| Climate data for St. Louis, Missouri (Lambert–St. Louis Int'l), 1991−2020 normals,[a] extremes 1874−present[b] | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Record high °F (°C) | 77 (25) |
85 (29) |
92 (33) |
93 (34) |
98 (37) |
108 (42) |
115 (46) |
110 (43) |
104 (40) |
94 (34) |
86 (30) |
76 (24) |
115 (46) |
| Mean maximum °F (°C) | 64.7 (18.2) |
71.0 (21.7) |
79.4 (26.3) |
86.4 (30.2) |
90.4 (32.4) |
95.5 (35.3) |
99.2 (37.3) |
99.1 (37.3) |
93.4 (34.1) |
87.0 (30.6) |
75.5 (24.2) |
66.9 (19.4) |
100.7 (38.2) |
| Mean daily maximum °F (°C) | 40.4 (4.7) |
45.8 (7.7) |
56.6 (13.7) |
68.0 (20.0) |
77.1 (25.1) |
85.9 (29.9) |
89.6 (32.0) |
88.3 (31.3) |
81.1 (27.3) |
69.2 (20.7) |
55.5 (13.1) |
44.5 (6.9) |
66.8 (19.3) |
| Daily mean °F (°C) | 32.1 (0.1) |
36.7 (2.6) |
46.6 (8.1) |
57.5 (14.2) |
67.5 (19.7) |
76.5 (24.7) |
80.4 (26.9) |
78.8 (26.0) |
71.0 (21.7) |
59.1 (15.1) |
46.5 (8.1) |
36.5 (2.5) |
57.4 (14.1) |
| Mean daily minimum °F (°C) | 23.8 (−4.6) |
27.6 (−2.4) |
36.7 (2.6) |
47.0 (8.3) |
57.9 (14.4) |
67.2 (19.6) |
71.1 (21.7) |
69.3 (20.7) |
60.9 (16.1) |
49.1 (9.5) |
37.4 (3.0) |
28.5 (−1.9) |
48.0 (8.9) |
| Mean minimum °F (°C) | 4.4 (−15.3) |
9.6 (−12.4) |
17.8 (−7.9) |
32.2 (0.1) |
43.5 (6.4) |
55.5 (13.1) |
61.4 (16.3) |
60.1 (15.6) |
47.1 (8.4) |
33.6 (0.9) |
22.0 (−5.6) |
11.0 (−11.7) |
1.2 (−17.1) |
| Record low °F (°C) | −22 (−30) |
−18 (−28) |
−5 (−21) |
20 (−7) |
31 (−1) |
43 (6) |
51 (11) |
47 (8) |
32 (0) |
21 (−6) |
1 (−17) |
−16 (−27) |
−22 (−30) |
| Average precipitation inches (mm) | 2.59 (66) |
2.23 (57) |
3.50 (89) |
4.73 (120) |
4.82 (122) |
4.49 (114) |
3.93 (100) |
3.38 (86) |
2.96 (75) |
3.15 (80) |
3.42 (87) |
2.50 (64) |
41.70 (1,059) |
| Average snowfall inches (cm) | 5.7 (14) |
4.3 (11) |
2.3 (5.8) |
0.2 (0.51) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.9 (2.3) |
3.2 (8.1) |
16.6 (42) |
| Average precipitation days (≥ 0.01 in) | 9.3 | 8.7 | 10.8 | 11.5 | 12.6 | 9.8 | 8.9 | 8.4 | 7.3 | 8.5 | 9.0 | 9.0 | 113.8 |
| Average snowy days (≥ 0.1 in) | 4.7 | 3.9 | 1.7 | 0.2 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.8 | 3.2 | 14.5 |
| Average relative humidity (%) | 73.0 | 72.0 | 68.3 | 63.5 | 66.5 | 67.1 | 68.0 | 70.0 | 71.6 | 68.7 | 72.2 | 75.8 | 69.7 |
| Average dew point °F (°C) | 20.1 (−6.6) |
24.1 (−4.4) |
33.1 (0.6) |
42.3 (5.7) |
52.9 (11.6) |
62.1 (16.7) |
66.6 (19.2) |
65.1 (18.4) |
58.6 (14.8) |
46.0 (7.8) |
36.0 (2.2) |
25.5 (−3.6) |
44.4 (6.9) |
| Mean monthly sunshine hours | 161.2 | 158.3 | 198.3 | 223.5 | 266.5 | 291.9 | 308.9 | 269.8 | 236.1 | 208.4 | 140.9 | 129.9 | 2,593.7 |
| Percent possible sunshine | 53 | 53 | 53 | 56 | 60 | 66 | 68 | 64 | 63 | 60 | 47 | 44 | 58 |
| Average ultraviolet index | 1.7 | 2.7 | 4.5 | 6.4 | 7.9 | 9.0 | 9.1 | 8.2 | 6.3 | 4.0 | 2.3 | 1.6 | 5.3 |
| Source 1: NOAA (relative humidity, dew point, and sun 1961−1990)[2][3][4] | |||||||||||||
| Source 2: UV Index Today (1995 to 2022)[5] | |||||||||||||
- ^ Mean monthly maxima and minima (i.e. the highest and lowest temperature readings during an entire month or year) calculated based on data at said location from 1991 to 2020.
- ^ Official records for St. Louis were kept at the Weather Bureau Office from January 1874 to December 1892, Eads Bridge from January 1893 to December 1929, and at Lambert–St. Louis Int'l since January 1930.[1]
- ^ ThreadEx
- ^ "Station Name: MO ST LOUIS LAMBERT INTL AP". U.S. Climate Normals 2020: U.S. Monthly Climate Normals (1991–2020). National Oceanic and Atmospheric Administration. Retrieved July 22, 2021.
- ^ "NowData – NOAA Online Weather Data". National Oceanic and Atmospheric Administration. Retrieved July 22, 2021.
- ^ "WMO Climate Normals for ST. LOUIS/LAMBERT, MO 1961–1990". National Oceanic and Atmospheric Administration. Retrieved July 22, 2021.
- ^ "Historical UV Index Data - St. Louis, MO". UV Index Today. Retrieved April 22, 2023.