Choke Canyon State Park - Calliham Unit
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Choke Canyon State Park - Calliham Unit clear sky chart from 2005-11-06 to 2025-06-10.

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	11% 6% 2 6% 4 4 4 4 6% 8% 46%	119888
	Night	13% 5% 2 5% 3 3 3 3 5% 7% 50%	118596
Transparency	Day	34% 7% 11% 22% 17% 10%	123735
	Night	32% 6% 12% 21% 17% 12%	122879
Seeing	Day	11% 5% 20% 30% 25% 8%	15365
	Night	13% 5% 27% 39% 15% 1	25383

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	18% 7% 3 5% 3 2 3 2 3 5% 48%	4077
	11th to 20th	Day	16% 5% 2 4 3 3 3 3 4 7% 50%	4103
	21st to end	Day	26% 8% 2 5% 3 3 3 3 5% 6% 35%	4994
February	1st to 10th	Day	16% 10% 4 5% 4 3 3 3 4 5% 44%	2000
	11th to 20th	Day	18% 7% 3 5% 3 3 3 3 4 5% 45%	1949
	21st to end	Day	16% 5% 2 5% 4 3 4 3 4 6% 48%	1650
March	1st to 10th	Day	11% 6% 2 6% 4 4 4 3 5% 7% 47%	4889
	11th to 20th	Day	15% 7% 3 5% 3 3 3 3 3 4 51%	4980
	21st to end	Day	14% 7% 2 6% 4 3 3 3 5% 6% 48%	5462
April	1st to 10th	Day	11% 6% 2 6% 3 4 5% 4 6% 6% 47%	2200
	11th to 20th	Day	14% 7% 2 7% 5% 3 4 3 5% 5% 44%	2176
	21st to end	Day	12% 7% 2 6% 4 4 4 4 5% 6% 46%	2457
May	1st to 10th	Day	14% 8% 3 8% 5% 5% 5% 4 7% 8% 34%	5862
	11th to 20th	Day	7% 4 2 5% 4 4 4 4 6% 8% 52%	5862
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 4 7% 10% 43%	6434
June	1st to 10th	Day	4 3 1 4 3 5% 5% 5% 8% 10% 51%	2588
	11th to 20th	Day	4 3 1 5% 5% 6% 5% 4 7% 9% 50%	2470
	21st to end	Day	6% 5% 2 5% 6% 7% 6% 5% 8% 9% 39%	2470
July	1st to 10th	Day	6% 5% 1 5% 5% 5% 5% 4 6% 9% 47%	4120
	11th to 20th	Day	5% 5% 2 7% 5% 5% 6% 5% 8% 10% 40%	4120
	21st to end	Day	7% 6% 2 6% 6% 6% 5% 5% 7% 10% 40%	4465
August	1st to 10th	Day	1 1 1 2 2 3 4 3 5% 9% 69%	3913
	11th to 20th	Day	2 2 1 3 3 4 5% 4 8% 10% 57%	3726
	21st to end	Day	5% 3 2 5% 5% 5% 6% 5% 8% 12% 44%	3974
September	1st to 10th	Day	9% 4 3 7% 6% 7% 6% 6% 7% 8% 37%	2090
	11th to 20th	Day	11% 5% 2 7% 5% 5% 5% 4 6% 8% 42%	2090
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 4 6% 9% 47%	2090
October	1st to 10th	Day	6% 4 2 5% 4 4 4 4 6% 7% 55%	2090
	11th to 20th	Day	12% 4 2 4 4 4 4 3 5% 7% 51%	2000
	21st to end	Day	10% 4 1 4 4 3 3 2 4 5% 60%	2090
November	1st to 10th	Day	11% 5% 3 6% 4 5% 4 3 5% 7% 46%	1958
	11th to 20th	Day	13% 6% 2 6% 4 3 3 3 4 6% 51%	1920
	21st to end	Day	15% 7% 2 7% 5% 4 3 4 5% 5% 43%	1800
December	1st to 10th	Day	32% 10% 3 6% 3 2 3 2 3 5% 32%	2940
	11th to 20th	Day	15% 8% 3 7% 4 4 3 2 5% 6% 42%	3391
	21st to end	Day	10% 5% 2 6% 4 4 3 3 4 6% 53%	4488
January	1st to 10th	Night	19% 7% 2 5% 3 3 3 2 4 6% 46%	5888
	11th to 20th	Night	14% 4 1 4 3 3 3 2 5% 7% 54%	5900
	21st to end	Night	30% 6% 2 5% 3 3 3 3 5% 6% 34%	6002
February	1st to 10th	Night	15% 7% 2 4 4 5% 3 3 5% 7% 46%	2400
	11th to 20th	Night	20% 6% 2 5% 3 2 3 2 4 6% 48%	2338
