I found a few spools of mono that have been in my uninsulated garage for probably 2 years. It inadvertently ended up out there instead of my indoor spot where I usually keep it. Mono is cheap so I can just chuck it, but how much does heat effect it over that amount of time? 

Should be no issue unless it got blisteringly hot in there...I store all mine in the garage and have for years - no problems after many, many years.

I'd use it as long as it hasn't been sitting in direct sun.

No direct sun, just the heat of the garage. Thanks guys. 

Sunlight and swings between extreme heat and extreme cold might affect it. I had a couple of combos leaning against the wall over a baseboard heater one winter. That line was useless come spring.

I think you can get a good overall idea the condition by just pulling some off the spool and feeling it. If it has an excessive memory to it than just throw it away. 

I have a lot of older mono. I store it in a room with no windows that stays high 60s to low 80s year round. I have some that is over 20 years old, and it's still good. UV will degrade line even if it's not direct sunlight. 2 years, should be fine. I would test it just to be safe. 

Haha I have 3000yd spools that have been in the garage in a dark cabinet for 20yrs. 
Think it’s good?

I would discard the first 50 yards and give it a go. In think you will know after one outing. 

If you discard it burn it or cut it into small segments so that birds don't get tangled in it.  

I didn’t know Oregon had heat.?

56 minutes ago, Tennessee Boy said:

I didn’t know Oregon had heat.?

It's a wet heat.

Know how I know neither one of you have ever spent a summer in Southern Oregon? ?

Wrap 2-3 turns around your hand and give the snap test. It the breaks easy it’s bad.

Tom

I would take off a few yards and check the color.  If what you took of is a different color than what is below, then it's bad.  Also, like to suggested check it for breaking strength.   Mono is cheap> a lost lure and/or a lost fish is costly and heartbreaking. 

2 hours ago, WRB said:

Wrap 2-3 turns around your hand and give the snap test. It the breaks easy it’s bad.

Tom

Beat me to it. Bad line breaks in your hands