Last verified: 2026-08-27 08:49 KST
Two things changed about Korean summer recently, and most English-language guides still describe the old version.
First, the records. The Korea Meteorological Administration (KMA) recorded a summer average of 25.7°C in 2025 — the highest since nationwide records began in 1973 — and Seoul logged 46 tropical nights, its most since observations started there in 1908. Across 2025 as a whole the country saw 29.7 heatwave days against a normal of 11.0, roughly 2.7 times the average.
Second, and more useful to you: on 1 June 2026 Korea overhauled its heat alert system for the first time in 18 years. There are alert levels that did not exist last summer, and the thresholds are not what older guides say.
What Summer Here Actually Feels Like
Korean summer arrives in two overlapping acts: the monsoon, then the heat.
Jangma (장마) is the monsoon front that stalls over the peninsula in early summer. On KMA’s 1991–2020 normals it reaches Jeju around 19 June and ends 20 July, the south 23 June to 24 July, and the central region including Seoul 25 June to 26 July — about 31 to 32 days.
Here is the part that surprises new arrivals: that is not a month of rain. The same normals put rainfall at roughly 17 days in each region — Jeju 17.5, the south 17.0, the central region 17.7. So it rains a little over half the days of jangma, and the rest are just grey and heavy. Note also that these are statistical normals, not a forecast. KMA declares the actual start and end dates as the season unfolds, and recent years have run well off the averages.
Once the rains lift, the heat settles in — and with it the tropical night (열대야), an overnight low that stays at or above 25°C and wrecks your sleep. Typhoons are the wildcard; a handful reach or brush Korea in a typical year, mostly July through October and peaking in August, though the count swings a lot year to year.
The 2026 Heat Alert Overhaul
Korea issues heat alerts on the feels-like temperature, which folds in humidity — so an alert can fire on a merely warm day that happens to be very humid. The two familiar levels are unchanged:
- Heat advisory (폭염주의보) — daily maximum feels-like temperature of 33°C or above, expected to last two days or more.
- Heat warning (폭염경보) — the same, at 35°C or above.
What is new from 1 June 2026 are two additional alerts, and the details matter:
- Critical heat alert (폭염중대경보) — the first “critical” tier ever created in Korea’s weather alert system. In an area already under a heat warning, it fires when the feels-like maximum is forecast to hit 38°C, or the air temperature 39°C, even for a single day. That single-day trigger is the key difference from the two-day rule above.
- Tropical night advisory (열대야주의보) — issued at advisory level only, in areas already at heat-advisory level or above, when the overnight low is forecast at 25°C for even one night. The threshold is 26°C in cities over 500,000 people and in coastal and island areas, and 27°C on Jeju, to account for urban and maritime effects.
KMA’s reason for the night-time alert is worth knowing: at the same daytime feels-like temperature, heat-illness cases rise by up to about 90% when the previous night was a tropical night. The heat you did not sleep off is the heat that hurts you.
Two more changes landed at the same time. Alert zones were subdivided from 183 to 235 nationwide, so warnings now track your actual district more closely. And from 15 May 2026 a disaster-grade downpour text was added, sent when 100mm of rain falls in an hour, or 85mm in an hour combined with 25mm in 15 minutes.
Staying Safe In The Heat
The behavioural rules are simple: avoid outdoor work and exercise from roughly 2–5 p.m., drink water often, skip caffeine and alcohol, and wear light, loose, pale clothing.
Heat exhaustion can cause heavy sweating, dizziness and weakness: stop activity, move to a cool place and seek medical advice. Heat stroke is an emergency and can occur with either dry skin or heavy sweating. Confusion, slurred speech, seizures or loss of consciousness after heat exposure require 119 immediately. Cool the person with water, wet cloths and moving air while help is coming; do not give drinks to an unconscious person. See CDC guidance on heat-related illness (checked October 6, 2026) and our seeing a doctor guide.
Cooling Shelters: Free, And There Are More Than You Think
Korea runs a national network of air-conditioned cooling shelters (무더위쉼터). As of 12 August 2026 the Ministry of the Interior and Safety put the count at 93,375 locations — up from 20,448 when the scheme started in 2006. The official heat response period runs 15 May to 30 September.