	21st to end	Night	17% 6% 2 5% 4 3 3 3 5% 5% 48%	1980
March	1st to 10th	Night	16% 6% 3 6% 4 3 3 3 5% 6% 46%	4967
	11th to 20th	Night	17% 6% 2 6% 3 3 3 2 3 4 51%	4980
	21st to end	Night	17% 6% 2 4 3 2 3 3 5% 6% 50%	5467
April	1st to 10th	Night	11% 5% 2 5% 3 4 5% 3 8% 9% 45%	2200
	11th to 20th	Night	14% 6% 2 6% 3 3 4 3 5% 6% 48%	2173
	21st to end	Night	15% 7% 2 6% 4 4 4 4 5% 7% 42%	1935
May	1st to 10th	Night	18% 9% 3 7% 3 4 4 4 5% 7% 35%	4053
	11th to 20th	Night	9% 5% 2 4 3 4 4 3 6% 8% 53%	4053
	21st to end	Night	10% 7% 3 6% 4 4 5% 4 6% 10% 41%	4443
June	1st to 10th	Night	4 2 1 3 2 2 3 4 6% 10% 61%	1796
	11th to 20th	Night	4 2 1 3 2 3 4 3 5% 9% 64%	1710
	21st to end	Night	4 5% 2 4 4 3 4 4 7% 10% 53%	1710
July	1st to 10th	Night	4 4 1 4 3 3 4 4 6% 10% 57%	2850
	11th to 20th	Night	4 5% 2 6% 4 4 5% 3 7% 10% 50%	2850
	21st to end	Night	6% 4 2 5% 4 4 4 4 7% 10% 49%	3098
August	1st to 10th	Night	1 1 2 1 2 2 2 3 6% 80%	3021
	11th to 20th	Night	2 2 1 3 3 3 4 3 7% 12% 60%	3113
	21st to end	Night	4 3 1 4 2 4 3 3 6% 11% 59%	3673
September	1st to 10th	Night	6% 5% 1 6% 4 5% 5% 3 7% 9% 46%	2090
	11th to 20th	Night	8% 5% 2 6% 4 4 4 4 6% 8% 48%	2090
	21st to end	Night	7% 4 1 5% 3 4 4 3 6% 8% 56%	2090
October	1st to 10th	Night	4 3 1 3 3 2 3 3 5% 7% 65%	2090
	11th to 20th	Night	11% 4 1 4 2 3 3 3 4 5% 59%	2157
	21st to end	Night	10% 4 1 3 2 2 2 2 3 5% 64%	2508
November	1st to 10th	Night	12% 5% 2 5% 4 3 3 3 5% 7% 53%	2340
	11th to 20th	Night	13% 4 2 4 4 3 3 3 5% 6% 55%	2475
	21st to end	Night	15% 5% 2 6% 5% 3 3 3 4 6% 48%	2600
December	1st to 10th	Night	34% 10% 3 4 3 2 2 2 3 3 33%	4250
	11th to 20th	Night	13% 8% 3 6% 3 4 3 3 4 6% 47%	4816
	21st to end	Night	12% 5% 2 4 3 3 3 3 4 6% 55%	6490

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	39% 4 6% 17% 22% 12%	4078
	11th to 20th	Day	35% 3 5% 21% 23% 14%	4103
	21st to end	Day	50% 3 4 14% 18% 11%	4994
February	1st to 10th	Day	43% 4 7% 10% 20% 16%	2000
	11th to 20th	Day	42% 5% 7% 16% 18% 12%	1959
	21st to end	Day	38% 6% 8% 17% 18% 13%	1650
March	1st to 10th	Day	35% 6% 8% 20% 12% 20%	4889
	11th to 20th	Day	37% 5% 5% 8% 18% 27%	4980
	21st to end	Day	36% 7% 8% 21% 17% 11%	5464
April	1st to 10th	Day	35% 6% 11% 16% 18% 14%	2200
	11th to 20th	Day	41% 6% 8% 17% 16% 13%	2176
	21st to end	Day	38% 7% 8% 18% 17% 12%	2457
May	1st to 10th	Day	44% 8% 12% 20% 12% 5%	5900
	11th to 20th	Day	29% 8% 11% 24% 18% 10%	5866
	21st to end	Day	31% 8% 11% 34% 14% 1	6447
June	1st to 10th	Day	23% 8% 16% 28% 20% 3	2588
	11th to 20th	Day	28% 7% 14% 24% 21% 5%	2470
	21st to end	Day	37% 9% 16% 24% 11% 3	2470
July	1st to 10th	Day	31% 8% 17% 37% 7%	4056
	11th to 20th	Day	36% 9% 17% 24% 13% 1	4051
	21st to end	Day	35% 10% 19% 28% 8%	4325
August	1st to 10th	Day	13% 6% 13% 46% 22% 1	3899
	11th to 20th	Day	20% 9% 26% 35% 10% 1	3762
	21st to end	Day	29% 12% 20% 24% 15% 1	3973
