| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 8.1° | 2.5° | 87.8mm | 18.4 | 32 |
| February | 8.9° | 2.7° | 73.2mm | 16.2 | 34 |
| March | 10.4° | 3.4° | 73mm | 15.9 | 39 |
| April | 12.7° | 5° | 58.4mm | 14 | 49 |
| May | 15.5° | 7.4° | 65.7mm | 14.9 | 56 |
| June | 17.9° | 10.2° | 77.1mm | 13.8 | 66 |
| July | 19.4° | 11.8° | 75.4mm | 14.9 | 68 |
| August | 19.2° | 11.8° | 88.3mm | 16.5 | 67 |
| September | 17.2° | 10.3° | 77mm | 14.4 | 62 |
| October | 14° | 7.9° | 109.4mm | 17.9 | 51 |
| November | 10.7° | 4.8° | 102mm | 18.9 | 40 |
| December | 8.5° | 2.9° | 94.4mm | 18.3 | 33 |
January in Castlereagh averages a daily high of 8.1°C with nights around 2.5°C. Expect roughly 18.4 wet days totalling 87.8mm. A hard month to visit for comfort alone.
February in Castlereagh averages a daily high of 8.9°C with nights around 2.7°C. Expect roughly 16.2 wet days totalling 73.2mm. A hard month to visit for comfort alone.
March in Castlereagh averages a daily high of 10.4°C with nights around 3.4°C. Expect roughly 15.9 wet days totalling 73mm. Demanding conditions — pack for it and plan indoor options.
April in Castlereagh averages a daily high of 12.7°C with nights around 5°C. Expect roughly 14 wet days totalling 58.4mm. Demanding conditions — pack for it and plan indoor options.
May in Castlereagh averages a daily high of 15.5°C with nights around 7.4°C. Expect roughly 14.9 wet days totalling 65.7mm. Generally workable, with some weather to plan around.
June in Castlereagh averages a daily high of 17.9°C with nights around 10.2°C. Expect roughly 13.8 wet days totalling 77.1mm. Generally workable, with some weather to plan around.
July in Castlereagh averages a daily high of 19.4°C with nights around 11.8°C. Expect roughly 14.9 wet days totalling 75.4mm. Generally workable, with some weather to plan around.
August in Castlereagh averages a daily high of 19.2°C with nights around 11.8°C. Expect roughly 16.5 wet days totalling 88.3mm. Generally workable, with some weather to plan around.
September in Castlereagh averages a daily high of 17.2°C with nights around 10.3°C. Expect roughly 14.4 wet days totalling 77mm. Generally workable, with some weather to plan around.
October in Castlereagh averages a daily high of 14°C with nights around 7.9°C. Expect roughly 17.9 wet days totalling 109.4mm. Demanding conditions — pack for it and plan indoor options.
November in Castlereagh averages a daily high of 10.7°C with nights around 4.8°C. Expect roughly 18.9 wet days totalling 102mm. Demanding conditions — pack for it and plan indoor options.
December in Castlereagh averages a daily high of 8.5°C with nights around 2.9°C. Expect roughly 18.3 wet days totalling 94.4mm. A hard month to visit for comfort alone.
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. Castlereagh peaks at 68.
Based on 30 years of records, June–September scores highest for comfort in Castlereagh, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 19.4°C.
October is the wettest, averaging 109.4mm of rain across roughly 17.9 wet days.
January is the coolest month, with average daily highs around 8.1°C.