Huntington
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Huntington clear sky chart from 2005-11-06 to 2025-04-11.

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	14% 10% 4 8% 5% 4 4 4 5% 7% 34%	113212
	Night	15% 10% 4 8% 5% 4 4 3 5% 6% 35%	115215
Transparency	Day	49% 4 11% 23% 13% 1	116842
	Night	49% 3 10% 22% 14% 2	119727
Seeing	Day	18% 11% 27% 23% 15% 6%	16142
	Night	19% 9% 28% 29% 13% 1	26121

By Month

Percentage Cloud Cover SE (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	13% 15% 9% 18% 6% 4 4 3 4 4 19%	3617
	11th to 20th	Day	14% 15% 9% 12% 7% 7% 6% 5% 4 4 17%	3620
	21st to end	Day	23% 18% 8% 12% 4 4 3 3 3 4 19%	4174
February	1st to 10th	Day	17% 15% 6% 13% 7% 5% 4 3 4 5% 21%	1920
	11th to 20th	Day	16% 13% 4 11% 8% 5% 4 4 4 6% 25%	1948
	21st to end	Day	17% 15% 6% 9% 5% 4 3 3 4 6% 28%	1650
March	1st to 10th	Day	19% 15% 7% 9% 4 4 3 2 3 4 30%	4480
	11th to 20th	Day	11% 11% 4 6% 4 4 4 3 6% 8% 40%	4879
	21st to end	Day	18% 14% 5% 9% 5% 5% 5% 3 5% 6% 24%	5599
April	1st to 10th	Day	17% 13% 4 7% 5% 5% 4 4 4 7% 30%	2400
	11th to 20th	Day	17% 9% 3 7% 5% 4 4 3 5% 8% 34%	2282
	21st to end	Day	20% 9% 3 6% 5% 4 4 4 5% 7% 33%	2470
May	1st to 10th	Day	20% 9% 2 7% 6% 5% 5% 4 6% 7% 29%	4082
	11th to 20th	Day	18% 6% 2 6% 4 5% 4 4 6% 9% 36%	4081
	21st to end	Day	10% 6% 2 6% 5% 5% 5% 5% 7% 9% 40%	4594
June	1st to 10th	Day	11% 5% 2 6% 5% 5% 5% 5% 7% 8% 41%	2660
	11th to 20th	Day	9% 5% 2 6% 5% 4 5% 4 6% 8% 45%	2660
	21st to end	Day	10% 6% 2 7% 6% 4 6% 5% 7% 10% 38%	2660
July	1st to 10th	Day	14% 6% 3 7% 5% 5% 5% 4 6% 9% 36%	4440
	11th to 20th	Day	7% 4 2 5% 4 4 5% 4 7% 11% 48%	4440
	21st to end	Day	8% 6% 3 7% 6% 5% 5% 5% 6% 9% 40%	4670
August	1st to 10th	Day	9% 5% 2 5% 4 4 5% 5% 7% 11% 44%	4104
	11th to 20th	Day	10% 4 2 6% 4 4 5% 4 7% 8% 46%	4017
	21st to end	Day	8% 4 2 6% 3 4 4 4 6% 10% 50%	4180
September	1st to 10th	Day	11% 6% 2 6% 5% 5% 5% 3 5% 7% 47%	2227
	11th to 20th	Day	10% 5% 2 5% 4 4 4 4 6% 9% 47%	2090
	21st to end	Day	14% 7% 3 5% 5% 4 4 3 5% 7% 43%	2090
October	1st to 10th	Day	13% 6% 2 6% 4 4 4 3 6% 7% 44%	2090
	11th to 20th	Day	15% 6% 3 5% 5% 5% 4 4 5% 7% 40%	1916
	21st to end	Day	19% 9% 3 9% 5% 4 5% 4 5% 7% 30%	1881
November	1st to 10th	Day	10% 7% 2 6% 3 4 4 3 6% 7% 48%	1762
	11th to 20th	Day	18% 13% 4 9% 5% 4 4 3 5% 7% 30%	1800
