Continue below for the in depth forecast and explanation of the factors which are expected to influence the weather this Summer.
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.
A record sunny 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. After all, the dry weather already started in February. 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. For example, in January of this year we were still talking about a year and a half in a row with almost uninterrupted wetter weather than normal. 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.
However, 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 drought we are currently experiencing can continue to have an effect on the summer, if rain only falls occasionally at the beginning of the summer. If the soil remains dry, this increases the chance of heat. The air warms up more easily above dry soil, because less energy is used to evaporate the moisture. Because less moisture is available, fewer clouds will also form. And that means more sun, which leads to further drying out of the soil and warming of the air. As a result, heat will also flare up more easily. Given the dry conditions since February, if large amounts of rain do not occur, the chance of heat and extreme drought this summer is higher than normal
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. The Atlantic is already up to 5C warmer than normal just west of the UK and Ireland, while the water in North Sea is now about two degrees warmer than normal, as a result of the sunny spring. This means that it is less fresh when there is wind from the sea, especially on the coast.
When the weather becomes changeable, showers or thunderstorms 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.
Statistically, the chance of a warm summer is high. The United Kingdom's hottest summer ever recorded was in 2018, with an average temperature of 15.76 degrees Celsius. Meanwhile, 2023 saw the eighth hottest summer in the UK, with an average temperature of 15.35 degrees. In the last couple of decades, five of the top 10 warmest summers in the UK were recorded.
Another indicator to how this summer may pan out is the very early Final Stratospheric Warming on the 9th March, where the zonal (westerly) winds collapse and shift to an easterly regime until autumn. When this phenomenon occurs early in the year, as is the case this year, it can have repercussions on atmospheric dynamics in the months that follow. The recent years of 2016, 2022, 1985, and 1986 all experienced an early FSW, and were marked by dry summers in southern UK to average rainfall in northern UK.
La Niña was present at the beginning of this year and likely contributed to the dry and sunny spring that the UK experienced. However, La Niña has now passed and cool neutral conditions are now present. However, the dry initial situation, helped along by La Niña, can still leave its mark into the summer.
ENSO-neutral is favoured through the Northern Hemisphere summer 2025 (NOAA CPS74% chance during June-August), with chances exceeding 50% through August-October 2025. ENSO-neutral conditions are when the Pacific Ocean is neither warmer or cooler than average, or it’s transiting into or out of El Nino or La Nina, the water is considered to be in a neutral state. Though a cool neutral phase is currently present going into summer.
The neutral state of the El Niño-Southern Oscillation (ENSO) occurs when water temperature anomalies in the eastern and central tropical Pacific are between 0.5 °C and -0.5 °C. The status means neither La Niña or El Niño are in control and is sometimes referred to as La Nada.
However, similar to when El Niño and La Niña are in control, neutral conditions impact weather across the country and around the globe.
Cool neutral cycles were present in late spring and early summer since the start of the 1990s, after which the world has warmed rapidly, in the following years: 1996, 1998, 2001, 2003, 2006. 2007, 2011, 2013, 2020, 2021.
We will use mean sea level pressure composites of summers which featured a cool-neutral ENSO at the start of those summers.
June composite of cool-neutral ENSO years
July composite of cool-neutral ENSO years
August composite of cool-neutral ENSO years
Tropical Storm activity over the tropical N Atlantic can influence mid-latitude weather patterns later in the summer, usually late July onwards. The ECMWF forecast is for a normal season, but with perhaps reduced probability over parts of the western N Atlantic.
Generally speaking, La Niña years are known to produce more activity in the Atlantic than El Niño seasons, with neutral conditions being a wildcard.
Neutral years can either have just a handful of storms to being one of the most active on record.
2005 was a year dominated by neutral conditions but was active one for tropical storms - 28 named storms formed, of which 15 turned into hurricanes and seven reached major status with winds of at least 115 mph.
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 into phase 6 and 7 in the first week of June. It may briefly reach phase 8 before collapsing into the Circle of Death. Phase 6 and 7 composites of 500 hPa heights for June show low pressure over northwestern Europe, then phase 8 shows high pressure over Europe and low pressure to the northwest and so something we’ll consider.
