Monthly climate averages for Ballwin, United States. Based on 10-year ERA5 reanalysis data.
Cfa Humid Subtropical
Climate OverviewBallwin, United States in May has warm conditions, with highs averaging 24.1°C (75°F). Rain falls on about 14 days this month.
This month falls at the end of Spring.
Daily highs in May gradually rise from around 21°C (70°F) at the start to 26°C (79°F) by month's end.
May sees fairly even rainfall, totalling about 131 mm across the month.
Expect around 8.5h of sunshine at the start of May, increasing to 11.3h by the end.
The warmest days tend to fall around the 30th, averaging 26.3°C (79°F).
Compared to April, this month is about 5°C warmer with 2 more rainy days. Temperatures will rise further into June.
Daily averages based on historical data (2016–2025)
Daytime temperatures around 24°C (75°F) are ideal for full-day outdoor exploration. Keep afternoons flexible as tropical showers are common — they typically clear within an hour.
Rain usually comes in shorter passing showers rather than all-day rain.
2 of the last 5 yearly records were warmer than this month's long-run average.
| Month | Temp | Feels Like | Rain | Sun | Humidity | UV | Status | Details |
|---|---|---|---|---|---|---|---|---|
| January | 5°C / -3°C | 1°C / -8°C | 8days (75 mm) Wet | 5.7h Fair | 69% Muggy | 2.6 Moderate | Poor | View Details |
| February | 9°C / -1°C | 5°C / -6°C | 8days (69 mm) Wet | 7h Good | 67% Muggy | 3.7 Moderate | Poor | View Details |
| March | 15°C / 4°C | 12°C / 1°C | 12days (118 mm) Wet | 7.6h Good | 66% Muggy | 5.2 High | Fair | View Details |
| April | 19°C / 9°C | 18°C / 6°C | 12days (129 mm) Wet | 9h Good | 65% Muggy | 5.8 High | Good | View Details |
| May best | 24°C / 15°C | 25°C / 14°C | 14days (129 mm) Wet | 10h Excellent | 72% Muggy | 6.9 High | Excellent | View Details |
| June best | 30°C / 20°C | 33°C / 21°C | 10days (89 mm) Wet | 12.1h Excellent | 67% Muggy | 7.4 Very High | Excellent | View Details |
| July | 31°C / 22°C | 35°C / 25°C | 13days (107 mm) Wet | 12h Excellent | 72% Muggy | 7.4 Very High | Fair | View Details |
| August best | 30°C / 21°C | 33°C / 23°C | 11days (117 mm) Wet | 11h Excellent | 72% Muggy | 6.8 High | Good | View Details |
| September best | 28°C / 18°C | 29°C / 19°C | 7days (74 mm) Good | 10.3h Excellent | 68% Muggy | 5.8 High | Excellent | View Details |
| October best | 21°C / 12°C | 20°C / 10°C | 9days (83 mm) Wet | 7.9h Good | 67% Muggy | 4.4 Moderate | Good | View Details |
| November | 13°C / 5°C | 10°C / 1°C | 8days (70 mm) Wet | 6.9h Fair | 68% Muggy | 3 Moderate | Fair | View Details |
| December | 8°C / 0°C | 5°C / -4°C | 8days (59 mm) Wet | 5.8h Fair | 70% Muggy | 2.3 Moderate | Poor | View Details |
Summer clothing like shorts, t-shirts, and sundresses will be comfortable. Bring a light cardigan for air-conditioned spaces.
A waterproof jacket or compact umbrella is recommended for occasional showers.
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