First timer

Hello all, I started auto skunk #1. The weather usually let's me plant them outside by now. NOT!I started them inside to put outside but the weather isn't cooperating.  Im worried they will start bolting. Im not set up for indoor grow. The temps should be in the 70s during the day and upper 50s at night but the temps are 60 during the day and 30s at night. Im using a small starter light. I just usually use it to get them started then put outside. Starts are 3 inches tall and starting there second set of leaves.

Anyone know what I can do to stop them from bolting.

Thanks for your help