Huntington Beach
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Huntington Beach clear sky chart from 2005-11-06 to 2026-08-30.

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 5% 2 4 3 3 3 3 5% 7% 61%	152676
	Night	5% 8% 2 5% 3 3 4 3 5% 7% 54%	147091
Transparency	Day	14% 35% 5% 13% 18% 16%	147767
	Night	17% 36% 5% 13% 16% 13%	142976
Seeing	Day	7% 7% 24% 36% 19% 7%	18253
	Night	9% 3 8% 33% 36% 11%	28081

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	8% 4 2 4 3 3 3 2 3 6% 62%	4818
	11th to 20th	Day	5% 3 1 3 2 2 2 3 4 7% 67%	5712
	21st to end	Day	8% 5% 2 6% 4 4 4 4 5% 8% 50%	6500
February	1st to 10th	Day	9% 5% 1 4 3 3 3 3 6% 7% 56%	2100
	11th to 20th	Day	8% 4 2 4 3 2 3 3 6% 9% 57%	2050
	21st to end	Day	6% 5% 1 4 3 4 4 3 6% 7% 57%	1730
March	1st to 10th	Day	8% 4 2 5% 3 3 4 5% 7% 8% 52%	4618
	11th to 20th	Day	7% 4 1 4 3 3 3 3 6% 9% 55%	4780
	21st to end	Day	8% 5% 2 4 3 3 4 3 6% 8% 53%	6101
April	1st to 10th	Day	4 5% 1 4 3 3 4 3 5% 8% 60%	2520
	11th to 20th	Day	3 4 1 3 3 3 4 3 5% 6% 64%	2489
	21st to end	Day	3 5% 2 3 3 3 3 3 5% 8% 63%	2520
May	1st to 10th	Day	3 5% 2 4 4 3 4 3 5% 7% 61%	7225
	11th to 20th	Day	4 8% 3 6% 3 4 4 3 4 6% 56%	7596
	21st to end	Day	5% 7% 2 6% 4 3 3 3 4 7% 57%	8370
June	1st to 10th	Day	7% 9% 2 5% 3 3 3 4 5% 8% 52%	2730
	11th to 20th	Day	4 6% 1 4 3 3 3 2 4 8% 63%	2862
	21st to end	Day	3 6% 1 4 3 4 3 2 4 7% 62%	2940
July	1st to 10th	Day	1 4 2 4 3 3 3 3 4 7% 67%	8219
	11th to 20th	Day	1 5% 2 4 3 4 4 3 5% 8% 60%	7918
	21st to end	Day	2 3 1 3 3 3 3 3 4 7% 70%	7728
August	1st to 10th	Day	1 2 1 3 3 2 3 3 4 7% 72%	5466
	11th to 20th	Day	1 4 1 3 2 2 2 2 4 6% 71%	5484
	21st to end	Day	1 3 1 3 2 2 3 3 4 7% 70%	6093
September	1st to 10th	Day	2 3 1 3 2 2 3 3 5% 7% 69%	2400
	11th to 20th	Day	3 5% 2 3 2 2 3 3 4 8% 65%	2241
	21st to end	Day	1 3 1 4 2 2 3 2 5% 7% 69%	2200
October	1st to 10th	Day	2 2 1 5% 3 3 3 3 5% 7% 65%	3600
	11th to 20th	Day	4 5% 2 4 2 2 3 3 5% 8% 61%	3404
	21st to end	Day	3 3 1 3 3 3 3 4 7% 8% 63%	3480
November	1st to 10th	Day	3 3 2 4 3 3 3 2 4 8% 65%	1854
	11th to 20th	Day	5% 4 2 3 3 2 4 3 5% 7% 64%	1890
	21st to end	Day	5% 4 1 4 4 3 3 4 5% 8% 59%	1890
December	1st to 10th	Day	3 4 2 5% 2 3 4 4 7% 8% 58%	3040
	11th to 20th	Day	7% 4 2 4 3 4 5% 5% 7% 8% 51%	3499
	21st to end	Day	8% 9% 4 8% 6% 5% 5% 4 7% 9% 37%	4609
January	1st to 10th	Night	8% 6% 2 4 3 3 3 3 4 5% 58%	8023
	11th to 20th	Night	5% 5% 1 3 2 2 2 2 4 7% 66%	7222
	21st to end	Night	9% 7% 2 5% 3 4 4 4 5% 6% 50%	7747
February	1st to 10th	Night	8% 6% 3 5% 4 3 2 2 4 6% 56%	2520
	11th to 20th	Night	9% 6% 2 5% 3 3 4 2 4 6% 55%	2458
	21st to end	Night	9% 5% 2 5% 4 4 3 3 4 6% 55%	2076
March	1st to 10th	Night	8% 6% 2 6% 4 4 4 3 6% 9% 50%	5496
	11th to 20th	Night	7% 6% 2 6% 4 4 4 3 5% 7% 52%	5433
