Summer weather: will there be a heatwave? - BBC Weather
This video can not be played Summer weather: will there be a heatwave? With its longer days - and bank holidays - the advance of May might have you dreaming of the summer ahead. You'd be forgiven for thinking things have taken their time to warm up this year. While overall temperatures have been around average this spring, there's been a real lack of very warm days. England and Wales had to wait longer for the thermometer to climb above 19C than in any year since 1986. Even in early May temperatures only edged into the low 20s. In many recent years we had already seen 25C or higher by this point in the year. It's also been a very wet spring for many, especially in the south and east of the UK. Torrential downpours and thunderstorms have caused flash flooding in places . In a typical year July is normally the warmest month overall. But over and above that, we have to rely on long-range seasonal weather outlooks. These aren't like the short-range forecasts on TV or the BBC Weather app. The computer models we use to drive those predictions simply can't forecast the weather accurately for a whole season ahead. The atmosphere is a chaotic system. A tiny deviation from the forecast today could easily grow into a complete turnaround 10 days from now, let alone three months in the future. Long-range weather forecasters consider many factors - including large scale global weather phenomena such as El Nino or La Nina, the effects of climate change, and the typical conditions we'd normally expect - to create seasonal outlooks. These aren't specific weather forecasts for individual places. Instead they give a broad overview of the most likely conditions across the country as a whole. This is the seasonal outlook from the Met Office which covers the three months from May to July. It gives the percentage chance that the weather will be wetter, drier, warmer or colder than average. The most likely scenario is for temperatures and rainfall to be around the average. But there's a much greater chance of it turning out warmer as opposed to cooler than normal - 35% versus 5%. It's also more likely to be wet than dry. It's summer - we'll almost definitely have hot weather at some point! You may see stories forecasting heatwaves but it's always worth pausing to check the detail. Sometimes the predictions are based on extreme computer model runs that are looking weeks into the future at conditions which will often change. And don't forget, just because it's warm doesn't mean it's technically a heatwave. The official definition is quite strict. Temperatures have to meet or exceed a certain level for three consecutive days and this threshold varies depending on where you are. The Met Office raised the temperature thresholds for eight counties by one degree Celsius last year because climate change is pushing what we see as "normal" upwards. Last summer the UK set a new record high temperature - 40.3C in Lincolnshire - something which scientists say would have been "basically impossible" without global warming. What's the risk it'll get that hot again this year? It's extremely unlikely. Scientists estimate that - in our current climate - the hottest parts of the country would only expect the temperature to reach those record levels about once every 1000 years. So if it were to happen again in 2023 that would be very worrying indeed. You can follow BBC Weather on Twitter @ bbcweather , on Instagram @ bbcweather and online . A really simple guide to climate change Climate Check: 2022 heatwave Unexplained ocean warming alarms scientists Weather for the Week Ahead. Video Weather for the Week Ahead UK heatwave swelters on - but storms loom for many Floods turn Hong Kong streets into raging rivers Hurricane Lee now a category four storm What is a heatwave? Video What is a heatwave? Storm Daniel lashes Greece. Video Storm Daniel lashes Greece Streets turn to rivers in Bulgaria. Video Streets turn to rivers in Bulgaria 2023 BBC.