First time uk oudoor grower

Hey guys just want some tips
I am going to bring my blackberry kush outside at 3 weeks old because rn the highest temp is 15 degrees Celsius
Will my plant stunt when I bring it outside or even die.
Ps here is a pic

Mate I’m in Aus; so I’m sure you would agree the sun is way more intense here than the UK....I have started them inside and put them out at a similar age to yours in the sun and no issues; as long I keep them moist until they grow a little....basically out the bitch out I personally don’t believe you will have any issues; I never have. Good Luck