  Using the Green Bank Telescope (GBT), we have detected the (J,K) = (1,1) to
(10,10) ammonia inversion lines, up to 1030 K above the ground state, in a
face-on spiral galaxy viewed against the radio continuum of the lensed
background source PKS 1830-211. The ammonia absorption lines, seen at redshift
0.886, appear to be optically thin with absolute peak flux densities up to 2.5
percent of the total continuum of the background source. Measured intensities
are consistent with a kinetic temperature of 80 K for 80-90 percent of the
ammonia column. The remaining gas is warmer, reaching at least 600 K. Column
density and fractional abundance are of order (5-10) x 10^14 cm^-2 and
(1.5-3.0) x 10^-8. Similarities with a hot ammonia absorption component
observed toward the Sgr B2 region close to the Galactic center may suggest that
the Sgr B2 component also originates from warm diffuse low-density molecular
gas. The warm ammonia column observed toward PKS 1830-211 is unique in the
sense that it originates in a spiral arm.