September	1st to 10th	Day	41% 11% 14% 16% 14% 5%	2090
	11th to 20th	Day	37% 8% 15% 20% 15% 4	2090
	21st to end	Day	32% 7% 13% 19% 17% 11%	2090
October	1st to 10th	Day	20% 5% 7% 12% 23% 34%	3480
	11th to 20th	Day	25% 5% 11% 18% 20% 21%	3305
	21st to end	Day	23% 5% 8% 17% 30% 17%	3428
November	1st to 10th	Day	37% 6% 9% 19% 18% 12%	1958
	11th to 20th	Day	35% 5% 9% 17% 20% 14%	1920
	21st to end	Day	43% 4 7% 16% 17% 13%	1800
December	1st to 10th	Day	57% 4 5% 12% 16% 6%	2940
	11th to 20th	Day	42% 5% 7% 16% 15% 13%	3389
	21st to end	Day	32% 4 5% 21% 23% 15%	4488
January	1st to 10th	Night	38% 5% 6% 15% 17% 18%	5888
	11th to 20th	Night	31% 2 6% 20% 21% 20%	5900
	21st to end	Night	51% 4 5% 11% 18% 11%	6002
February	1st to 10th	Night	38% 5% 9% 13% 16% 19%	2400
	11th to 20th	Night	38% 4 8% 17% 18% 14%	2338
	21st to end	Night	38% 6% 7% 18% 18% 13%	1980
March	1st to 10th	Night	39% 6% 8% 18% 14% 15%	4967
	11th to 20th	Night	37% 5% 7% 11% 16% 24%	4980
	21st to end	Night	34% 6% 12% 20% 18% 10%	5467
April	1st to 10th	Night	33% 7% 13% 19% 15% 12%	2200
	11th to 20th	Night	36% 6% 10% 17% 14% 16%	2173
	21st to end	Night	41% 7% 10% 18% 15% 10%	1935
May	1st to 10th	Night	44% 9% 10% 18% 13% 5%	4080
	11th to 20th	Night	26% 7% 14% 21% 22% 9%	4054
	21st to end	Night	37% 8% 17% 29% 8% 1	4452
June	1st to 10th	Night	17% 8% 19% 34% 20% 2	1796
	11th to 20th	Night	17% 7% 13% 35% 24% 4	1710
	21st to end	Night	26% 9% 19% 30% 15% 1	1710
July	1st to 10th	Night	23% 8% 26% 37% 6%	2805
	11th to 20th	Night	28% 9% 25% 26% 12%	2796
	21st to end	Night	28% 9% 26% 30% 7%	2999
August	1st to 10th	Night	8% 5% 16% 51% 21%	3011
	11th to 20th	Night	18% 6% 35% 35% 6%	3143
	21st to end	Night	20% 11% 27% 31% 11% 1	3673
September	1st to 10th	Night	32% 10% 21% 20% 13% 5%	2090
	11th to 20th	Night	31% 9% 15% 24% 17% 3	2090
	21st to end	Night	26% 6% 14% 26% 19% 10%	2090
October	1st to 10th	Night	15% 4 8% 18% 21% 33%	3480
	11th to 20th	Night	20% 4 11% 19% 25% 20%	3578
	21st to end	Night	19% 4 10% 20% 32% 16%	4120
November	1st to 10th	Night	31% 7% 9% 19% 22% 12%	2340
	11th to 20th	Night	31% 6% 12% 17% 19% 16%	2475
	21st to end	Night	36% 5% 9% 20% 18% 12%	2600
December	1st to 10th	Night	58% 4 5% 11% 13% 9%	4250
	11th to 20th	Night	37% 5% 9% 16% 17% 16%	4817
	21st to end	Night	29% 5% 7% 18% 24% 17%	6490

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	20% 9% 31% 28% 10% 2	300
	11th to 20th	Day	20% 9% 30% 29% 12% 1	300
	21st to end	Day	23% 9% 31% 26% 11% 1	330
February	1st to 10th	Day	20% 9% 28% 25% 15% 3	300
	11th to 20th	Day	22% 10% 35% 23% 8% 1	300
	21st to end	Day	20% 10% 33% 31% 6%	249
March	1st to 10th	Day	19% 8% 37% 26% 9%	300
	11th to 20th	Day	16% 10% 40% 26% 8%	300
	21st to end	Day	13% 10% 38% 32% 7% 1	330
April	1st to 10th	Day	15% 7% 35% 30% 13%	300
	11th to 20th	Day	14% 14% 32% 27% 13% 1	294
