This week’s weather pattern is set to deliver a spell of exceptional heat across the UK, with temperatures climbing to potentially record-breaking levels and humidity playing a key role in how the heat is experienced.
Alongside the heat, there is also the risk of thunderstorms, both as a symptom of the current conditions and as a signal of a gradual change later in the week.
Recent storms and an unsettled start
The week began with notable thunderstorm activity, particularly across parts of southern England. Rapidly developing storms brought intense lightning, heavy downpours and localised flooding in some areas.
These storms developed quickly through the afternoon and evening, before moving away and being followed by a second batch overnight across parts of the southeast.
This sequence highlights how unstable the atmosphere can become when warm, moist air is present. Thunderstorms thrive on this combination, using rising air currents to build vertically into the atmosphere. In some cases, these storms grew so strongly that cloud tops pushed beyond the typical ceiling of the troposphere, demonstrating the energy available in the atmosphere.
Although conditions have since settled, these storms provided an important signal of the changing air mass and the increasing warmth and moisture feeding into the UK.
The big picture: Why temperatures are rising
At the heart of this heatwave is a large area of high pressure positioned near the UK. This high-pressure system is being supported by a dip in the jet stream to the west, allowing warm air to move northwards.
High pressure plays a critical role in the build-up of heat. As air sinks under high pressure, it becomes compressed and warms. Combined with strong sunshine at this time of year, this leads to a steady rise in temperatures day by day.
The result is a gradual intensification of heat through the week, with temperatures expected to peak around Thursday.
This process also allows warmer air from further south and east to be drawn into the UK, reinforcing the heat and maintaining settled, sunny conditions for many areas.
READ MORE: How unusual is this week’s extreme heat, and why does it feel so intense?
The role of humidity
While the temperatures themselves are notable, one of the defining features of this spell is the level of humidity. This is a key factor in how the heat feels and how it affects people.
Humidity is linked to the source of the air mass. In this case, air arriving at the surface has travelled over the Atlantic before reaching the UK, meaning it carries more moisture.
This is a significant difference compared with previous extreme heat events. Higher moisture levels increase dew point temperatures, which in turn make it more difficult for the body to cool itself through sweating.
As a result, even if temperatures are similar to previous hot spells, the added humidity can make conditions feel more oppressive and increase the potential for heat-related impacts.
Temperature outlook through the week
Temperatures are expected to peak on Thursday before decreasing steadily, with the most intense heat focused across England and Wales.
On Wednesday, temperatures are likely to reach the mid to high 30s across central and southern areas, with some locations approaching the upper 30s.
By Thursday, the heat is expected to extend further north, with parts of northern England also seeing temperatures in the mid-30s. Further south, highs around 38°C are possible in a broad zone stretching across the Midlands, southeast Wales and southern England.
While Scotland and Northern Ireland will also be warm, temperatures here will generally be lower, with a greater influence from cloud and slightly fresher air.
⚠️⚠️🔴 Red weather warning issued 🔴⚠️⚠️
— Met Office (@metoffice) June 22, 2026
Extreme heat across parts of central/southern England and Wales
Wednesday 0900 - Thursday 2100
Latest info 👉 https://t.co/QwDLMfRBfs
Stay #WeatherAware ⚠️ pic.twitter.com/IwXnyU1E7y
Warm nights and sustained heat
Another important aspect of this weather pattern is the lack of overnight cooling. Night-time temperatures are expected to remain very high, particularly in southern areas.
Tropical nights, where temperatures remain above 20 °C, are likely across parts of England and Wales.
These warm nights are a direct result of the high humidity and persistent air mass. Without sufficient cooling overnight, buildings retain heat, increasing discomfort and placing additional strain on vulnerable individuals.
Sustained warmth, both day and night, is a key reason why warnings are issued. It reduces the opportunity for recovery and contributes to heat stress over multiple days.
Heat warnings and impacts
With these conditions, both amber and red heat warnings are in place across parts of the UK, particularly affecting England and Wales.
These warnings are based not only on peak temperatures but also on the duration of the heat, the extent of the affected area, and the high humidity.
The combination of these factors increases the likelihood of impacts, including health risks, infrastructure strain and disruption to travel or services.
It is important to note that impacts are not limited to extreme temperatures alone. Prolonged heat, especially when combined with warm nights, can affect a wide range of people, including those who are otherwise healthy.
READ MORE: Heat alerts explained as UK and Europe faces extreme temperatures
A thundery change on the horizon
While much of the week will be dominated by sunshine and heat, there are signs of a transition towards more unsettled conditions.
As the jet stream begins to shift, an area of lower-pressure will attempt to move in from the west.
This will introduce more cloud and the potential for showers or thunderstorms, particularly later on Thursday and into Friday.
Thunderstorms may develop where the hot, humid air becomes unstable. These storms could produce heavy rain, lightning and gusty winds, though their exact location and timing remain uncertain.
This phase of the weather is often referred to as a transition period, where the atmosphere begins to shift from prolonged heat to more changeable conditions.
Gradual cooling into the weekend
A gradual easing of temperatures is expected as we move into the weekend, although the change will not be immediate.
By Friday, parts of western UK will begin to see slightly lower temperatures as fresher air moves in, though eastern areas may remain very hot.
Through Saturday and Sunday, temperatures are likely to fall further, returning closer to more typical levels for the time of year.
However, the transition may bring further showers or thunderstorms, especially where the incoming fresher air meets the lingering heat.
Looking ahead
Beyond the weekend, a more changeable pattern is expected, with weather fronts bringing a mix of cloud, showers and some sunshine.
While high pressure may still influence southern areas at times, the overall trend is towards a more typical summer pattern with less extreme temperatures.
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.