All seasonal forecast models predict that summer will be warmer than average for the UK. The average results of eight different models predict for the 3 months:
A June that is warmer than average across the country, with an average temperature 1-2°C above normal nationwide.
A July that is warmer than average across the country, with an average temperature 0.5 to 1°C above normal for northern UK, 1-2°C above normal for southern UK
An August that is warmer than average across the country, with an average temperature 0.5 to 1°C above normal for northern UK, 1-2°C above normal for southern UK
The European model (ECMWF) shows increasing influence of high pressure through summer. Temperature-wise, for June projects 1-2°C above normal for most of England and Wales, Scotland 0.5-1C above. For July, 0.5 to 1°C above normal for most of the UK, apart from southern England & East Anglia - which are 1-2C above. For August, 0.5 to 1°C above normal for most the UK, Scotland around average.
Some beneficial rain looks likely in early June, but high pressure could dominate more in summer thereafter, looking at ECMWF seasonal forecast, more particularly in the south, bringing the risk of below normal rainfall here. However, the projections from ECMWF and C3S (multi-models) is quite weak, with average the greatest signal, but hint of drier in the far south.
The seasonal models show remarkably clear signals for a warm summer while being fairly dry in the south, wetter in the north. All seasonal models show warmer weather than normal in June, July and August. It will not be as dry as this spring, but it does seem to remain on the dry side for southern areas. Nevertheless, there will likely be showers spells of rain every now and then breaking through predominantly dry and settled conditions in the south.
Because it will remain drier than normal in the south, the prevailing deficit of rain so far this year will not disappear and may even increase slightly. This also means that when we are faced with southerly winds, the chance of extreme heat is greater than normal. As already explained, less energy is ‘lost’ to the evaporation of soil moisture. Towards high summer, the chance of this will increase if large amounts of rain do not occur.
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 fairly dry summer is still most likely. The chance of a warm than average summer is higher than normal and the dry soil across much of northern Europe increases the chance of heatwaves. But, as ever with long-range forecasting, there are no certainties!
It may take a while for any real heat to arrive, with low pressure tending to limit progress north of heat that may build over mainland Europe, but it could turn hotter at times from later in the second through the third week, as high pressure builds.
An active jet stream will run into NW Europe for the first and perhaps 1st half of second week, bringing areas of low pressure and spells of rain or showers, while windy at times. Temperatures remaining around average, perhaps slightly below in the north.
From around 11-12th, there is a signal is for the jet stream to shift north, with high pressure building in across mainland Europe and perhaps UK. This would mean it turns warmer and sunnier, but with a risk of thundery showers in places. Potential for high pressure to build further north across UK into third week and continue to influence into the 4th week, with drier more settled conditions more likely prevailing and also potentially a hot spell. But also a risk of thundery showers, especially in the south.
Temperatures overall for the month likely to end up above average. Rainfall will likely be average, most of the rain falling in the first half of the month.
Probability for temperatures against 1991-2020 average: 60% chance of above average, 30% chance of average, or 10% below average.
Probabilities for rainfall: 40% of chance for average, 30% chance of above average, 30% chance of below average.
Overall signal from sub-seasonal and seasonal models (albeit not strong) and best analog years is for some low pressure influence, most likely at the start of the month following a dry second half to June. Unsettled conditions possible in early July, with low pressure over or near UK bringing spells of rain or showers, though wettest in the north. Low pressure retreating north towards mid-month. Drier second half to the month, as high pressure builds in from the west or southwest, this could include some hot weather. But occasional thundery breakdowns can’t be ruled out.
Confidence is quite good concerning the temperatures being above average, perhaps 0.5-1C above. Rainfall we have less confidence, slightly below average for England and Wales, but perhaps above in Scotland, especially towards the northwest.
Probability for temperatures against 1991-2020 average: 70% chance of above average, 20% chance of average, or 10% below average.
Probabilities for rainfall: 40% chance of average, 40% chance of below average, 30% chance of above 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 often settled and sometime hot weather, but with some brief breakdowns too. Unsettled towards the end of the month. Temperatures 1-2C above the 30-year average. Rainfall signal looking most likely to be below average.
Probability for temperatures against 1991-2020 average: 60% chance of above average, 30% chance of average, or 10% below average.
Probabilities for rainfall: 50% of chance for below average, 30% chance of average, 20% chance of above average.
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