Quick decision
Quick decision
If subzero cold is the main concern, treat December through February as the demanding period
Their 10th-percentile daily minimums range from -9.4 °C to -11.1 °C in this dataset.
If high heat and frequent precipitation days are the main concern, July and August require the strongest backup plan
Their monthly means are 26.9 °C and 27.4 °C, with 90th-percentile daily maximums above 35 °C.
If you prefer milder monthly means, compare April, May and October
Their means are 13.6 °C, 18.4 °C and 15.3 °C, but their daily tails remain wide enough that layers and a trip-date forecast still matter.
Do not treat these three options as a universal comfort ranking
Humidity, wind, snow, daylight, events and crowds are not scored.
What this decision covers
This page uses 2,922 daily KMA observations from Seoul station 108, covering every date from January 1, 2018 through December 31, 2025. It compares historical temperature distributions and observed precipitation-day counts. It is not a current forecast or an official 30-year climate normal.
Weather decision at a glance
This is a weather-only shortlist. It does not rank crowds, events, daylight, air quality or cost.
Choose by your weather tolerance
You want to avoid the colder tail
December, January and February have 10th-percentile daily minimums of -11.1 °C, -10.9 °C and -9.4 °C. If cold is difficult for you, do not plan from the monthly mean alone.
You want to avoid the hottest, wetter part of this record
July and August have the highest monthly means, the highest upper-temperature tails and the highest observed precipitation-day counts in this table. The evidence supports carrying both a heat plan and a wet-weather alternative. It does not measure humidity or rainfall intensity.
You want a milder monthly mean
April, May and October sit between 13 °C and 19 °C by monthly mean. Their lower and upper tails are still broad: April spans 4.1 °C to 25.1 °C on the displayed tail measures, May 9.6 °C to 28.3 °C, and October 5.8 °C to 24.4 °C. Pick among them for your itinerary, not because the data declares one winner.
What to do after choosing a month
- Recheck the official forecast close to departure.
- Pack for the displayed lower and upper tails rather than the mean alone.
- Keep an indoor alternative when historical precipitation-day counts are higher.
- Treat event timing and crowd levels as separate decisions because this evidence does not measure them.
Decision limits
Limitations
- This is Seoul station 108, not a Korea-wide comparison and not neighborhood-level weather.
- Coverage is 2018 through 2025, not an official 30-year climate normal.
- An observed precipitation day means a non-null daily value of at least 0.1 mm; missing precipitation is not changed to zero.
- Humidity, wind, snow, daylight, air quality, holidays, events and crowds are not compared.
- No universal best month or personal comfort score is produced.
OFFICIAL SOURCES
Sources
Official source used for the daily observations:
- Korea Meteorological Administration API Hub: ASOS daily observations: Official information used in this guide.