September weather forecast
Mission Viejo, CA

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The calm waters on Lake Mission Viejo, California,
The calm waters on Lake Mission Viejo, California,

Weather in September

September, the first month of the autumn in Mission Viejo, is still a warm month, with an average temperature varying between 63.3°F (17.4°C) and 79.7°F (26.5°C).

Temperature

Mission Viejo indicates an average high-temperature of a still moderately hot 79.7°F (26.5°C) in September, showing minor variation from August's 80.8°F (27.1°C). Throughout September, Mission Viejo witnesses a consistent average low-temperature of 63.3°F (17.4°C).

Humidity

The average relative humidity in September in Mission Viejo is 63%.

Rainfall

In September, the rain falls for 4.4 days. Throughout September, 0.24" (6mm) of precipitation is accumulated. Throughout the year, there are 64.1 rainfall days, and 5.67" (144mm) of precipitation is accumulated.

Daylight

The average length of the day in September is 12h and 22min.
On the first day of the month, sunrise is at 6:25 am and sunset at 7:15 pm. On the last day of September, sunrise is at 6:44 am and sunset at 6:35 pm PDT.

Sunshine

In September, the average sunshine is 10.5h.

UV index

The months with the highest UV index are June through September, with an average maximum UV index of 6. A UV Index estimate of 6 to 7 represents a high health hazard from exposure to the Sun's UV radiation for ordinary individuals.
Note: A maximum daily UV index of 6 during September morphs into the following directions:
Adopt measures and apply sun safety strategies. Shielding from skin and eye damage is necessary. UV radiation from the sun is at its strongest between 10 a.m. and 4 p.m. Try to limit direct exposure during these hours. For effective sun eye protection, rely on sunglasses certified for UVA and UVB resistance.
Updated: Aug 24, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What are September temperatures?

In Mission Viejo, 79.7°F (26.5°C) is the average high-temperature and 63.3°F (17.4°C) is the average low-temperature during September. The average heat index (a.k.a. 'feels like', 'felt air temperature'), which takes the relative humidity and factors it into the air temperature reading, in August is evaluated at 84.2°F (29°C).

What is the average humidity in September?

The average relative humidity in September is 63%.

How many days does it rain in September?

In Mission Viejo, during September, the rain falls for 4.4 days and regularly aggregates up to 0.24" (6mm) of precipitation.

How many hours of daylight does Mission Viejo have in September?

The average day length in September is 12h and 22min.

When are sunrise and sunset in September?

On the first day of September in Mission Viejo, sunrise is at 6:25 am and sunset at 7:15 pm. On the last day of the month, sunrise is at 6:44 am and sunset at 6:35 pm PDT.

How many hours of sunshine does Mission Viejo have in September?

The average sunshine duration in September is 10.5h.

What are the months with the highest UV index?

The months with the highest UV index are June through September, with an average maximum UV index of 6.

What is the UV index intensity in September?

In Mission Viejo, the average daily maximum UV index in September is 6. A UV Index reading of 6 to 7 represents a high health vulnerability from unsafe exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Mission Viejo, CA

Average temperature in September - Mission Viejo, CA
  • Average high temperature in September: 79.7°F

The warmest month (with the highest average high temperature) is August (80.8°F).
The month with the lowest average high temperature is December (63°F).

  • Average low temperature in September: 63.3°F

The month with the highest average low temperature is August (64°F).
The coldest month (with the lowest average low temperature) is February (48.7°F).

Average pressure in September
Mission Viejo, CA

Average pressure in September - Mission Viejo, CA
  • Average pressure in September: 29.88"Hg

The month with the highest atmospheric pressure is January (30.1"Hg).
The months with the lowest atmospheric pressure are June and September (29.88"Hg).

Average wind speed in September
Mission Viejo, CA

Average wind speed in September - Mission Viejo, CA
  • Average wind speed in September: 4.6mph

The windiest month (with the highest average wind speed) is April (5.8mph).
The calmest month (with the lowest average wind speed) is August (4.5mph).

Average humidity in September
Mission Viejo, CA

Average humidity in September - Mission Viejo, CA
  • Average humidity in September: 63%

The months with the highest relative humidity are May and June (70%).
The month with the lowest relative humidity is November (56%).

Average rainfall in September
Mission Viejo, CA

Average rainfall in September - Mission Viejo, CA
  • Average rainfall in September: 0.24"

The wettest month (with the highest rainfall) is December (0.98").
The driest month (with the least rainfall) is June (0.08").

Average rainfall days in September
Mission Viejo, CA

Average rainfall days in September - Mission Viejo, CA
  • Average rainfall days in September: 4.4 days

The month with the highest number of rainy days is March (8.4 days).
The month with the least rainy days is June (2.3 days).

Average daylight in September /
Average sunshine in September
Mission Viejo, CA

Average daylight in September / Average sunshine in September - Mission Viejo, CA
  • Average daylight in September: 12h and 2min

The month with the longest days is June (Average daylight: 14h and 18min).
The month with the shortest days is December (Average daylight: 10h and 0min).

  • Average sunshine in September: 10h and 3min

The months with the most sunshine are July and August (Average sunshine: 12h and 0min).
The month with the least sunshine is December (Average sunshine: 6h and 36min).

Average sunshine days in September
Mission Viejo, CA

Average sunshine days in September - Mission Viejo, CA
  • Average sunshine days in September: 22.1 days

The months with the most sunshine days are January and August (24.4 days).
The month with the least sunshine days is May (19.5 days).

Average UV index in September
Mission Viejo, CA

Average UV index in September - Mission Viejo, CA
  • Average UV index in September: 6

The months with the highest UV index are June, July, August and September (UV index 6).
The months with the lowest UV index are January, February, March, November and December (UV index 4).

Average cloud cover in September
Mission Viejo, CA

Average cloud cover in September - Mission Viejo, CA
  • Average cloud cover in September: 11

The months with the most cloud cover are March and December (Cloud cover 25).
The month with the least cloud cover is August (Cloud cover 7).

Average visibility in September
Mission Viejo, CA

Average visibility in September - Mission Viejo, 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).

Mission Viejo, California, USA

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