Sydney is 6.4°C (11.5°F) warmer by day, Sydney has 9.5°C (17.1°F) warmer nights, Seattle gets 292 mm (11.5 in) more rain a year.
Seattle is at its warmest in August and coolest in December, while Sydney peaks in January and bottoms out in July. Month for month, Sydney is the warmer of the two in 9 of 12 months.
Seattle is the wetter of the two, collecting 1,255 mm (49.4 in) of rain a year against 963 mm (37.9 in) in Sydney. The most comfortable time to visit is July, August and September in Seattle and March, April and December in Sydney.
| Seattle | Metric | Sydney |
|---|---|---|
| 🌡️ Temperature | ||
| 14.7°C | 🌡️Average daytime high | 21.1°C |
| 6.6°C | 🌙Average nighttime low | 16.1°C |
| August | 🔥Hottest month | January |
| December | ❄️Coldest month | July |
| 🌧️ Rain | ||
| 1,255 mm | 🌧️Annual rainfall | 963 mm |
| November | ☔Wettest month | February |
| July | 🏜️Driest month | September |
| 💨 Climate | ||
| 83% | 💧Average humidity | 73% |
| 0.7 m/s | 💨Average wind speed | 3.2 m/s |
Overnight, Seattle typically falls to around 6.6°C (43.9°F) while Sydney settles near 16.1°C (61°F).
Seattle is hottest in August and coldest in December, whereas Sydney peaks in January and is coolest in July.
Seattle sees the most rain in November and the least in July; Sydney is wettest in February and driest in September.
Seattle feels the more humid of the two, averaging 83% relative humidity against 73%.
For Sydney, the pick of the year is March, April and December.
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 | Seattle | Sydney | ||||
|---|---|---|---|---|---|---|
| Min | Avg | Max | Min | Avg | Max | |
| January | 1.7 | 4.5 | 7.2 | 20.2 | 22.8🔥 | 25.4 |
| February | 1.6 | 5 | 8.4 | 20.5 | 22.8 | 25.1 |
| March | 3.2 | 7.1 | 10.9 | 19.6 | 21.8 | 24 |
| April | 4.9 | 9.2 | 13.6 | 17.5 | 19.7 | 21.9 |
| May | 7.9 | 12.6 | 17.2 | 15 | 17.2 | 19.3 |
| June | 10.4 | 15.1 | 19.8 | 12.6 | 14.7 | 16.8 |
| July | 12.8 | 17.9 | 22.9 | 11.4 | 13.8❄️ | 16.1 |
| August | 13.2 | 18.3🔥 | 23.5 | 11.7 | 14.4 | 17.1 |
| September | 10.8 | 15.8 | 20.8 | 13.4 | 16.3 | 19.3 |
| October | 7.2 | 11.2 | 15.3 | 15.2 | 18.2 | 21.2 |
| November | 3.8 | 6.8 | 9.8 | 16.9 | 19.7 | 22.5 |
| December | 1.3 | 3.9❄️ | 6.5 | 18.7 | 21.5 | 24.3 |
| Annual Avg | 6.6 | 10.6 | 14.7 | 16.1 | 18.6 | 21.1 |
Min / mean / max temperature (°C). 🔥 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 Seattle and Sydney feel alike; where they separate, they are genuinely different places to be.
Hover or tap any point to read the exact figures. Seattle Sydney
See how Seattle and Sydney 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 Seattle and Sydney — each drawn straight from the climate figures above.
Sydney is the warmer of the two. It averages daytime highs of 21.1°C (70°F) against 14.7°C (58.5°F) in Seattle — roughly 6.4°C (11.5°F) warmer by day. Nights are milder in Sydney, with average lows of 16.1°C (61°F) versus 6.6°C (43.9°F).
Seattle is hottest in August, averaging highs of about 23.5°C (74.3°F), while Sydney peaks in January at around 25.4°C (77.7°F). That makes Sydney the hotter of the two at the height of summer.
Seattle gets colder. In its coldest month (December) overnight lows average about 1.3°C (34.4°F), compared with 11.4°C (52.6°F) at the low point of the year in Sydney.
Seattle is the wetter city, collecting about 1,255 mm (49.4 in) of rain a year versus 963 mm (37.9 in) in Sydney. Seattle is wettest in November and driest in July; Sydney is wettest in February and driest in September.
Seattle is the more humid of the two, averaging 83% relative humidity over the year against 73% in Sydney.
The most comfortable months in Seattle are July, August and September, when average temperatures are at their mildest.
Sydney is at its most pleasant around March, April and December, based on the mildest average temperatures of the year.
Sydney is the warmer city in 9 of the 12 months of the year. The gap is widest in January, about 18.3°C (32.9°F), and narrowest in June, about 0.4°C (0.7°F).
Seattle has the bigger seasonal swing, about 14.4°C (25.9°F) between its coldest and hottest months versus 9°C (16.2°F) in Sydney — so Sydney has the steadier, more even climate.
On climate alone, Sydney comes out ahead — it offers warmer days, less rain and lower humidity than Seattle. Seattle is the better fit only if you'd actually prefer cooler weather, more rainfall and a more humid climate.
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 Seattle and Sydney, not a single year's weather or a short-range forecast.
