An active jet stream will run into NW Europe for the first half of the month, bringing areas of low pressure off the Atlantic and spells of rain or showers, while windy at times too. Temperatures slightly below average while rainfall will be above average.
From around mid-month, perhaps a few days earlier in the south, there is a signal is for the jet stream to shift north, with high pressure building in across mainland Europe extending north across the south initially, then perhaps all areas. This would mean it turns warmer and sunnier, perhaps with a hot spell, though occasional potential for thundery showers in places.
Temperatures overall for the month likely to end up around average. Rainfall slightly above average, most of the rain falling in the first half of the month.
Temperatures against 1991-2020 average: 50% chance of average, 30% chance of above average, or 20% below average.
Rainfall: 40% of chance for above average, 30% chance of above average, 30% chance of below average.
Sub seasonal runs from ECMWF signal for low pressure influence at the start of the month following a drier second half to June. The July composite in years with similar transition into El Nino is characterised by mixed pressure patterns through July. So, high pressure may build in at times after perhaps an unsettled first start, this could include some hot weather, though not sustained, but also some spells of unsettled weather. However, the month is looking warmer than average overall, given potential for hot spells.
Temperatures against 1991-2020 average: 50% chance of above average, 30% chance of average, or 20% below average.
Rainfall: 40% chance of average, 30% chance of average, 30% chance of below average.
The evolution for the month of August, as would be expected two months away, is less clear than for June and July. But it looks like high pressure could be a dominant feature in the month, bringing mostly settled weather, perhaps hot or very hot for a time too, but with an occasional risk of rain or thunderstorms in places. Any more sustained unsettled weather most likely towards the end of the month, but even then, most of any rain falling in the west. Temperatures 1-2C above the 30-year average, largest departure above average in the south. Rainfall signal looking most likely to be below average.
Temperatures against 1991-2020 average: 60% chance of above average, 30% chance of average, or 10% below average.
Rainfall: 50% of chance for below average, 30% chance of average, 20% chance of above average.
Seasonal forecasts for summer and winter are more likely to be correct than those for spring and autumn. This is because the predictability of the atmosphere in the transitional seasons, where cold and warmth often alternate, is less.
However, producing a summer forecast is probably more challenging than producing one for winter, with less impact from global atmospheric drivers that influence weather patterns than during the winter. Global temperatures are rising due to climate change, so it is perhaps no surprise when a seasonal forecast goes with above average temperatures. Rainfall more susceptible to local scale short-term changes and regional variations, particularly in summer, when localised convective rainfall events can make a difference.
Conventional forecasts and seasonal forecasts are two completely different things. Conventional forecasts, produced by supercomputers from meteorological data collected from all over the globe on the ground and at altitude, make it possible to predict the weather in detail up to a week or even 10-12 days in the case of stable situations. Even though computers are still evolving and improving, this limit of around ten days can only be exceeded with difficulty or low confidence.
However, large-scale phenomena that happen over long periods of time can be a useful pointer to how the atmosphere and thus our weather patterns can be driven and play out over long periods. Ocean temperatures which can impact global weather patterns, such as El Niño Southern Oscillation (ENSO) in the tropical Pacific and North Atlantic Sea Surface Temperatures (SSTs), tend to change very slowly, so can be a useful predictive tool over longer periods and this one of the main drivers looked at when making this summer forecast. While the movements and temperatures of air masses vary greatly from one day to the next, those of the oceans are much slower due to inertia. However, there is a constant exchange of energy between the atmosphere and the oceans. A warmer than normal ocean will tend to warm and humidify the atmosphere more than usual and therefore influence the climate. This can be local (like the North Sea, the near Atlantic for our regions) but also remote: the surface waters of the equatorial Pacific off the coast of Peru, when they are warmer than normal, is a known as "El Niño" - which affects the climate of the entire planet.