	21st to end	Night	8% 9% 3 5% 3 3 3 4 6% 8% 49%	5116
April	1st to 10th	Night	8% 7% 2 5% 3 2 3 3 5% 8% 54%	2100
	11th to 20th	Night	6% 9% 2 5% 2 3 3 2 4 5% 60%	2079
	21st to end	Night	7% 11% 2 5% 3 3 3 3 5% 6% 52%	2100
May	1st to 10th	Night	6% 15% 2 6% 4 3 3 3 4 5% 49%	5741
	11th to 20th	Night	5% 16% 3 6% 3 3 3 3 4 6% 47%	5296
	21st to end	Night	8% 12% 3 6% 3 3 3 2 5% 6% 48%	5837
June	1st to 10th	Night	8% 17% 4 7% 4 3 4 3 5% 6% 39%	1890
	11th to 20th	Night	5% 12% 2 5% 3 3 4 3 5% 8% 49%	1749
	21st to end	Night	6% 14% 3 7% 3 4 3 4 5% 7% 43%	1680
July	1st to 10th	Night	2 8% 2 5% 3 4 5% 4 6% 8% 54%	4740
	11th to 20th	Night	1 8% 2 5% 4 4 4 4 6% 8% 53%	5040
	21st to end	Night	4 6% 1 4 3 4 3 3 5% 6% 60%	6395
August	1st to 10th	Night	1 4 2 4 4 5% 4 4 6% 8% 58%	4586
	11th to 20th	Night	3 9% 2 5% 4 4 3 3 5% 8% 54%	4606
	21st to end	Night	2 5% 2 4 3 4 4 4 5% 7% 60%	5105
September	1st to 10th	Night	5% 6% 1 5% 3 4 4 3 5% 7% 58%	2000
	11th to 20th	Night	4 5% 2 4 3 3 3 3 4 9% 60%	2157
	21st to end	Night	2 7% 3 4 3 2 3 2 4 6% 63%	2200
October	1st to 10th	Night	2 3 2 8% 4 4 4 3 4 6% 58%	3600
	11th to 20th	Night	5% 12% 3 5% 3 3 3 3 4 6% 52%	3737
	21st to end	Night	3 3 1 3 2 3 4 3 5% 6% 66%	4315
November	1st to 10th	Night	3 5% 2 4 3 3 3 2 5% 7% 62%	2665
	11th to 20th	Night	4 5% 2 4 3 2 3 2 4 7% 64%	2730
	21st to end	Night	5% 6% 2 5% 4 4 4 3 6% 8% 54%	2730
December	1st to 10th	Night	4 6% 2 5% 3 3 4 4 5% 7% 56%	4370
	11th to 20th	Night	8% 6% 2 6% 3 3 5% 4 5% 8% 50%	4941
	21st to end	Night	8% 8% 3 7% 5% 5% 5% 5% 6% 8% 39%	6611

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	19% 22% 6% 15% 20% 19%	4819
	11th to 20th	Day	13% 21% 9% 10% 12% 35%	5712
	21st to end	Day	24% 23% 3 13% 16% 20%	6500
February	1st to 10th	Day	13% 59% 3 7% 9% 8%	2100
	11th to 20th	Day	12% 58% 3 8% 10% 10%	2060
	21st to end	Day	10% 59% 3 11% 10% 8%	1730
March	1st to 10th	Day	20% 31% 8% 15% 15% 11%	4618
	11th to 20th	Day	18% 31% 9% 21% 13% 9%	4780
	21st to end	Day	20% 31% 9% 24% 12% 4	6101
April	1st to 10th	Day	8% 60% 5% 10% 12% 5%	2520
	11th to 20th	Day	8% 60% 3 9% 12% 8%	2492
	21st to end	Day	9% 59% 5% 14% 9% 4	2520
May	1st to 10th	Day	15% 26% 5% 20% 27% 7%	7225
	11th to 20th	Day	18% 26% 5% 18% 25% 9%	7599
	21st to end	Day	17% 27% 5% 24% 21% 6%	8371
June	1st to 10th	Day	13% 59% 2 10% 12% 4	2730
	11th to 20th	Day	9% 58% 2 6% 14% 11%	2862
	21st to end	Day	9% 58% 1 6% 13% 13%	2940
July	1st to 10th	Day	11% 21% 3 7% 17% 42%	8151
	11th to 20th	Day	15% 22% 5% 13% 31% 14%	7844
	21st to end	Day	9% 21% 4 19% 26% 22%	7557
August	1st to 10th	Day	8% 35% 2 13% 27% 15%	4010
	11th to 20th	Day	5% 35% 2 10% 18% 30%	4000
	21st to end	Day	7% 35% 2 7% 18% 30%	4420
September	1st to 10th	Day	6% 57% 2 6% 17% 12%	2400
	11th to 20th	Day	9% 57% 2 6% 16% 10%	2241
	21st to end	Day	7% 57% 2 8% 16% 9%	2200
