Ojai
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ojai clear sky chart from 2005-11-06 to 2026-04-17.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	4 3 1 3 2 2 3 3 4 5% 71%	139793
	Night	5% 3 1 3 2 2 3 3 4 5% 72%	139903
Transparency	Day	16% 4 5% 18% 29% 28%	134875
	Night	16% 3 5% 17% 28% 30%	135795
Seeing	Day	6% 8% 27% 37% 17% 5%	17496
	Night	5% 3 16% 35% 32% 9%	27318

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	10% 3 1 3 2 2 2 2 3 4 67%	4824
	11th to 20th	Day	5% 2 1 2 2 2 2 2 3 6% 75%	5340
	21st to end	Day	7% 4 1 4 3 3 4 4 6% 9% 56%	6004
February	1st to 10th	Day	9% 5% 2 3 3 3 2 3 4 5% 61%	2100
	11th to 20th	Day	9% 3 1 3 3 3 3 2 5% 8% 60%	2050
	21st to end	Day	8% 4 1 4 3 3 3 3 4 7% 60%	1730
March	1st to 10th	Day	12% 4 1 4 3 3 3 3 4 6% 57%	4618
	11th to 20th	Day	8% 3 1 4 3 3 3 3 4 5% 63%	4970
	21st to end	Day	5% 5% 2 5% 4 4 5% 4 6% 8% 51%	6027
April	1st to 10th	Day	5% 3 1 4 3 3 3 2 5% 8% 62%	2520
	11th to 20th	Day	4 4 1 4 3 3 3 3 4 7% 64%	2442
	21st to end	Day	4 4 2 3 3 2 2 3 5% 7% 67%	2400
May	1st to 10th	Day	4 5% 2 6% 2 2 3 3 3 4 65%	5440
	11th to 20th	Day	2 6% 2 3 2 4 4 3 5% 6% 62%	5792
	21st to end	Day	2 6% 2 5% 3 2 3 3 4 6% 65%	6440
June	1st to 10th	Day	3 4 2 4 3 3 3 3 4 7% 65%	2800
	11th to 20th	Day	2 2 1 3 2 2 2 2 4 7% 74%	2800
	21st to end	Day	2 1 1 2 2 2 2 3 4 82%	2800
July	1st to 10th	Day	1 1 1 1 1 2 3 89%	6319
	11th to 20th	Day	1 1 2 1 2 2 3 3 4 81%	6145
	21st to end	Day	1 1 1 2 1 2 1 2 2 3 84%	6196
August	1st to 10th	Day	1 1 1 2 1 2 2 2 3 4 82%	5346
	11th to 20th	Day	1 1 1 1 3 2 3 87%	5364
	21st to end	Day	1 1 1 1 1 2 1 2 3 88%	5984
September	1st to 10th	Day	1 1 1 2 1 2 2 2 4 4 81%	2400
	11th to 20th	Day	2 1 1 2 2 2 3 2 3 4 80%	2316
	21st to end	Day	1 2 1 2 2 2 2 2 3 4 80%	2200
October	1st to 10th	Day	2 1 1 1 1 1 2 1 3 4 83%	3518
	11th to 20th	Day	2 1 1 2 3 3 3 4 4 5% 73%	3261
	21st to end	Day	2 3 1 3 3 3 3 2 4 4 72%	3558
November	1st to 10th	Day	2 2 1 2 2 2 2 2 4 4 76%	1889
	11th to 20th	Day	6% 3 1 3 2 2 3 2 4 6% 68%	1890
	21st to end	Day	4 2 1 3 3 4 3 3 4 7% 64%	1890
December	1st to 10th	Day	4 3 1 3 2 4 4 3 5% 7% 65%	3040
	11th to 20th	Day	12% 4 2 4 2 3 4 3 5% 6% 55%	3288
	21st to end	Day	9% 4 1 5% 4 3 4 3 6% 8% 53%	4092
January	1st to 10th	Night	10% 4 1 3 2 2 2 2 3 4 65%	8060
	11th to 20th	Night	4 2 1 3 2 2 3 2 3 6% 73%	7650
	21st to end	Night	8% 4 2 5% 3 3 4 3 5% 6% 57%	8203
February	1st to 10th	Night	9% 5% 2 4 2 2 2 2 3 5% 64%	2520
	11th to 20th	Night	8% 3 1 3 2 2 3 2 4 6% 64%	2458
	21st to end	Night	9% 4 1 3 3 3 3 3 3 5% 63%	2076
March	1st to 10th	Night	8% 5% 1 4 3 3 3 3 5% 7% 58%	5496
	11th to 20th	Night	6% 3 1 4 3 3 3 3 4 6% 65%	5245
	21st to end	Night	9% 4 2 4 3 3 4 2 4 5% 59%	5189
