5-day weather forecast St. Louis Sep 9, 2026

37°25° · Sunny

Weather forecast St. Louis tomorrow Sep 9, 2026: sunny, temperature from 25 °C to 37 °C.

Precipitation probability 56%. Wind up to 6.11 m/s (gusts 14.11 m/s). Air humidity 27–88%, atmospheric pressure 759–762 mm Hg, UV index up to 7.7.

Weather Alerts

WarningSep 7, 05:53 PM — Sep 9, 12:00 AMTranslate with Google

Air Quality Alert issued September 7 at 5:53PM CDT by NWS St Louis MO

Air Quality Alert

The St. Louis Clean Air Partnership has issued an air quality alert for the St. Louis metropolitan area from 10 AM to 8 PM CDT Tuesday. An Orange air quality forecast means that maximum ozone concentrations are expected to reach levels that pose a health risk. Adverse health effects increase as air quality deteriorates. Ground- level ozone is an air contaminant which can cause breathing difficulties for children, older adults, as well as persons with respiratory problems. Reducing outdoor physical activity is recommended. If it is a regularly scheduled work day you are urged to consider telecommuting, carpooling, or utilizing public transit. Avoid excessive idling and do not top off when refueling motor vehicles. The use of gasoline-powered lawn equipment should be reduced or postponed until late in the day. For more information visit the St. Louis Clean Air Partnership at http://cleanair-stlouis.com/ For current Air Quality Index (AQI) values visit https://www.airnow.gov/

WarningSep 7, 03:40 PM — Sep 8, 03:45 PMTranslate with Google

Air Quality Alert issued September 7 at 3:40PM CDT by NWS St Louis MO

Air Quality Alert

5 days at a glance — tap a day to open it

Sunrise 06:37
Sunset 19:19

New Moon2% illuminated
Moonrise 04:27 · Moonset 18:26

Chart

Table

← Tue, Sep 8

Wed, Sep 9, 2026

Thu, Sep 10 →

Forecast from 25 °C to 37 °C and precipitation

Temperature & Precipitation
Time	00:00	01:00	02:00	03:00	04:00	05:00	06:00	07:00	08:00	09:00	10:00	11:00	12:00	13:00	14:00	15:00	16:00	17:00	18:00	19:00	20:00	21:00	22:00	23:00
Temperature (°C)	30	28	28	27	26	26	26	26	27	28	32	32	36	37	32	34	35	36	35	32	28	25	26	25
Precipitation (mm/hr)	0	0	0	0	0	0	0	0	0	0	0	0	0	0.24	0.55	0	0	0	0	0	0.86	0.01	0.25	0.5

Cloud cover and precipitation probability

Cloud cover & Rain chance
Time	00:00	01:00	02:00	03:00	04:00	05:00	06:00	07:00	08:00	09:00	10:00	11:00	12:00	13:00	14:00	15:00	16:00	17:00	18:00	19:00	20:00	21:00	22:00	23:00
Cloud cover (%)	7	6	2	5	0	5	2	62	91	51	99	11	27	71	84	46	0	7	29	66	100	100	100	83
Rain chance (%)	1	1	1	1	2	2	3	8	10	4	9	1	2	17	36	3	0	1	2	6	50	23	33	56

Wind speed and direction

Wind & Wind gust
Time	00:00	01:00	02:00	03:00	04:00	05:00	06:00	07:00	08:00	09:00	10:00	11:00	12:00	13:00	14:00	15:00	16:00	17:00	18:00	19:00	20:00	21:00	22:00	23:00
Wind (m/s)	3.19	4.5	4.81	4.89	4.61	4.19	4.19	3.81	3.81	3.89	3.89	3	3.19	6	4.61	2.5	2.5	1.19	2.19	1.81	6.11	4	2.89	2
Wind gust (m/s)	8.61	11.81	13.39	14.11	13.92	13.11	12.33	11.42	11.42	10.33	8.39	5.83	6.92	7	5.42	4	2.83	3.31	6.19	3.42	8.81	9.22	10.31	2.5
Wind direction (°)	S 178°	SSE 167°	S 172°	S 180°	S 184°	S 185°	S 181°	S 191°	SSW 198°	SSW 204°	SW 228°	W 281°	W 279°	WNW 293°	NW 311°	NW 321°	N 356°	NW 315°	ENE 60°	ESE 110°	W 280°	WNW 294°	WSW 253°	E 82°

