Heatwave returns but will it last?

This summer has brought persistently above average temperatures to the southern half of the UK, although the picture in the north has been more mixed. While the absolute UK record, set on 19th July 2022 when 40.3°C was recorded at Coningsby, Lincolnshire, hasn't been beaten, a new June high was set, with the Met Office's weather assessment team verifying a report of 38°C.

Cooler in the short term

Fresher air will push down from the northwest during the last couple of days of July bringing temperatures back to a much more comfortable mid-20s (Celsius) across southern, central and eastern England.

However, there won't be much, if any, rain in the southern half of the UK, offering little or no relief from the ongoing drought conditions which are now officially affecting more than half of England. The forecast rainfall totals in mm for 29th July to 3rd August, based on data from the Met Office's high-resolution UKV model, are shown in the chart above.

Heatwave conditions return?

The cooler interlude probably won't last long, with temperatures expected to climb at the start of August, at least across England and Wales. Values could reach 30°C again, but Scotland and Northern Ireland will stay cooler.

There are indications of a more changeable spell of weather developing from about 3rd August. This could potentially bring some much needed rain to the south as pressure falls and weather fronts push in from the Atlantic. 

Nonetheless, computer forecasting models suggest this unsettled blip won't last long. As we head towards the end of the first week of the month and into the second, conditions may become very warm or hot. While there is uncertainty at this range, the prospect of the heatwave threshold being reached in parts of the UK isn't out of the question.

The GEFS Hovmöller chart above covers the period from 29th July to 14th August. The vertical axis represents time, while the horizontal axis shows longitude. The 0 degree vertical line marks the Greenwich Meridian, providing a handy reference point for predicting how broader weather patterns will affect the UK.  

On the chart, orange shading highlights areas where pressure is forecast to be higher than average (ridges). Blue shading indicates lower than average pressure (troughs). This colour coding makes it easy to track how weather systems evolve over time.

In early August blue shading approaches the 0 degree line. This suggests low pressure systems will become more influential, bringing a greater chance of rain and potentially cooler conditions. However, from around 7th August this signal fades. Orange shading takes over, pointing towards higher pressure and a return to more settled weather.  

The second half of August

When looking further ahead, forecasting in the UK becomes more about identifying trends. Currently the overarching signal points towards above average temperatures continuing for much of the period. Although the days are noticeably shorter by late August, recent years have shown that hot conditions remain very possible in the south well into September. Because of this, late season heatwave conditions are still firmly on the cards.

The drought continues?

 Although recent weather models have hinted at a slightly more mixed picture than we saw in early summer, most still indicate that rainfall totals in the south will remain stubbornly low. Given the growing rainfall deficit and tinderbox dry landscapes, an extended period of wetter than average conditions is desperately needed to restore the balance in reservoirs and rivers. There are early suggestions that a shift towards wetter weather might arrive in the autumn, but there is still a long journey ahead before we reach that point.