Sun, rain and 85,000 happy revellers: it's Scotland to a T

Around 85,000 people are expected at Scotland's biggest music festival - where the big attractions include the Arctic Monkeys, Primal Scream, The Strokes, Pulp, Foo Fighters, Manic Street Preachers and Coldplay.

Thunder is forecast for tonight, when fans will be watching international R&B superstar Beyonce appear on a Scottish stage for the first time in five years.

• Follow our live coverage of T in the Park throughout the weekend at scotsman.com/titp2011

Organisers of the festival at Balado, Kinross-shire, said this year's bill featured a strong Scottish contingent, including Big Country, who are playing the event for the first time, 30 years after the band first formed.

The View, Kassidy, KT Tunstall, Calvin Harris and Twin Atlantic are among the other acts playing close to home, while cult rockers Primal Scream will be performing their classic album Screamadelica in its entirety.

Two-hundred acts will appear on 11 stages during the course of the festival, which lasts until tomorrow.

Last night, Sheffield's Arctic Monkeys and Welsh crooning legend Tom Jones were topping the bill. As the festival got underway many revellers were wearing retro outfits in honour of Fancy Dress Friday - the traditionally light-hearted first night of the festival.

Nathaniel Bicker, 29, from South Shields, and his friends dressed as Pink Ladies to get into the spirit of the event.

He said: "This is our first time at T in the Park after hearing amazing things about it. We came up last night and we spent hours in a queue to get here and then even longer trying to put our tent up, but it's all going to be worth it.

"I'm especially looking forward to seeing Coldplay and Swedish House Mafia. I'm just going to try to see as much as I can."

Stacey Wishart, 20, from Fife, said Beyonce was the big attraction this year.

The R&B star delivered a stunning set at Glastonbury just two weeks ago and was a last-minute addition to the line-up."I can't wait to see her and anyone you talk to in the camp is definitely wanting to see Beyonce," she said.

"It's only the first night, but the atmosphere is already brilliant with everyone talking to everyone."

Met Office forecaster Helen Chivers said festival-goers should be well prepared for lots of changes in the weather over the weekend.

"You'll definitely need your wellies, but you might take some sun screen as well - because when it's dry it could feel pretty warm."

Heavy rain hit Balado on Thursday leaving the ground wet and muddy as the early birds put up their tents, but yesterday stayed mostly dry as most of the weekend campers arrived on site.

More showers were expected overnight, but the outlook for today is unsettled with a possibility of thunder in the evening.

Ms Chivers said: "It is one of those days where you could have sunshine and you could have showers.

"Sunday is due to be the best day of the lot. There is a good chance you could end up with sunshine. Temperatures could reach 18 or 19 degrees and there won't be much wind, so it should feel warm."

Craig Allan, 23, from Livingston, said the warnings of bad weather would not dampen the party mood among the famously robust music lovers of T in the Park.

He said: "I've got my shorts and T-shirt on and I don't care if it rains. This is what we are used to here - you just have to go with it.

"It's my seventh year at T and every year everybody is always up for it."

Radio One DJ Reggie Yates announced on Twitter he had come prepared: "Currently in wellies waiting to jump on my flight to Glasgow. T in the Park here we go!"

Five-thousand extra camping places have been provided this year with the hope of spreading the arrivals and easing the traffic congestion around the festival.

Tayside Police issued a special warning to festival-goers about the dangers of drug use following recent deaths linked to a spate of high strength ecstasy. According to police sources, the pills sell for around 10 each.

Chief Superintendent Craig Suttie, event commander for T in the Park, said: "We are aware of ecstasy tablet that is being peddled in certain parts of Scotland that is reported to be six times the strength of other ecstasy pills.

"Clearly, anyone who takes such a drug is dicing with death. Indeed, anyone who takes drugs can have no inkling of what its strength is or what other chemicals it might contain. Please listen to the advice and avoid drugs altogether."Our officers will take action against anyone we suspect of dealing or using illegal drugs - at T in the Park or anywhere else."

Police said the Citizen T initiative launched last year would continue for the 2011 festival.

It encourages positive community behaviour, including looking out for friends and fellow campers, binning litter and taking tents home at the end of the weekend.

Tayside Police said the Red Cross and NHS Lothian were among the organisations sending out health and safety tips and travel advice to revellers.