We sometimes fly in the teens, a little lighter fluid and a good glow driver and starter, as well as a place that's good for warmups and you are set. 40-50?, a regular heat wave for us, shirtsleves and all, we go water skiing when it's that hot[8D]
A good thing to remember is to not throttle way down for long periods or the fire might go out! 4 strokes take longer to heat up also.