Arizona Air Quality Information

2021 Phoenix Air Quality Year In Review

Hard to believe 2022 is already here! Needless to say, 2021 saw many days of exciting activity in terms of weather and air quality.

The year started fairly quiet in terms of weather. Temperatures were remaining warmer than average, and precipitation was minimal throughout the state. Sky Harbor recorded 1.06 inches of rain from January 1st to May 31st. The normal precipitation amount for this period is 2.27 inches.

Between the months of April to October, the Valley sees higher levels of ozone as a result of many contributing factors. Some of these contributions include: longer periods of sunlight, calm winds, dominating high pressure, transport from other areas, and smoke from wildfires. In 2021, for ozone, Maricopa County had 176 days land in the Good Air Quality Index (AQI) category, 138 days in the Moderate AQI level, and 51 days exceeding the federal health standard. On average (over the past ten years), the Phoenix Valley sees 43 ozone exceedances each year, so this year was slightly above average. Last year the Valley exceeded 40 times and in 2019, only 39 times.

Learn more: View year-to-date reports>

Multiple wildfires burned across the Western United States as we just endured two years of nearly non-existent monsoon seasons in 2019 and 2020.
June 15th was not only the start of an active monsoon season but also the first time in nearly 20 years (Aug 2002) ozone has reached the "Very Unhealthy" Air Quality Index (AQI) category here in the Valley. Smoke from the Telegraph Fire was the main additional influence that made this a record-breaking day in terms of air quality. To put this into context, the AQI was 203 on June 15, 2021, which is the highest we have seen since August 1992. Winds shifted out of the east in the afternoon as our monsoon pattern began to set up over the state (high pressure centered over the Four Corners Region), which created optimal conditions for smoke to move over the Valley. Relief came on June 23rd as Sky Harbor recorded the first measurable rain of the 2021 monsoon season. 0.17 inches was recorded and this was just a glimpse of what was in store for Arizona.

Tremendous amounts of rainfall landed across the state for July, August, September, and October. As much as we love to see rain here in the Valley, the heavy precipitation amounts in areas such as Flagstaff, Globe, and Gila Bend caused hazardous flooding. With drought concerns and burn scars from previous wildfires, the copious amount of moisture was unable to absorb into the ground as quickly as it was falling.

To wrap things up for the 2021 calendar year, the "Big Four" days (Christmas Eve/Day and New Years Eve/Day) all occurred without a pollutant exceeding the Federal Health Standard! These four days often have some of the worst air quality of the year. So why were values lower than normal? Because of rain from back-to-back weather systems we had come through. It was the first time since 1896 that Phoenix saw measurable rain on all four of these days! It was a great way to ring in the New Year!

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