Its not the fuel's temp but your needle valve setting. Our engine carbs are not self adjusting and require tweaking for changes in air density, temperature, humidty etc...etc.. As little as a 5 degree temperature change will require a carb adjustment. Unfortunately, many in the RC family are of the "set it and forget it" mindset.

I flew in lower Alabama for many years and my fuel sat on asphalt in the hot sun for many hours and never had a problem flying.