Objective: To examine the relationship between relative humidity and childhood hand,foot and mouth disease(HFMD)in Hefei,China,and to explore whether the effect is different between urban and rural areas.Study design: Retrospective ecological study.Methods: A Poisson generalized linear model combined with a distributed lag non-linear model was used to examine the relationship between relative humidity and childhood HFMD in a temperate Chinese city during 2010e2012.Results: The effect of relative humidity on childhood HFMD increased above a humidity of 84%,with a 0.34%(95%CI: 0.23%e0.45%)increase of childhood HFMD per 1%increment of relative humidity.Notably,urban children,male children,and children aged 0e4 years appeared to be more vulnerable to the effect of relative humidity on HFMD.Conclusions: This article study indicates that high relative humidity may trigger childhood HFMD in a temperate area,Hefei,particularly for those who are young and from urban areas.