Perth is 6.3°C (11.3°F) warmer by day, Perth has 11°C (19.8°F) warmer nights, Seattle gets 560 mm (22 in) more rain a year.
Perth is at its warmest in January and coolest in August, while Seattle peaks in July and bottoms out in December. Month for month, Perth is the warmer of the two in 8 of 12 months.
Seattle is the wetter of the two, collecting 1,255 mm (49.4 in) of rain a year against 695 mm (27.4 in) in Perth. The most comfortable time to visit is April, May and November in Perth and June, July and August in Seattle.
| Perth | Metric | Seattle |
|---|---|---|
| 🌡️ Temperature | ||
| 27.8°C | 🌡️Average daytime high | 21.5°C |
| 13°C | 🌙Average nighttime low | 2°C |
| January | 🔥Hottest month | July |
| August | ❄️Coldest month | December |
| 🌧️ Rain | ||
| 695 mm | 🌧️Annual rainfall | 1,255 mm |
| July | ☔Wettest month | November |
| December | 🏜️Driest month | July |
| 💨 Climate | ||
| 69% | 💧Average humidity | 83% |
| 5.2 m/s | 💨Average wind speed | 0.7 m/s |
Overnight, Perth typically falls to around 13°C (55.4°F) while Seattle settles near 2°C (35.6°F).
Perth is hottest in January and coldest in August, whereas Seattle peaks in July and is coolest in December.
Perth sees the most rain in July and the least in December; Seattle is wettest in November and driest in July.
Seattle feels the more humid of the two, averaging 83% relative humidity against 69%.
For Seattle, the pick of the year is June, July and August.
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 | Perth | Seattle | ||||
|---|---|---|---|---|---|---|
| Min | Avg | Max | Min | Avg | Max | |
| January | 15.9 | 25.3 | 34.7 | -4.3 | 3.9 | 12.1 |
| February | 16.3 | 25.4🔥 | 34.5 | -4 | 4.8 | 13.6 |
| March | 15.6 | 24.4 | 33.2 | -1.2 | 8 | 17.2 |
| April | 14.3 | 21.7 | 29.1 | 1 | 11.5 | 22.1 |
| May | 12.9 | 19 | 25.1 | 3.7 | 14.8 | 26 |
| June | 11.2 | 16.6 | 22.1 | 6.7 | 17.5 | 28.3 |
| July | 10.4 | 15.5❄️ | 20.6 | 9.5 | 19.9 | 30.3 |
| August | 10 | 15.5 | 20.9 | 9.8 | 20🔥 | 30.2 |
| September | 10.4 | 16.7 | 23 | 6.9 | 17.5 | 28.1 |
| October | 11.3 | 19 | 26.8 | 2 | 12.3 | 22.5 |
| November | 12.9 | 21.7 | 30.5 | -2 | 6.8 | 15.5 |
| December | 14.6 | 24 | 33.4 | -4.5 | 3.7❄️ | 12 |
| Annual Avg | 13 | 20.4 | 27.8 | 2 | 11.7 | 21.5 |
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 Perth and Seattle feel alike; where they separate, they are genuinely different places to be.
Hover or tap any point to read the exact figures. Perth Seattle
See how Perth 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 Perth and Seattle — each drawn straight from the climate figures above.
Perth is the warmer of the two. It averages daytime highs of 27.8°C (82°F) against 21.5°C (70.7°F) in Seattle — roughly 6.3°C (11.3°F) warmer by day. Nights are milder in Perth, with average lows of 13°C (55.4°F) versus 2°C (35.6°F).
Perth is hottest in January, averaging highs of about 34.7°C (94.5°F), while Seattle peaks in July at around 30.3°C (86.5°F). That makes Perth 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 10°C (50°F) at the low point of the year in Perth.
Seattle is the wetter city, collecting about 1,255 mm (49.4 in) of rain a year versus 695 mm (27.4 in) in Perth. Perth is wettest in July and driest in December; 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 69% in Perth.
The most comfortable months in Perth are April, May and November, when average temperatures are at their mildest.
Seattle is at its most pleasant around June, July and August, based on the mildest average temperatures of the year.
Perth is the warmer city in 8 of the 12 months of the year. The gap is widest in January, about 21.4°C (38.5°F), and narrowest in September, about 0.8°C (1.4°F).
Seattle has the bigger seasonal swing, about 16.3°C (29.3°F) between its coldest and hottest months versus 9.9°C (17.8°F) in Perth — so Perth has the steadier, more even climate.
On climate alone, Perth 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 Perth and Seattle, not a single year's weather or a short-range forecast.
