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This study investigated the increase in the proliferation of mosquito populations in Rio de Janeiro's summers comparing seasons of ENSO climatic phenomena. The years of the study are related to the occurrence of strong and moderate weather phenomena in the country: 2015 and 2016, strong cycles of the El Niño that is associated with intense rains and high temperatures and a record of diseases transmitted by the Aedes aegypti mosquito. The research also studied the periods of 2017 and 2018, which had moderate cycles of the El Niña climate phenomenon, despite they had caused devastating global and regional effects on the environment and on the populations of several Brazilian areas it didn’t interfere the mosquito proliferation. Some weather phenomena, such as El Niño and La Niña, occurring repeatedly, can cause extreme events and together with human interference on the planet - deforestation, fires, misuse of land, decreased biodiversity, uncontrolled urbanization, among others, change the global climate. Normally, these ENSO weather phenomena change temperatures and amounts of rainfall in different regions of the country. There is an increase in temperature and rainfall and can have significant impacts on the country population, as can be seen in Rio de Janeiro city, especially in urban areas. Its effects can lead to exposure to extreme conditions, such as natural disasters, droughts, and floods, as well as an increase in the spread of mosquito-borne diseases. The combination of extreme global weather events, urban heat islands, population growth and poor sanitation conditions form the perfect combo for the proliferation of the most dangerous animal on the planet – the mosquito. In the case of Rio de Janeiro, in southeastern Brazil, Aedes aegypti, which transmits arboviruses – dengue, Zika, Urban Yellow Fever, and Chikungunya. El Niño has an impact on arbovirus cases because it causes an increase in the temperature of the environment and thus can accelerate the life cycle of Aedes aegypti, boosting the number of individuals and bites. The effects of El Niño phenomenon caused increased temperature and precipitation in the city of Rio de Janeiro – where floods and still water flooding were observed phenomena that evidence Aedes aegypti mosquito reproduction. La Niña moderate phenomenon influences the climate because it promotes abnormal change in atmosphere pressure in the Pacific Ocean, causing its cooling. These masses of air also make the atmosphere drier. That is, with less humidity it is difficult to form large clouds that cause rains, but the temperature rises. Data for the study were obtained by collecting mosquito larvae in homemade traps and weather gauges stored in GLOBE platform, official Brazilian data, and international website data. The results showed that cases of arboviruses, diseases transmitted by Aedes aegypti, increase considerably in years of ENSO climatic phenomena, as observed in 2015/2016, periods of very strong El Niño cycles, but in the moderate La Niña cycle, observed in 2017/2018, there was a decrease in rainfall, higher temperatures causing drier environmental conditions with low humidity. Despite the high temperatures, the reproduction of Aedes needs rain (water), therefore, La Niña cycle periods are not conducive to the increase of Aedes aegypti mosquito’ proliferation. Keywords: Aedes aegypti, ENSO climatic phenomena, El Niño, La Niña, precipitation, temperature, breeding sites, arboviruses, life cycle.