Dangerous wind chills were likely in an area stretching from northern Pennsylvania to Maine starting early on Friday and through Saturday evening, the National Weather Service said in its forecast. "The wind chills have the potentially to be once-in-a- generation cold," the weather service said, urging people to either stay indoors or take precautions against frostbite and hypothermia. The wind chill factor describes the combined effect of wind and cold temperatures on exposed skin. In New Hampshire's Mount Washington State Park, atop the Northeast's highest peak, record-breaking wind chills of -110 degrees and wind speeds topping 100 miles (160 km) per hour were expected. Boston Mayor Michelle Wu declared a cold emergency for New England's biggest city for Friday through Sunday, as the city is expecting below-zero wind chills starting Friday.

---