UV and heat in Phoenix
In Phoenix, the average daily peak UV index is 3 or above from January to November, and reaches 10.4 in July.
The warmest month is July, with average highs of 42°C. UV figures come from five years of NASA satellite data, 2020 to 2024, and temperatures from the nearest long-running weather station.
- 10.4Average daily peak UV in July, very high
- 11Months with an average peak of UV 3 or more
- 42°CAverage high in July
- 8.4 hA day at UV 3 or more in July, on average
When is the UV index highest in Phoenix?
The sun is strongest from January to November, with the highest average peak in July. In July, about 95% of days reach a UV index of 8 or more, which the World Health Organization calls very high.
How hot and humid does Phoenix get?
Average highs range from 20°C to 42°C through the year. Relative humidity averages 17% to 47%. Day length ranges from 9.9 to 14.4 hours.
Month by month
| Month | Peak UV | Days UV 8+ | Hours UV 3+ | High | Low | Humidity | Daylight |
|---|---|---|---|---|---|---|---|
| January | 3.0 | 0% | 2.2 | 20°C | 8°C | 47% | 10.2 h |
| February | 4.7 | 0% | 4.6 | 22°C | 9°C | 43% | 11.0 h |
| March | 6.3 | 18% | 5.9 | 26°C | 13°C | 43% | 12.0 h |
| April | 8.4 | 84% | 7.0 | 31°C | 17°C | 28% | 13.0 h |
| May | 9.6 | 99% | 7.8 | 35°C | 21°C | 20% | 13.9 h |
| June | 10.3 | 98% | 8.6 | 41°C | 27°C | 17% | 14.4 h |
| July | 10.4 | 95% | 8.4 | 42°C | 30°C | 28% | 14.1 h |
| August | 9.7 | 94% | 7.4 | 41°C | 29°C | 34% | 13.4 h |
| September | 8.1 | 79% | 6.7 | 39°C | 26°C | 29% | 12.4 h |
| October | 5.9 | 0% | 5.4 | 33°C | 19°C | 27% | 11.3 h |
| November | 3.8 | 0% | 3.6 | 25°C | 12°C | 30% | 10.4 h |
| December | 2.7 | 0% | 1.6 | 20°C | 8°C | 40% | 9.9 h |
When should you protect your skin in Phoenix?
The World Health Organization advises sun protection whenever the UV index is 3 or above, and the advice gets stronger from 8. In Phoenix, that means from January to November, for about 8.4 hours around midday in July. The forecast on any day can be higher or lower than these averages, so check it each morning.
How do you protect yourself?
Cancer Council Australia recommends five steps together when the UV index is 3 or higher: slip on covering clothing, slop on SPF 50 or SPF50+ broad-spectrum, water-resistant sunscreen, slap on a hat, seek shade and slide on some sunglasses.
Clothing covers skin all day without reapplying. Sleeves usually stop at the wrist and the collar, so the backs of your hands and your neck are easy to miss; the Meriggio · Italian · say it “meh-REED-joh”The shady spot where you rest through the midday heat. has hand covers and a neck shade for those two places. Women’s fit, men’s fit.
Other cities in United States
UV and heat across United States. All cities.
Sources and data
- UV index: NASA POWER Hourly API, NASA Langley Research Center, CERES SYN1deg (UV index), MERRA-2 (temperature, humidity). Hourly values for 2020 to 2024, around 33.45, -112.07. Satellite and reanalysis grid values for the area around the city, not a single weather station. Peak UV is the mean of each day’s highest hourly UV index. Fetched 18 October 2026.
- Temperature: NOAA NCEI Global Summary of the Month, weather station PHOENIX AP (USW00023183), 6.6 km from the city centre, 2010 to 2024. Highs and lows are the average of each month’s mean daily maximum and minimum.
- Relative humidity is an area average from NASA POWER for a grid square about 55 km wide.
- Day length calculated from latitude for the 15th of each month.
- World Health Organization: Radiation, the ultraviolet (UV) index, 20 June 2022
- Cancer Council Australia: Be SunSmart