Teen girls are notoriously fickle, particularly when it comes to movies.

For every “Twilight” or “The Hunger Games,” there’s a film such as “Mortal Instruments,” a hot literary property that lost its sizzle in the transition from page to screen.

If I Stay” is the latest attempt to capture this coveted demographic, and while the low-budget weepy won’t hit the lofty numbers of “The Fault in Our Stars,” it’s shaping up to sell a lot of tickets along with Kleenex.

“It looks like it could be a breakout based on the reactions on Facebook and Twitter,” said Phil Contrino, vice president and chief analyst of BoxOffice.com. “It seems to be connecting with the same crowds that lined up for ‘Fault in Our Stars.’ This month has had a lot of male-skewing action pictures, so the timing is good.”

Look for “If I Stay,” which is being backed by Warner Bros./New Line and Metro-Goldwyn-Mayer and is based on a best-seller by Gayle Forman, to make $18 million to $20 million when it debuts in 2,902 locations this weekend. If tracking holds, that would represent a nice return for the $11 million production. The film centers on a young girl (Chloë Grace Moretz) who finds herself in a coma after a car accident kills her parents and brother — in that state, she’s forced to choose between living or dying. It’s a premise tailor made to send viewers into paroxysms of grief.

Also opening, and appealing to a radically different sector of the movie-going public, is “Sin City: A Dame to Kill For.” The sequel to the 2005 graphic novel adaptation is being distributed by the Weinstein Co. and will bow in 2,894 locations. It is on pace to make $15 million when it debuts.

The picture employs the same ripped from the funny pages aesthetic as its predecessor and brings back Bruce Willis and Mickey Rourke along with directors Robert Rodriguez and Frank Miller (“Sin City’s” creator), but nearly a decade has passed since the first film came out and made $158.7 million globally.

“The question is how long between films is too long?,” said Paul Dergarabedian, senior media analyst at Rentrak.

That leaves one other new wide-release jockeying for attention. Sony Pictures is making a play for the family and faith-based crowds with the sports drama “When the Game Stands Tall.” The film was produced for $15 million and is based on the true story of Bob Ladouceur (Jim Caviezel), the high school football coach behind a record-breaking 151-game winning streak.

“When the Game Stands Tall” should make between $8 million and $10 million when it debuts in 2,670 locations in North America.

The biggest challenge to “If I Stay’s” supremacy will be the continued strength of “Guardians and the Galaxy” and “Teenage Mutant Ninja Turtles,” which should bring in between $14 million and $15 million in their fourth and third weeks in theaters.

After a dreadful summer that saw the box office down nearly 20% at the end of July, August has fielded an impressive number of hits. Thanks to their success, the month is currently running 17% ahead of last year.

“We’re going out on a high note,” said Dergarabedian.

For Hollywood, it’s nice to string together a few weeks in August that aren’t quite as chilly.