Contents
- Weather in August
- Frequently asked questions
- Average temperature in August
- Average pressure in August
- Average wind speed in August
- Average humidity in August
- Average rainfall in August
- Average rainfall days in August
- Average snowfall in August
- Average snowfall days in August
- Average daylight in August
- Average sunshine in August
- Average sunshine days in August
- Average UV index in August
- Average cloud cover in August
- Average visibility in August
Weather in August
Temperature
Johnston sees the arrival of August with an average high-temperature of a still warm 81.3°F (27.4°C), indicating a subtle variation from July. Johnston records a mean low-temperature of 62.2°F (16.8°C) in August.Heat index
August's mean heat index is estimated at a tropical 87.8°F (31°C). Exhaustion is likely with prolonged exposure and activity. Sustaining activity may result in heat cramps.When referencing the heat index, its values are suitable for shady environments and light breezes. If directly exposed to the sun, the heat index could rise by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'real feel' or 'felt air temperature', provides an understanding of perceived warmth by combining temperature and relative humidity. Physical activity, clothing, and metabolic variations are additional factors that impact an individual's perception of temperature. Direct exposure to the sun's rays can enhance the felt temperature, increasing the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are essentially critical for children. Children often fail to understand the importance of rest and rehydration. Thirst is a late manifestation of dehydration - hence, it is crucial to stay hydrated, especially during ongoing physical activities.
Humidity
In Johnston, the average relative humidity in August is 79%.Rainfall
In Johnston, during August, the rain falls for 12.3 days and regularly aggregates up to 1.81" (46mm) of precipitation. Throughout the year, there are 114.6 rainfall days, and 15.51" (394mm) of precipitation is accumulated.Snowfall
In Johnston, snow does not fall in June through September.Daylight
In Johnston, the average length of the day in August is 13h and 48min.On the first day of August, sunrise is at 6:09 am and sunset at 8:32 pm. On the last day of the month, sunrise is at 6:40 am and sunset at 7:49 pm CDT.
Sunshine
In August, the average sunshine is 9.9h.UV index
In August, the average daily maximum UV index is 5. A UV Index reading of 3 to 5 represents a moderate threat to health from unsafe exposure to UV radiation for average individuals.Note: The UV index of 5 during August leads to these advisories:
Preventative actions are necessary - Suggestions to safeguard against sun damage are in order. When the Sun's UV radiation is most intense during midday, it's best to find shade and limit exposure. Arm yourself against UV rays' harm with protective apparel and UV-filtering shades.
Frequently asked questions
What is the usual temperature for Johnston in August?
What is the average humidity in August in Johnston?
How much does it rain in Johnston in August?
When it does not snow in Johnston?
What is the average length of the day in August in Johnston?
What time are sunrise and sunset in August in Johnston?
How many hours of sunshine does Johnston have in August?
What is the UV index intensity in August in Johnston?
Average temperature in August
Johnston, IA
- Average high temperature in August: 81.3°F
The warmest month (with the highest average high temperature) is July (82.4°F).
The month with the lowest average high temperature is January (27.9°F).
- Average low temperature in August: 62.2°F
The month with the highest average low temperature is July (65.1°F).
The coldest month (with the lowest average low temperature) is January (14.4°F).
Average pressure in August
Johnston, IA
- Average pressure in August: 29.96"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.88"Hg).
Average wind speed in August
Johnston, IA
- Average wind speed in August: 7mph
The windiest month (with the highest average wind speed) is April (10.4mph).
The calmest months (with the lowest average wind speed) are July and August (7mph).
Average humidity in August
Johnston, IA
- Average humidity in August: 79%
The month with the highest relative humidity is January (83%).
The month with the lowest relative humidity is October (70%).
Average rainfall in August
Johnston, IA
- Average rainfall in August: 1.81"
The wettest months (with the highest rainfall) are May and June (2.52").
The driest month (with the least rainfall) is January (0.47").
Average rainfall days in August
Johnston, IA
- Average rainfall days in August: 12.3 days
The month with the highest number of rainy days is May (16.3 days).
The month with the least rainy days is February (3.5 days).
Average snowfall in August
Johnston, IA
- Average snowfall in August: 0"
The month with the highest snowfall is January (2.2").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in August
Johnston, IA
- Average snowfall days in August: 0 days
The month with the highest number of snowfall days is January (8.4 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in August /
Average sunshine in August
Johnston, IA
- Average daylight in August: 13h and 5min
The month with the longest days is June (Average daylight: 15h and 12min).
The month with the shortest days is December (Average daylight: 9h and 12min).
- Average sunshine in August: 9h and 5min
The month with the most sunshine is July (Average sunshine: 10h and 24min).
The month with the least sunshine is January (Average sunshine: 4h and 18min).
Average sunshine days in August
Johnston, IA
- Average sunshine days in August: 15.6 days
The month with the most sunshine days is December (22.8 days).
The month with the least sunshine days is June (11.2 days).
Average UV index in August
Johnston, IA
- Average UV index in August: 5
The months with the highest UV index are June and July (UV index 6).
The month with the lowest UV index is January (UV index 1).
Average cloud cover in August
Johnston, IA
- Average cloud cover in August: 30
The month with the most cloud cover is January (Cloud cover 53).
The month with the least cloud cover is September (Cloud cover 28).
Average visibility in August
Johnston, IA
- Average visibility in August: 6mi
The months with the highest visibility are January, February, March, April, May, June, August, September, October, November and December (6mi).
The month with the lowest visibility is July (5mi).
Johnston, Iowa, USA
Weather forecast for your location
2. Allow the app to use your location
