Help! -- Note enough space to store temporary files

[Dennis Wicks]

I am trying to install Qt on Debian 3.16.7-ckt20-1+deb8u2 
and I get a message that there is not enough disk space to 
store temporary files. It needs 580+ meg and only has 300+ meg.

After searching here and there I tried entering the command
        sudo mount -o remount,size=1G tmpfs /tmp

which is supposed to increase the size temporarily and 
"on-the-fly" but I still get the same error message.

Any ideas??

TIA for your help!

Dennis