Wintry showers and cold return to UK

We may have seen the warmest weather of the year so far over the weekend, but now wintry weather has made another comeback - prompting us to reach for the winter woollies again.

With a switch in wind direction to a northerly, temperatures have already plummeted across the UK and are expected to remain below average for the rest of this week.

Temperatures will widely be in single digits by day with a return to overnight frosts for many.

Although there will be a lot of dry weather with sunny spells, we can expect to see showers this week - some with sleet and hill snow, especially across the north and east of the UK.

Sunday was the warmest day of the year so far in the UK with the temperature reaching 19.7C in Crosby, near Liverpool.

But widely, most of us had some warm spring sunshine with temperatures in the mid to high teens.

Temperatures were around 6 to 8 degrees above the early March average and similar to what we would expect on a May day.

As we head toward the spring equinox on 20 March, daylight hours are rapidly increasing and we are feeling more warmth from the Sun as we transition to the summer months.

Wind direction at this time of year is really influential to our weather. At the beginning of March, southerly winds brought warmer air up from the tropics to bring above average temperatures across the UK. With a switch in wind direction to a northerly this week, the - still very cold - Arctic winds will bring temperatures below average.

From Tuesday, all of the UK will feel the cold with maximums of 5 to 9C, a ten degree drop from the weekend. Temperatures overnight will also drop close to and just below freezing for many of us.

For some context, the average mid-March daytime maximum temperatures are around 7 to 11C.

With colder air this week there's also a chance of some wintry showers. Sleet is possible even to low levels across Scotland, England and Wales into Wednesday. Over the higher ground of Scotland and northern England, a small covering of snow is also likely.

There is much talk about how a polar vortex collapse is responsible for the colder weather this week. However, this is not accurate.

The colder weather this week is purely down to the change in wind direction to a northerly bringing the colder air from the Arctic. This confusion has most likely come from the fact that the polar vortex - a fast wind very high in the atmosphere over the North Pole which keeps very cold air in place - is showing signs of breaking down.

Over the last few days observations have shown 'sudden stratospheric warming' where the temperature at six miles high in the atmosphere has warmed from -75C to -30C. This sudden warming high in the atmosphere can potentially lead to much colder weather in the UK a few weeks after it happens; but not always.

We are therefore keeping a close eye on the forecast for the end of March to see how this event will affect our weather.

For the shorter term however, it will remain chilly for most of this week before temperatures rise with milder air next week.