Look at your sunrise and sundown times from the last week. Does the amount of daylight increase as the week progresses or does it decrease. Decrease would mean its flowering time If you watch it closely youll know when the time comes. Aftef you check the first week you only gotta check weekly, and just compare he prior week to the week your testing
In the Northern Hemisphere its time for plants to start flowering any time now. Sativas will take a little longer to get going, but August is the normal outdoor flowering time. Like Chief said, check your sunrise/sundown charts for your area. You want to look for when the daylight gets to be less than 14 hours per day. Here that's in a couple days, but a few of my plants have already started to flower.
Alright soo i should expect a harvest maybe october ish right? My plants are sativa dom. (well atleast some)