Yo-yo Ferment Temp

So I'm trying to get back into brewing after a several year hiatus.

After snagging some goods I got all excited and jumped with both feet into an all grain batch, which I'd never done.

I didn't stop to think that I live in the foothills with no air conditioning. My house gets hot in the day time and pretty cold at night.

I'm making an attempt at an oatmeal stout using Wyeast's British Ale Yeast.

I pitched at about 8pm and put it in the coolest room in the house. I would say the house was at 70 and then dropped down to lower 60s until about 8am the next day when it started climbing and peaked at about 83 or 84. Then the next night it of course dropped down to low sixties.

After bubbling furiously away for the first 36-ish hours, it has now calmed down to near silence.

Assuming that it is going to continue to yo-yo temp for now, what can I expect to happen to my little project? Are there things I can do to mitigate any bad effects?

Put it in a water bath inside a ice chest if you have one large enough, that should help average it out. You can also try using the swamp cooler method to keep it down.

You are likely done w/ most of your fermentation at this point, next time try a tub w/ water, try and keep the water bath coolish, 65 degrees during the first several days of fermentation by adding a little ice or frozen water bottles, after that it is not as critical AFAIK.

What should I be looking for when I taste it? Is the high or yo-yo temp situation going to make it taste like banana and bubble gum (i've heard those terms thrown around).

The off flavors created by higher fermentation temps depend greatly on the yeast strain, and I don't have much experience with that particular yeast. The most common ones are fruity tasting esters or harsh tasting fusel alcohols.