The cold and snowy winter we have had creates good conditions for a mosquito-filled summer. If it is also followed by a warm spring, there are suddenly unusually many conditions for mosquitoes and mosquito bites to become the biggest summer plague in 2026.

Snow and cold make beds for mosquito eggs
A thick blanket of snow acts as an insulating layer over the ground, protecting the mosquito eggs that lie dormant during the winter. When temperatures drop sharply and the ground is covered in snow, more eggs survive than during dry, snowless winters with bare frost.

The high snow depth that has covered unusually large parts of the country for most of the winter also means that a lot of water will be released when the snow melts. As the snow melts, temporary pools of water form in forests and fields, and there is a risk of heavy spring flooding along watercourses. In areas around the Dalälven River, for example, it has previously been seen how abundant snowmelt can lead to extensive hatching of flood mosquitoes. A scenario that now risks affecting not only individual parts of the country, but larger parts of Sweden.

Warm spring and snowmelt boost mosquito growth
If snowmelt also coincides with a rapid rise in temperature during spring, the development from larvae to mature mosquitoes can be rapid. This increases the risk of an intense and early mosquito season. On the other hand, if the spring is slow and cold, the effect may be somewhat mitigated, but the basic conditions – good wintering and plenty of meltwater – suggest that the summer of 2026 may be mosquito rich in many places.

All in all, the cold, snowy winter points to a summer where mosquitoes may be more numerous than usual, especially in humid and flood-prone areas. So it might be a good idea to start thinking about mosquito protection now. Some mosquito repellent products work over time and need to be placed in gardens and house areas early in the season, even before the mosquitoes have hatched and grown.

Mosquitoes are becoming more numerous and more dangerous
Until now, Sweden has been spared mosquitoes that carry infections that can cause serious diseases, such as dengue fever, malaria, chikungunya, Zika virus and yellow fever. Diseases that are commonplace in other parts of the world, killing between 700 000 and 1 000 000 people every year. Recently, however, there have been reports that mosquitoes carrying diseases have been both sighted and established closer to Sweden, and researchers agree on a few things: mosquitoes are becoming more and more dangerous, and we in Sweden will not be spared for long.