Our objective was to evaluate the effect of commercial aluminized reflective covers (ARC) for polyethylene hutches on behavior, health, and performance of pre-weaned Holstein calves during summer in Northern Colorado. Hutch interior THI and inner wall temperature were also assessed. Heifers (n = 195) enrolled at 1d of life and housed in individual hutches with (n = 97) or without (n = 98) ARC were monitored until 60d of life. Behavior, health, rectal temperature, respiratory rate, and hutch wall temperature were measured twice per week between 12:00 and 2:00 p.m. Calves were weighed at birth and at 60d. Ambient and hutch temperature and humidity were continuously recorded using automatic loggers (4 covered and 4 control empty hutches). Fecal, nasal, eye, ear, and hydration abnormalities were assessed using a health score system. Days were categorized according to max ambient THI as low (<72 units) and high. Behavior and health scores were analyzed using logistic regression analysis. Temperature, THI, rectal temperature and respiratory rate were evaluated as repeated measures. Use of ARC and ambient THI were associated with calf behavior (P = 0.02 and P < 0.0001): The odds of remaining inside the hutch were 1.3 times greater for calves in control hutches vs. those in covered hutches. When THI >72 the odds of remaining inside of the hutch were 2 times greater. Health scores were not associated with use of ARC. Rectal temperature and respiratory rate did not differ among calves in covered and control hutches (39.2 ± 0.02 vs. 39.2 ± 0.02°C and 61 ± 1.2 vs. 58 ± 1.2 breaths/min). ADG did not differ between covered and control hutches (0.54 ± 0.02 vs. 0.53 ± 0.02 kg/day, respectively). The average ambient THI was 66.8 (min 43.2, max 81.1 units). THI was greater in covered (64.8 ± 0.05) compared with control (64.1 ± 0.05) hutches (P < 0.001). Inner wall temperature was lower in covered vs. control hutches by 1°C (P < 0.001). Even though ARC effectively reduced wall temperature, this effect was not sufficient to have a positive impact on calf health and performance under these study settings. Higher THI in covered hutches may explain differences in behavior, where control calves preferred to stay inside the hutches on high THI periods.