The best time to visit Pacific Northwest (Seattle) is Jul–Sep. Month by month, the verdicts rate May–Sep as comfortable on both daytime heat and rainfall — 5 months in all.
Wet grey winters, glorious summers
| Month | High °C | High °F | Rainy days | Verdict |
|---|---|---|---|---|
| January | 7.2 | 45 | 63% | Too wet |
| February | 8.7 | 48 | 58% | Too wet |
| March | 10.9 | 52 | 62% | Too wet |
| April | 13.6 | 56 | 58% | Too wet |
| May | 17.4 | 63 | 42% | Go |
| June | 19.6 | 67 | 39% | Go |
| July | 23.0 | 73 | 17% | Go |
| August | 23.4 | 74 | 17% | Go |
| September | 20.9 | 70 | 30% | Go |
| October | 15.2 | 59 | 50% | Fair |
| November | 10.0 | 50 | 67% | Too wet |
| December | 6.7 | 44 | 64% | Too wet |
Verdict combines mean daytime high with rainy-day frequency. “Rainy days” is the share of days in the month with at least 1 mm of rain.
July is the driest month, with rain on 17% of days and daytime highs near 23.0°C (73°F). November is the wettest, at 67%. The warmest month is August at 23.4°C (74°F); the coolest is December at 6.7°C (44°F). The record rules out too wet in Nov–Apr.