Last fall we rebuilt our front porch steps. Now we are finally getting warmer weather and I want to paint these as soon as I can. The primer I have does not give a minimum temp rating. I figured if it is in the 50s I would probably be OK.
Primer dries fast, so 50's will probally be OK, especially if it gets some direct sunshine. Give it some time however, before painting. I have used exterior paints as low as the 40's as long as night time temps are not going much lower, or paint/primer at least 4 hours before temps drop a bit. Some paints do give a temperature range. There are low temperature paints that will cure down to upper 30's with no problem. The main problem with priming or painting in cooler temps, is that you must let it cure enough before applying the next coat. That may take a couple of moderate temp days as it will not cure in the colder nights, dew or excessive moisture, as that will delay the curing process or discolor the finish.