If winter weather was an issue it would extend beyond March....

If winter weather was an issue it would extend beyond March. Winter causes issues with breaking ground, but you can put a "burn on" in small scale situations to break it. I don't know what active mines do to deal with the frost other than perhaps straight force and rip it maybe. The real problem comes during the spring break up when the frost thaws and large transport begins to tear the roads apart causing some municipalities to ban transport for some time. Sayona has the rail contract though so it may not affect them as much. I haven't done any research on the route.