Too cold, the yeast will stop fermenting and go to sleep, leaving you with some hoppy half-fermented cough syrup. Too hot, and the yeast will kick off all sorts of nasty flavors - an overripe-banana taste, a harsh alcoholic burn, or an unpleasant medicinal twang. In this climate I'm more likely to get the latter. High-end brewers either have a dedicated fridge or a fermentation chamber with temperature control that they can adjust up and down with an iPhone app. My cutting edge technology is more along the lines of setting up a "swamp cooler" - wrapping a T-shirt raround the fermenter, putting it in a tub of water, and setting a fan on it. Another high-tech alternative is putting the carboy inside a cooler and leaving frozen water bottle inside. If I pay proper attention to it, I can ferment in the low 60s with no problem. If I forget, it can heat up well past the 70 degree danger zone, meaning I could get back from work to the smell of banana Jolly Ranchers emanating from what might have been a tasty ale.
You can see this in action for a small two-gallon batch:
Omega Hothead is my new knight in shining armor.
This is a yeast strain that can ferment as hot as 100 degrees with no impact on flavor. I've finally found the yeast strain that belongs in the tropics! One that originally comes from ... Norway? That's right. Kveik, as they call it in Norway, is now being sold as commercial yeast for homebrewers. The frigid north seems like a strange provenance for this microbe. But ultimately it doesn't matter where a particular yeast strain is from because it can be cultivated in laboratories anywhere.
I used this to make a pale ale with Cascade hops, the style's signature hops since Sierra Nevada pioneered the American Pale Ale in the early 1980s. By this point the moniker "Norwegian swelter" should be pretty self explanatory. It pours a thick head with solid retention. The aroma is predictably citrus-like, as one would expect from this hop, though this particular bottle somehow seemed to be a little flat on aroma.
It has a mild bitterness that stays in the mouth and on the front of the palate rather than chasing down the throat. The flavor is overall fruity with some citrus, but I don't think I could be much more specific than that. I don't get the lemon-lime sensation that people talk about with Hothead. It probably could have fermented out a little more, which means that flavor is bit mellower than what I usually shoot for in a pale ale. Perhaps it's because my taste buds are so blown out by raucous hopping that I can't taste anything that's utterly flooded with hops. I've somehow managed to make another surprisingly "user friendly" pale ale.