COVID-19 has been disturbing human society with an intensity never seen since the Influenza epidemic (Spanish flu). COVID-19 and Influenza are both respiratory viruses and, in this study, we explore the relations of COVID-19 and Influenza with atmospheric variables and socio-economic conditions for tropical and subtropical climates in Brazil . Atmospheric variables, mobility, socio-economic conditions and population information were analyzed using a generalized additive model for daily COVID-19 cases from March 1st to May 15th , 2020, and for daily Influenza hospitalizations (2017-2019) in Brazilian states representing tropical and subtropical climates . Our results indicate that temperature combined with humidity are risk factors for COVID-19 and Influenza in both climate regimes, and the minimum temperature was also a risk factor for subtropical climate . Social distancing is a risk factor for COVID-19 in all regions . For Influenza and COVID-19, the highest relative risks (RR) generally occurred in 3 days (lag=3). Altogether among the studied regions, the most important risk factor is the Human Developed Index (HDI), with a mean RR of 1.2492 (95% CI : 1.0926-1.6706) for COVID-19, followed by the elderly fraction for both diseases . The risk factor associated with socio-economic inequalities for Influenza is probably smoothed by Influenza vaccination, which is offered free of charge to the entire Brazilian population . Finally, the findings of this study call attention to the influence of socio-economic inequalities on human health.