Although temperatures at the end of June were the highest for five years (33C in Kent) there was no repeat of the pollution problems that we experienced at Easter. Hot weather began on Sunday 26 June, but a fresh Atlantic air feed meant that pollution stayed low. Air over eastern England on Monday 27 June was more polluted, having spent Sunday over France.
Moderate levels of ozone were measured across eastern England including the south-east, the east Midlands and parts of Yorkshire, but two factors enabled us to avoid serious smog. First, relatively low traffic levels and industrial emissions over France on Sunday meant there was insufficient pollution to form smog over the UK on Monday. Second, summertime smog does not form quickly; it can take two or three days for hot sunlight to drive the chemical reactions between air pollutants that lead to harmful levels of ozone and airborne particles. In this case, there was insufficient time for the smog to form before the polluted air was pushed eastwards as violent thunderstorms spread across the UK on Tuesday, 28 June. The residents of Paris were not so lucky, and the heat wave caused the city authorities to declare a surprise pollution alert.
Earlier in June, sunny spells caused brief moderate ground level ozone across many parts of the UK. Grangemouth, in central Scotland, experienced sulphur dioxide problems from nearby industry on three days in mid June.