	21st to end	Day	20% 14% 4 9% 4 4 4 3 4 5% 28%	1800
December	1st to 10th	Day	13% 13% 4 10% 5% 4 4 3 5% 6% 33%	2930
	11th to 20th	Day	17% 18% 6% 10% 5% 5% 4 3 4 5% 23%	3017
	21st to end	Day	28% 19% 7% 11% 5% 5% 4 3 3 4 10%	3982
January	1st to 10th	Night	16% 15% 7% 14% 5% 5% 4 4 4 5% 21%	6348
	11th to 20th	Night	12% 19% 8% 16% 7% 6% 5% 3 3 3 17%	6360
	21st to end	Night	21% 13% 7% 9% 5% 4 4 3 4 4 26%	6794
February	1st to 10th	Night	19% 15% 5% 11% 6% 4 4 3 4 5% 25%	2475
	11th to 20th	Night	13% 14% 4 9% 6% 5% 5% 3 4 7% 30%	2338
	21st to end	Night	19% 13% 4 9% 4 4 3 4 5% 6% 30%	1980
March	1st to 10th	Night	18% 12% 4 6% 4 4 3 3 4 6% 36%	5373
	11th to 20th	Night	12% 7% 2 5% 4 5% 5% 4 6% 7% 43%	5079
	21st to end	Night	17% 10% 3 8% 5% 4 4 3 5% 6% 35%	5358
April	1st to 10th	Night	16% 10% 3 6% 4 5% 4 3 5% 8% 35%	2000
	11th to 20th	Night	18% 8% 2 6% 5% 4 4 3 5% 6% 38%	1853
	21st to end	Night	19% 9% 3 6% 4 4 4 3 5% 5% 37%	1710
May	1st to 10th	Night	17% 9% 3 8% 5% 5% 5% 4 5% 8% 31%	2813
	11th to 20th	Night	20% 6% 2 5% 4 3 3 4 5% 8% 39%	2812
	21st to end	Night	11% 5% 2 6% 4 4 4 4 7% 7% 45%	2960
June	1st to 10th	Night	8% 5% 3 6% 4 4 4 4 5% 8% 48%	1520
	11th to 20th	Night	8% 5% 2 6% 4 4 4 4 6% 9% 47%	1520
	21st to end	Night	10% 4 2 6% 5% 4 6% 4 5% 9% 44%	1520
July	1st to 10th	Night	10% 5% 2 6% 4 4 4 4 6% 9% 46%	2530
	11th to 20th	Night	7% 3 1 5% 3 4 4 3 6% 9% 56%	2530
	21st to end	Night	10% 6% 2 7% 5% 4 4 4 7% 9% 42%	2886
August	1st to 10th	Night	12% 5% 2 6% 4 4 4 4 5% 8% 45%	2825
	11th to 20th	Night	9% 5% 2 5% 4 5% 4 3 6% 6% 49%	2808
	21st to end	Night	7% 4 2 6% 4 4 5% 3 6% 8% 52%	3476
September	1st to 10th	Night	10% 5% 2 5% 5% 3 4 3 5% 7% 52%	1933
	11th to 20th	Night	9% 4 1 4 3 4 3 3 5% 7% 56%	2090
	21st to end	Night	12% 7% 2 5% 4 4 4 3 5% 6% 48%	2090
October	1st to 10th	Night	11% 5% 2 4 3 4 4 4 4 8% 52%	2090
	11th to 20th	Night	17% 8% 2 6% 4 4 3 3 4 6% 43%	2259
	21st to end	Night	19% 9% 2 6% 4 3 4 3 5% 6% 38%	2717
November	1st to 10th	Night	13% 8% 3 6% 4 3 3 3 5% 6% 45%	2536
	11th to 20th	Night	15% 12% 3 7% 4 4 4 4 5% 7% 35%	2600
	21st to end	Night	18% 13% 4 9% 5% 5% 3 4 5% 6% 28%	2600
December	1st to 10th	Night	14% 10% 4 8% 5% 5% 6% 4 6% 7% 32%	4250
	11th to 20th	Night	19% 16% 9% 11% 5% 4 4 3 4 4 20%	5186
	21st to end	Night	28% 18% 7% 11% 5% 5% 4 3 4 4 12%	6996

