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It may be autumn and the nights are drawing in but we haven't seen the last of the summer yet.

It's going to get much warmer over the next few days. Southerly winds from the southern Europe and the Mediterranean will be bringing blue skies and lots of sunshine to Wales with temperatures rising into the low to mid 20's Celsius.

The highest temperature ever recorded in September in Wales is 31C, 88F on 1st September 1961 at Gogerddan in Ceredigion.

Later into the month and the highest temperature is 26 Celsius, 79 Fahrenheit at Abergwyngregyn in Gwynedd on 30th September 1985 but this could be smashed this week with temperatures on the north coast predicted to reach 27 Celsius, 81 Fahrenheit at - on a par with Barcelona in Spain!

The reason for the warm and sunny spell of weather is down to the shape of the jet stream. The jet stream in the upper atmosphere is shaped like a roller coaster at the moment and we're on the warm side of a big dipper.

In meteorology this is called an because it resembles the shape of the Greek letter Omega and these blocks can last for some time before breaking down.

The weather we get depends on which part of the Omega block we are stuck under. At the moment we are in the middle which is warm and dry but either side of it is cooler and more unsettled.

In winter, Omega Blocks can lead to cold and snowy weather if they are in the right place which was the case last December which was the coldest on record.

At this time of year, some people often refer to warm weather as being an Indian Summer but these occur in October and November.

In Welsh, fine and warm in late September is called a 'haf bach mihangel' or a St. Michael's little summer, which I have written about before.

So, forget the soups and duvets, it's time to hit the beach and get the BBQ out over the next few days. In fact it could be the best spell of weather we've had since last April.

The sunshine will really show off the autumn colours at their best so if you take a photo please email it to dereksdiary@bbc.co.uk.

And you never know, I may be able to show them off on the telly.

Derek