So if you have a 56 days-to-finish strain, relatively short, I think it would often get freeze-killed early if it started flowering as late as the third week of August if my understanding is correct. I'm a little unsure how the steady shortening of the days affects the days-to-finish though and I could be wrong. >>>>

Generally speaking August 21st is about the trigger period and yes depending on your longitued and latitude that could vary some. I could be wrong but the closer you get to fall the quicker the days become shorter? My brother lives at about 4800 feet and said the last week of august and the first week of Sept. are the only two weeks of the year he knows he won't get any frost. He has to run a heater in his greenhouse every night into the first week of June.