Stretch wrote:

He may have a defective thermometer :-)

True. Does it always read 84 F?

Watson did not say what size window unit he had, what size & how many
windows were there, if the room was insulated or how well...

I'm thinking most window units are at least 5K Btu/h, and windows and
insulation aren't a big factor 30-40 mins after the AC is initially
turned on, starting with indoor and outdoor temps in equilibrium.

...or how many drums of water or other stuff was in the room.

Lots of mass with a small time constant (eg lots of drywall) could
initially keep room air warmer, but a 55 gallon drum with a 12 hour
time constant wouldn't do that.

We need more information.

Agreed. Maybe W. Watson has a huge unshaded west window
and only turns on the AC when sun begins to shine in.

Nick