Help meh

Mark is your average 15 year old guy. He does good in school despite getting lazy here and there. He's destined for great things in his life, everybody says so, but everybody is wrong. All of a sudden the Earth's temperatures begin to change. The sun gives off massive flares heating the Earth to extreme temperatures. The sun also has dark spots now, giving parts of the Earth freezing temperatures. To top it all off, people start getting sick from an unknown origin and it seems impossible to stop. Mark isn't there when his family goes into a dark spot. He is with his two new friends, Cola and Jay. They met at a diner. They are in a subway train going to a home. When it stops they decide to sneak in a new tunnel that's under construction. Mark doesn't think it's the greatest idea but he goes anyway. That protects them from the cold for now. Will they survive? The odds are stacked against them, but the new girls are anything but helpless, as Mark thought he'd be dragging them along.