Air Quality in San Marcos, United States
Windy
38.1°C · 31.9% humidity
38.1°
Feels 38.1°
70
Moderate
Unusually sensitive people should consider reducing prolonged outdoor exertion.
1 station
Nearby Monitoring Stations
San Marcos's air quality — share it
AQI Forecast
54
12pm
54
54
70
3pm
65
62
60
6pm
58
57
56
9pm
56
55
55
12am
55
54
54
3am
54
54
54
6am
54
54
54
9am
54
54
Air Quality Index Trend
48h · 4 stnSan Marcos's air quality is primarily affected by vehicle emissions and industrial activity. Seasonal wildfire smoke and weather patterns can cause periodic air quality deterioration. Current PM2.5 concentration in San Marcos is 1.4× the WHO 24-hour guideline of 15 µg/m³.
31.9%
Humidity
55.3 km/h
Wind SSW
1005.3 hPa
Pressure
24.9
UV Extreme
GoodModerateUSGUnhealthyVery UnhealthyHazardous
Which pollutant is driving the AQI?
PM2.5▲
21.0 µg/m³
PM10
41.15 µg/m³
050100150200300500
What is the weather forecast for San Marcos?
Temperature & Precipitation
PM2.5 Trend
48h · 4 stationsPM2.521.0 µg/m³
×1.4 WHO
Moderate
PM1041.15 µg/m³
Good
UV INDEX24.9
Extreme
Station readings (1 station within 25 km)
21.0
Median
21.0
Average
21.0
Low
21.0
High
PM2.5 µg/m³ · Model: 13.5 · Bias: -7.5
What is the 7-day forecast for San Marcos?
07-21
38.1° 24.0°
1.37 mm
07-22
35.1° 22.9°
7.37 mm
07-23
37.9° 20.4°
5.75 mm
07-24
35.0° 23.5°
0.19 mm
07-25
35.3° 22.9°
07-26
36.3° 22.5°
07-27
37.0° 25.1°
Both models agree
Avg diff: 2.9°C
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Data sources: AQI from ground-level monitoring stations via AQICN. Weather forecast from ECMWF (IFS & CAMS models). AQI calculated using US EPA standard. Updated 2026-07-21T20:55 UTC.