Although the late Paleozoic deglaciation is arguably one of the best deep-time analogs for current and predicted climate change, quantitative paleotemperature data from this interval are generally lacking. We reconstruct extreme paleoweather conditions and paleoclimate changes from Permian Nippewalla Group (probably uppermost Leonardian/Kungurian; North America) ephemeral lake halite by using fluid inclusion homogenization temperatures to directly measure the water temperature when the halite precipitated; in these depositional settings, this is an excellent air temperature proxy. Extremely high temperatures, to 73 °C, and large diurnal temperature ranges are evidenced in the lower Nippewalla Group, suggesting conditions more extreme than anywhere on Earth today. In contrast, the upper Nippewalla Group was cooler; maximum temperature was 43 °C and diurnal temperature ranges were smaller, though even these conditions are similar to modern extremely hot environments. Comparison to prior studies suggests that these results may be indicative of regional patterns. This study represents the first pre-Quaternary high-resolution quantitative data set of extreme paleoweather and possible paleoclimate trends from fluid inclusions in halite, and provides new insight into climate change during the late Paleozoic deglaciation.