| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 8.6° | 2.9° | 138.5mm | 19.4 | 34 |
| February | 9.7° | 2.7° | 87.8mm | 16.1 | 37 |
| March | 12.1° | 4° | 98.3mm | 18.4 | 45 |
| April | 14.9° | 5.9° | 70.1mm | 15.4 | 54 |
| May | 18.5° | 9.1° | 56.6mm | 12.3 | 71 |
| June | 21.4° | 11.6° | 41.3mm | 10.4 | 79 |
| July | 25.2° | 13.8° | 14.8mm | 4.6 | 91 |
| August | 25.2° | 14.1° | 25.8mm | 5.8 | 88 |
| September | 21.8° | 11.9° | 49.3mm | 9.2 | 82 |
| October | 16° | 8.3° | 97.2mm | 15 | 57 |
| November | 11.2° | 5° | 149.1mm | 18.6 | 42 |
| December | 8.1° | 2.9° | 147.1mm | 19.9 | 32 |
January in Sammamish averages a daily high of 8.6°C with nights around 2.9°C. Expect roughly 19.4 wet days totalling 138.5mm. A hard month to visit for comfort alone.
February in Sammamish averages a daily high of 9.7°C with nights around 2.7°C. Expect roughly 16.1 wet days totalling 87.8mm. Demanding conditions — pack for it and plan indoor options.
March in Sammamish averages a daily high of 12.1°C with nights around 4°C. Expect roughly 18.4 wet days totalling 98.3mm. Demanding conditions — pack for it and plan indoor options.
April in Sammamish averages a daily high of 14.9°C with nights around 5.9°C. Expect roughly 15.4 wet days totalling 70.1mm. Demanding conditions — pack for it and plan indoor options.
May in Sammamish averages a daily high of 18.5°C with nights around 9.1°C. Expect roughly 12.3 wet days totalling 56.6mm. Generally workable, with some weather to plan around.
June in Sammamish averages a daily high of 21.4°C with nights around 11.6°C. Expect roughly 10.4 wet days totalling 41.3mm. Comfortable conditions for being outdoors all day.
July in Sammamish averages a daily high of 25.2°C with nights around 13.8°C. Expect roughly 4.6 wet days totalling 14.8mm. Comfortable conditions for being outdoors all day.
August in Sammamish averages a daily high of 25.2°C with nights around 14.1°C. Expect roughly 5.8 wet days totalling 25.8mm. Comfortable conditions for being outdoors all day.
September in Sammamish averages a daily high of 21.8°C with nights around 11.9°C. Expect roughly 9.2 wet days totalling 49.3mm. Comfortable conditions for being outdoors all day.
October in Sammamish averages a daily high of 16°C with nights around 8.3°C. Expect roughly 15 wet days totalling 97.2mm. Generally workable, with some weather to plan around.
November in Sammamish averages a daily high of 11.2°C with nights around 5°C. Expect roughly 18.6 wet days totalling 149.1mm. Demanding conditions — pack for it and plan indoor options.
December in Sammamish averages a daily high of 8.1°C with nights around 2.9°C. Expect roughly 19.9 wet days totalling 147.1mm. 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. Sammamish peaks at 91.
Based on 30 years of records, July–August scores highest for comfort in Sammamish, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 25.2°C.
November is the wettest, averaging 149.1mm of rain across roughly 18.6 wet days.
December is the coolest month, with average daily highs around 8.1°C.