Seattle is 2.5°C (4.5°F) warmer by day, Seattle gets 288 mm (11.3 in) more rain a year.
Chicago is at its warmest in August and coolest in January, while Seattle peaks in August and bottoms out in December. Month for month, Seattle is the warmer of the two in 7 of 12 months.
Seattle is the wetter of the two, collecting 1,255 mm (49.4 in) of rain a year against 967 mm (38.1 in) in Chicago. The most comfortable time to visit is July, August and September in Chicago and July, August and September in Seattle.
| Chicago | Metric | Seattle |
|---|---|---|
| 🌡️ Temperature | ||
| 54°F | 🌡️Average daytime high | 58.5°F |
| 43.9°F | 🌙Average nighttime low | 43.9°F |
| August | 🔥Hottest month | August |
| January | ❄️Coldest month | December |
| 🌧️ Rain | ||
| 38.1 in | 🌧️Annual rainfall | 49.4 in |
| May | ☔Wettest month | November |
| January | 🏜️Driest month | July |
| 💨 Climate | ||
| 81% | 💧Average humidity | 83% |
| 4.4 m/s | 💨Average wind speed | 0.7 m/s |
Overnight, Chicago typically falls to around 6.6°C (43.9°F) while Seattle settles near 6.6°C (43.9°F).
Chicago is hottest in August and coldest in January, whereas Seattle peaks in August and is coolest in December.
Chicago sees the most rain in May and the least in January; Seattle is wettest in November and driest in July.
Seattle feels the more humid of the two, averaging 83% relative humidity against 81%.
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 | Chicago | Seattle | ||||
|---|---|---|---|---|---|---|
| Min | Avg | Max | Min | Avg | Max | |
| January | 22.1 | 26.6❄️ | 31.1 | 35.1 | 40.1 | 45 |
| February | 23.7 | 28.4 | 33.1 | 34.9 | 41 | 47.1 |
| March | 30.9 | 36 | 41 | 37.8 | 44.8 | 51.6 |
| April | 38.5 | 44.1 | 49.6 | 40.8 | 48.6 | 56.5 |
| May | 47.1 | 52.9 | 58.6 | 46.2 | 54.7 | 63 |
| June | 57.9 | 63.5 | 69.1 | 50.7 | 59.2 | 67.6 |
| July | 66.2 | 71.1 | 75.9 | 55 | 64.2 | 73.2 |
| August | 66.6 | 71.4🔥 | 76.1 | 55.8 | 64.9🔥 | 74.3 |
| September | 60.1 | 65.3 | 70.5 | 51.4 | 60.4 | 69.4 |
| October | 48.7 | 54 | 59.2 | 45 | 52.2 | 59.5 |
| November | 37.4 | 42.1 | 46.6 | 38.8 | 44.2 | 49.6 |
| December | 27.7 | 31.6 | 35.8 | 34.3 | 39❄️ | 43.7 |
| Annual Avg | 43.9 | 48.9 | 54 | 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 Chicago and Seattle feel alike; where they separate, they are genuinely different places to be.
Hover or tap any point to read the exact figures. Chicago Seattle
See how Chicago 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 Chicago 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 12.2°C (54°F) in Chicago — roughly 2.5°C (4.5°F) warmer by day.
Chicago is hottest in August, averaging highs of about 24.5°C (76.1°F), while Seattle peaks in August at around 23.5°C (74.3°F). That makes Chicago the hotter of the two at the height of summer.
Chicago gets colder. In its coldest month (January) overnight lows average about -5.5°C (22.2°F), compared with 1.3°C (34.4°F) at the low point of the year in Seattle.
Seattle is the wetter city, collecting about 1,255 mm (49.4 in) of rain a year versus 967 mm (38.1 in) in Chicago. Chicago is wettest in May and driest in January; 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 81% in Chicago.
The most comfortable months in Chicago are July, August and September, 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.
Seattle is the warmer city in 7 of the 12 months of the year. The gap is widest in January, about 7.5°C (13.5°F), and narrowest in May, about 1°C (1.8°F).
Chicago has the bigger seasonal swing, about 24.9°C (44.8°F) between its coldest and hottest months versus 14.4°C (25.9°F) in Seattle — so Seattle has the steadier, more even climate.
It depends what matters most to you: choose Seattle for warmer weather and pick Chicago if you prefer drier conditions. There is no single "better" climate — it comes down to whether you value warmth, dryness or comfort most.
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 Chicago and Seattle, not a single year's weather or a short-range forecast.