Air humidity

Humidity
Time	00:00	01:00	02:00	03:00	04:00	05:00	06:00	07:00	08:00	09:00	10:00	11:00	12:00	13:00	14:00	15:00	16:00	17:00	18:00	19:00	20:00	21:00	22:00	23:00
Humidity (%)	33	33	37	45	52	54	56	57	50	42	32	31	27	28	42	35	32	31	32	47	59	77	69	88

Atmospheric pressure

Pressure
Time	00:00	01:00	02:00	03:00	04:00	05:00	06:00	07:00	08:00	09:00	10:00	11:00	12:00	13:00	14:00	15:00	16:00	17:00	18:00	19:00	20:00	21:00	22:00	23:00
Pressure (mm Hg)	761	762	762	762	762	761	761	761	762	762	762	762	761	761	761	761	760	760	759	760	761	761	761	761

Ultraviolet index

UV Index
Time	00:00	01:00	02:00	03:00	04:00	05:00	06:00	07:00	08:00	09:00	10:00	11:00	12:00	13:00	14:00	15:00	16:00	17:00	18:00	19:00	20:00	21:00	22:00	23:00
UV Index	0	0	0	0	0	0	0	0	0.5	1.5	3.2	5.2	7.3	7.7	7.2	5.5	3.5	0.9	0.3	0	0	0	0	0

Air quality & pollen

Air quality
Time	00:00	01:00	02:00	03:00	04:00	05:00	06:00	07:00	08:00	09:00	10:00	11:00	12:00	13:00	14:00	15:00	16:00	17:00	18:00	19:00	20:00	21:00	22:00	23:00
PM2.5 (µg/m³)	9.4	9.1	8.7	8.4	8.1	7.9	7.9	8	8.4	9.1	9.7	10.2	10.9	11.7	11.6	11.6	11.1	11	10.9	10.1	11.9	13.6	13.5	13.1
PM10 (µg/m³)	10	9.7	9.2	8.8	8.6	8.4	8.3	8.4	8.8	9.5	10.1	10.6	11.4	12.4	12.3	12.4	11.8	11.8	11.5	10.4	12.2	13.9	13.8	13.4
Ozone (O₃) (µg/m³)	62	62	65	69	73	72	69	73	90	113	134	149	162	167	162	150	135	118	98	79	59	39	27	30
NO₂ (µg/m³)	19.8	19.1	17	14.1	11.8	11	10.8	10.3	9	7.4	5.9	4.7	3.6	2.8	2	1.5	2.4	5.2	9.4	14.9	23.6	33.7	39.5	37.6
SO₂ (µg/m³)	2.3	2.2	2.1	2	2	1.9	1.9	2	2.2	2.6	3	3.6	4.3	4.6	4.4	3.9	3.3	2.8	2.2	1.8	1.7	1.8	2	2.2
CO (µg/m³)	173	165	158	153	149	149	152	155	159	164	164	155	141	132	129	132	141	164	194	217	227	230	229	225

← Tue, Sep 8

Wed, Sep 9, 2026

Thu, Sep 10 →

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Data Sources & Methodology

Our weather forecasts are powered by a professional weather data provider that aggregates data from national weather services, satellite observations, radar networks, and over 80,000 weather stations worldwide. Forecast data is updated multiple times daily. We convert raw data into clear summaries — wind speed in m/s, pressure in mmHg — so you can plan your day with confidence.

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