"Ambient air temperature sets the temperature of the alcohol (before it cools by evaporation). So going from 30 C to 5 C ambient means you have to warm the alcohol up more to get it to boil, and burn. That takes more priming time and fuel."
There are differing types of alcohol used in DIY / MYOG stoves. Everclear in both 190 and 151 varieties, Heet in the yellow bottle, DNA with varying mixtures of Methanol, Ethanol and "denaturing agents" and Isopropyl in the 91% and 70% varieties. All have different BTU outputs and boiling points.
Alcohol stoves do have the "problem" of difficulty in lighting when the temperature dips really low.