Public schools in Worcester will be closed Friday due to dangerous arctic cold hitting Massachusetts. The school district cited “hazardous wind conditions” in an announcement Thursday evening. All public school athletic events scheduled for the afternoon and evening on Friday will still take place as scheduled. Dangerously cold wind chills between minus 10 and minus 20 degrees will move into the state Thursday night into Friday, according to the National Weather Service. The weather agency issued a cold weather advisory for nearly all of Massachusetts from 7 p.m. Thursday to 11 a.m. Friday.