Seattle is 0.6°C (1.1°F) warmer by day, Seattle has 2.1°C (3.8°F) warmer nights, and both get similar annual rainfall.
Boston is at its warmest in July and coolest in January, while Seattle peaks in August and bottoms out in December. Month for month, Boston is the warmer of the two in 6 of 12 months.
Both collect a similar amount of rain over the year — 1,213 mm (47.8 in) in Boston and 1,255 mm (49.4 in) in Seattle. The most comfortable time to visit is June, July and August in Boston and July, August and September in Seattle.
| Boston | Metric | Seattle |
|---|---|---|
| 🌡️ Temperature | ||
| 57.4°F | 🌡️Average daytime high | 58.5°F |
| 40.1°F | 🌙Average nighttime low | 43.9°F |
| July | 🔥Hottest month | August |
| January | ❄️Coldest month | December |
| 🌧️ Rain | ||
| 47.8 in | 🌧️Annual rainfall | 49.4 in |
| October | ☔Wettest month | November |
| February | 🏜️Driest month | July |
| 💨 Climate | ||
| 80% | 💧Average humidity | 83% |
| 0.7 m/s | 💨Average wind speed | 0.7 m/s |
Overnight, Boston typically falls to around 4.5°C (40.1°F) while Seattle settles near 6.6°C (43.9°F).
Boston is hottest in July and coldest in January, whereas Seattle peaks in August and is coolest in December.
Boston sees the most rain in October and the least in February; Seattle is wettest in November and driest in July.
Seattle feels the more humid of the two, averaging 83% relative humidity against 80%.
For Seattle, the pick of the year is July, August and September.
Month by month, here is the coldest night, the average day and the hottest afternoon each city can expect. Switch Compare to read rainfall, humidity, wind or solar instead, and Period to move between the long-term 45-year average and any single year — the shading is a quick warm-to-cool guide.
| Month | Boston | Seattle | ||||
|---|---|---|---|---|---|---|
| Min | Avg | Max | Min | Avg | Max | |
| January | 17.8 | 25❄️ | 32.4 | 35.1 | 40.1 | 45 |
| February | 19.4 | 27.1 | 34.9 | 34.9 | 41 | 47.1 |
| March | 26.4 | 34.7 | 43 | 37.8 | 44.8 | 51.6 |
| April | 35.8 | 45.1 | 54.5 | 40.8 | 48.6 | 56.5 |
| May | 46.4 | 55.9 | 65.5 | 46.2 | 54.7 | 63 |
| June | 55.9 | 65.1 | 74.3 | 50.7 | 59.2 | 67.6 |
| July | 62.4 | 71.8🔥 | 81.1 | 55 | 64.2 | 73.2 |
| August | 61.3 | 71.1 | 80.8 | 55.8 | 64.9🔥 | 74.3 |
| September | 54.1 | 64 | 73.8 | 51.4 | 60.4 | 69.4 |
| October | 43.7 | 52.5 | 61.5 | 45 | 52.2 | 59.5 |
| November | 33.8 | 41.5 | 49.3 | 38.8 | 44.2 | 49.6 |
| December | 24.8 | 31.5 | 38.1 | 34.3 | 39❄️ | 43.7 |
| Annual Avg | 40.1 | 48.7 | 57.4 | 43.9 | 51.1 | 58.5 |
Min / mean / max temperature (°F). 🔥 marks each city's hottest month, ❄️ its coldest; shading runs cool blue to warm red.
The same figures plotted out, so the shape of a typical year is easier to see than in a grid. Where the two lines run close together Boston and Seattle feel alike; where they separate, they are genuinely different places to be.
Hover or tap any point to read the exact figures. Boston Seattle
See how Boston and Seattle stack up against other cities. Swipe for more.
Choose which city to keep, then search for any other city in our database — we'll build the comparison for you.
Quick answers to the questions people ask most when comparing Boston and Seattle — each drawn straight from the climate figures above.
Seattle is the warmer of the two. It averages daytime highs of 14.7°C (58.5°F) against 14.1°C (57.4°F) in Boston — roughly 0.6°C (1.1°F) warmer by day. Nights are milder in Seattle, with average lows of 6.6°C (43.9°F) versus 4.5°C (40.1°F).
Boston is hottest in July, averaging highs of about 27.3°C (81.1°F), while Seattle peaks in August at around 23.5°C (74.3°F). That makes Boston the hotter of the two at the height of summer.
Boston gets colder. In its coldest month (January) overnight lows average about -7.9°C (17.7°F), compared with 1.3°C (34.4°F) at the low point of the year in Seattle.
They get a similar amount of rain over a year — about 1,213 mm (47.8 in) in Boston and 1,255 mm (49.4 in) in Seattle. Boston is wettest in October and driest in February; Seattle is wettest in November and driest in July.
Seattle is the more humid of the two, averaging 83% relative humidity over the year against 80% in Boston.
The most comfortable months in Boston are June, July and August, when average temperatures are at their mildest.
Seattle is at its most pleasant around July, August and September, based on the mildest average temperatures of the year.
Boston is the warmer city in 6 of the 12 months of the year. The gap is widest in January, about 8.4°C (15.1°F), and narrowest in October, about 0.2°C (0.4°F).
Boston has the bigger seasonal swing, about 26°C (46.8°F) between its coldest and hottest months versus 14.4°C (25.9°F) in Seattle — so Seattle has the steadier, more even climate.
On climate alone, Seattle comes out ahead — it offers warmer days than Boston. Boston is the better fit only if you'd actually prefer cooler weather.
Every figure on this page is calculated from NASA POWER satellite climate data spanning 1981–2025 (45 years). The averages describe the long-term climate of Boston and Seattle, not a single year's weather or a short-range forecast.
