BACKGROUND: Previous studies have demonstrated associations of frequency of vasoocclusive crisis with weather conditions in adults, although relationships have been inconsistent. OBJECTIVES: Our objective was to determine if there is an association between weather conditions and pediatric emergency department (ED) visits, hospital admissions, and day and severity of pain precipitation for vasoocclusive crisis (VOC). METHODS: A retrospective observational study was performed at a large tertiary care pediatric center. We reviewed health records of all VOC patients under the age of 18 years with a chief complaint of pain and performed correlations between daily and average weekly and monthly weather conditions and frequency of painful crises. RESULTS: A total of 430 visits for VOC to the ED were documented from January 2005 to December 2006. Significant correlations were noted between the daily and weekly number of painful crises and colder temperatures (rhoEuro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin)-0.11, pEuro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin)0.004 for daily data and rEuro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin)0.25, pEuro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin)0.01 weekly) and wind speed (rhoEuro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin)0.13, p<0.001 and rEuro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin)0.25, pEuro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin)0.01). The monthly number of painful crises was moderately correlated with temperatures (rEuro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin)-0.42, pEuro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin)0.04). The average monthly pain score was higher in more humid months (rEuro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin)0.44, pEuro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin)0.03). CONCLUSION: We found significant correlations of VOC with weather conditions where colder temperatures and higher wind speed were associated with a higher incidence of VOC in children. Health care providers as well as parents should be aware of these findings and ensure that preventive measures are instituted in patients at risk.