Creating a cooler environment with a cardboard box

Had a funky idea and i wanted to bounce the idea off everyone. So here goes...
I live in So Cal and i only have a dorm fridge. My room temp is fairly consistent at 72-74F. I want to ferment at lower temps so i was thinking to ferment outside in my patio where temps reach about 50F at night. My initial concern was contamination with dust and everything outside but i got to thinking and i came up with my funky idea. I have a very large cardboard box that can fit two 5 gallon buckets. I figured i could put the fermenting buckets in the box and then seal all the cracks with tape and after two weeks. open it up.
Temps outside range from daytime 75F to night time 50F. Is that too volatile of a fluctuation in temp? Is the cardboard box not going to keep out the bad stuff and avoid contamination? Just an idea.....

it would probably hold the temp better if you took some cheap insulation and lined the box with it. Or for that matter fill it with styrofoam peanuts.

you want a more consistent temp than that...i'd keep it inside and make a chiller

I made myself a Son-of-fermentation Chiller. Works wonders