In order to determine what would happen, we have to think about the temperatures' effects on yeast. If it is too cold or too hot, the yeast will not grow! Why does this happen?
Each enzyme, in order to work, needs to fold a certain way to allow the active site to form and change its conformation properly to catalyze a chemical reaction. If an environment is too hot, there may be too much energy to guarantee the optimal conformation during folding. If an environment is too cold, there may not be enough energy to produce the desired reaction, the reaction may go too slowly, or the enzyme may not fold correctly or even be synthesized!
Fermentation, like most other cellular processes, is carried out by an enzyme, and this enzyme, like any other, has a range of functional values. A specific value for temperature is difficult to find online, but many sites talk about optimal brewing temperatures for fermentation for beer or wine.
A scholarly publication I found says that the optimal temperature for a certain species of yeast to produce ethanol is 40 degrees Celcius (104 degrees Fahrenheit). Therefore, if you have the same sort of yeast (Kluyveromyces marxianus), you could expect that ethanol output would increase with temperature until you hit that temperature. At that point, ethanol production would decrease.