April	1st to 10th	Night	6% 3 1 3 3 2 3 2 4 6% 66%	2100
	11th to 20th	Night	4 3 1 3 2 2 2 3 5% 6% 70%	2039
	21st to end	Night	3 3 1 3 2 3 3 3 3 6% 71%	2000
May	1st to 10th	Night	1 3 1 5% 3 3 3 3 4 4 70%	4560
	11th to 20th	Night	1 2 2 3 2 2 3 3 4 4 75%	4123
	21st to end	Night	1 2 1 2 2 1 3 2 3 4 80%	4438
June	1st to 10th	Night	1 3 1 2 1 3 3 3 4 6% 73%	1600
	11th to 20th	Night	1 2 1 1 2 2 2 3 3 4 81%	1600
	21st to end	Night	1 1 1 1 1 1 2 3 3 87%	1600
July	1st to 10th	Night	1 1 1 1 3 2 3 88%	3640
	11th to 20th	Night	1 1 1 1 2 3 3 3 85%	3817
	21st to end	Night	1 1 1 1 1 1 1 3 4 88%	4671
August	1st to 10th	Night	1 1 1 1 2 2 3 4 84%	4486
	11th to 20th	Night	1 1 1 1 1 2 92%	4506
	21st to end	Night	1 1 1 1 1 2 3 89%	5015
September	1st to 10th	Night	2 1 1 1 1 2 1 1 3 3 85%	2000
	11th to 20th	Night	2 1 1 2 1 1 2 1 2 3 84%	2082
	21st to end	Night	1 2 1 1 1 2 2 1 3 4 83%	2200
October	1st to 10th	Night	2 1 1 1 1 1 1 2 2 87%	3678
	11th to 20th	Night	1 2 1 2 2 1 3 8% 4 5% 71%	3897
	21st to end	Night	2 3 1 2 2 2 2 1 2 4 80%	4253
November	1st to 10th	Night	3 2 2 2 2 2 2 4 5% 75%	2627
	11th to 20th	Night	5% 3 1 2 2 2 2 2 4 5% 72%	2730
	21st to end	Night	5% 3 1 3 3 2 3 4 4 6% 66%	2730
December	1st to 10th	Night	4 3 1 3 2 3 3 3 4 6% 69%	4370
	11th to 20th	Night	13% 4 1 3 3 3 4 4 6% 7% 53%	5138
	21st to end	Night	9% 4 1 4 4 4 4 4 6% 10% 49%	7106

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	23% 3 5% 21% 31% 18%	4825
	11th to 20th	Day	14% 3 8% 14% 23% 38%	5340
	21st to end	Day	24% 4 4 17% 28% 22%	6004
February	1st to 10th	Day	26% 4 4 16% 25% 25%	2100
	11th to 20th	Day	24% 3 6% 19% 28% 20%	2060
	21st to end	Day	24% 5% 6% 21% 27% 17%	1730
March	1st to 10th	Day	28% 5% 8% 18% 23% 17%	4618
	11th to 20th	Day	23% 5% 10% 30% 19% 13%	4970
	21st to end	Day	25% 10% 10% 28% 21% 6%	6027
April	1st to 10th	Day	23% 5% 11% 24% 27% 11%	2520
	11th to 20th	Day	21% 4 8% 27% 28% 12%	2445
	21st to end	Day	18% 4 9% 27% 31% 10%	2400
May	1st to 10th	Day	18% 9% 7% 21% 30% 16%	5440
	11th to 20th	Day	21% 4 9% 26% 29% 11%	5795
	21st to end	Day	16% 7% 7% 29% 31% 10%	6441
June	1st to 10th	Day	19% 5% 9% 24% 30% 14%	2800
	11th to 20th	Day	13% 3 7% 17% 34% 27%	2800
	21st to end	Day	8% 3 3 11% 35% 40%	2800
July	1st to 10th	Day	4 1 1 7% 19% 68%	6251
	11th to 20th	Day	7% 3 2 9% 34% 45%	6070
	21st to end	Day	5% 5% 3 17% 37% 33%	6017
August	1st to 10th	Day	8% 2 2 11% 44% 33%	3890
	11th to 20th	Day	4 1 1 11% 30% 53%	3880
	21st to end	Day	5% 2 1 11% 30% 51%	4311
September	1st to 10th	Day	8% 3 4 10% 30% 46%	2400
	11th to 20th	Day	10% 3 3 14% 34% 37%	2316
	21st to end	Day	10% 3 3 13% 36% 35%	2200
October	1st to 10th	Day	8% 2 4 11% 20% 55%	3518