Three things foreigners get wrong about them:
- They are free and open to anyone. There is no registration, no residency check, and no requirement to be elderly or vulnerable. Walk in.
- They are not just community centres any more. The network now includes banks, railway stations, public libraries, and rest spaces for delivery and gig workers.
- About 13,000 of them extend hours into the night when a heat alert is in force — useful precisely on the tropical nights when your one-room will not cool down.
To find the nearest one, search 무더위쉼터 in Naver Map, KakaoMap or TMAP, or use the government’s Emergency Ready App. The map apps are the practical route if your Korean is limited — the pin appears whether or not you can read the label.
Those Loud Phone Alerts Are Normal
Sooner or later your phone will erupt with a siren and a wall of Korean text. It is a disaster text, and there are three grades — with genuinely different volumes and different opt-out rights:
- Safety guidance (안전안내문자) — heat and weather advisories, air quality. Delivered like a normal message, so you can set it to silent, vibrate or sound. Heat alerts arrive this way, which is why summer is noisy. Can be turned off.
- Emergency (긴급재난문자) — evacuation-level events. Sounds at 40dB or above. Can be turned off, though you should not.
- Critical (위급재난문자) — reserved for war and air raids, plus major earthquakes. Sounds at 60dB or above and cannot be turned off on any phone.
So the constant summer buzzing is almost always the mildest grade. If it was genuinely the top tier, you would not have been able to silence it. These arrive by cell broadcast, which any recent phone on a Korean SIM receives automatically.
On a foreign phone or older handset and getting nothing? Install the government’s Emergency Ready App, which runs in English. Our essential apps guide covers the setup, and Papago will translate a screenshot of any alert you do receive.
When The Rain Really Comes
Most jangma days are just wet. The danger is the localised downpour — the scenario the new disaster-grade text was created for.
- Stay out of underground roadways, underpasses and low bridges — they flood fast and without warning — and away from streams, riversides and mountain valleys, which surge in minutes.
- If you live in a semi-basement (반지하), treat any water coming in as your cue to leave immediately — this is the scenario Korea tightened rules around after the 2022 Seoul floods.
- If water rises around your car, abandon it and go to high ground. Move a car out of a low-lying spot before the rain, not during.
- Stay clear of manholes and utility poles. Floodwater hides live hazards.
The Mold War
Indoor humidity during jangma climbs high enough that mold takes hold readily, and Korean apartments and one-rooms are built tight. Watch the four usual hotspots: bathroom silicone and grout, wallpaper on exterior or north-facing walls, the space behind wardrobes and furniture, and window frames where condensation collects.
Defence first: ventilate after the rain stops rather than during it, since opening windows mid-downpour just invites moisture in. Pull furniture a few centimetres off the walls. Drop moisture absorbers — the tubs sold everywhere as mulmeokneun hama — into closets and shoe cabinets. When mold appears, a mold remover or diluted bleach clears it, window open.
Never mix bleach (락스) with an acidic cleaner. The combination releases toxic chlorine gas. One product at a time, always ventilated.
If mold traces to a structural cause such as a leak, that is generally treated as the landlord’s responsibility, while poor ventilation is treated as the tenant’s. This is not legal advice — but photograph it and notify your landlord in writing as soon as you spot it, because the written record is what decides the argument later.
Laundry That Won’t Dry
That sour smell on indoor-dried laundry is bacteria multiplying while the clothes stay damp, so the whole game is drying them faster: run an extra spin cycle, hang items with wide gaps between them, and point a fan at them with a dehumidifier running. For laundry that already smells, soak or boil it with oxygen bleach (과탄산소다). When your place simply cannot dry a load, a coin laundromat will.
Your AC, Decoded — And The Bill
Most one-rooms have a wall-mounted air conditioner with an all-Korean remote. The decoder (labels vary slightly by brand):
- 냉방 = Cool · 제습 = Dry · 송풍 = Fan
- 자동 = Auto · 난방 = Heat · 취침 = Sleep · 예약 = Timer
- 풍량 = Fan speed · 온도 ▲▼ = Temperature · 회전 = Swing
Clean the filter yourself every two weeks to a month — it rinses under a tap — and run Fan mode briefly after cooling to dry the unit’s insides and stop mildew smells. Keep the outdoor unit clear of anything flammable.