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	69% 2 7% 17% 4	3618
	11th to 20th	Day	73% 2 8% 7% 8% 2	3620
	21st to end	Day	72% 2 7% 12% 6%	4174
February	1st to 10th	Day	67% 2 9% 13% 7% 1	1920
	11th to 20th	Day	61% 3 9% 20% 7% 1	1958
	21st to end	Day	58% 3 12% 18% 8% 1	1650
March	1st to 10th	Day	61% 2 5% 22% 10%	4480
	11th to 20th	Day	44% 2 10% 34% 9% 1	4879
	21st to end	Day	61% 2 14% 17% 5% 1	5601
April	1st to 10th	Day	55% 3 10% 20% 12%	2400
	11th to 20th	Day	49% 4 10% 22% 12% 3	2282
	21st to end	Day	51% 2 12% 21% 12% 3	2470
May	1st to 10th	Day	55% 3 10% 23% 9%	4120
	11th to 20th	Day	47% 3 13% 27% 10% 1	4085
	21st to end	Day	40% 4 10% 26% 19% 2	4607
June	1st to 10th	Day	39% 5% 11% 26% 16% 3	2660
	11th to 20th	Day	36% 4 12% 26% 20% 3	2660
	21st to end	Day	40% 5% 14% 22% 15% 3	2660
July	1st to 10th	Day	44% 5% 11% 22% 16% 3	4371
	11th to 20th	Day	29% 5% 15% 31% 19% 1	4365
	21st to end	Day	39% 6% 14% 19% 19% 3	4522
August	1st to 10th	Day	33% 7% 16% 28% 15% 1	4091
	11th to 20th	Day	33% 5% 13% 31% 16% 1	4056
	21st to end	Day	30% 5% 13% 30% 19% 3	4179
September	1st to 10th	Day	37% 4 13% 24% 19% 3	2227
	11th to 20th	Day	35% 4 9% 28% 23% 2	2090
	21st to end	Day	40% 3 9% 26% 20% 1	2090
October	1st to 10th	Day	28% 3 11% 33% 24% 1	3480
	11th to 20th	Day	36% 4 11% 23% 26% 1	3158
	21st to end	Day	44% 4 9% 27% 14% 1	3081
November	1st to 10th	Day	37% 4 12% 28% 18% 1	1762
	11th to 20th	Day	55% 3 12% 18% 11% 2	1800
	21st to end	Day	59% 3 11% 19% 7% 1	1800
December	1st to 10th	Day	53% 3 16% 22% 5%	2930
	11th to 20th	Day	65% 2 11% 17% 4	3014
	21st to end	Day	79% 3 6% 8% 4	3982
January	1st to 10th	Night	66% 3 8% 16% 7%	6348
	11th to 20th	Night	74% 2 6% 10% 8% 1	6360
	21st to end	Night	63% 3 10% 16% 7% 1	6794
February	1st to 10th	Night	63% 2 10% 16% 7% 1	2475
	11th to 20th	Night	55% 3 9% 21% 10% 1	2339
	21st to end	Night	56% 3 11% 19% 10% 2	1980
March	1st to 10th	Night	51% 2 8% 28% 10% 1	5373
	11th to 20th	Night	40% 3 10% 29% 15% 2	5079
	21st to end	Night	52% 2 10% 26% 10% 1	5358
April	1st to 10th	Night	48% 3 10% 22% 15% 1	2000
	11th to 20th	Night	47% 3 8% 22% 16% 3	1853
	21st to end	Night	49% 3 9% 23% 13% 4	1710
May	1st to 10th	Night	54% 2 10% 23% 10% 2	2840
	11th to 20th	Night	46% 3 13% 28% 10% 1	2813
	21st to end	Night	38% 4 12% 24% 19% 3	2968
June	1st to 10th	Night	34% 4 10% 27% 21% 3	1520
	11th to 20th	Night	33% 5% 12% 26% 21% 3	1520
	21st to end	Night	35% 6% 16% 23% 16% 4	1520
July	1st to 10th	Night	35% 5% 13% 25% 17% 6%	2490
	11th to 20th	Night	25% 5% 16% 28% 24% 2	2482
	21st to end	Night	37% 6% 15% 17% 20% 4	2794
August	1st to 10th	Night	37% 5% 14% 30% 13% 1	2814
	11th to 20th	Night	34% 5% 12% 31% 17% 1	2835
	21st to end	Night	31% 5% 12% 27% 21% 3	3476
September	1st to 10th	Night	33% 4 12% 25% 20% 6%	1933
	11th to 20th	Night	29% 3 8% 31% 27% 3	2090
	21st to end	Night	37% 4 10% 25% 21% 3	2090
October	1st to 10th	Night	22% 3 7% 33% 34% 1	3480
	11th to 20th	Night	34% 3 9% 23% 30% 1	3756
	21st to end	Night	35% 3 8% 32% 20% 2	4467
November	1st to 10th	Night	40% 3 9% 26% 20% 1	2536
	11th to 20th	Night	49% 3 11% 21% 15% 2	2600
	21st to end	Night	58% 3 11% 21% 8%	2600
December	1st to 10th	Night	51% 4 14% 26% 6%	4250
	11th to 20th	Night	68% 3 10% 12% 7% 1	5188
	21st to end	Night	77% 3 8% 9% 3	6996