October	1st to 10th	Day	6% 37% 2 7% 15% 33%	3600
	11th to 20th	Day	13% 36% 3 10% 24% 13%	3404
	21st to end	Day	11% 36% 3 8% 23% 20%	3480
November	1st to 10th	Day	5% 53% 3 7% 13% 20%	1854
	11th to 20th	Day	12% 54% 3 7% 9% 14%	1890
	21st to end	Day	11% 54% 5% 9% 8% 13%	1890
December	1st to 10th	Day	11% 35% 4 17% 12% 20%	3040
	11th to 20th	Day	19% 32% 5% 12% 20% 12%	3498
	21st to end	Day	31% 30% 10% 16% 9% 5%	4609
January	1st to 10th	Night	23% 22% 5% 12% 20% 18%	8023
	11th to 20th	Night	15% 21% 7% 11% 13% 32%	7222
	21st to end	Night	26% 25% 3 11% 16% 19%	7747
February	1st to 10th	Night	14% 59% 2 8% 8% 8%	2520
	11th to 20th	Night	15% 57% 3 7% 7% 10%	2459
	21st to end	Night	12% 59% 2 8% 11% 8%	2076
March	1st to 10th	Night	19% 32% 10% 14% 18% 7%	5496
	11th to 20th	Night	21% 31% 7% 21% 11% 9%	5433
	21st to end	Night	21% 33% 12% 19% 13% 2	5116
April	1st to 10th	Night	11% 60% 3 11% 10% 5%	2100
	11th to 20th	Night	10% 60% 2 9% 13% 6%	2079
	21st to end	Night	11% 59% 6% 12% 8% 4	2100
May	1st to 10th	Night	26% 26% 6% 18% 21% 3	5739
	11th to 20th	Night	22% 27% 7% 20% 19% 4	5297
	21st to end	Night	23% 27% 8% 23% 15% 5%	5838
June	1st to 10th	Night	19% 59% 4 6% 9% 3	1890
	11th to 20th	Night	13% 59% 2 6% 13% 8%	1749
	21st to end	Night	16% 58% 1 5% 10% 10%	1680
July	1st to 10th	Night	16% 23% 3 12% 15% 31%	4700
	11th to 20th	Night	16% 25% 6% 14% 28% 10%	4991
	21st to end	Night	15% 22% 6% 22% 22% 13%	6255
August	1st to 10th	Night	11% 37% 3 17% 21% 11%	3356
	11th to 20th	Night	11% 36% 3 13% 18% 19%	3356
	21st to end	Night	11% 35% 2 8% 22% 22%	3698
September	1st to 10th	Night	11% 57% 2 5% 15% 10%	2000
	11th to 20th	Night	10% 57% 3 6% 14% 10%	2157
	21st to end	Night	9% 57% 2 7% 16% 9%	2200
October	1st to 10th	Night	13% 38% 3 9% 13% 24%	3600
	11th to 20th	Night	19% 38% 4 9% 17% 14%	3737
	21st to end	Night	9% 36% 3 10% 23% 20%	4315
November	1st to 10th	Night	6% 53% 3 7% 11% 19%	2665
	11th to 20th	Night	12% 55% 3 8% 8% 14%	2730
	21st to end	Night	14% 54% 4 8% 8% 11%	2730
December	1st to 10th	Night	15% 35% 3 13% 16% 18%	4370
	11th to 20th	Night	21% 33% 5% 9% 16% 16%	4941
	21st to end	Night	29% 31% 13% 18% 5% 5%	6611

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	13% 5% 21% 37% 20% 5%	238
	11th to 20th	Day	11% 5% 24% 35% 20% 4	479
	21st to end	Day	10% 9% 27% 34% 17% 4	594
February	1st to 10th	Day	13% 8% 28% 28% 18% 6%	540
	11th to 20th	Day	13% 12% 31% 29% 13% 3	535
	21st to end	Day	8% 11% 32% 32% 15% 2	446
March	1st to 10th	Day	13% 13% 34% 27% 11% 2	540
	11th to 20th	Day	12% 10% 29% 29% 16% 4	540
	21st to end	Day	11% 14% 33% 27% 12% 4	594
April	1st to 10th	Day	8% 11% 30% 31% 15% 4	540
	11th to 20th	Day	5% 14% 36% 30% 10% 5%	532
	21st to end	Day	6% 13% 30% 35% 11% 5%	540
May	1st to 10th	Day	5% 13% 31% 33% 14% 5%	543
