Heatwave conditions possible to end May
Blog by Jo Farrow
Issued: 28th May 2020 15:52

Heatwave conditions possible to end May

Spring 2020 has been dry and often warm and sunny with the fine weather coinciding with the UK lockdown. High pressure is once again over the UK and as it eases eastwards warmer air will flow up from the south. The highest temperatures are expected for western and northern areas as a cool breeze off the North Sea sets in, for the end of the week.

The highest UK temperature so far in 2020 was 28.2°C recorded at Santon Downham, Suffolk on Weds 20th May. Temperatures of 27 or 28C are likely in the coming days with Highland Scotland being favoured in the southerly flow. Many parts of the UK will see 20s Celsius. These high temperatures are for some areas, well above the May average. Actually, moving into the heatwave category.

Location May Average Max Temp
UK 14.8c
England 15.8c
Scotland 13c
Wales 14.9c
N.Ireland 14.6c

 “A UK heatwave threshold is met when a location records a period of at least three consecutive days with daily maximum temperatures meeting or exceeding the heatwave temperature threshold. The threshold varies by UK county.” Met Office

Met Office UK heatwave threshold

Greater London would have to see 28C or above for three days in a row, this is not expected. The easterly flow will keep coastal counties of SE England and East Anglia cooler with that North Sea flow spreading to more of eastern England and eastern Scotland at the weekend.

SW England has seen temperatures of 25C or above on Wednesday, likely on Thursday but less so on Friday. So worth watching for NE Devon. Wales also could reach 25C for a few days, whether that will be in the same location though.

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Merseyside and Manchester will be very warm on Friday, but it is Scotland that could see temperatures tipping over 25C. Friday in the southerly flow, north-western and western Scotland on Saturday in the SE breeze. The southerly wind picks up by Sunday but still mid 20sC is possible for the inland Highland/ Moray area.

Heatwave criteria are different around the world. Obviously in India with pre-monsoon temperatures in the high 40sC even 50C their criteria won’t be in the 20sC, but Ireland has a longer length of time. Met Eireann's guidelines are for temperatures to be 'Above 25C for five consecutive days.'

The Met Office will issue their climate summaries in a few days, showing the rainfall and temperatures data for May and for spring (meteorologically March, April and May). The ongoing lack of rain is beginning to attract attention as the warm, sunny conditions continue.

The grass pollen season is now underway with high pollen levels forecast for southern Britain. With cloudless skies for many parts of the UK and high UV levels do remember your sunscreen, hat and shades if outside.

What about June? - Netweather forecaster Nick Finnis said: “There are tentative signs of a pattern change as we head into early June, to something cooler and more unsettled. The high pressure could retreat westwards to allow low pressure to drop south across Scandinavia and eastern Europe from mid-week, bringing a cooler northerly flow with showers. But some uncertainty over this outcome for now.”

Check your latest local weather forecast.

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