	11th to 20th	Day	12% 4 2 16% 39% 27%	3261
	21st to end	Day	17% 3 3 10% 34% 34%	3558
November	1st to 10th	Day	13% 3 3 18% 31% 33%	1889
	11th to 20th	Day	19% 2 5% 14% 26% 33%	1890
	21st to end	Day	20% 4 6% 15% 23% 31%	1890
December	1st to 10th	Day	20% 3 5% 11% 30% 32%	3040
	11th to 20th	Day	30% 4 6% 17% 27% 16%	3287
	21st to end	Day	28% 4 10% 25% 23% 9%	4092
January	1st to 10th	Night	24% 3 5% 16% 31% 21%	8060
	11th to 20th	Night	15% 3 5% 14% 17% 46%	7650
	21st to end	Night	27% 5% 3 13% 26% 26%	8203
February	1st to 10th	Night	25% 3 4 16% 26% 26%	2520
	11th to 20th	Night	23% 3 5% 20% 26% 23%	2459
	21st to end	Night	25% 3 6% 18% 26% 22%	2076
March	1st to 10th	Night	25% 6% 6% 18% 26% 19%	5496
	11th to 20th	Night	21% 5% 9% 26% 23% 15%	5245
	21st to end	Night	25% 5% 9% 24% 27% 9%	5189
April	1st to 10th	Night	20% 5% 9% 25% 27% 15%	2100
	11th to 20th	Night	17% 5% 7% 23% 30% 18%	2039
	21st to end	Night	18% 3 7% 25% 35% 12%	2000
May	1st to 10th	Night	14% 9% 10% 17% 30% 20%	4557
	11th to 20th	Night	11% 3 10% 32% 24% 20%	4124
	21st to end	Night	8% 5% 7% 32% 36% 13%	4438
June	1st to 10th	Night	13% 3 11% 29% 29% 15%	1600
	11th to 20th	Night	8% 2 7% 21% 33% 30%	1600
	21st to end	Night	5% 2 3 13% 33% 43%	1600
July	1st to 10th	Night	3 1 1 6% 17% 71%	3600
	11th to 20th	Night	4 2 2 9% 36% 47%	3769
	21st to end	Night	4 2 2 19% 36% 36%	4539
August	1st to 10th	Night	7% 1 2 13% 39% 38%	3256
	11th to 20th	Night	4 1 1 8% 30% 55%	3256
	21st to end	Night	4 1 1 10% 33% 51%	3608
September	1st to 10th	Night	8% 2 2 8% 30% 50%	2000
	11th to 20th	Night	9% 2 3 11% 38% 37%	2082
	21st to end	Night	8% 2 3 12% 35% 40%	2200
October	1st to 10th	Night	7% 2 2 9% 20% 60%	3678
	11th to 20th	Night	10% 4 2 18% 35% 32%	3897
	21st to end	Night	12% 2 2 8% 31% 45%	4253
November	1st to 10th	Night	13% 3 4 14% 32% 34%	2627
	11th to 20th	Night	17% 2 5% 13% 25% 37%	2730
	21st to end	Night	21% 3 5% 17% 22% 33%	2730
December	1st to 10th	Night	18% 2 3 12% 29% 36%	4370
	11th to 20th	Night	29% 5% 7% 15% 24% 20%	5138
	21st to end	Night	30% 4 8% 26% 23% 9%	7106

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	16% 12% 32% 30% 9% 1	257
	11th to 20th	Day	12% 9% 32% 35% 10% 1	430
	21st to end	Day	10% 15% 36% 29% 8% 2	503
February	1st to 10th	Day	11% 12% 37% 29% 9% 2	540
	11th to 20th	Day	12% 15% 37% 27% 8% 1	535
	21st to end	Day	11% 14% 40% 27% 7% 1	446
March	1st to 10th	Day	14% 18% 39% 22% 7%	540
	11th to 20th	Day	13% 13% 37% 26% 10% 1	540
	21st to end	Day	11% 17% 34% 31% 7%	594
April	1st to 10th	Day	9% 13% 35% 30% 11% 3	540
	11th to 20th	Day	7% 14% 37% 31% 9% 3	517
	21st to end	Day	6% 12% 32% 31% 14% 5%	500
May	1st to 10th	Day	11% 11% 28% 37% 10% 4	503
	11th to 20th	Day	5% 12% 28% 34% 17% 3	528
