I've read the posts below , and I'm still confused. I've got a low-tech operation here.
Brew it, set it in a dark corner for two weeks , take a hydrometer reading, and if that plus a taste indicates I've got alcohol in it, prime and bottle it.
My only temp control is the thermostat for the furnace/ac for the house. If fermentation is complete --which it should be after two weeks in normal circumstances -- then I would think the temp I should use in calculating priming sugar would the warmest temperature my thermostat was set at.
Do you agree?
By the way, I recently primed a sweet stout with Domino sugar cubes (one per 12 oz bottle) with my thermostat set at 68 F as described above with really good carbonation after eight days. Much better results than I've had by adding priming sugar to the bottling bucket.
That is going to be my method of choice for priming from now on as long as it continues to work as well as it did for this batch.