August weather forecast
St. Louis, MO

The weather in August carries forward the warmth and high humidity of July. Despite a slight dip in temperatures, the average remains notably high at 69.4°F (20.8°C). St. Louis continues to bask in long daylight hours, frequently punctuated by sudden bursts of summer rainstorms. The residency starts planning for the transition towards the autumn season. The prolonged summer augments the enjoyment of the city's many outdoor parks and amenities.

Temperature

As August takes its course, St. Louis's average high-temperature registers at a still tropical 88°F (31.1°C), closely aligning with the preceding month. During August, St. Louis experiences a consistent low-temperature average of 69.4°F (20.8°C).

Heat index

The heat index for August is estimated at a sweltering 100.4°F (38°C). Additional precautions are required to avert heat cramps and heat exhaustion. Persistent activity may culminate in heatstroke.
Metrics for the heat index primarily focus on shaded spots and light wind conditions. If directly exposed to the sun, the heat index could rise by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature' or 'real feel', shows a temperature sensation when both heat and moisture conditions are combined. The impact of weather is personal, differing among a variety of people based on differences in body mass, height, and the level of physical exertion. Consider that direct sun exposure can intensify the felt heat, adding potentially 15 Fahrenheit (8 Celsius) degrees to the heat index. Heat index values are quite important for babies and toddlers. Kids are generally in more danger than adults because they perspire less. Their large skin surface area compared to their small bodies and the excessive heat due to their actions raises their risk.
When temperatures rise, the human body turns to perspiration, using the cooling power of evaporating sweat. Relative humidity in excess curtails evaporation, therefore reducing heat dissipation from the body, leading to feelings of excess heat. Excessive heat that's not properly managed leads to increased body temperatures and resultant health issues.

Humidity

In August, the average relative humidity in St. Louis is 70%.

Rainfall

In St. Louis, Missouri, in August, during 8.2 rainfall days, 2.99" (76mm) of precipitation is typically accumulated. Throughout the year, in St. Louis, there are 112.6 rainfall days, and 40.94" (1040mm) of precipitation is accumulated.

Snowfall

May through October are months without snowfall in St. Louis.

Daylight

The average length of the day in August in St. Louis is 13h and 37min.
On the first day of August in St. Louis, sunrise is at 6:03 am and sunset at 8:11 pm. On the last day of the month, sunrise is at 6:29 am and sunset at 7:31 pm CDT.

Sunshine

The average sunshine in August in St. Louis is 8.7h.

UV index

The months with the highest UV index in St. Louis are June through August, with an average maximum UV index of 9. A UV Index estimate of 8 to 10 represents a very high health risk from unprotected exposure to Sun's UV rays for ordinary individuals.
Note: The daily high UV index of 9 during August translates into the following recommendations:
Be sure to take precautions. Without protection, skin might suffer damage quickly. Stay in the shade and avoid direct Sun exposure from 10 a.m. to 4 p.m., a time when UV radiation is at its strongest, and remember that parasols or canopies do not offer full protection. Equip yourself with UVA and UVB-filtering sunglasses on clear, sunny days. Even if the day is cloudy, sunscreen with SPF of at least 30 should be applied generously and reapplied often, particularly after swimming or outdoor exercise.