Why is the weather so bad this summer? And when will it get warm?

Indoor barbecues, soggy washing, cool and cloudy at best: summer’s been a damp squib so far. At a time when people are checking flood alerts instead of eating strawberries and cream in the garden, the big question is: will we ever get any sun?

Last week saw parts of North Wales and Scotland at risk of flooding and temperatures barely reaching double figures. Thunder and lightning are forecast in Northern Ireland and in London, the weather was blamed for low attendance at the first week at Wimbledon.

Summer looked promising at first, with the Met Office recording a warmer May than usual, but the first two weeks of June were two degrees below average. There were three days of hot weather in some places towards the end of June (24th to 27th), with Heathrow recording temperatures over 30°C. But earlier in the month, sub-zero temperatures were recorded in the village of Kinbrace in the north of Scotland.

With the summer solstice behind us and days getting shorter, hope of a long, hot summer is fizzling out. Sara Thornton, TV presenter and meteorology expert from Vacay Weather, says: “The problem with this summer so far is that we've only had brief periods of completely dry or warm weather.

“May was actually warmer than average across the UK, but we forget that because June was definitely cooler for a good deal of it, particularly with temperatures running around two degrees Celsius below normal in the first half. In the end, because of that late warm spell, the average temperature across the UK for the month was only half a degree below normal.”

Although it was cold, June wasn’t even that wet. “You might be surprised to hear it, but we had only 71% of the average rainfall across the UK as a whole in that month,” says Thornton. That average conceals some differences around the UK - Scotland recorded very close to its average rainfall, but England and Wales were on only half of their average rainfall and Northern Ireland 74%.

July so far has continued to be cool across the UK, with recent daytime maximum temperatures generally in the high teens or low 20s Celsius, as well as frequent periods of cloud and rain.

Blame it on the jet stream

With the sun breaking through in some places and many newspaper headlines promising a heatwave is just around the corner, you might be forgiven for thinking that summer is on the way, but the longer-term forecast doesn’t guarantee it.

The problem lies in the jet stream, a narrow band of air high up in the atmosphere, which affects the UK weather. Even a small shift can affect what’s happening on the ground.

“In your typical hot summer, the jet stream is north of the UK, and we see areas of high pressure build in from the south, keeping frontal systems at bay, and drawing up warm or hot air from the south,” says Thornton.

“The jet stream is one of the great drivers of the UK’s weather. Sometimes, when we have rubbish summers, it’s because the jet stream is sitting across or to the south of the UK, steering low pressure systems towards us, which is what we’re experiencing now.”

This is what brings bands of rain and wind – and those frequent afternoon showers. “In simple terms, we can think of the jet stream as having a warm, sunny, southern side, or a colder, rainy, northern side. It's no surprise to learn that we've often been on the northern side of it this summer.”

Good for the gardens

While you might prefer to be packing your umbrella away until autumn, there are some advantages of this unsettled weather. Because there’s been plenty of rain, water butts are full, lawns are looking lush and green and there’s no hosepipe ban in sight. That’s not just down to what’s happening now, but the culmination of a long period where rain dominated the weather. “We had a wet winter, and a very wet spring - especially in May, so we started the summer with water reserves close to, or more than, 100% in some parts of the UK,” says Thornton.

But the big question is: with the weather threatening to brighten up, can we look forward to sunshine in the next few months?

“Despite the fact that our days are getting shorter through the summer, and our sun is becoming a little less strong, our temperatures are actually increasing due to a lag in the ground and sea heating up. But that doesn't necessarily all equate to more sun or settled conditions,” says Thornton.

“I'm afraid there's nothing exceptionally warm or very settled in the forecast, although there are hints of something briefly a bit warmer later this week with temperatures into the mid-20s for some. But until I see continued signals for the jet stream to move away from us, I'm not holding my breath!”