The 19-year-old woman and a man in her hiking group, taken by helicopter to an area hospital, were not adequately equipped for their trip up Cadillac Mountain, the Bangor (Maine) Daily News reported Tuesday.
The woman was "kind of conscious, not alert and had some heart issues," said Supervisory Park Ranger Richard Rechholtz.
He and a paramedic responded to the 911 call from other hikers about 7:30 a.m. Tuesday.
Rechholtz said the woman, the man and a third person "didn't have the proper gear, they just weren't ready for the conditions at all" when they began ascending the mountain about 4:15 a.m.
He described the snow as "very, very deep in the park right now."
A hiker who helped the group before emergency help arrived said the woman was dressed in long underwear, skinny jeans, wool socks and uninsulated furry dress boots.
The identities of the assisted hikers were not released.