Bank holiday weather: Will it be warm or wet this weekend?

The bank holiday weekend is nearly here.

And after some warmer weather over the last few days you might be hoping for more spring warmth and sunshine.

Well, temperatures are expected to be around or just above the seasonal norm and skies will sometimes be blue - but that does not mean it will stay completely dry.

Downpours are likely to dampen the mood but there is still uncertainty about exactly where and when they will crop up because our weather patterns are far from straightforward at the moment.

You might be pining for warm weather because of what felt like a cold April but statistically temperatures were actually slightly above average.

It was a month of two halves, though. It started on a mild note with above average temperatures, especially at night, but colder weather developed from mid-month - just at the time of year when we normally expect it to start feeling warmer.

It was a dull month too with just 79% of the usual sunshine, while rain also featured heavily. In fact the Met Office says England and Wales have already had all their typical spring rainfall - with a whole month of the season still to go.

Over the last few days things have started to change.

A feed of warm air from continental Europe has lifted temperatures with the thermometer climbing into the low 20s Celsius in the sunniest places, although it has also brought some downpours and thunderstorms.

North-west Scotland could still see 20°C on Saturday but generally temperatures will take a downturn for the weekend. They will still be around - or just above - typical early May highs of 12 to 17°C and where the Sun comes out it will feel fairly warm.

Before you dust off the barbecue or race to the beach it is worth bearing in mind that low pressure will be close by, so rain also features in the forecast.

Northern and western areas look most likely to see wet weather on Saturday with drier conditions for a time further south and east - although a few isolated showers are still possible.

Sunday and Monday will bring more widespread downpours and it could turn particularly wet in southern England by bank holiday Monday.

But there has been a lot of uncertainty in computer forecast models and even at this late stage precise details from place to place are still likely to change.

The passage of weather systems around the globe is governed by the jet stream, a band of fast-flowing winds high in the atmosphere that circles the globe.

Often the jet stream flows strongly from west to east, across the Atlantic, sending weather systems quickly across our shores in an orderly way - a bit like a conveyor belt. This is typically among the easiest type of weather to forecast.

But at the moment the pattern of the jet stream is more meandering, waving northwards and southwards with big peaks and troughs which steer the weather systems more weakly. Areas of low pressure and frontal systems move more slowly and erratically and it can be harder for computer models to pick out the details.

Spring weather is notoriously fickle and this long weekend will be no exception. So the best advice is to check your local forecast online or on the BBC Weather app to see exactly what's coming your way.