	21st to end	Day	12% 13% 40% 29% 6% 1	557
May	1st to 10th	Day	13% 11% 37% 29% 9%	703
	11th to 20th	Day	12% 9% 32% 32% 14% 2	725
	21st to end	Day	9% 4 28% 40% 18% 1	789
June	1st to 10th	Day	5% 2 14% 41% 33% 5%	726
	11th to 20th	Day	5% 1 13% 47% 27% 6%	680
	21st to end	Day	7% 1 11% 34% 34% 12%	680
July	1st to 10th	Day	7% 1 10% 31% 38% 13%	671
	11th to 20th	Day	4 1 6% 30% 47% 12%	668
	21st to end	Day	4 1 5% 32% 46% 12%	739
August	1st to 10th	Day	2 5% 32% 41% 21%	563
	11th to 20th	Day	4 7% 29% 39% 21%	477
	21st to end	Day	6% 5% 21% 35% 33%	424
September	1st to 10th	Day	9% 1 5% 18% 44% 23%	300
	11th to 20th	Day	9% 5% 13% 40% 33%	300
	21st to end	Day	9% 1 6% 15% 41% 28%	300
October	1st to 10th	Day	8% 1 8% 24% 38% 21%	300
	11th to 20th	Day	12% 1 10% 29% 32% 15%	300
	21st to end	Day	14% 7% 21% 27% 23% 9%	330
November	1st to 10th	Day	13% 2 21% 31% 27% 6%	300
	11th to 20th	Day	19% 4 16% 31% 23% 8%	300
	21st to end	Day	21% 9% 27% 25% 13% 5%	300
December	1st to 10th	Day	22% 4 21% 26% 20% 6%	300
	11th to 20th	Day	24% 9% 23% 24% 19% 1	300
	21st to end	Day	17% 9% 25% 32% 16% 2	330
January	1st to 10th	Night	20% 7% 26% 36% 11% 1	1000
	11th to 20th	Night	21% 7% 29% 35% 8%	1000
	21st to end	Night	22% 7% 27% 37% 7%	885
February	1st to 10th	Night	20% 10% 32% 32% 6%	800
	11th to 20th	Night	23% 8% 36% 28% 6%	784
	21st to end	Night	20% 9% 40% 27% 3	660
March	1st to 10th	Night	20% 11% 41% 24% 4	624
	11th to 20th	Night	14% 13% 39% 30% 3	600
	21st to end	Night	14% 10% 47% 27% 3	660
April	1st to 10th	Night	12% 10% 49% 25% 4	600
	11th to 20th	Night	16% 8% 45% 28% 3	593
	21st to end	Night	14% 11% 45% 25% 5% 1	600
May	1st to 10th	Night	13% 8% 50% 27% 3	600
	11th to 20th	Night	12% 5% 42% 34% 7%	591
	21st to end	Night	8% 4 41% 40% 6%	650
June	1st to 10th	Night	4 2 25% 53% 16% 1	599
	11th to 20th	Night	5% 1 29% 52% 13% 1	570
	21st to end	Night	4 2 20% 49% 23% 1	570
July	1st to 10th	Night	7% 2 13% 53% 23% 2	555
	11th to 20th	Night	4 12% 57% 26% 1	552
	21st to end	Night	5% 11% 55% 28% 1	624
August	1st to 10th	Night	1 11% 58% 27% 3	567
	11th to 20th	Night	4 1 11% 53% 28% 2	564
	21st to end	Night	7% 7% 44% 39% 3	627
September	1st to 10th	Night	7% 1 9% 44% 34% 5%	570
	11th to 20th	Night	10% 1 9% 36% 40% 4	570
	21st to end	Night	9% 11% 40% 37% 4	570
October	1st to 10th	Night	5% 1 13% 46% 34% 2	570
	11th to 20th	Night	13% 1 21% 45% 18% 1	637
	21st to end	Night	11% 5% 26% 38% 20% 2	836
November	1st to 10th	Night	12% 6% 21% 40% 20% 1	780
	11th to 20th	Night	13% 5% 22% 43% 17% 1	875
	21st to end	Night	17% 6% 25% 36% 16% 1	1000
December	1st to 10th	Night	21% 4 23% 37% 14% 1	1000
	11th to 20th	Night	23% 7% 24% 35% 11%	1000
	21st to end	Night	18% 6% 25% 39% 11%	1100

Page generated at 2025-06-07 09:28:16. Version ac07

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