Autoflower Vegging Question!

My plant is currently at 3 and a half weeks and is still pretty small (couple of inches tall, 4 small leaves), I'm in the uk and outdoors is the only option. The weather here has gone from being great to really overcast, which has limited the amount of light it's recieving. I'm hoping the sun comes out soon so my girl can get as many rays as possible!

Basically my question is...
Will my plant start flowering even though it's still a sprout, or will it keep vegging and start flowering when it's bigger?

I'm aware autoflowers rely on time instead of the light/dark schedual but I'm not sure if it's even possible for a plant to start flowering when it's that small!

Thanks guys

its not necessarily the size that matters, but the sexual maturity, if its old enough it will flower, although some plants that are too small may tend to be hermaphroditic