Why did mosquito numbers rise sharply in Korea as autumn began?

The article says scorching temperatures near 40 degrees Celsius had suppressed mosquito activity until mid-August. Rains during the Liberation Day holiday raised humidity, and cooler mornings and evenings created more favorable conditions as the weather turned cooler.

What did the Korea Disease Control and Prevention Agency find in its latest mosquito monitoring data?

The agency said the mosquito index reached 100.9 in week 35, from Aug. 24 to 29, based on daily mosquito monitoring systems in seven regions. It was the first time the index had gone above 100 since the equipment was introduced and monitoring began earlier this year.

What mosquito precautions does the article recommend through October?

People are advised to limit outdoor activities after sunset, when mosquitoes are most active, and to wear light-colored clothing with long sleeves and long pants at night. The article also recommends checking window screens and removing standing water around the home to reduce breeding grounds.

Mosquito numbers double in just a week as scorching summer heat eases

Listen

Summary

Mosquito numbers in Korea nearly doubled in one week as cooler fall weather followed the summer heat. The Korea Disease Control and Prevention Agency said the mosquito index reached 100.9 in week 35, the first time it has exceeded 100 since monitoring began earlier this year. The index for Culex tritaeniorhynchus also rose to an average of 102, though it remained below last year’s level. Officials advised people to limit outdoor activity after sunset through October and remove standing water around homes.

Key Facts

The mosquito index rose from 53 in week 34 to 100.9 in week 35, covering Aug. 24 to 29.
Daily mosquito monitoring systems across seven regions nationwide automatically trap mosquitoes and use artificial intelligence to count and analyze them in real time.
The index for Culex tritaeniorhynchus increased by 34 from the previous week to an average of 102 in week 35.
The Culex tritaeniorhynchus figure was still below the 228 recorded during the same period last year.
The article says mosquitoes are most active and lay the most eggs at temperatures of around 25 to 30 degrees Celsius.

By Hankookilbo

Published Sep 7, 2026 1:00 pm KST

Paldal District Public Health Center workers spray for mosquitoes near Hwaseong Haenggung Palace in Suwon, Gyeonggi Province, Aug. 25. Yonhap

Mosquitoes are out in force this fall as the summer heat eases and the weather turns cooler, with the latest mosquito index nearly doubling in just one week.

According to the Korea Disease Control and Prevention Agency’s real-time mosquito surveillance data released Sunday, the mosquito index reached 100.9 in week 35 of this year, covering Aug. 24 to 29. The figure, based on catches from daily mosquito monitoring systems (DMS) across seven regions nationwide, rose by 47.9 from 53 the previous week.

DMS automatically trap mosquitoes and use artificial intelligence to count and analyze them in real time. This marks the first time the index has exceeded 100 since the agency introduced the equipment and began monitoring earlier this year.

The index hovered between 40 and 50 from weeks 28 through 32 before surging to 99.5 in week 33. It then fell to 53 in week 34 before climbing sharply again in week 35.

The index for Culex tritaeniorhynchus, a mosquito species that transmits Japanese encephalitis — a rare but serious viral infection — also rose by 34 from the previous week to an average of 102 in week 35. The figure was still below the 228 recorded during the same period last year, however.

The increase continues a trend of more mosquitoes appearing across Korea in autumn, partly due to warmer fall temperatures brought on by climate change. Mosquitoes are most active and lay the most eggs at temperatures of around 25 to 30 degrees Celsius. This year, scorching temperatures approaching 40 degrees Celsius suppressed mosquito activity until mid-August. However, rains beginning over the Liberation Day holiday raised humidity, while cooler mornings and evenings appear to have created more favorable conditions for mosquitoes.

People are advised to limit outdoor activities after sunset through October, when mosquitoes are most active, and wear light-colored clothing with long sleeves and long pants when going out at night. Checking window screens and removing standing water around the home can also help eliminate mosquito breeding grounds.

This article from the Hankook Ilbo, the sister publication of The Korea Times, is translated by a generative AI system and edited by The Korea Times.

Explore More