OBJECTIVES/GOALS: The increasing frequency and severity of heat waves due to climate change present unique risks to children. We aim to assess how various heat wave definitions impact pediatric acute care utilization across California. We also hope to examine heat waves’localized effects at the zip code level and how contextual factors modulate these effects. METHODS/STUDY POPULATION: A time-stratified case crossover will evaluate the association between different heat wave definitions and pediatric acute care utilization throughout California. A within-community matched design analysis coupled with a bayesian model will examine heat waves’ effects at the zip code level. A random effect meta-regression will determine which contextual factors modulate heat waves’ impact on different zip codes. Temperature data will be pulled from Cal-Adapt and interpolated to each zip code population centroid. Data for all unscheduled pediatric hospitalizations and ED visits for selected ICD codes in California from 2000–2019 will be obtained from the California Department of Health Care Access and Information. Contextual factors will be sourced from the US Census and the Healthy Places Index. RESULTS/ANTICIPATED RESULTS: We anticipate that heat waves will be associated with increased pediatric acute care utilization throughout California for select ICD codes. At the zip code level, we anticipate that there will be considerable spatial variation in the association between heat waves and care utilization based on region and zip code characteristics. Furthermore, we expect to see significant variation in the association between heat waves and hospitalizations based on the selected heat wave definition. We predict that zip codes with the highest increases in care utilization will have higher percentages of non-white residents, lower socioeconomic status, and fewer heat protective factors like park density and tree coverage. DISCUSSION/SIGNIFICANCE: As global temperatures continue to rise, children will be increasingly susceptible to health consequences associated with heat exposure. Understanding which pediatric populations are most vulnerable during heat waves is critical for designing policies and interventions that protect the most vulnerable communities.