| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 1.8° | — | 3mm | 1 | 43 |
| February | 5.2° | — | 0.8mm | 2 | 49 |
| March | 10.9° | — | 45.7mm | 4 | 63 |
| April | 17.8° | — | 78.8mm | 6 | 81 |
| May | 23.7° | — | 158.4mm | 13 | 74 |
| June | 27.8° | — | 66.6mm | 5 | 87 |
| July | 29.1° | — | 501.2mm | 18 | 62 |
| August | 29.9° | — | 548.5mm | 15.3 | 58 |
| September | 26.3° | — | 253.7mm | 21 | 70 |
| October | 20.3° | — | — | — | 94 |
| November | 12° | — | — | — | 68 |
| December | 3.9° | — | — | — | 42 |
January in Seongnam-si averages a daily high of 1.8°C. Rain is rare — about 1 wet days and 3mm across the month. Demanding conditions — pack for it and plan indoor options.
February in Seongnam-si averages a daily high of 5.2°C. Rain is rare — about 2 wet days and 0.8mm across the month. Demanding conditions — pack for it and plan indoor options.
March in Seongnam-si averages a daily high of 10.9°C. Expect roughly 4 wet days totalling 45.7mm. Generally workable, with some weather to plan around.
April in Seongnam-si averages a daily high of 17.8°C. Expect roughly 6 wet days totalling 78.8mm. Comfortable conditions for being outdoors all day.
May in Seongnam-si averages a daily high of 23.7°C. Expect roughly 13 wet days totalling 158.4mm. Generally workable, with some weather to plan around.
June in Seongnam-si averages a daily high of 27.8°C. Expect roughly 5 wet days totalling 66.6mm. Comfortable conditions for being outdoors all day.
July in Seongnam-si averages a daily high of 29.1°C. Expect roughly 18 wet days totalling 501.2mm. Generally workable, with some weather to plan around.
August in Seongnam-si averages a daily high of 29.9°C. Expect roughly 15.3 wet days totalling 548.5mm. Generally workable, with some weather to plan around.
September in Seongnam-si averages a daily high of 26.3°C. Expect roughly 21 wet days totalling 253.7mm. Generally workable, with some weather to plan around.
October in Seongnam-si averages a daily high of 20.3°C. Comfortable conditions for being outdoors all day.
November in Seongnam-si averages a daily high of 12°C. Generally workable, with some weather to plan around.
December in Seongnam-si averages a daily high of 3.9°C. Demanding conditions — pack for it and plan indoor options.
Each month scores out of 100. It starts at 100 and loses points for daytime highs outside a 20–27°C band, for wet days, and for nights below 2°C. Nothing else is weighted in — no crowd data, no prices, no opinion. Seongnam-si peaks at 94.
Based on 30 years of records, June scores highest for comfort in Seongnam-si, balancing daytime temperature against rainfall.
August is the warmest, averaging a daily high of 29.9°C.
August is the wettest, averaging 548.5mm of rain across roughly 15.3 wet days.
January is the coolest month, with average daily highs around 1.8°C.