Quick decision
Quick decision
December through February require a cold-weather plan
The 10th-percentile daily minimum is -11.1 °C in December, -10.9 °C in January and -9.4 °C in February.
July and August require both heat and wet-weather plans
Their monthly means are 26.9 °C and 27.4 °C, while their 90th-percentile daily maximums are 35.5 °C and 35.3 °C. They also have the highest observed precipitation-day counts in this dataset.
April, May and October sit in the middle of the annual mean-temperature range, but the daily tails still matter
Their monthly means are 13.6 °C, 18.4 °C and 15.3 °C. A mean is not a trip-date forecast or a complete packing list.
There is no universal best month in this evidence
Comfort, humidity, wind, snow, daylight, events and crowd conditions are not ranked here.
What this guide measures
This guide uses 2,922 daily observations from KMA ASOS Seoul station 108, covering every calendar date from January 1, 2018 through December 31, 2025. The monthly figures below are derived from that fixed eight-year selection.
The mean column averages daily mean temperature. The lower and upper columns show the 10th percentile of daily minimum temperature and the 90th percentile of daily maximum temperature. They are planning tails, not a promise that every day stays inside the interval.
An observed precipitation day means a non-null KMA daily precipitation value of at least 0.1 mm. The annualized count divides the eight-year monthly total by eight. A missing precipitation value is not changed to zero.
Seoul weather by month
How the seasons change the planning decision
Winter: December through February
Monthly mean temperatures range from -1.3 °C to 1.1 °C across these three months. The lower daily tail reaches about -9.4 °C to -11.1 °C, so planning only around the mean understates the colder days in the historical selection.
Spring: March through May
The monthly mean rises from 8.0 °C in March to 18.4 °C in May. March still has a 10th-percentile daily minimum of -0.9 °C, while May has a 90th-percentile daily maximum of 28.3 °C. Layers are more useful than treating spring as one fixed temperature band.
Summer: June through August
Monthly means rise from 23.5 °C in June to 27.4 °C in August. The 90th-percentile daily maximum is above 32 °C in all three months and above 35 °C in July and August. July and August average 14.2 and 14.4 observed precipitation days per covered year, the two highest monthly counts in this table.
Autumn: September through November
The monthly mean falls from 22.9 °C in September to 8.4 °C in November. The 10th-percentile daily minimum falls from 15.6 °C to -1.6 °C over the same period, so early and late autumn require different packing assumptions.
Comfort and uncertainty
These figures describe a historical distribution, not personal comfort. The dataset supports temperature and observed precipitation comparisons, but it does not support a comfort score or one best month. Humidity, wind, snow, daylight, air quality, holidays, events and crowds are outside this source material.
A current forecast closer to the trip should replace historical ranges for day-specific decisions. This page does not present current conditions or forecast a future date.
Packing implications
- For winter, plan around the subzero lower tail rather than the monthly mean alone.
- For July and August, prepare for high-temperature days and carry a wet-weather alternative for outdoor plans.
- For spring and autumn, use layers because monthly means do not show the full lower-to-upper daily spread.
- Recheck a trip-date forecast before departure. Historical observations cannot tell you what a specific future day will do.
Decision limits
Limitations
- Coverage is January 1, 2018 through December 31, 2025, not a 30-year official climate normal.
- All observations come from KMA ASOS Seoul station 108 and do not measure neighborhood-level variation.
- The table is historical climatology, not current weather and not a future forecast.
- Null precipitation is not treated as zero; the table reports observed qualifying precipitation days.
- Humidity, wind, snow, daylight, air quality, holidays, events and crowds are not compared.
- No universal comfort ranking or best-month recommendation is made.
OFFICIAL SOURCES
Sources
Official source used for the daily observations:
- Korea Meteorological Administration API Hub: ASOS daily observations: Official information used in this guide.