2003 civic lx sedan,
AC blowing warm air all summer so far...
Green AC light on dash button lights up.
Belt is intact...
Any ideas?

 

When you push the button with the engine running and the interior fan on, which (if any) of the following occur?

-Condenser fan starts
-Engine idle speed increases slightly
-Compressor engages

 

one word
feron

 

Answers to mk's questions are definitely the first step in troubleshooting the problem.

You may also want to check whether the radiator fan runs when the A/C button is pushed.

Also check whether fuse 1 or 4 under the dash or fuse 14 under the hood is blown.

Finally, try to retrieve a trouble code from the heater/AC system:

 

The one word is probably "freon".

Low freon is generally a symptom rather than a cause for A/C problems. The cause would be a leak in some component of the system.