Air Quality in San Marcos, United States
Rain
27.0°C · 69.9% humidity
27.0°
Feels 31.3°
68
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
1pm
54
54
68
4pm
64
61
59
7pm
58
57
56
10pm
55
55
55
1am
54
54
54
4am
54
54
54
7am
54
54
54
10am
54
54
Air Quality Index Trend
48h · 3 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.
69.9%
Humidity
28.5 km/h
Wind NW
1003.7 hPa
Pressure
17.4
UV Extreme
GoodModerateUSGUnhealthyVery UnhealthyHazardous
Which pollutant is driving the AQI?
PM2.5▲
20.29 µg/m³
PM10
41.15 µg/m³
050100150200300500
What is the weather forecast for San Marcos?
Temperature & Precipitation
PM2.5 Trend
48h · 3 stationsPM2.520.29 µg/m³
×1.4 WHO
Moderate
PM1041.15 µg/m³
Good
UV INDEX17.4
Extreme
Station readings (1 station within 25 km)
20.29
Median
20.29
Average
20.29
Low
20.29
High
PM2.5 µg/m³ · Model: 13.5 · Bias: -6.8
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 2026-07-21T21:45 UTC.