An Oscar-nominated actress completes her “Naomi vs. Nature” trilogy with “Infinite Storm,” a psychological battle against the primal elements starring Naomi Watts.

As in “The Impossible,” her character — a 50something New Hampshire search-and-rescue hiker named Pam Bales — faces an extreme event, this time a blizzard. Pam is tested. And as in Watts’ “The Sea of Trees,” when she stumbles into an out-of-his-depth hiker, that test grows more harrowing as she tries to get him off that frigid mountain in a howling gale.

Here, it’s not the life that she wants to get back to that drives Pam through hallucinatory flashbacks. It’s memories of the pictures of two little girls that this loner keeps in her remote riverside cabin.

There’s a dreamy, existential sadness that hangs over this Polish co-production, filmed in Slovenia and directed by Malgorzata Szumowsk (“Never Gonna Snow Again”). It begins with Pam, the fatalism she puts into her packing-for-the-hike routine, the radio weather warnings echoed by her innkeeper pal (Denis O’Hare). When she tells him “You know what day it is,” he knows better than to insist she not take this hike in that coming weather.

Something happened to those two little girls.

As she hears cries in the blizzard, we wonder if her ears are playing tricks on her. But when she sees tracks, she knows someone got caught in the blizzard.

“You have GOT to be kidding,” she gripes. “SNEAKERS?”

When she stumbles into the stranger (Billy Howle), he is all but frozen — stubborn, silent and maybe even stoned.

“Jesus, you’re dressed for the BEACH.”

He seems to have little interest in surviving, but she’s not leaving this dope behind. So begins their long trek down, with all the usual obstacles added to the life-threatening stumbles Pam had to overcome just to reach the summit.

“Inspired by a true story” or not, movies like this have their own formula and tropes, some of which I’ve listed above. I’m a big fan of the genre, and if this isn’t up there with “Wild,” “Into the Wild” and the like, it still works and Watts makes us invest in her character’s quest to survive. But what’s most interesting about “Infinite Storm” is the gutting grief that’s layered on top of that. We wonder who is more messed up. Will he kill himself? Will he get her killed?

Following up her woodlands sprint to a school shooting drama “The Desperate Hour” with this film gives one the impression that Watts is making a point about women over 50, actresses included. She’s perfectly credible in these roles, accomplishing physical feats that any fit woman could manage and performing in these movies with a sort of dogged “I’m still here, dammit” determination.

Watts’ stoic, sturdy performance and the film’s affecting and formula-busting third act make this “Infinite Storm” well worth weathering.

Rating: R, profanity, injuries

Cast: Naomi Watts, Denis O’Hare and Billy Howle

Credits: Directed by Malgorzata Szumowska, scripted by Joshua Rollins. A Bleecker Street release.

Running time: