LONDON, England (CNN) -- If Potions Professor Horace Slughorn had mixed a brew to conjure up torrential rain, the weather could not have been worse for the premiere of "Harry Potter and the Half-Blood Prince."
A fan gets caught in the rain at the premiere of "Harry Potter and the Half-Blood Prince."
Dedicated fans braved thunder, lightning and Biblical downpours in London's Leicester Square to catch a glimpse of the film's stars arriving at the opening of the sixth film in the wildly popular "Harry Potter" franchise.
While dreadful weather has become an unfortunate tradition at Potter premieres (it rained during the 2007 premiere of "Harry Potter and the Order of the Phoenix"), the latest installment holds something new for fans.
"The Half-Blood Prince" offers up an uncommonly large helping of humor as Harry, Hermione and Ron enter their sixth year at Hogwarts School of Witchcraft and Wizardry. Are you excited about the new Harry Potter film or is it just hype? Tell us below in the Sound Off box.
"I think this film's funnier," said star Daniel Radcliffe who plays the titular young hero. "There are a couple of moments which I laughed out loud at."
Hormones are also running high inside the castle walls, with romances blossoming between some of the formerly chaste characters. But, says director David Yates, for all the romance and humor, the film still has a very dark side.
"It is a bit bipolar," Yates told CNN. "On the one hand, there's all this snogging and romance and on the other hand people are getting killed and bridges are being blown up."
"The humor is there to kind of leaven the intensity of what happens later on in the movie," he added. The latest on the Harry Potter video game »
If the latest Harry Potter installment treads more adult terrain, it's not just because the three lead actors -- who started as unknown children -- have grown up. iReport.com: Tell us what you thought of the movie
The three have amassed huge fortunes and international recognition off the back of the films. Daniel Radcliffe wowed Broadway by going nude in "Equus," Emma Watson has become the face of Burberry and Rupert Grint recently hit the headlines with a dose of swine flu.
A dark storyline runs through the core of "The Half-Blood Prince": The ascendancy of the malevolent Lord Voldemort threatens the wizarding world, while tragic events provide some genuinely scary moments and spell the end of childhood for Harry and the others.
"I think it's aimed at a slightly older audience," says Emma Watson, 19, who plays bookish heroine Hermione Granger in the franchise. "I think the films have grown up with the audience." In pictures: Fans at the premiere on their favorite Harry Potter characters »
The change of pace also affords a bigger role for Draco Malfoy, Potter's long-time enemy, when he is charged by Voldemort with a very special evil mission.
"It's fantastic for me personally to get a chance to sink my teeth slightly more into this young lad we've spent five years establishing as a vile evil so-and-so," said Tom Felton, who plays Malfoy. "This film was a chance to show some other side of him -- some vulnerability and guilt for the first time."
The relationship between Harry and Hogwarts headmaster, Professor Albus Dumbledore, reprised by award-winning Brit Michael Gambon, is also explored in more depth in this film. Potter has changed from a schooboy into a young man and their relationship becomes more of a close friendship.
It is Harry that Dumbledore takes with him on the quest for a "horcrux" that forms the genuinely chilling and visually stunning climax of the film.
Fans have had to wait an extra eight months for the latest installment after Warner Bros (which, like CNN, is owned by Time Warner) delayed the release of the movie after the success of "The Dark Knight" to spread out its blockbusters. It is estimated the film cost $250 million to make.
The last film, "Harry Potter and the Order of the Phoenix," came out in 2007 and took $938 million at the box office worldwide. The five films have so far made $4.5 billion in worldwide box office, making it the most successful movie franchise in history.
The Harry Potter franchise is based on the best-selling series of books by British writer J.K Rowling. The first film, "Harry Potter and the Sorcerer's Stone," directed by Chris Columbus, was released in 2001.