The warmest April day in 70 years caused a spike in deaths, ONS figures have revealed. Temperatures reached almost 30 degrees in parts of the UK in a “mini-heatwave” on Thursday April 19, making it the hottest April day since 1949. Figures released by the Office for National Statistics show that there were more than 240 extra deaths on April 18 and 19, when temperatures reached a high of 29.1 degrees in central London. “Between 18 and 19 April 2018, 243 more deaths were observed than the five-year average for the same period and rose well above the maximum number of deaths seen on those dates from 2013 to 2017,” the ONS said. There were then almost 400 fewer deaths over the following weekend between April 21 and 23. “This sharp rise then fall in the number of deaths coincided with a period of higher than average temperature between 18 and 19 April 2018,” it added.The pattern could be down to “short-term mortality displacement”, the report added, which is where a short-term event happens which causes vulnerable people to die who then are removed from the pool of people who would have died during the following few days. The five-year average number of deaths for April 19 is 1,240, with April 19 this year seeing 1,372 deaths. The average for April 18 and 19 is 2,460, while the two days added together saw more than 2,700 deaths this year. Earlier this year, MPs warned that the UK was underprepared for an increase in extreme weather and the impact this could have on public health. The environmental audit committee said that heat-related deaths would triple in under 35 years unless the Government took action to make buildings and urban areas more tolerable at high temperatures. There were instances of increased mortality that coincided with hot weather in Q2 in England. A detailed analysis of deaths that may be attributable to a heatwave will be addressed in our next quarterly release https://t.co/wMEHYV888F pic.twitter.com/chZHF7iRrQ— ONS (@ONS) September 17, 2018 If temperatures rise above 24.5 degrees, Public Health England warns that heat-related deaths may start to occur.Overall there were almost 3,000 more deaths than the five-year average amount during April, May and June. However, based on the mortality rate, the number of deaths was lower than expected, the ONS said. During the first three months of the year, there were 18,145 more deaths than the five-year average. Extremely cold weather over the winter also contributed to a much higher than average number of deaths.All but one day had a higher number of deaths than the five-year average, and almost two-thirds of days had a higher number of deaths than any of the corresponding days in the past five years. “Deaths began to climb well above the five-year average during this cold spell and remained high for almost two weeks after temperatures began to rise,” the ONS said. A similar pattern happened during the June heatwave, with 382 more people dying between June 25 and June 30 than the average for 2013 to 2017. Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. A large spike occurred around the end of January. 1,781 people died on January 23, compared to an average of 1,450 over the previous five years.The pattern continued throughout late February and early March, as the country was hit by the so-called Beast from the East, which led to extremely low temperatures and snow and ice. In the UK, 17 people were believed to have died in incidents such as car accidents and falls that were a direct consequence of the weather, as well as Storm Emma, which hit parts of the country at the beginning of March, causing high winds.