Cooperative breeding has been hypothesized to buffer against harsh environmental conditions. However, such buffering has rarely been quantified. Cooperatively breeding chestnut-crowned babblers, Pomatostomus ruficeps, inhabit the semi-arid zone in southeastern Australia. The habitat is characterized by low and highly variable annual rainfall. I tested whether negative impacts of harsh weather on offspring care are lessened in larger groups. Mean provisioning rate was sensitive to high wind speed and high temperature. In addition, extended periods of little rainfall deteriorated provisioning quality by reducing its mean and temporal stability. I found no evidence for buffering in larger groups for high wind and protracted dry period. Furthermore, the negative effect of temperature was amplified in larger groups, which suggests that large groups are becoming less productive in the face of warming climate. These results suggest that buffering of the challenging weather is not the primary mechanism of adaptation to the hash environment in this species.