| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 21.4° | 7.2° | 99.5mm | 6.3 | 87 |
| February | 21.1° | 7.7° | 114.7mm | 6.8 | 86 |
| March | 23° | 9.3° | 70mm | 5.2 | 90 |
| April | 24.3° | 10.4° | 18.7mm | 2.3 | 95 |
| May | 25.7° | 13.8° | 13mm | 1.8 | 96 |
| June | 27.8° | 15.6° | 2.8mm | 0.5 | 96 |
| July | 31° | 17.7° | 0.4mm | 0.3 | 83 |
| August | 31.9° | 17.7° | 8.2mm | 0.2 | 80 |
| September | 31.2° | 16.7° | 4.4mm | 0.5 | 82 |
| October | 27.9° | 13.4° | 13.2mm | 1.5 | 93 |
| November | 24.3° | 9.9° | 21.5mm | 2.7 | 95 |
| December | 20.8° | 6.7° | 48.2mm | 5 | 90 |
January in Rosemead averages a daily high of 21.4°C with nights around 7.2°C. Expect roughly 6.3 wet days totalling 99.5mm. Comfortable conditions for being outdoors all day.
February in Rosemead averages a daily high of 21.1°C with nights around 7.7°C. Expect roughly 6.8 wet days totalling 114.7mm. Comfortable conditions for being outdoors all day.
March in Rosemead averages a daily high of 23°C with nights around 9.3°C. Expect roughly 5.2 wet days totalling 70mm. Comfortable conditions for being outdoors all day.
April in Rosemead averages a daily high of 24.3°C with nights around 10.4°C. Rain is rare — about 2.3 wet days and 18.7mm across the month. Comfortable conditions for being outdoors all day.
May in Rosemead averages a daily high of 25.7°C with nights around 13.8°C. Rain is rare — about 1.8 wet days and 13mm across the month. Comfortable conditions for being outdoors all day.
June in Rosemead averages a daily high of 27.8°C with nights around 15.6°C. Rain is rare — about 0.5 wet days and 2.8mm across the month. Comfortable conditions for being outdoors all day.
July in Rosemead averages a daily high of 31°C with nights around 17.7°C. Rain is rare — about 0.3 wet days and 0.4mm across the month. Comfortable conditions for being outdoors all day.
August in Rosemead averages a daily high of 31.9°C with nights around 17.7°C. Rain is rare — about 0.2 wet days and 8.2mm across the month. Comfortable conditions for being outdoors all day.
September in Rosemead averages a daily high of 31.2°C with nights around 16.7°C. Rain is rare — about 0.5 wet days and 4.4mm across the month. Comfortable conditions for being outdoors all day.
October in Rosemead averages a daily high of 27.9°C with nights around 13.4°C. Rain is rare — about 1.5 wet days and 13.2mm across the month. Comfortable conditions for being outdoors all day.
November in Rosemead averages a daily high of 24.3°C with nights around 9.9°C. Rain is rare — about 2.7 wet days and 21.5mm across the month. Comfortable conditions for being outdoors all day.
December in Rosemead averages a daily high of 20.8°C with nights around 6.7°C. Expect roughly 5 wet days totalling 48.2mm. 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. Rosemead peaks at 96.
Based on 30 years of records, March–June scores highest for comfort in Rosemead, balancing daytime temperature against rainfall.
August is the warmest, averaging a daily high of 31.9°C.
February is the wettest, averaging 114.7mm of rain across roughly 6.8 wet days.
December is the coolest month, with average daily highs around 20.8°C.