Weather in Phoenix in August

The month to avoid. August is the month most people should skip in Phoenix. Daytime highs average 40.8 °C and the afternoon is not negotiable — outdoor plans move to early morning or evening.

August ranks 11 of 12 — near the bottom of Phoenix's year. November is the month that works, and the swing between the two is 67 points, which is a different holiday rather than a slightly better one.

Rain on 8 days, 0 of them heavy. Enough to need a plan B, not enough to need a plan around it. Pack for heat management rather than style: shade, water, and a schedule that gives up on the middle of the day.

What the averages hide

Averages flatten a month, and this one hides a few things: 29 days of the month clear 35 °C — that is not a heatwave, it is the month. Across the twenty years measured, the hottest August day reached 47.6 °C and the coldest night fell to 20.1 °C.

August is moderately variable: 9 mm in the driest year against 75 mm in the wettest, around an average of 33 mm. Roughly two Augusts in three land near that average, and the third does something else entirely.

Wind is light at 6.3 km/h, so the temperature on the page is close to the temperature on your skin, and the air is dry at 35% humidity, which makes the heat far more bearable than the same figure somewhere humid — and dehydrates you faster than you expect.

How August sits in the year

Temperatures hold steady either side: 41.9 °C in July, 40.8 here, 38.6 in September. Nothing about the timing within the month matters much.

Daylight in August

13.4 hours of daylight, losing 0.9 hours across the month. That is between Phoenix's extremes of 14.4 and 10 hours, so days are long enough not to constrain the plan.

An inland climate

With no coast nearby, the year swings a fair way — 35.6 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage.

How busy it gets

Off season. The genuine off season: cheapest by a distance, with the caveat that some tours and restaurants close entirely.

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

August in Phoenix versus nearby

If Phoenix is one option among several, the nearby comparison is worth making. Sedona is a better bet in August — 7.3 °C cooler, 6 days more rain. Tucson is close enough to be a coin toss — 4.2 °C cooler, 8 days more rain.

So: August is a compromise. November is 67 points better and is what Phoenix is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in Phoenix

See all twelve months in Phoenix, or where else to go in August.