As well as ENSO and other ocean temperature – atmosphere interactions that drive weather patterns, there are other parameters we look at that may drive weather on a seasonal basis, such as certain cycles, such as the Madden-Julian Oscillation (MJO) cycle. Some cycles are multi-annual, others monthly, etc. The knowledge and integration of these cycles helps us refine the seasonal forecasts.
But there are also the seasonal forecasts, issued once a month, from numerical weather prediction (NWP) supercomputers, that take all global atmospheric drivers into account. Numerical models, calculate from data from observations on a global scale, then make it possible to predict seasonal trends. There are about ten models offering forecasts of this type (American, European, British, Japanese and even French for the most reliable).
Also, it is worth looking at past weather, such as the past spring, which has been very dry and also by using analogs of months or seasons that had similar patterns or cycles, such as La Nina or El Nino along with similar North Atlantic SST patterns.
After a remarkably warm and dry spring, with record-breaking May temperatures, summer 2026 could continue this warm trend in the UK. Current trends indeed favour above-average temperatures throughout the season. However, rainfall patterns appear more varied.
A warm and very dry spring, like this year, often triggers a comment like: “Then the weather will be wet and cool in the summer.” The idea here is that we’ve already had our quota of warm and sunny weather this year. Although ‘the weather’ has no ‘memory’, this idea is not entirely illogical. In our climate, we see that long periods of dry weather often alternate with long changeable periods. These long wet and dry periods seem to be getting longer and longer in our changing climate. However, there have been years where a dry spring has also been followed by a dry summer. Summers of 1976, 1990 and 1995 come to mind.
Statistically there is no clear connection between a dry spring and a dry summer. In the UK, we do not often have such stable weather, like that in southern Europe, where there is high chance that both seasons are very dry. The weather often changes after a few months. In that sense, so we may take into account that it will be more changeable in the summer than it is now in this spring, but my no means is this certain.
After such a dry spring, there does not have to be much precipitation to make it a wetter summer than spring this year, but that does not mean that it will also be wetter than normal. In the past, a dry spring was usually followed by a normal amount of rain.
The North Atlantic Ocean is also an important factor for our summer forecast. If the temperature here deviates significantly from normal, this can have a major impact on the temperature, particularly in the coastal areas.
In late May 2026, several countries in Western Europe faced above-average temperatures, meanwhile, large areas of the Atlantic Ocean and the Mediterranean Sea also recorded above-average sea surface temperatures.
The map below shows sea surface temperature anomalies on 30 May 2026. Areas in red and dark red indicate warmer than average waters, which extend along the northern and western coasts of France and across parts of the western Mediterranean Sea, with anomalies more than 5°C above the usual temperatures for this time of year, as a result of the warm Spring and hot end to May. This means maritime airmasses off the northeast Atlantic, especially from the southwest, will be warmer than normal over coming weeks, while the marine heatwave in the Mediterranean could also mean higher temperatures over southern Europe, perhaps leading to extreme heat, which could spread to the UK at times in the form of heatwaves.
Also, the extra warmth in the atmosphere means that rainfall can be heavier than normal, as warmer air holds greater moisture.
Air temperature anomalies during the European summer can be predicted by studying the heat of the Atlantic Ocean. However, the Atlantic Ocean has been experiencing record-breaking warmth over recent summers too, though the Atlantic to the west is probably the most anomalously warm area of sea in the world, warmer than this time last year in the same area. So is likely to have some influence on air temperatures.
Our summers have warmed up considerably due to climate change. The average summer maximum temperature at Heathrow has risen from around 21.5C in the 1961-1990 period to around 23C in the 1991-2020 period. This warming makes it easier to have summer days than in the middle of the previous century. The number of tropical nights has increased also increased. Since the start of this century, all but three years have recorded at least one tropical night. In contrast, only half the years between 1961-2000 recorded tropical nights. May this year saw 2 tropical nights, never recorded before.
