| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 19.6° | 6.7° | 56mm | 5.2 | 88 |
| February | 19.6° | 7.1° | 72.8mm | 6.3 | 86 |
| March | 21.6° | 8.9° | 40.5mm | 5.7 | 89 |
| April | 23.9° | 10.6° | 19.5mm | 3.5 | 93 |
| May | 26.2° | 13.1° | 7.4mm | 1.6 | 97 |
| June | 30.2° | 15.5° | 0.3mm | 0.3 | 87 |
| July | 34.1° | 18.3° | 1.6mm | 0.6 | 70 |
| August | 34.6° | 18.6° | 2.4mm | 0.3 | 69 |
| September | 32.6° | 17.4° | 3mm | 0.9 | 76 |
| October | 27.9° | 13.8° | 10.5mm | 2.1 | 92 |
| November | 23.3° | 9.2° | 20.8mm | 3.5 | 93 |
| December | 19.1° | 6.4° | 51.4mm | 5.7 | 86 |
January in Fontana averages a daily high of 19.6°C with nights around 6.7°C. Expect roughly 5.2 wet days totalling 56mm. Comfortable conditions for being outdoors all day.
February in Fontana averages a daily high of 19.6°C with nights around 7.1°C. Expect roughly 6.3 wet days totalling 72.8mm. Comfortable conditions for being outdoors all day.
March in Fontana averages a daily high of 21.6°C with nights around 8.9°C. Expect roughly 5.7 wet days totalling 40.5mm. Comfortable conditions for being outdoors all day.
April in Fontana averages a daily high of 23.9°C with nights around 10.6°C. Expect roughly 3.5 wet days totalling 19.5mm. Comfortable conditions for being outdoors all day.
May in Fontana averages a daily high of 26.2°C with nights around 13.1°C. Rain is rare — about 1.6 wet days and 7.4mm across the month. Comfortable conditions for being outdoors all day.
June in Fontana averages a daily high of 30.2°C with nights around 15.5°C. Rain is rare — about 0.3 wet days and 0.3mm across the month. Comfortable conditions for being outdoors all day.
July in Fontana averages a daily high of 34.1°C with nights around 18.3°C. Rain is rare — about 0.6 wet days and 1.6mm across the month. Generally workable, with some weather to plan around.
August in Fontana averages a daily high of 34.6°C with nights around 18.6°C. Rain is rare — about 0.3 wet days and 2.4mm across the month. Generally workable, with some weather to plan around.
September in Fontana averages a daily high of 32.6°C with nights around 17.4°C. Rain is rare — about 0.9 wet days and 3mm across the month. Comfortable conditions for being outdoors all day.
October in Fontana averages a daily high of 27.9°C with nights around 13.8°C. Rain is rare — about 2.1 wet days and 10.5mm across the month. Comfortable conditions for being outdoors all day.
November in Fontana averages a daily high of 23.3°C with nights around 9.2°C. Expect roughly 3.5 wet days totalling 20.8mm. Comfortable conditions for being outdoors all day.
December in Fontana averages a daily high of 19.1°C with nights around 6.4°C. Expect roughly 5.7 wet days totalling 51.4mm. Comfortable conditions for being outdoors all day.
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. Fontana peaks at 97.
Based on 30 years of records, March–May scores highest for comfort in Fontana, balancing daytime temperature against rainfall.
August is the warmest, averaging a daily high of 34.6°C.
February is the wettest, averaging 72.8mm of rain across roughly 6.3 wet days.
December is the coolest month, with average daily highs around 19.1°C.