Over temp in primary/secondary

Hello all.

Im just curious as too how long in a temperature above 24C does it take for a beer to get the banana taste people are always talking about?

Normally here in Ireland its pissing rain and cold but were having an odd last few weeks. My outdoor storage area drops below 18C at night but my indoor area is normally between 18-22C. The other day for a few hours it went up to 24-26C and again today for about 2, maybe 3 hours. Will this be a problem?
Does anyone have a solution (an inexpensive one) too keep beer at a constant?

Thanks in advance!

24 is a bit warm for the yeast, but not as bad as some folks have experienced...

Do a search for Swamp Cooler for lots of ideas -
generally, a tub of water to set the fermenter in - then either a tee shirt to soak up water and a fan (evaporative cooling) or frozen bottles swapped out every several hours to keep warm temps at bay...

High temperatures will affect the beer most during the first 5-7 days, after that if they creep up it shouldn't have a lot of impact. During warmer weather I use a water bath for the fermenter, with frozen water bottles as needed. Once I'm 5-7 days in and things have slowed down I don't worry about changing the frozen bottles.