I have a small fan in the ceiling pointed down at an angle, that runs 24/7. It keeps air circulating & is beneficial to plants.
A little air movement helps the O2 that is on the leaves release & keeps CO2 moving around to replace the O2 & helps to keep
even air temp, helps cool them on hot days & helps dry the inside some.
50 degrees is optimum at night & 85 days, (some researcher says anyway & some toms have better cold & heat tolerance)
I have an exhaust fan come on at 90 to heat soak everything a little warmer now, so it
has more heat to release at night. I have 3 - 5 gallon buckets of water (with lids) that warm in day & release heat at night to.
Next month I set it to come on at 85, longer days then.
Of course talking to them helps, I exhale some co2 that the plants like
Below 40°f, the leaves will show a purple color on the under side, turn under a little, sign of too cold. /won't get very many ripe toms.
Like BeGreen says above 40, 50 is best, below 95 & adequate water, specially during hot days, they use over a gallon/day when about 4' tall.