Weather in Perth in May

Prime time. May is about as good as Perth gets. Highs average 20.9 °C, lows 15.9 °C, and rain falls on 10 days — nothing in the month is working against you.

May ranks 8 of 12 in Perth: past the worst of the year but short of January, which is the month to book if the dates are open.

Rain on 10 days, 3 of them heavy. Enough to need a plan B, not enough to need a plan around it. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

What the averages hide

Averages flatten a month, and this one hides a few things: it never really gets hot: not one day in an average May reaches 30 °C; the day barely swings — 5 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest May day reached 27.9 °C and the coldest night fell to 11.2 °C, and the wettest single day dropped 54 mm — roughly 64% of the month's rain in one day.

May is moderately variable: 13 mm in the driest year against 190 mm in the wettest, around an average of 84 mm. Roughly two Mays in three land near that average, and the third does something else entirely.

Wind sits around 17.4 km/h — a steady breeze rather than a nuisance, and welcome on the warmer days, and humidity is unremarkable at 69%.

How May sits in the year

The month is on the way down: 2.3 °C cooler than April, with June dropping another 2 °C. The first week and the last are not the same trip.

Daylight in May

May sits at the dark end of Perth's year — 10.5 hours of daylight against 14.2 at midsummer, losing 0.7 hours across the month. Sightseeing days are genuinely shorter, and an itinerary built for summer will not fit.

Sea temperature

The sea sits at about 22.1 °C in May — comfortable for a proper swim. The sea peaks at 22.9 °C in March and bottoms out at 19 °C — water lags the air by a month or two, which is why the best swimming often comes after the best weather.

How busy it gets

Shoulder. The value months — prices ease off and you get the place closer to itself.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

May in Perth versus nearby

If Perth is one option among several, the nearby comparison is worth making. Bunbury is close enough to be a coin toss — within a degree on temperature, 2 days more rain. Geraldton is close enough to be a coin toss — within a degree on temperature, 3 days less rain.

So: May works, with January the better month by 17 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Perth

See all twelve months in Perth, or where else to go in May.