WE TRY to pretend it doesn't matter; we're used to it, we're intrepid, we'll sit through a three-hour play in blustering wind and showers, if necessary. The truth is, though, that for outdoor performance, sunshine makes all the difference; and if this weekend's Merchant City Festival in Glasgow was the most successful in the history of the event - with crowds thronging between George Square and the Tron, thriving street markets everywhere, and bars and cafes packed to the sunny pavements - then the gods of the weather have to take at least half the credit. Much of the other half, though, goes to the intrepid band of promoters, producers and performers who gave the event a classy touch of artistic edge, to go along with the food, drink, shopping, and get-set pre-Commonwealth Games event in George Square. My own Merchant City day started on the area's western edge, at Sloans Bar in the Argyll Arcade, where a blisteringly talented bunch of musicians, singers and actors known as Noise Opera were presenting a 75-minute fully-fledged modern classical work by composer Gareth Williams and librettist David Brook, known simply as The Sloans Project. Beginning in the bar, and then moving on to four other spaces on the upper floors of this beautiful historic building - a pub since 1797 - the show featured five musicians, five superb singers, and four actors, and a series of scenes involving a wedding, a funeral, and a strange historical flashback to a fierce moment of connection between a 19th-century manageress of the howff, and Frederic Chopin, on tour in Scotland. After that, it was out into the sun-soaked streets, to search out a range of events created by UZ Events' Roofless programme, and co-commissioned by In Situ, the international street theatre network to which UZ belongs. These included a sequence of tours of the Merchant City streets led by four different artists, under the title Derive; which is how I and a half-a-doze others found ourselves wandering along the Trongate and up Candleriggs in pursuit of Alex Rigg, a wan, corpse-like but strangely engaging Vivienne Westwood figure who looked like the wrecked ghost of a long-dead dowager, but talked like a lost child in search of his "mam", poignantly interrogating every passer-by, and every sign in or on the road, for possible messages. In King's Court, near Paddy's Market, I saw a Growling Tent devour a team of officials who approached to investigate it, in convincing style; and an old-style towing caravan being "pimped" by a gang of cutting-edge graffiti artists. Then, at the stroke of three, Ljud of Slovenia presented their street-theatre Invasion of fabulous pink figures, half man, half alien, with a touch of the sea-monster and the friendly farmyard animal. The crowds shrieked, screamed, then peered, poked, patted and tried to feed them; sometimes, the four performers would simply gather, and form shapes like a gleaming pink sculpture, in the sun.That, on a rough calculation, was only about one-thirtieth of all the fun, games and entertainment on offer. Rumour has it that Glasgow City Council are so pleased with this year's event that they're now planning a much bigger one, for the Commonwealth Games year of 2014; let's hope that the weather continues to smile, and doesn't rain on their parade.