Despite consensus that projected climate changes may result in significant threats to human health, and considerable research on extreme temperature-health risks in adults, there is a paucity of information on pediatric health impacts from extreme temperature conditions. Weather data from Chicago’s O’Hare Airport measured at multiple times/hour were collected for January 1, 2009 to August 1, 2018. Generalized Additive Models (GAMs) were used to investigate the relationships between air temperature and electronic health record data for emergency department (ED) and pediatric intensive care unit (PICU) admissions at a quaternary-pediatric medical center, for the same period. Daily environmental temperatures increased over time as expected, while unexpectedly ED and PICU admissions decreased. Even when temporal trends in each admission-high risk condition variable were accounted for, a consistent negative relationship was found with 0.406 fewer total (0.038 fewer high risk) ED encounters and 0.012 fewer total (0.010 fewer high risk) PICU admissions per 1°F increase in daily environmental temperature using both regression and GAMs. Our results for the ED and PICU admissions are not consistent with previously reported studies. Many of the previous studies were from under-resourced countries in which factors not considered in this study (e.g., food insecurity, other diseases, air quality, natural disasters) existed. These differences point to the need for further clarification of the relationship between environmental temperature and child health.