Sydney is 5°C (9°F) warmer by day, Sydney has 11°C (19.8°F) warmer nights, Seattle gets 292 mm (11.5 in) more rain a year.
Seattle is at its warmest in July 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 June, July and August in Seattle and April, October and November in Sydney.
| Seattle | Metric | Sydney |
|---|---|---|
| 🌡️ Temperature | ||
| 21.5°C | 🌡️Average daytime high | 26.5°C |
| 2°C | 🌙Average nighttime low | 13°C |
| July | 🔥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 2°C (35.6°F) while Sydney settles near 13°C (55.4°F).
Seattle is hottest in July 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 April, October and November.
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 | -4.3 | 3.9 | 12.1 | 17.8 | 25.4🔥 | 32.9 |
| February | -4 | 4.8 | 13.6 | 18 | 24.8 | 31.6 |
| March | -1.2 | 8 | 17.2 | 16.6 | 22.9 | 29.3 |
| April | 1 | 11.5 | 22.1 | 14 | 20.1 | 26.2 |
| May | 3.7 | 14.8 | 26 | 11.4 | 17.2 | 23 |
| June | 6.7 | 17.5 | 28.3 | 9 | 14.4 | 19.8 |
| July | 9.5 | 19.9 | 30.3 | 8.4 | 14❄️ | 19.6 |
| August | 9.8 | 20🔥 | 30.2 | 8.8 | 15 | 21.2 |
| September | 6.9 | 17.5 | 28.1 | 10.3 | 17.6 | 24.9 |
| October | 2 | 12.3 | 22.5 | 12.1 | 20.1 | 28.1 |
| November | -2 | 6.8 | 15.5 | 13.5 | 21.6 | 29.8 |
| December | -4.5 | 3.7❄️ | 12 | 15.7 | 23.7 | 31.8 |
| Annual Avg | 2 | 11.7 | 21.5 | 13 | 19.7 | 26.5 |
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 26.5°C (79.7°F) against 21.5°C (70.7°F) in Seattle — roughly 5°C (9°F) warmer by day. Nights are milder in Sydney, with average lows of 13°C (55.4°F) versus 2°C (35.6°F).
Seattle is hottest in July, averaging highs of about 30.3°C (86.5°F), while Sydney peaks in January at around 32.9°C (91.2°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 -4.5°C (23.8°F), compared with 8.4°C (47.1°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 June, July and August, when average temperatures are at their mildest.
Sydney is at its most pleasant around April, October and November, 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 21.5°C (38.7°F), and narrowest in September, about 0.1°C (0.2°F).
Seattle has the bigger seasonal swing, about 16.3°C (29.3°F) between its coldest and hottest months versus 11.4°C (20.5°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.
