| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 28.8° | 21.1° | 116mm | 17.8 | 63 |
| February | 28.9° | 21.1° | 101.7mm | 15.9 | 62 |
| March | 29.6° | 21.6° | 95mm | 13.4 | 63 |
| April | 30.3° | 22.6° | 132.7mm | 14 | 59 |
| May | 31.1° | 23.7° | 187.9mm | 14.9 | 54 |
| June | 31.9° | 24.7° | 127.2mm | 13.6 | 53 |
| July | 31.7° | 24.7° | 189.3mm | 18.3 | 51 |
| August | 32.1° | 25° | 206.6mm | 19.6 | 50 |
| September | 32.2° | 24.4° | 180.9mm | 18 | 49 |
| October | 32.1° | 24.1° | 175.9mm | 18.3 | 50 |
| November | 30.5° | 23° | 215.7mm | 19.4 | 56 |
| December | 29.1° | 21.8° | 158.3mm | 18.9 | 62 |
January in San Juan averages a daily high of 28.8°C with nights around 21.1°C. Expect roughly 17.8 wet days totalling 116mm. Generally workable, with some weather to plan around.
February in San Juan averages a daily high of 28.9°C with nights around 21.1°C. Expect roughly 15.9 wet days totalling 101.7mm. Generally workable, with some weather to plan around.
March in San Juan averages a daily high of 29.6°C with nights around 21.6°C. Expect roughly 13.4 wet days totalling 95mm. Generally workable, with some weather to plan around.
April in San Juan averages a daily high of 30.3°C with nights around 22.6°C. Expect roughly 14 wet days totalling 132.7mm. Generally workable, with some weather to plan around.
May in San Juan averages a daily high of 31.1°C with nights around 23.7°C. Expect roughly 14.9 wet days totalling 187.9mm. Demanding conditions — pack for it and plan indoor options.
June in San Juan averages a daily high of 31.9°C with nights around 24.7°C. Expect roughly 13.6 wet days totalling 127.2mm. Demanding conditions — pack for it and plan indoor options.
July in San Juan averages a daily high of 31.7°C with nights around 24.7°C. Expect roughly 18.3 wet days totalling 189.3mm. Demanding conditions — pack for it and plan indoor options.
August in San Juan averages a daily high of 32.1°C with nights around 25°C. Expect roughly 19.6 wet days totalling 206.6mm. Demanding conditions — pack for it and plan indoor options.
September in San Juan averages a daily high of 32.2°C with nights around 24.4°C. Expect roughly 18 wet days totalling 180.9mm. Demanding conditions — pack for it and plan indoor options.
October in San Juan averages a daily high of 32.1°C with nights around 24.1°C. Expect roughly 18.3 wet days totalling 175.9mm. Demanding conditions — pack for it and plan indoor options.
November in San Juan averages a daily high of 30.5°C with nights around 23°C. Expect roughly 19.4 wet days totalling 215.7mm. Generally workable, with some weather to plan around.
December in San Juan averages a daily high of 29.1°C with nights around 21.8°C. Expect roughly 18.9 wet days totalling 158.3mm. 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. San Juan peaks at 63.
Based on 30 years of records, November–April scores highest for comfort in San Juan, balancing daytime temperature against rainfall.
September is the warmest, averaging a daily high of 32.2°C.
November is the wettest, averaging 215.7mm of rain across roughly 19.4 wet days.
January is the coolest month, with average daily highs around 28.8°C.