Depends on roof design. I have maybe 4 1/2 foot of height in my attic, temps at top 125 degrees or more and middle 90’s at lowest level.

Storage in garage attic.
 

You should consider a SpaceLift - best and safest way to put things in your garage attic. No more risking a fall carrying a tote up and down the attic stairs. Call (352)406-6966 for more information

Not a great place for storage
 

Not the best place to store anything of great concern. We stored some wood and a few decoration totes up there. There were some old metal braces put up there also. A set of golf clubs were destroyed by the attic heat because the grips melted to nothing. It is definitely the HOTTEST spot in your house. Plastics and rubbers don’t have a chance.

Don't store anything glued, it becomes a melted blob. Our attic hits 135 degrees in the summer.

We have quite a bit of storage in our attic. I even added more plywood flooring to the outer perimeters. To moderate the temperature, I had The Solar Guys install to solar power vents to move the air around. I also had Magic Stairs install an electronic lift to minimize the risk of using the ladder to carry larger items.

Nope

NO CANDLES in the attic

I've been here for a little over 12 years and am no youngster, I had the same set up when I moved in, and I extended the flooring out on both sides almost tripling the storage space. I did that by myself but I'm sure you can get someone to do that for you. Also, I installed florescent lighting, the one 60W bulb was a joke.

RubberMaid Wire Shelves
 

Various length and width of like-new RubberMaid Wire shelves that I would like to sell, half of what they would cost at Lowes or Home Depot. We replaced the wire shelving in a large walk-in closet with built-in shelving and drawers.

Anything you can carry up there should be fine for the roof structure. Don't put anything up there that is heat sensitive.

yes the nails and my bald head. That is why I picked up a Baseball plastic helmet.

Also, a place that wine corks can be recyled with a cut or two .

Spray foam insulation on the attic ceiling will make the attic as cool as the rest of the house. Get Magic stairs to safely go up and down. Both are
costly but worth it.

Hot
 

will melt anything meltable or dry out maybe fad it

When the wheels of our luggage disintegrated while walking down a super long corridor in T.F. Green Airport we decided it wasn’t a good idea to store luggage in the attic here! We had to buy new luggage to get home …and stored them in the house from then on….

As long as you don't park a third car up there, you're fine.