Also in England it is well possible to grow weed plants outdoors, however a couple of disadvantages are associated with this. First of all you can only do it in summer, when you plant them in spring you will get a nice yield in August, September. The second disadvantage is that you can not grow more than 5 plants because then the chance is high you are caught or your neighbours will start to complain. The third disadvantage is that you will loose your harvest to the boys next door.
But growing outdoors also has its advantages. For example you do not need to buy expensive material like for example a lamp or a ventilator. You just make use of mother nature.