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	21% 17% 40% 16% 5% 1	300
	11th to 20th	Day	25% 17% 39% 15% 4 1	300
	21st to end	Day	28% 16% 35% 16% 5% 1	330
February	1st to 10th	Day	28% 20% 34% 16% 3	300
	11th to 20th	Day	27% 18% 35% 16% 4	300
	21st to end	Day	27% 19% 39% 13% 2	249
March	1st to 10th	Day	23% 23% 38% 14% 2 1	300
	11th to 20th	Day	27% 13% 31% 20% 7% 1	451
	21st to end	Day	32% 16% 28% 18% 6% 1	550
April	1st to 10th	Day	24% 13% 34% 20% 8% 1	500
	11th to 20th	Day	21% 19% 28% 19% 10% 3	452
	21st to end	Day	24% 15% 31% 18% 9% 2	460
May	1st to 10th	Day	25% 12% 30% 21% 8% 3	463
	11th to 20th	Day	23% 6% 26% 25% 13% 6%	487
	21st to end	Day	11% 6% 28% 27% 18% 9%	595
June	1st to 10th	Day	12% 8% 29% 29% 17% 6%	680
	11th to 20th	Day	12% 7% 26% 29% 20% 6%	680
	21st to end	Day	12% 7% 29% 26% 19% 7%	680
July	1st to 10th	Day	12% 3 18% 30% 23% 14%	671
	11th to 20th	Day	7% 4 22% 32% 21% 14%	668
	21st to end	Day	9% 5% 16% 32% 28% 11%	658
August	1st to 10th	Day	9% 3 14% 29% 26% 19%	486
	11th to 20th	Day	10% 5% 19% 27% 28% 12%	479
	21st to end	Day	8% 4 13% 28% 33% 14%	539
September	1st to 10th	Day	13% 5% 17% 27% 28% 11%	490
	11th to 20th	Day	9% 3 14% 25% 32% 17%	490
	21st to end	Day	18% 9% 20% 24% 22% 6%	490
October	1st to 10th	Day	12% 6% 26% 28% 20% 8%	490
	11th to 20th	Day	17% 17% 29% 25% 10% 2	444
	21st to end	Day	26% 16% 34% 20% 3 1	330
November	1st to 10th	Day	12% 14% 37% 23% 10% 4	300
	11th to 20th	Day	25% 18% 30% 16% 9% 1	300
	21st to end	Day	30% 16% 32% 20% 2	300
December	1st to 10th	Day	22% 22% 35% 14% 6%	300
	11th to 20th	Day	23% 16% 42% 13% 6%	300
	21st to end	Day	31% 21% 29% 16% 2	330
January	1st to 10th	Night	24% 16% 35% 21% 5% 1	1000
	11th to 20th	Night	23% 15% 36% 21% 4	1000
	21st to end	Night	23% 14% 36% 22% 4	1015
February	1st to 10th	Night	27% 13% 33% 24% 3	800
	11th to 20th	Night	22% 14% 39% 22% 3	783
	21st to end	Night	27% 14% 36% 20% 3	660
March	1st to 10th	Night	22% 13% 33% 25% 7%	800
	11th to 20th	Night	19% 12% 36% 25% 7% 1	800
	21st to end	Night	25% 11% 32% 26% 5%	835
April	1st to 10th	Night	21% 11% 33% 28% 7% 1	600
	11th to 20th	Night	19% 11% 34% 28% 8% 1	565
	21st to end	Night	22% 8% 36% 25% 8% 1	570
May	1st to 10th	Night	22% 7% 33% 31% 8%	570
	11th to 20th	Night	22% 4 24% 32% 16% 1	561
	21st to end	Night	12% 4 23% 42% 18% 2	617
June	1st to 10th	Night	9% 3 23% 48% 17%	570
	11th to 20th	Night	10% 4 25% 39% 20% 2	570
	21st to end	Night	11% 3 23% 38% 23% 1	570
July	1st to 10th	Night	9% 2 15% 42% 28% 5%	555
	11th to 20th	Night	8% 3 13% 40% 32% 3	552
	21st to end	Night	7% 5% 12% 44% 31% 1	624
August	1st to 10th	Night	8% 2 12% 41% 32% 5%	567
	11th to 20th	Night	10% 3 13% 40% 31% 3	564
	21st to end	Night	7% 2 15% 35% 37% 4	627
September	1st to 10th	Night	12% 3 14% 35% 32% 4	603
	11th to 20th	Night	11% 2 14% 37% 32% 4	760
	21st to end	Night	15% 6% 22% 34% 20% 3	760
October	1st to 10th	Night	14% 5% 24% 33% 20% 4	760
	11th to 20th	Night	21% 13% 26% 28% 11% 1	760
	21st to end	Night	24% 11% 31% 25% 8%	836
November	1st to 10th	Night	18% 11% 33% 26% 12% 1	780
	11th to 20th	Night	21% 14% 33% 26% 6%	800
	21st to end	Night	26% 13% 29% 25% 7%	800
December	1st to 10th	Night	25% 14% 34% 22% 5%	800
	11th to 20th	Night	26% 13% 32% 24% 5%	987
	21st to end	Night	32% 13% 31% 21% 3	1100

Page generated at 2025-04-08 09:17:26. Version ac07

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