When should the plants be put outside? at the optimal temps, they only will get about 6 hours of proper sunlight.

at this age , it doesnt really matter about the light, but it does matter a lot about the temperature and the humidity. low humidity is bad low temperature is bad. do you best to cover them with a humidity dome which hopefully will protect them a bit, also try to put them where there is not so much wind maybe. you can also wrap the pot with a protective cover (like an old tshirt) to keep the soil warm. same thing with the surface of the soil, anything you can do to keep it warm like using straw, hay , volcanic rocks, clay balls, etc . If you do this maybe they have a chance. Hope this helps ! 🚀

You will need to harden them off and get them used to your weather. Like below said low temps will slow them down. Since your growing auto's I would not recommend putting them outside unless the temp hit's 20C. Photo period plants you would have all summer so a slowdown from the cold would not be that bad. Or like mouse said make a greenhouse and you could do 15. Even using a large water jug and cutting the top off works. But if they have only seen grow lights you need to adjust them to the outside by putting them outside for short periods of time. Here is a general guide, You will have to keep an eye on them and adjust the amount of full sun accordingly( morning or evening sun is best as it is not as strong as mid day sun ). shade only for the first 3 days is recommended. Day 1 - outside in shade for 1h Day 2 - outside in shade for 2h Day 3 - outside in shade for 3h Day 4 - outside with 1h sun and 3h shade. Day 5 - outside with 2h sun and 3h shade.

Bit to cold for them. They will start to tun purple and self canalbilzse. If you have any artifical lighting indoors it would be good. OR Construct a make shit greenhouse out of clear plastic bags and the sun should heat that room up to 20c if its out. if its not it still may get to cold. Good Luck!

During the vegetative growth period, cannabis plants feel best between 21 and 29°C. And during the flowering period, between 18 and 26°C. The temperature fluctuation should be around 6°C between the night cycle and the light cycle. So 10°C is a bit cold and growth will be impacted.