| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 11.3° | — | 74.7mm | 6.5 | 59 |
| February | 11.8° | — | 97.1mm | 8.2 | 57 |
| March | 15.2° | — | 143.4mm | 11.5 | 62 |
| April | 19.3° | — | 173.2mm | 11.4 | 75 |
| May | 23.1° | — | 161.5mm | 10.8 | 78 |
| June | 25.6° | — | 201.8mm | 12.1 | 76 |
| July | 29.3° | — | 161mm | 9 | 73 |
| August | 31.1° | — | 116.4mm | 8.2 | 67 |
| September | 28.1° | — | 215.8mm | 11.6 | 72 |
| October | 23.3° | — | 271.6mm | 12.3 | 75 |
| November | 18.7° | — | 167.1mm | 10.6 | 75 |
| December | 13.8° | — | 92.9mm | 7.2 | 66 |
January in Tateyama averages a daily high of 11.3°C. Expect roughly 6.5 wet days totalling 74.7mm. Generally workable, with some weather to plan around.
February in Tateyama averages a daily high of 11.8°C. Expect roughly 8.2 wet days totalling 97.1mm. Generally workable, with some weather to plan around.
March in Tateyama averages a daily high of 15.2°C. Expect roughly 11.5 wet days totalling 143.4mm. Generally workable, with some weather to plan around.
April in Tateyama averages a daily high of 19.3°C. Expect roughly 11.4 wet days totalling 173.2mm. Comfortable conditions for being outdoors all day.
May in Tateyama averages a daily high of 23.1°C. Expect roughly 10.8 wet days totalling 161.5mm. Comfortable conditions for being outdoors all day.
June in Tateyama averages a daily high of 25.6°C. Expect roughly 12.1 wet days totalling 201.8mm. Comfortable conditions for being outdoors all day.
July in Tateyama averages a daily high of 29.3°C. Expect roughly 9 wet days totalling 161mm. Generally workable, with some weather to plan around.
August in Tateyama averages a daily high of 31.1°C. Expect roughly 8.2 wet days totalling 116.4mm. Generally workable, with some weather to plan around.
September in Tateyama averages a daily high of 28.1°C. Expect roughly 11.6 wet days totalling 215.8mm. Generally workable, with some weather to plan around.
October in Tateyama averages a daily high of 23.3°C. Expect roughly 12.3 wet days totalling 271.6mm. Comfortable conditions for being outdoors all day.
November in Tateyama averages a daily high of 18.7°C. Expect roughly 10.6 wet days totalling 167.1mm. Comfortable conditions for being outdoors all day.
December in Tateyama averages a daily high of 13.8°C. Expect roughly 7.2 wet days totalling 92.9mm. Generally workable, with some weather to plan around.
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. Tateyama peaks at 78.
Based on 30 years of records, April–July scores highest for comfort in Tateyama, balancing daytime temperature against rainfall.
August is the warmest, averaging a daily high of 31.1°C.
October is the wettest, averaging 271.6mm of rain across roughly 12.3 wet days.
January is the coolest month, with average daily highs around 11.3°C.