Noob Help - Ontario Outdoor Grow

I just dropped 2 seeds 12 days ago, and these babies are going nuts. (Free seeds, seems to be 2 different strains (I can see purple starting in the top leaves of one)
I'm shocked because the weather here has been absolutely SHIT- cold, rainy, cloudy etc, but maybe that's why both the stalks seem pretty thick already for their size?

I planned to let these go until September or October if possible with nothing but sun and water - so am I going to need to cover them completely outside for 12 hours, or will weather getting colder, sun fading etc naturally force it to flower?

They should start flowering sometime in August naturally from the research I've done. They will out grow that pot though. You will want 2 separate pots probably 10 gallon + . Also look into topping and getting a set neutrients. They won't need the neuts for awhile but they are going to need the boost going into flower for sure.