California · County air quality · 2025
Santa Cruz County, California
Median AQI 35 (Good). 87.7% of monitored days rated Good, direct from EPA Air Quality System stations.
- 35
- Median AQI
- 87.7%
- Good-air days
- 0
- Unhealthy days
- 76%
- Cleaner than US counties
Santa Cruz County's 2025 annual median AQI is 35 (Good), with 87.7% Good days
According to the U.S. EPA Air Quality System, Santa Cruz County, California posted a 2025 median AQI of 35 (Good) across 365 monitored days, with 87.7% rated Good and 0 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Santa Cruz County's 87.7% Good-day share places it cleaner than 76% of US counties in 2025.
- Closest median-AQI peer
- Atascosa County (76.0% Good, median AQI 35) is the closest nationwide median-AQI peer to Santa Cruz County.
- 2020–2025 trend
- Santa Cruz County's floor-qualifying Good-day share is improving from 2020 to 2025 (72.1% → 87.7%).
- Median AQI
- Median AQI: 35
According to the 2025 EPA AQS county release on PlainAirData, Santa Cruz County, California ranks #191 of 951 by median AQI (35) and #229 by good-day share (87.7%). Ponce County, Puerto Rico is #1 of 951 by median AQI (3, 91.4% Good days) at good-day-share #159 ≠ largest of 7 at 100.0% Good days #1 by good-day share (100.0%, median AQI 9) at median-AQI #7.
Annual release change
What changed in the 2025 EPA annual release
- Santa Cruz County's Good-day share rose from 80.1% to 87.7% between the 2024 and 2025 EPA annual releases, a change of +7.6 percentage points.
- Santa Cruz County's median AQI fell from 39 to 35 between the 2024 and 2025 EPA annual releases, a change of -4 points.
Data updated August 2026
- Good · 320 d · 87.7%
- Moderate · 45 d · 12.3%
How did Santa Cruz County's air break down in 2025?
Across 365 monitored days, 320 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 71 (Moderate).
EPA AQS →Share of monitored days at AQI 0-50 (Good band).
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
Where Santa Cruz County sits nationally
COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Santa Cruz County's Good-day share is 87.7% - cleaner than 76% of that comparison set.
Santa Cruz County Good-day share vs. every US county
Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
87.7% Cleaner than 76% higher than 76% of 951 US counties
Each bar is a band; taller bars hold more US counties. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source U.S. Environmental Protection Agency, Air Quality System (AQS) · 2025
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Santa Cruz County.
- Ozone · 192 days · 52.6%
- PM2.5 · 173 days · 47.4%
2024 daily-monitor rhythm in Santa Cruz County
Month-by-month median AQI from EPA day-level county monitors (366 reported days in 2024). Jun posted the highest typical readings (median AQI 49, peak 66); Sep was cleanest at median 34. Summer months (Jun–Aug) averaged median AQI 42 vs 40 in Dec–Feb.
Five-year seasonal record
EPA day-level county files · 2020–20241,827 daily readings show a recurring local pattern: Nov has the highest matched-month median AQI (44), while Jul is lowest (32). Each cell is that month’s median daily AQI, not a current-air forecast.
Lower AQI is better. The colors summarize EPA AQI bands; gaps mean the county had no day-level record for that month.
Health Impact Assessment
Santa Cruz County's air quality is rated Good based on 87.7% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 87.7% of monitored days in 2025, with a median AQI of 35. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 192 of 365 monitored days.
5-Year Air Quality Trend
Air quality is improving in Santa Cruz County. Highest Good-day share: 2025 (87.7%, 320 of 365 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 261 | 85 | 6 | 10 | 39 | 624 |
| 2021 | 298 | 67 | 0 | 0 | 37 | 80 |
| 2022 | 287 | 78 | 0 | 0 | 35 | 93 |
| 2023 | 300 | 64 | 1 | 0 | 36 | 130 |
| 2024 | 293 | 73 | 0 | 0 | 39 | 80 |
| 2025 | 320 | 45 | 0 | 0 | 35 | 71 |
How does Santa Cruz County compare?
How Santa Cruz County compares
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Santa Cruz County, California · 2020–2025
Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.
Every figure on PlainAirData is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.