All UK nations have experienced recent heatwave conditions but in southern England, the heatwave has now continued for 13 days. Sarah Keith-Lucas looks at how unusual this spell of…

Places in southern England have recorded an unbroken run of 13 days above their heatwave criteria, and with Merryfield in Somerset reaching 30.6C (87.1F) on Thursday, the UK has seen 12 consecutive days at or above 30C, the longest such spell since 2006. In Bournemouth and Heathrow, temperatures above 26C and 28C respectively have continued now for nearly two weeks and whilst some slightly cooler air will arrive from the north this weekend, a few locations may well see another few days of heatwave yet. However, the 1976 UK record of 16 days at or above 30C seems unlikely to be broken. One of the most striking features of this heatwave has been how long it has lasted. Several factors have come together to create this intense and lengthy spell. First, our climate is changing - fast. Temperatures in the UK are now on average 1.33C warmer than they were during 1961-1990. However, the very hottest days have warmed three times quicker than this - by 4.5C in the Greater London region - according to the Met Office. Secondly, the weather set-up so far this summer has been especially conducive for building heat. The jet stream has meandered well to the north of the UK, allowing high pressure to build and warm air to drift in from south. As the high pressure has been so slow moving we have seen the development of a "heat dome". This weather pattern results in air sinking downwards, compressing and heating up as it hits the ground. This air also dries out, meaning no clouds can form, so strong sunshine is able to heat the ground even further.