Statistically, the chance of a warm summer is high. Summer 2025 ranks first as the warmest summer on record for the UK so far, with a mean temperature of 16.10°C, which is 1.51°C above the long-term meteorological average, in records dating back to 1884. Last summer surpasses the previous record holder (2018 at 15.76°C) and pushes the famous 1976 summer out of the top five. The top five warmest summers are, in order from 1st to 5th: 2025, 2018, 2006, 2003, 2022
El Niño Southern Oscillation (ENSO) is one of the most important sources of annual global climate variability, second only to the earth–sun relationship that drives the seasons. El Niño and its counterpart La Niña phenomena occur in the tropical Pacific Ocean - involving fluctuating ocean temperatures in the central and eastern equatorial Pacific, coupled with changes in the overlying atmosphere. They affect the global climate, though, in general, La Niña events are less pronounced than El Niño events.
The latest seasonal forecasts strengthen the signal for El Nino development in the next few months. The US NOAA’s ENSO: Recent Evolution, Current Status and Predictions update on 26th May states:
El Niño is likely to emerge soon (82% chance in May-July 2026) and continue through Northern Hemisphere winter 2026-27 (96% chance in December 2026 – February 2027).
As a result, seasonal models will likely show patterns that are consistent with typical El Nino teleconnections through the summer.
An El Niño event is characterised by very warm ocean waters building across the Equatorial Pacific, typically lasting between 12 and 18 months.
As a result, an El Niño event will contribute to raising the Earth's surface temperature for several months. The occurrence of a strong El Niño event in 2026-2027, combined with the effects of climate change, would increase the likelihood of observing a global average temperature in 2026 or 2027 close to or exceeding the record set in 2024. That year, the influence of El Niño, as well as that of all ocean basins, contributed, in addition to global warming, to unprecedented global temperatures since records began, exceeding the symbolic threshold of 1.5°C of warming since the pre-industrial period of 1850-1900.
We will use mean sea level pressure composites of summers which featured a developing strong El Nino.
El Niño generally lessens hurricane activity in the Atlantic Ocean via increased vertical wind shear across the region, making it harder for thunderstorms to organize into hurricanes.
Tropical Storm activity over the tropical North Atlantic can influence mid-latitude weather patterns later in the summer, usually late July onwards. The ECMWF seasonal forecast is for a below average number of hurricanes during the season. And as hurricanes tend to peak in September, we don’t expect there to be much influence on the summer weather from tropical storms.
The MJO is a large-scale coupling between atmospheric circulation and tropical convection. It differs from ENSO in being a travelling pattern across the warm tropical oceanic areas of the globe rather than the standing pattern of El Nino / La Nina over the tropical Pacific. It is characterised by an eastward progression of large regions of either enhanced or supressed tropical rainfall, this anomalous rainfall area is mostly evident over the western Indian Ocean, then the warm tropical western and central Pacific as the MJO progresses eastward. The MJO wave of enhanced or supressed tropical rainfall is usually less evident when it moves over the eastern tropical Pacific and tropical Atlantic.
The MJO affects the Indian and Monsoon, plays a role in the onset of ENSO events, has an impact on tropical cyclogenesis but also has more far-reaching impacts on northern hemisphere extratropical weather through Rossby Wave propagation. The Rossby Wave propagation depends on the longitude of where the enhanced convection associated with the MJO wave takes place. As the MJO has a significant impact on northern hemisphere weather patterns, including the North America, Atlantic and Europe, there are correlations that can be made between the 8 different phases of the MJO and the lagged impacts on the upper air patterns that might be expected over the North Atlantic and Europe based on composites of previous events.
The Madden-Julian Oscillation (MJO) is expected to continue through phase 8 in the first week of June, perhaps reaching phase 1 by mid-month. Phase 8 composite of 500 hPa heights for June shows low pressure over the north and northeast Atlantic and high pressure over mainland Europe, this ties in with the current unsettled phase over the UK, with low pressure in control, though high pressure close-by over mainland Europe may extend its influence later in the month and this ties in with the phase 1 composite of 500 hPa heights. Beyond a month, the MJO is too unpredictable to use as a tool, so we only use it for forecasting a month ahead.
