Rising temperatures and more frequent droughts are posing new challenges to livestock producers in the Southwest. Our objective was to evaluate long-term perennial grass production (PGP) in the Chihuahuan Desert in relation to ambient temperature and precipitation. PGP was correlated with precipitation (mm) and ambient temperature (oC) over a 49-year period (1969 – 2017). Increasing precipitation in December through September was associated with higher PGP (r = 0.74, n = 49) whereas rising maximum average temperatures in March through September were associated with a reduction in PGP (r = -0.54, n = 49). Two-sample t-tests comparing averages of each variable for the first and last 25 years of the study period (1969-1993 vs. 1994-2017) revealed that mean PGP decreased by 35% (220.7 ± 12.5 vs. 143.92 ± 15.89 kg DM*ha-1; P < 0.01), precipitation was more variable and decreased by 21% (264.88 ± 1.30 vs. 211.13 ± 16.67 mm; P = 0.01), whereas mean maximum temperature (24.48 ± 0.14 vs. 25.22 ± 0.13°C; P < 0.01) and mean temperature (14.45 ± 0.13 vs. 15.04 ± 0.13°C; P < 0.01) increased by  0.7oC and 0.6o C, respectively. Over this 49-year period, Chihuahuan Desert rangelands at our research site lost 35% of grazing capacity (approximately 84 AUMs/1000 ha [7 AUYs/1000 ha]). Our research shows that increased temperatures and more frequent droughts are severely impacting forage and range livestock production in the southwest.