Now the bill, which is where the real money is. Korean household electricity is progressive: cross a usage threshold and both your standing charge and your per-unit rate step up. In July and August only, the government widens the bands to soften air-conditioning season:
- Tier 1 covers up to 300 kWh in summer, versus 200 kWh the rest of the year.
- Tier 2 runs to 450 kWh in summer, versus 400 kWh otherwise.
- Tier 3 applies above that, at roughly 307 won per kWh.
Two traps worth knowing. The 450 kWh line is a cliff, not a slope — crossing it changes your standing charge for the whole month as well as the rate on the excess, so a modest increase in usage can produce a disproportionate jump in the bill. And above 1,000 kWh in July or August a “super user” rate of about 736 won per kWh applies, more than double the tier 3 rate. If you are running air conditioning around the clock in a poorly insulated flat, that is the number that produces the horror stories.
The practical read: your headroom in summer is larger than you fear, but the penalty past the top line is worse than you expect. Check your monthly cumulative usage rather than guessing from the daily weather.
Cooling Gear, Sleep, And Summer Eats
You can cool down cheaply. Daiso and convenience stores carry hand fans, neck fans, cooling arm sleeves and cooling sleep mats through the season. The convenience-store ritual is an ice cup topped with a pouch drink, and the go-to electrolyte drinks are Pocari Sweat, Toreta and Gatorade. You will also see parasols carried by men and women alike — they genuinely cut the felt heat, and nobody will look twice.
For sleeping through a tropical night, set a 2–3 hour AC timer rather than running all night, and take a lukewarm shower an hour or two before bed. A cold shower feels better for five minutes, then jolts you awake.
Then the food. The boknal (복날) — the three “dog days” — fall on 15 July, 25 July and 14 August in 2026. The dates move each year because they follow the traditional calendar. One quirk this year: 2026 is a wolbok (월복) year, so the gap between the second and third boknal stretches to 20 days instead of the usual 10 — traditionally read as a sign the heat will run long. The custom is to fight heat with heat, with samgyetang on the day. Round out the season with cold naengmyeon, nutty kongguksu, shaved-ice bingsu, and chimaek by the Han River at dusk.
Bug Season
Warm damp air brings the insects. Your first line of defence is the window screen (방충망) — check it for gaps and patch holes with repair tape. Mosquito nets, electric swatters and plug-in vaporizer mats all cost very little; just ventilate if you run a vaporizer in a sealed room.
The other classic one-room pest is fruit flies and drain flies breeding in your drains. Fit a drain trap and keep it clean — and note that leaving home for two weeks or more lets the trap’s water evaporate and the problem come roaring back. Sealing and emptying your food waste often cuts fruit flies off at the source; our trash and recycling guide covers doing that properly.
Summer Food Safety
Heat spoils food fast, and Korea’s Ministry of Food and Drug Safety publishes a six-rule standard that is worth following literally:
- Wash hands under running water with soap for 30 seconds or more.
- Separate raw and cooked food, with different knives and cutting boards.
- Cook through — core temperature 75°C for meat, 85°C for fish and shellfish, held for at least one minute.
- Boil water before drinking it where you are unsure.
- Wash and disinfect ingredients and cooking tools.
- Hold the right temperature — refrigerated food at 5°C or below, frozen at −18°C or below, and hot food kept at 60°C or above.
The rule that matters most here: eat cooked food within about two hours, and refrigerate delivery leftovers immediately rather than leaving the container on the table.
FAQ
Is “fan death” real? No. The belief that an electric fan in a closed room can kill you has no scientific basis, and Koreans treat it as an old wives’ tale in Korea now too. Run your fan all night if you like.
Do I need an umbrella every day during jangma? Not every day — the normals put rain at roughly 17 of the season’s ~31 days. But the downpours arrive suddenly, so carry a compact umbrella through the peak weeks.
Can foreigners use the cooling shelters? Yes. They are free, open-access public facilities with no registration and no residency check.
