Phoenix weather and climate guide

7-day forecast for Phoenix

Tonight in Phoenix, AZ brings slight chance showers and thunderstorms then chance showers and thunderstorms. Across the 8-day outlook, highs average 88°F and lows average 72°F, ranging from 67°F to 95°F. 3 of the 8 days carry at least a 30% chance of precipitation, so keep rain gear handy.

Current conditions

Observed at Phoenix, Phoenix Sky Harbor International Airport (KPHX) at 7:50 PM MST.

How hot, exactly

July averages a high of 107 °F. The all-time record is 122 °F, set in June 1990. In 2023, Phoenix recorded 31 consecutive days at or above 110 °F, and 2024 broke the record for annual days above 100. These are not anomalies anymore; they are the trend.

The dry air changes what that heat feels like. At 110 °F with 15% humidity, the heat index is close to the air temperature — sweat evaporates efficiently and the body can cool itself, provided you drink enough. This is why 110 in Phoenix is survivable in a way that 100 in Houston is not, and why the standard heat index table is less useful here than in the Southeast.

The danger in dry heat is different, not smaller. Evaporation is so efficient that you can lose a liter of water an hour without feeling wet, which makes dehydration sneak up on people. Direct sun on desert pavement pushes surface temperatures past 160 °F, hot enough to cause contact burns within seconds — Phoenix-area burn centers see a predictable summer surge in pavement contact burns, often from falls. Every summer also brings deaths among hikers who started a trail at Camelback or South Mountain in mid-morning with one small water bottle.

Monsoon season

From mid-June through September, the regional wind pattern shifts and draws moisture north from the Gulf of California and the eastern Pacific. The National Weather Service defines the North American Monsoon season as June 15 through September 30. This is when Phoenix gets roughly half its annual precipitation, delivered in violent, highly localized bursts.

A monsoon thunderstorm can drop an inch of rain on one neighborhood and nothing three miles away. Because the desert soil is baked hard and much of the metro is paved, that water runs immediately into normally dry washes and streets. Flash flooding kills people here every year, usually in vehicles. Arizona's so-called Stupid Motorist Law exists specifically to bill drivers for rescues after they drive around barricades into flooded washes.

Monsoon storms also produce outflow winds well ahead of any rain — a wall of dry, 60 mph wind arriving under a clear sky. That is what generates the dust storms.

Haboobs and dust storms

A haboob is a dust wall driven by thunderstorm outflow, and Phoenix gets several each monsoon season. They can be several thousand feet tall and miles wide, and they arrive fast enough that visibility drops from ten miles to near zero in under a minute.

The NWS issues Dust Storm Warnings for these. The correct response while driving is counterintuitive and worth memorizing: pull completely off the roadway, stop, turn off your lights and take your foot off the brake. Leaving taillights on invites a following driver to steer toward what they assume is a moving vehicle. Interstate 10 between Phoenix and Tucson has produced multi-vehicle pileups this way.

The urban heat island is unusually severe here

Phoenix has one of the most pronounced urban heat islands in the country, and it shows up mainly at night. Asphalt and concrete absorb solar energy all day and release it after sunset, so the metro core can run 10 °F or more warmer than surrounding desert overnight. The average July low has risen several degrees since the mid-twentieth century, far faster than daytime highs.

This matters medically. Human heat tolerance depends heavily on overnight recovery. When the low is 95 °F instead of 80, people without functioning air conditioning never cool down, and consecutive-day heat mortality climbs sharply. Maricopa County now tracks heat-associated deaths formally, and the counts have run in the hundreds annually in recent years.

The city's response includes a publicly funded heat response office, cool pavement coatings and a large shade-tree program — an honest attempt at a problem with no easy fix.

Winter is the payoff

From November through April, Phoenix has close to ideal weather: highs in the 60s and 70s, abundant sun, cool nights and almost no humidity. December averages 67 °F by day. Frost is uncommon in the urban core, though outlying areas do freeze.

Winter precipitation comes from Pacific storm systems and, in strong El Niño years, from atmospheric rivers that reach this far southeast. These are slow, soaking rains rather than the monsoon's cloudbursts, and they are what produce the spring wildflower displays.

One practical note: Arizona does not observe daylight saving time, so from March to November Phoenix is on the same clock as Pacific cities and an hour behind Denver. It confuses visitors constantly.

Weather hazards to know about

• Extreme heat

  May through September

  The primary cause of weather deaths in Arizona. Around 110 days above 100 °F per year, with overnight lows that increasingly stay in the 90s inside the urban core.

• Flash flooding

  Mid-June through September, and winter storm events

  Hard-baked soil and dry washes turn modest rainfall into fast-moving water. Most deaths involve vehicles crossing flooded roadways.

• Dust storms

  Monsoon season

  Visibility to zero in seconds. Pull fully off the road, stop, and turn all lights off so nobody follows you.

• Microbursts and damaging outflow winds

  Monsoon season

  Wind gusts to 70 mph ahead of storms take down trees, power lines and shade structures with little warning.

• High UV exposure

  Year-round, extreme April through September

  Low latitude, high sun angle, thin cloud cover and elevation combine for a UV index of 11 or higher on summer days.

What to wear and pack, by season

Spring (March to May)

Warm-weather clothing plus sun protection. Pleasant in March, genuinely hot by mid-May.

Summer (June to September)

Loose, light, long-sleeved sun-protective layers work better than less fabric. A hat, sunglasses, sunscreen and far more water than you think you need.

Fall (October to November)

Summer clothes for the day, a light layer for evenings once the desert cools after dark.

Winter (December to February)

Daytime shirtsleeves, a real jacket for nights. The diurnal swing is often 25 to 30 °F.