Climate change affects malaria by altering the conditions that mosquitoes and malaria parasites need to thrive. Warmer temperatures speed up parasite development inside mosquitoes, shifting rainfall patterns create new breeding grounds, and rising temperatures push transmission into highland and temperate regions where it was previously rare. The World Health Organization estimates that between 2030 and 2050, climate change will cause roughly 250,000 additional deaths per year from malaria, diarrheal disease, malnutrition, and heat stress combined.
Warmer Temperatures Speed Up Parasite Development
Malaria isn’t transmitted the moment a mosquito picks up the parasite from an infected person. The parasite has to mature inside the mosquito first, a process called the extrinsic incubation period. This development is entirely temperature-dependent. The most dangerous malaria parasite, Plasmodium falciparum, stops developing below 16°C and needs accumulated warmth totaling about 111 degree-days to complete its cycle. The other common species, P. vivax, has a slightly lower threshold of 14.5°C.
What this means in practice: at 20°C, the parasite takes roughly 28 days to mature inside the mosquito. At 25°C, that drops to about 12 days. At 28°C, it takes just 9 days. Since most mosquitoes only live two to four weeks, faster parasite development dramatically increases the odds that an infected mosquito will survive long enough to bite someone and pass the disease along. Even a 1 or 2 degree rise in average temperature in a region near the threshold can flip the math from “most mosquitoes die before the parasite matures” to “transmission is now viable.”
Rainfall Creates and Destroys Breeding Sites
Mosquitoes that carry malaria lay their eggs in standing water. Rainfall is the primary driver of how many breeding sites exist at any given time, but the relationship isn’t straightforward. Moderate rain creates shallow, temporary pools, puddles in tire tracks, flooded footprints, and erosion pits that are ideal nurseries for mosquito larvae. Research in western Kenya found that these temporary habitats were far more common during rainy seasons and dried out completely when rain stopped, cutting off local mosquito populations.
Heavy rainfall, however, can actually suppress mosquito breeding. Flooding washes larvae out of habitats along riverbanks, drainage canals, and erosion pits, making those sites temporarily unsuitable. Climate change is projected to make rainfall more erratic in many tropical regions, with longer dry spells punctuated by more intense storms. This pattern of boom-and-bust rainfall can create unpredictable surges in mosquito populations. In highland areas that were historically too cool or dry for malaria mosquitoes, new seasonal rains are opening up habitats suitable for egg-laying and larval development for the first time.
Humidity Determines Whether Mosquitoes Live Long Enough
Temperature and rainfall get most of the attention, but humidity plays a quietly decisive role. Mosquitoes need to survive at least 8 days after picking up the parasite for transmission to occur. When average monthly relative humidity drops below 60%, mosquitoes simply don’t live long enough to pass malaria along. Above 60%, their survival rates and activity levels both increase significantly. The sweet spot for sustained transmission sits in the range of 21 to 32°C with humidity at or above 60%.
Climate change is altering humidity patterns in complex ways. Some regions are becoming more humid as warmer air holds more moisture, potentially extending the window in which mosquitoes can survive and transmit disease. Cities, which tend to trap heat and moisture, may see particular increases in transmission suitability.
Malaria Is Moving to Higher Altitudes
One of the most measurable effects of climate change on malaria is the upward creep of transmission into highland regions. Communities living at higher elevations in East Africa, South America, and Southeast Asia have historically been protected by cool temperatures that prevented parasite development. That protection is eroding.
In Papua New Guinea, researchers found that the median altitude limit for malaria transmission shifted upward by about 46 meters between the 1960s and the 2010s. Projections for 2021 to 2040 show that limit climbing by an additional 263 meters, pushing the transmission ceiling from roughly 1,574 meters to about 1,837 meters above sea level. In tropical highlands across Africa, the Eastern Mediterranean, and the Americas, modeling studies project an average increase of 1.6 additional months per year of conditions suitable for malaria transmission.
This matters enormously because highland populations have little to no acquired immunity. People living in areas with year-round malaria develop partial immunity through repeated exposure, which reduces the severity of infections. When malaria arrives in a community for the first time, everyone is vulnerable, including adults, and outbreaks can be severe. Public health systems in these areas are also typically unprepared, lacking the bed nets, diagnostic tools, and treatment supplies that lowland endemic areas have built up over decades.
An Urban Mosquito Is Spreading Across Africa
A mosquito species called Anopheles stephensi is complicating the picture. Unlike most malaria-carrying mosquitoes, which breed in rural areas, this species thrives in cities. It lays eggs in water storage containers, construction sites, and other artificial water sources common in urban environments. Originally found in South Asia and the Arabian Peninsula, it has now established robust populations in the Horn of Africa, with confirmed presence in Djibouti, Ethiopia, and several other countries.
CDC research in Djibouti found that seasonal conditions and temperature were the strongest predictors of An. stephensi abundance. Temperatures at or below 30°C were associated with more than double the mosquito counts, and cooler seasons (winter and spring in that region) saw the highest populations. As climate change reshapes urban temperature and rainfall patterns across Africa, this mosquito could bring malaria transmission into densely populated cities that have historically been relatively free of the disease. Africa’s rapid urbanization makes this a particularly concerning trend.
Heat Undermines Malaria Control Tools
Insecticide-treated bed nets are the most widely used malaria prevention tool in endemic regions. They work in two ways: physically blocking mosquitoes and killing those that land on the treated fabric. But their effectiveness degrades over time, and environmental conditions accelerate that process.
Lengthy exposure to intense sunlight breaks down the insecticide coating, reducing its ability to kill mosquitoes on contact. Modeling studies show that the peak human disease burden occurs at temperatures around 28°C and that high seasonal temperature swings can trigger major outbreaks even in areas with relatively low average temperatures. The combination of rising temperatures boosting transmission intensity while simultaneously degrading the primary prevention tool creates a compounding problem. Nets that are replaced before they expire perform significantly better, but in many regions, replacement cycles are tied to donor funding and don’t account for accelerated degradation in hotter climates.
The Financial Toll of Climate-Driven Malaria
The economic costs of climate-driven malaria expansion are substantial. Projections estimate that managing the additional malaria cases caused by climate change in 2030 will cost between $2 billion and $5.6 billion, depending on the emissions scenario. Total global investment needed to combat malaria, including both baseline and climate-attributable cases, could reach $36 billion to $50 billion annually.
These costs fall disproportionately on the countries least equipped to absorb them. Sub-Saharan Africa carries roughly 95% of the global malaria burden, and the regions facing the greatest climate-driven expansion, highlands and newly urbanizing areas, often have the weakest health infrastructure. If global malaria reduction targets were met, the additional costs attributable to climate change would drop to an estimated $4 billion to $12 billion under moderate emissions scenarios. The gap between those figures represents the price of delayed action on both climate mitigation and malaria control.