Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average snowfall days in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
The arrival of September brings an average high-temperature of a still hot 87.8°F (31°C), closely following the temperature pattern of August. Despite the intense daytime heat, Rialto sustains a steady low-temperature average of 63°F (17.2°C) during September.Heat index
September's average heat index is appraised at a hot 87.8°F (31°C). Long-lasting exposure and activity potentially induce a sense of weariness, with the risk of heat cramps.Observations indicate that the heat index values are for shady locations with light wind. Direct sunlight can cause a surge in the heat index by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature' or 'real feel', combines air temperature and relative humidity to represent a human perceived temperature equivalent. Factors such as metabolic variation, pregnancy, and physical activity play a role in one's impression of weather. Given the impact of direct sunlight, it's noteworthy that the felt temperature can rise by 15 Fahrenheit (8 Celsius) degrees. Heat index values are quite important 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 Rialto, the average relative humidity in September is 41%.Rainfall
In Rialto, during September, the rain falls for 2.5 days and regularly aggregates up to 0.12" (3mm) of precipitation. Throughout the year, in Rialto, there are 43.5 rainfall days, and 5.43" (138mm) of precipitation is accumulated.Snowfall
In Rialto, California, snow does not fall in January, March through December.Daylight
In Rialto, the average length of the day in September is 12h and 22min.On the first day of September, sunrise is at 6:23 am and sunset at 7:14 pm. On the last day of the month, sunrise is at 6:43 am and sunset at 6:34 pm PDT.
Sunshine
The average sunshine in September in Rialto is 10.7h.UV index
In September, the average daily maximum UV index in Rialto is 6. A UV Index reading of 6 to 7 represents a high threat to health from unsafe exposure to UV radiation for average individuals.Note: The maximum UV index of 6 during September leads to these instructions:
Escape overexposure. People with light skin may incur burns in fewer than 20 minutes. Remember that UV radiation from the Sun is strongest between 10 a.m. and 4 p.m. Make an effort to limit direct sun exposure during this time. To cut down UV radiation exposure by about half, sport a wide-brim hat.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
How hot does it get in Rialto in September?
What is the average humidity in September in Rialto?
How much does it rain in Rialto in September?
When it does not snow in Rialto?
What is the average length of the day in September in Rialto?
When are sunrise and sunset in September in Rialto?
How many hours of sunshine does Rialto have in September?
How high is the UV index in September in Rialto?
Average temperature in September
Rialto, CA
- Average high temperature in September: 87.8°F
The warmest month (with the highest average high temperature) is August (91.9°F).
The month with the lowest average high temperature is December (59.9°F).
- Average low temperature in September: 63°F
The month with the highest average low temperature is August (65.8°F).
The coldest month (with the lowest average low temperature) is February (43.3°F).
Average pressure in September
Rialto, CA
- Average pressure in September: 29.87"Hg
The month with the highest atmospheric pressure is January (30.1"Hg).
The month with the lowest atmospheric pressure is June (29.85"Hg).
Average wind speed in September
Rialto, CA
- Average wind speed in September: 4.5mph
The windiest month (with the highest average wind speed) is April (6.2mph).
The calmest month (with the lowest average wind speed) is September (4.5mph).
Average humidity in September
Rialto, CA
- Average humidity in September: 41%
The months with the highest relative humidity are February and March (52%).
The month with the lowest relative humidity is August (38%).
Average rainfall in September
Rialto, CA
- Average rainfall in September: 0.12"
The wettest months (with the highest rainfall) are February and December (1.14").
The driest month (with the least rainfall) is June (0.04").
Average rainfall days in September
Rialto, CA
- Average rainfall days in September: 2.5 days
The month with the highest number of rainy days is December (5.5 days).
The month with the least rainy days is June (1.3 days).
Average snowfall days in September
Rialto, CA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (0.1 days).
The months with the least snowfall days are January, March, April, May, June, July, August, September, October, November and December (0 days).
Average daylight in September /
Average sunshine in September
Rialto, CA
- Average daylight in September: 12h and 2min
The month with the longest days is June (Average daylight: 14h and 24min).
The month with the shortest days is December (Average daylight: 9h and 54min).
- Average sunshine in September: 10h and 4min
The months with the most sunshine are June and July (Average sunshine: 12h and 6min).
The month with the least sunshine is December (Average sunshine: 6h and 54min).
Average sunshine days in September
Rialto, CA
- Average sunshine days in September: 24.7 days
The month with the most sunshine days is June (27.8 days).
The month with the least sunshine days is February (22.6 days).
Average UV index in September
Rialto, CA
- Average UV index in September: 6
The months with the highest UV index are June, July and August (UV index 7).
The month with the lowest UV index is December (UV index 3).
Average cloud cover in September
Rialto, CA
- Average cloud cover in September: 6
The month with the most cloud cover is December (Cloud cover 21).
The month with the least cloud cover is August (Cloud cover 5).
Average visibility in September
Rialto, CA
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
Rialto, California, USA
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