	11th to 20th	Day	5% 9% 31% 36% 13% 5%	568
	21st to end	Day	8% 11% 29% 34% 14% 4	617
June	1st to 10th	Day	7% 5% 25% 39% 20% 4	570
	11th to 20th	Day	6% 3 26% 37% 21% 7%	570
	21st to end	Day	4 4 21% 44% 18% 9%	570
July	1st to 10th	Day	2 1 13% 49% 25% 10%	566
	11th to 20th	Day	3 1 8% 46% 27% 15%	564
	21st to end	Day	2 1 11% 45% 25% 16%	619
August	1st to 10th	Day	3 2 11% 47% 24% 13%	567
	11th to 20th	Day	3 1 12% 48% 25% 12%	557
	21st to end	Day	3 2 15% 41% 26% 12%	620
September	1st to 10th	Day	4 1 20% 41% 23% 11%	530
	11th to 20th	Day	5% 5% 26% 37% 20% 7%	530
	21st to end	Day	4 6% 24% 38% 21% 7%	530
October	1st to 10th	Day	5% 7% 24% 37% 22% 6%	530
	11th to 20th	Day	7% 5% 25% 37% 20% 7%	530
	21st to end	Day	5% 7% 23% 32% 25% 9%	541
November	1st to 10th	Day	7% 6% 15% 33% 26% 13%	330
	11th to 20th	Day	7% 7% 18% 34% 26% 9%	330
	21st to end	Day	6% 6% 21% 35% 25% 7%	330
December	1st to 10th	Day	8% 4 18% 35% 28% 8%	330
	11th to 20th	Day	6% 5% 18% 31% 28% 12%	330
	21st to end	Day	18% 4 23% 34% 16% 4	363
January	1st to 10th	Night	11% 3 11% 43% 27% 5%	840
	11th to 20th	Night	7% 3 13% 42% 31% 5%	840
	21st to end	Night	11% 3 16% 38% 26% 5%	924
February	1st to 10th	Night	11% 4 12% 38% 30% 6%	840
	11th to 20th	Night	10% 6% 12% 41% 26% 5%	824
	21st to end	Night	12% 4 12% 43% 25% 5%	692
March	1st to 10th	Night	12% 4 14% 43% 23% 4	840
	11th to 20th	Night	11% 4 12% 39% 27% 8%	840
	21st to end	Night	9% 4 12% 39% 31% 5%	924
April	1st to 10th	Night	10% 5% 10% 41% 28% 6%	840
	11th to 20th	Night	9% 4 12% 37% 33% 5%	831
	21st to end	Night	9% 5% 10% 36% 32% 7%	840
May	1st to 10th	Night	10% 4 11% 36% 32% 6%	777
	11th to 20th	Night	9% 3 11% 33% 34% 9%	621
	21st to end	Night	8% 4 12% 35% 34% 7%	683
June	1st to 10th	Night	10% 4 9% 34% 35% 7%	630
	11th to 20th	Night	8% 2 5% 28% 43% 13%	489
	21st to end	Night	10% 3 1 23% 48% 14%	420
July	1st to 10th	Night	5% 3 8% 61% 22%	410
	11th to 20th	Night	3 2 1 17% 47% 29%	512
	21st to end	Night	7% 2 1 18% 45% 27%	896
August	1st to 10th	Night	5% 3 1 20% 46% 25%	836
	11th to 20th	Night	9% 1 1 15% 45% 28%	832
	21st to end	Night	5% 1 1 17% 49% 27%	916
September	1st to 10th	Night	6% 1 2 21% 49% 21%	800
	11th to 20th	Night	7% 2 2 24% 51% 14%	800
	21st to end	Night	5% 3 4 27% 48% 14%	800
October	1st to 10th	Night	6% 1 5% 33% 47% 9%	800
	11th to 20th	Night	10% 1 6% 32% 40% 11%	800
	21st to end	Night	5% 2 6% 35% 38% 14%	880
November	1st to 10th	Night	6% 4 6% 33% 40% 11%	820
	11th to 20th	Night	6% 2 7% 37% 36% 12%	840
	21st to end	Night	8% 2 10% 42% 32% 6%	840
December	1st to 10th	Night	9% 3 9% 42% 31% 6%	840
	11th to 20th	Night	14% 3 10% 40% 29% 5%	840
	21st to end	Night	12% 5% 13% 41% 23% 6%	924

Page generated at 2026-08-27 01:07:14. Version ac07

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