For June, we usually look at the ECMWF sub seasonal forecasts, which are updated daily, these give a much more reliable indication for the outlook a month ahead, than using a seasonal forecast, which is issued earlier in the month.
A look at the current sub seasonal weeklies from ECMWF shows low pressure in charge bringing unsettled conditions during the first half of the month, but high pressure returns during the second half, though influence waning with signal for low pressure to return from the west into early July, which may mean turning less settled again.
For July and August, we look at a combination of weather model seasonal forecast for each of those months.
For Europe, the latest multi-model C3S seasonal forecast issued on 10 May showed that summer will be influenced by a relatively weak atmospheric pressure pattern with anomalously high sea-level pressure in northern regions. The individual weather model seasonal predictions are more mixed but do together show the anomalous high pressure signal in northern parts of Europe.
Seasonal temperature is forecast to be above average in all regions, with the most confident signal over southeastern parts of the continent. As is usually the case, signal for precipitation are much weaker than for temperature for June-August.
We won’t go into too much detail with what each individual weather model seasonal forecasts are showing, the main ones we use are ECMWF, Met Office and the NCEP (US).
ECMWF – already looks wrong for June
UKMO
NCEP
Beyond a month, as well as using seasonal model forecasts we also make composite charts of pressure patterns for summer months in years which had similar ENSO status, i.e. this summer having a developing strong El Nino, such as 1997.
A list of key years where El Niño conditions initiated or actively formed during the summer months includes:
2023: A well-documented, strong El Niño developed during the summer and peaked in late 2023. June was the hottest in recorded history, July was actually cooler than June and unsettled too, August was unsettled with low pressure dominating, there were two named-storms too.
2015: Warming accelerated in the tropical Pacific during the summer months, triggering one of the strongest events on record. June was dry and sunny with average temperatures, July unsettled and cool after a very hot 1st day of the month, August was generally cool and unsettled, very wet in the south.
1997: Summer development led into the exceptionally powerful "super El Niño" of 1997–1998. June that year was the wettest of the century, ‘June Monsoon’ and also cool, July was warm but changeable, August was the 2nd hottest of the 20th century (after 1995).
1991: A strong El Niño developed during the summer and extended into the following year. June cool and wet, July warm but changeable, August warm and dry.
1987: Conditions began escalating during the summer, leading to a mature event that winter. Cool, dull and wet June, dry, fine & warm July until mid-month, then downhill thereafter through much of August - often cool, cloudy and wet but with a brief hot spell mid-August.
1982: A rapid warming phase established itself by summer, culminating in a historically strong event. June that year was the wettest that century before 1997, July warm and dry, August around average temperatures.
As you can see above, quite a mix bag of weather comparing each month of each year, though June in 1982, 1987, 1991 and 1997 were all cool and unsettled.
A 500 hPa height anomaly composite of the above years for July and August is shown below and will be used in the summer forecast. A composite for June won’t be used, as the sub-seasonal models will be more a reliable indicator a month ahead.
July
August
For July the composite shows higher 500 hPa height anomaly towards Iceland and over southern Europe, lower off SW Europe. This would infer a warm pattern but with no signal for lower or higher heights over the UK, potential for unsettled weather at times towards the southwest. For August, high 500 hPa height anomaly evident over southern UK and eastward, lower heights towards Iceland, a very warm and dry pattern.
If we take the above indicators discussed for the coming summer together, we can conclude that there is a good chance that it will be less dry than this spring, but a dry summer is still possible, given the propensity for seasonal models to show high pressure dominating.
The chance of a warm than average summer is higher than normal, given the signal that high pressure will dominate to the north or east. Although June is likely to be on the cool and wet side in the first few weeks, temperatures may recover later in the month, with July looking warm, despite a mixed signal for dry/unsettled. August is looking hot and dry for much of it too, given the seasonal model signal and historical comparisons of August in years with a developing Strong El Nino. But, as ever with long-range forecasting, there are no certainties!
Stay upto date with the long range forecast throughout the year with the Month Ahead Forecast - Updated Every Monday.
