Warmer weather on the way, but will it be a heatwave?

The transition from spring to summer looks set to continue next week, with higher temperatures in the forecast thanks to a spell of high pressure, but would it be classed as an official Met Office heatwave?

After an unsettled end to this week with some rain for western areas, high-pressure looks to be building back in from the south on Saturday, setting up what should be a relatively warm spell with temperatures likely reaching the low 20s for some areas, most likely in the south.

Alex Deakin presents the 10 Day Trend

Speaking in the Met Office’s Ten Day Trend, Presenter Alex Deakin said, “What happens to the jet stream over the weekend is a bit of a push out in the Atlantic, so the jet steam arches up to the north and this ridging high up in the atmosphere allows high pressure to build across the UK. This high pressure will bring most of us a fine and dry weekend… but not spectacularly warm.”

After the weekend, while there’s still some uncertainty as to the exact positioning of the high pressure, mild weather will continue to be the main theme for most.

Alex continued: “High pressure continues to dominate through the weekend, probably into the early part of next week and maybe even beyond. However, it is dependent on what happens on the other side of the Atlantic with weather fronts trying to push in during Monday and the exact position of the jet steam will dictate how low-pressure systems try and push in from the northwest.”

That set-up looks likely to continue for much of next week, with low pressure systems trying to move in from the northwest and the high pressure closer to the southeast. How these systems interact will determine the exact forecast for next week, although higher temperatures look to be continuing for most.

“We’re likely to be drawing our air in mostly from the south or southwest. That would bring the chance of some moisture from the Atlantic but it would also bring some warmth. However, a subtle shift in the pressure pattern could allow us to tap into some warmer air,” said Alex.

“If the high is just a little bit further east, it will allow low-pressure systems closer to the UK – so an increasing threat of showery rain in the northwest. But it would potentially allow more of a southerly flow and allowing us to tap into some warmer air coming up from the near continent. The exact amount of warmth we will see be down to the subtle positioning between the high and low pressure systems.”

Despite the outlook showing positive signs of some warmer weather next week, it’s still unclear how much cloud cover could have an impact on the weather. More details will be available on this element of the forecast closer to the time. Keep up-to-date with the latest forecast on the Met Office app, website or on social media.  

Will it be a heatwave?

Despite some media reporting of an imminent prolonged heatwave, most locations look shy to reach the required thresholds for three consecutive days in order for it to be considered an official heatwave by the Met Office’s standards.

A heatwave is defined by reaching a specific temperature threshold on three consecutive days. The threshold for a heatwave temperature differs by county, with some areas in the southeast having a threshold of 28C, while areas to the north and west have a threshold of 25C.

The heatwave threshold map of the UK. An official heatwave is when a county exceeds the threshold for three consecutive days.
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