Is Climate Change Making Mosquito Season Longer?

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Since the 1980s, the length of mosquito season has increased by as much as 37 days in many major US cities. This comes as a result of rising global temperatures and humidity. Similar trends can be seen across the rest of the world. With climate change accelerating, mosquito season is only going to get longer and longer.

The Dangers of Mosquito Season

Having more mosquitoes buzzing around for longer isn’t just an annoyance. In many tropical and subtropical countries, mosquitoes carry and transmit vector-borne diseases (VBDs) like malaria, yellow fever, dengue, Lyme disease, etc. Together, these result in more than 700,000 deaths per year. Rising temperatures and humidity along with a longer mosquito season means there will be a higher chance of VBDs affecting humans. With increased migration (some as a direct result of climate change), trade, and travel, there’s also an increased risk of VBDs spreading to the rest of the world. Read on to find out more about climate change and lengthening mosquito seasons.

Climate Change

Climate change, a result of human activity, is already a fact in many parts of the world. Global temperatures rose 1ºC over the 20th century. The 21st century has already seen more broken temperature records than at any time in recorded history. Each of the past three years has broken the record for global surface temperatures. Arctic sea ice is melting, sea levels are rising, climate refugees are on the move, and floods and extreme weather events are increasing, too. Things are only bound to get worse. In the absence of human action to reduce greenhouse gas emissions, the Earth’s temperature could rise by 6ºC by the end of the century.

Climate Change and Mosquitoes

The forecast of continuing climate change is great news for mosquitoes, but not so great for the rest of us. You see, mosquitoes, like other insects, can’t regulate their own body temperatures. They rely on external heat sources. If the temperature drops below a certain level, they can’t survive or thrive.

Rising temperatures lengthen the warm season during which mosquitoes can breed and survive. It also increases their geographical range to regions further from the equator.

Increased humidity, rainfall, and flooding are all associated with climate change. This is also a boon for mosquitoes as they need water as well as warm temperatures to breed. Flooding and heavy rainfall will leave more sources of standing water in which mosquitoes can lay their eggs. Moreover, the warmer weather and humidity will shorten the incubation time of the eggs. This means that the mosquito population can grow a lot in a very short amount of time.

What This Means For Us

As mentioned, this isn’t just a source of annoyance and irritation (even though that is true as well.) As everyone knows far too well, mosquitoes LOVE biting humans. Our blood is a source of the protein female mosquitoes need to produce eggs. The more mosquitoes there are breeding and laying eggs, the more of our blood they’re going to need.

But there’s a more frightening aspect to this. As we’ve seen, mosquitoes carry diseases. The longer the mosquito season, the more chance for infectious diseases to spread. VBDs overwhelmingly affect people in tropical and subtropical countries in the developing world. But increased migration – including by the refugees created by climate change – along with trade and travel increase the chances of these diseases spreading to temperate regions where the people aren’t immune to them.

Rising global temperatures and increased humidity, rainfall, and flooding will allow mosquitoes to thrive further from the equator. This is why health officials prepared for an increase in Zika and the West Nile virus after the 2016 Louisiana floods. This was owing to the increased range of the Aedes aegypti mosquitoes caused by the floods.


According to the Intergovernmental Panel on Climate Change (IPCC), there’s increasing evidence that particular diseases, like dengue fever and the West Nile virus, are emerging in places they were previously absent and that this is due in part to climate change.

This is why we must be extra vigilant in protecting ourselves against mosquito bites, even if you live in a location where VBDs were unheard of up to now. To find out what you can do to deter mosquitoes, please read some of our other articles. The world is changing rapidly, but not necessarily for the better!

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