When do I tough out the heat, and when do I see a doctor? Stop activity and cool down if you feel unwell in the heat; seek medical advice for heat exhaustion. Confusion, seizures or loss of consciousness may mean heat stroke: call 119 and start cooling. Sweating does not rule it out. Do not give an unconscious person water.
Verification note. On September 24, 2026 an AI-assisted check compared the alert zones subdivided from 183 to 235 and the feels-like maximum of 38°C for the critical heat alert against the Korea Meteorological Administration, and confirmed the official sources linked in this guide still resolve to the same pages. I publish this guide under my own name and am responsible for what it says. Rules and fees in Korea change often; if you spot something out of date, email hello@90dayskorea.com and it will be re-checked and corrected.
Official Resources
- Korea Meteorological Administration (English): kma.go.kr/neng — forecasts, advisories and typhoon tracking. Note that the older kma.go.kr/eng address no longer serves the English site.
- Disaster portal (English): eng.safekorea.go.kr/safekorea-eng — use the full address; the bare domain does not load reliably.
- National Safety 24 (Korean): safekorea.go.kr — shelter lookup and action guides.
- Emergency Ready App: from your app store; runs in English, and the best option on a foreign or older handset.
- Air quality (English): airkorea.or.kr/eng
- Help lines: 1330 (24-hour tourist help line, with interpretation) and 119 (fire and ambulance, with interpreter support) — see our emergency numbers guide.
Sources
Every figure above was checked against a primary Korean government source and confirmed against a second, independent one.
- 2026 heat alert overhaul — KMA press release, 12 May 2026 (Korean), — the 33/35°C thresholds, the 38°C / 39°C single-day critical alert, the 25/26/27°C tropical-night thresholds, the 183→235 zone split, and the disaster-grade rain text triggers of 100mm in an hour or 85mm plus 25mm in 15 minutes, effective 1 June 2026 (15 May for the rain text) / confirmed by Newsis and Daum News coverage reporting identical thresholds and dates.
- 2025 climate records — KMA, 2025 summer climate characteristics (Korean) — the 25.7°C summer average and Seoul’s 46 tropical nights since 1908 / confirmed by KMA’s 2025 annual release and the policy briefing carried by Water Journal, both giving 29.7 heatwave days against an 11.0-day normal.
- Jangma normals — KMA 1991–2020 climate normals / confirmed by Wikitree and Nate News summaries giving the same regional dates and ~17-day rainfall counts.
- Cooling shelters — Ministry of the Interior and Safety, 12 August 2026: 93,375 shelters, ~13,000 with extended night hours / confirmed by Newspim reporting the same count and by MOIS’s June 2026 release giving the 15 May–30 September period.
- Electricity tiers — Ministry of Trade, Industry and Energy approval of the summer band expansion, archived at KDI’s policy repository (Korean), — the July–August bands of 300 kWh and 450 kWh, against 200 kWh and 400 kWh the rest of the year / confirmed by Ajunews reporting the same bands in force for 2026, with tier 3 at 307.3 won per kWh and the summer super-user rate of 736.2 won per kWh above 1,000 kWh.
- Food safety rules — Ministry of Food and Drug Safety, six food-poisoning prevention rules (Korean) — 75°C for meat, 85°C for fish and shellfish, 5°C refrigerated, −18°C frozen, 60°C for hot holding / confirmed by the Seoul Metropolitan Government’s public information portal reproducing the same standards.
- Disaster text grades — the three-grade structure and 40dB / 60dB volume standards, critical alerts non-disableable, per Korea’s disaster text broadcasting regulations / confirmed by Sisa-IN’s explainer on the same rule.
- Boknal dates — 15 July, 25 July and 14 August 2026, from the traditional calendar / confirmed by Ajunews and multiple independent Korean outlets giving the same dates and the wolbok 20-day gap.
Deliberately excluded: we dropped the widely repeated figure for typhoons affecting Korea each year — published sources gave 3.1, 3.4 and 4, and we could not extract one authoritative number from KMA’s own statistics page. We describe the pattern in general terms rather than print a figure we cannot stand behind.