Hot spell June 2017
The UK experienced a spell of hot, sunny weather in June 2017 associated with high pressure drawing warm air from the near-continent. From 17 to 21 June temperatures exceeded 28 °C widely across parts of England, with some locations reaching 30 to 32 °C. On 21 June Heathrow (Greater London) recorded 34.5 °C, the UK's highest June temperature since 1976.
While many enjoyed the fine, sunny weather, the heat resulted in some speed restrictions on rail lines to avoid buckling, and there was an increased risk of high air pollution for congested areas such as the East Midlands. There were also several accidents associated with swimming. The hot weather also led to increased vulnerability from heat stress particularly to the elderly and frail.
The following link from BBC news provides some indication of impacts experienced through this period.
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The analysis chart at 1200 UTC on Wednesday 21 June 2017 shows high pressure centred to the east of the UK drawing a flow of hot air from the near continent to the south, but with cooler cloudier conditions across the north.
This panel of daily maximum temperature maps from 17 to 21 June 2017 shows the extent and duration of the hot weather across England. Initially the hottest areas were across eastern England, with the heat becoming more widespread by 19 June and peaking at over 32 °C across central southern England on 21 June.
The map below shows daily maximum temperatures across the southern half of the UK on 21 June 2017 at the peak of the hot spell. The hottest weather was to the west of London but the heat also extended further west included 30.2 °C at Porthmadog (Gwynedd), 31.5 °C at Chivenor, Devon and 31.8 °C at Pershore College (Worcestershire).
The map below shows stations which recorded their highest June daily maximum temperature since June 1976; for most of these stations these values occurred on the 21st.
Summer temperatures usually peak in July or August and this was not an particularly notable hot spell in the context of summer overall. Comparable or higher temperatures have been recorded recently including 34.4 °C in September 2016 and 36.7 °C in July 2015, and much more significant summer heat-waves occurred during July 2006 and August 2003. However, it is relatively unusual to have spells of weather as hot as this during June. The last time 32 °C was exceeded at several weather stations across England in June on the same day was on 27 June 2011, with earlier dates including 19 June 2000, 7 June 1996 and 30 June 1995.
The chart below provides a count of the number of station-days in June of each year from 1961 to date for the UK overall, where the daily maximum temperature exceeded 28/30 °C. This provides an overall indication of how unusual such a spell of hot weather is, although each individual spell will differ in terms of extent, duration and severity. In general, the most comparable spell of hot weather to June 2017 was from 28 to 30 June 1995. However, this is exceeded by far in 1976 with this heat extending into early July and being associated with severe drought conditions (the dry ground conditions contributing to the high air temperatures).
The panel of daily maximum temperature maps from 25 to 30 June 1976 indicates how much greater the extent and severity of the hot weather across England was from this event, with 32 °C being exceeded very widely on 26 to 28 June and 34 °C reached in several locations on each date. On 28 June 1976, 35.6 °C was recorded at Southampton, Mayflower Park, the equal-highest June temperature on record for the UK.