| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | -1.5° | -7.8° | 63.1mm | 11.3 | 8 |
| February | 1° | -5.5° | 44.8mm | 10.2 | 13 |
| March | 5.1° | -3.7° | 51.3mm | 10.6 | 23 |
| April | 10.7° | -0.2° | 56mm | 10.6 | 46 |
| May | 16.8° | 5.6° | 73.7mm | 12.9 | 64 |
| June | 21° | 10.1° | 91.3mm | 13.2 | 74 |
| July | 22.4° | 11.5° | 80.1mm | 12.4 | 75 |
| August | 20.4° | 10.4° | 89.2mm | 12.7 | 75 |
| September | 16.6° | 7.7° | 94.8mm | 12.2 | 65 |
| October | 9.9° | 3.1° | 119mm | 15.3 | 38 |
| November | 4.2° | -0.9° | 84.9mm | 13.8 | 17 |
| December | 0.8° | -4.9° | 68.9mm | 11.8 | 11 |
January in Lillestrøm averages a daily high of -1.5°C with nights around -7.8°C. Expect roughly 11.3 wet days totalling 63.1mm. A hard month to visit for comfort alone.
February in Lillestrøm averages a daily high of 1°C with nights around -5.5°C. Expect roughly 10.2 wet days totalling 44.8mm. A hard month to visit for comfort alone.
March in Lillestrøm averages a daily high of 5.1°C with nights around -3.7°C. Expect roughly 10.6 wet days totalling 51.3mm. A hard month to visit for comfort alone.
April in Lillestrøm averages a daily high of 10.7°C with nights around -0.2°C. Expect roughly 10.6 wet days totalling 56mm. Demanding conditions — pack for it and plan indoor options.
May in Lillestrøm averages a daily high of 16.8°C with nights around 5.6°C. Expect roughly 12.9 wet days totalling 73.7mm. Generally workable, with some weather to plan around.
June in Lillestrøm averages a daily high of 21°C with nights around 10.1°C. Expect roughly 13.2 wet days totalling 91.3mm. Generally workable, with some weather to plan around.
July in Lillestrøm averages a daily high of 22.4°C with nights around 11.5°C. Expect roughly 12.4 wet days totalling 80.1mm. Comfortable conditions for being outdoors all day.
August in Lillestrøm averages a daily high of 20.4°C with nights around 10.4°C. Expect roughly 12.7 wet days totalling 89.2mm. Comfortable conditions for being outdoors all day.
September in Lillestrøm averages a daily high of 16.6°C with nights around 7.7°C. Expect roughly 12.2 wet days totalling 94.8mm. Generally workable, with some weather to plan around.
October in Lillestrøm averages a daily high of 9.9°C with nights around 3.1°C. Expect roughly 15.3 wet days totalling 119mm. Demanding conditions — pack for it and plan indoor options.
November in Lillestrøm averages a daily high of 4.2°C with nights around -0.9°C. Expect roughly 13.8 wet days totalling 84.9mm. A hard month to visit for comfort alone.
December in Lillestrøm averages a daily high of 0.8°C with nights around -4.9°C. Expect roughly 11.8 wet days totalling 68.9mm. 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. Lillestrøm peaks at 75.
Based on 30 years of records, June–August scores highest for comfort in Lillestrøm, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 22.4°C.
October is the wettest, averaging 119mm of rain across roughly 15.3 wet days.
January is the coolest month, with average daily highs around -1.5°C.