	21st to end	Day	5% 10% 33% 34% 15% 4	573
June	1st to 10th	Day	4 8% 25% 36% 23% 5%	530
	11th to 20th	Day	2 4 27% 40% 20% 6%	530
	21st to end	Day	1 4 21% 45% 23% 7%	530
July	1st to 10th	Day	1 13% 49% 29% 8%	526
	11th to 20th	Day	2 7% 45% 31% 14%	524
	21st to end	Day	2 1 10% 47% 29% 13%	575
August	1st to 10th	Day	1 1 15% 47% 26% 10%	527
	11th to 20th	Day	2 1 11% 50% 24% 12%	517
	21st to end	Day	2 1 15% 48% 25% 9%	583
September	1st to 10th	Day	2 2 18% 46% 24% 8%	530
	11th to 20th	Day	3 5% 26% 45% 17% 4	530
	21st to end	Day	2 9% 22% 43% 22% 4	530
October	1st to 10th	Day	3 6% 29% 43% 17% 2	530
	11th to 20th	Day	2 6% 33% 40% 16% 3	530
	21st to end	Day	3 8% 27% 40% 17% 4	583
November	1st to 10th	Day	3 7% 25% 42% 20% 2	365
	11th to 20th	Day	8% 8% 34% 31% 17% 2	330
	21st to end	Day	7% 10% 31% 35% 15% 3	330
December	1st to 10th	Day	7% 8% 31% 35% 18% 2	330
	11th to 20th	Day	6% 8% 31% 34% 17% 4	278
	21st to end	Day	17% 14% 33% 24% 9% 2	242
January	1st to 10th	Night	12% 5% 24% 35% 17% 6%	840
	11th to 20th	Night	6% 5% 24% 41% 20% 4	840
	21st to end	Night	10% 5% 27% 39% 14% 4	924
February	1st to 10th	Night	10% 5% 22% 37% 20% 5%	840
	11th to 20th	Night	10% 3 26% 37% 18% 6%	824
	21st to end	Night	10% 5% 28% 37% 17% 3	692
March	1st to 10th	Night	10% 4 27% 38% 19% 3	840
	11th to 20th	Night	8% 3 22% 40% 22% 5%	840
	21st to end	Night	7% 3 22% 42% 22% 3	924
April	1st to 10th	Night	6% 4 20% 44% 23% 4	840
	11th to 20th	Night	5% 4 23% 37% 27% 4	815
	21st to end	Night	4 3 20% 40% 26% 8%	800
May	1st to 10th	Night	3 3 17% 38% 33% 5%	800
	11th to 20th	Night	3 2 18% 32% 37% 7%	614
	21st to end	Night	1 2 17% 40% 33% 7%	640
June	1st to 10th	Night	2 1 7% 32% 49% 9%	400
	11th to 20th	Night	1 1 9% 30% 52% 8%	400
	21st to end	Night	1 4 31% 52% 13%	400
July	1st to 10th	Night	1 1 1 19% 62% 17%	390
	11th to 20th	Night	1 2 8% 60% 28%	461
	21st to end	Night	1 2 14% 56% 27%	742
August	1st to 10th	Night	1 1 2 26% 55% 16%	796
	11th to 20th	Night	1 1 2 16% 61% 20%	792
	21st to end	Night	1 2 20% 56% 20%	880
September	1st to 10th	Night	3 1 4 26% 48% 18%	800
	11th to 20th	Night	3 2 6% 31% 47% 12%	800
	21st to end	Night	1 1 10% 33% 44% 12%	800
October	1st to 10th	Night	3 1 10% 43% 38% 5%	800
	11th to 20th	Night	3 1 16% 38% 34% 8%	800
	21st to end	Night	3 3 15% 39% 29% 10%	880
November	1st to 10th	Night	3 2 17% 42% 26% 9%	820
	11th to 20th	Night	6% 3 17% 37% 29% 8%	840
	21st to end	Night	7% 2 23% 40% 23% 5%	840
December	1st to 10th	Night	8% 5% 20% 39% 24% 4	840
	11th to 20th	Night	12% 2 25% 41% 17% 3	840
	21st to end	Night	12% 4 26% 38% 15% 5%	924

Page generated at 2026-04-13 23:44:30. Version ac07

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