Streetlights and security lamps are an overlooked reason why an outdoor sativa refuses to flower in late summer. These plants are sensitive to very low light levels during the dark period, and a nearby lamp post or a neighbour's motion sensor can be enough to keep them vegetating into October. The site selection notes on https://hazesativaseeds.com suggest standing in the planned spot at midnight and checking whether you can read a page, which is a rough but useful threshold. Moving the plant or screening the light source usually starts flowering within a couple of weeks.
