Dairy calves are susceptible to heat stress when environmental temperatures exceed 20°C. Heat stress conditions cause decreases in feed intake and compromises calf health. The objective of this study was to compare the behavior and well-being of Holstein heifer calves housed in 2 different housing systems during hot weather over the course of 2 summers (Trial 1 and Trial 2). At 24 – 48 h of age, calves were assigned to 1 of 2 treatments: (1) housed in stalls in a 3-sided barn (S; n = 14) or (2) housed in hutches placed outside (H; n = 8). Each calf was observed until weaning at 42 d of age. Calf BW were measured every 7 d and ADG was calculated. Calf body temperatures were measured hourly using temperature recording devices (iButton) attached to the underside of each calf’s tail. Blood samples were collected at 7, 24, and 42 d of age via jugular venipuncture and analyzed for cortisol and thyroxine concentrations using enzyme-linked immunosorbent assays (ELISA). Temperature and relative humidity within the housing systems were recorded at 1 h intervals using data loggers (HOBO) and used to calculate the temperature-humidity index (THI). Calf lying and standing behavior was recorded at 5-min intervals using time-lapse video cameras and analyzed using the scan sampling method. Data were analyzed using Pearson correlations and mixed model ANOVAs with repeated measures. The overall THI was significantly lower in hutches than in stalls (P < 0.0001). Calves housed in hutches had higher body temperatures (P < 0.0001), spent more observed time lying (P = 0.001), and had higher plasma thyroxine concentrations (P = 0.02) than calves housed in stalls. Feed efficiency improved (P = 0.004) and plasma cortisol concentrations decreased as calves aged (P = 0.04), but neither was affected by housing. Future studies should further analyze the environmental conditions each housing system offers calves during hot weather. For example, air flow and black globe temperatures should be measured to provide a better explanation of why hutches remained cooler during hot weather but calves housed in hutches had higher body temperatures.