecast on our website, on YouTube, by following us on X and Facebook, as well as on our mobile app which is available for iPhone from the App store and for Android from the Google Play store.

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This is the official blog of the Met Office news team, intended to provide journalists and bloggers with the latest weather, climate science and business news, and information from the Met Office.

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