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 2024-11-02.

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	10% 5% 2 6% 4 4 4 4 6% 8% 46%	100925
	Night	12% 5% 2 5% 3 3 3 3 5% 8% 51%	98149
Transparency	Day	34% 7% 12% 22% 17% 8%	100736
	Night	31% 7% 14% 22% 16% 10%	98009
Seeing	Day	11% 5% 20% 30% 26% 9%	14611
	Night	13% 5% 26% 39% 15% 1	24540

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	15% 6% 2 5% 3 3 3 3 3 5% 52%	2847
	11th to 20th	Day	16% 5% 2 4 3 2 2 2 4 6% 55%	2859
	21st to end	Day	20% 8% 2 6% 4 3 4 4 6% 7% 37%	3487
February	1st to 10th	Day	17% 10% 3 5% 4 3 3 3 4 5% 43%	1900
	11th to 20th	Day	18% 6% 3 6% 3 3 3 3 4 5% 46%	1849
	21st to end	Day	16% 5% 2 5% 4 3 4 3 5% 6% 48%	1570
March	1st to 10th	Day	14% 8% 2 7% 4 5% 5% 4 6% 8% 36%	3402
	11th to 20th	Day	21% 10% 4 7% 4 4 4 4 4 5% 32%	3480
	21st to end	Day	10% 5% 2 5% 4 3 4 4 6% 7% 51%	3814
April	1st to 10th	Day	11% 6% 2 6% 4 4 5% 4 6% 6% 46%	2090
	11th to 20th	Day	15% 7% 2 7% 5% 3 4 3 5% 5% 44%	2066
	21st to end	Day	12% 7% 2 6% 4 4 4 4 5% 6% 47%	2334
May	1st to 10th	Day	14% 7% 3 7% 5% 5% 4 4 6% 8% 37%	4082
	11th to 20th	Day	10% 6% 2 7% 5% 5% 4 4 6% 8% 44%	4082
	21st to end	Day	6% 4 2 5% 5% 4 5% 4 7% 10% 47%	4477
June	1st to 10th	Day	4 3 1 4 3 5% 5% 5% 8% 10% 51%	2470
	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	12% 6% 3 6% 4 5% 4 3 5% 7% 45%	1868
	11th to 20th	Day	13% 6% 2 6% 4 3 3 3 4 6% 50%	1824
	21st to end	Day	16% 7% 2 7% 5% 4 3 4 5% 5% 43%	1710
December	1st to 10th	Day	18% 8% 3 6% 3 3 4 3 4 7% 43%	1710
	11th to 20th	Day	18% 9% 2 6% 4 4 3 3 5% 6% 40%	2161
	21st to end	Day	13% 6% 2 6% 4 4 3 3 5% 7% 48%	3135
January	1st to 10th	Night	16% 7% 2 5% 3 3 3 3 5% 6% 48%	4108
	11th to 20th	Night	14% 4 1 3 2 2 2 2 4 6% 60%	4120
	21st to end	Night	23% 7% 2 6% 4 3 3 3 5% 7% 37%	4198
February	1st to 10th	Night	15% 7% 2 4 4 5% 3 3 5% 7% 45%	2280
	11th to 20th	Night	19% 6% 2 4 3 2 2 2 4 6% 50%	2218
	21st to end	Night	16% 6% 2 5% 4 3 3 3 5% 5% 49%	1884
March	1st to 10th	Night	18% 7% 3 7% 4 4 4 3 5% 6% 39%	3453
	11th to 20th	Night	24% 9% 3 8% 4 4 4 3 4 5% 32%	3480
	21st to end	Night	14% 5% 2 4 3 3 3 3 5% 6% 54%	3817
April	1st to 10th	Night	11% 5% 2 4 3 4 5% 3 8% 9% 44%	2090
	11th to 20th	Night	14% 6% 2 5% 3 3 4 3 5% 6% 47%	2063
	21st to end	Night	14% 7% 2 6% 4 4 4 4 5% 7% 43%	1839
May	1st to 10th	Night	16% 8% 2 6% 3 4 4 4 6% 8% 39%	2823
	11th to 20th	Night	13% 6% 2 5% 4 4 4 3 5% 8% 47%	2823
	21st to end	Night	9% 5% 2 5% 3 4 5% 4 6% 10% 48%	3090
June	1st to 10th	Night	4 2 1 3 2 2 3 4 6% 9% 62%	1710
	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 4 4 3 3 3 5% 7% 53%	2244
	11th to 20th	Night	13% 4 2 4 4 3 3 3 5% 6% 53%	2351
	21st to end	Night	16% 4 1 6% 5% 3 4 3 4 6% 47%	2470
December	1st to 10th	Night	17% 6% 2 3 3 3 3 3 5% 6% 49%	2470
	11th to 20th	Night	17% 7% 3 4 4 4 4 3 5% 7% 43%	3036
	21st to end	Night	14% 6% 2 5% 4 3 3 3 5% 8% 47%	4532

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	35% 5% 5% 12% 26% 17%	2848
	11th to 20th	Day	32% 3 5% 20% 23% 17%	2859
	21st to end	Day	46% 4 5% 15% 23% 8%	3487
February	1st to 10th	Day	44% 4 7% 11% 19% 15%	1900
	11th to 20th	Day	40% 5% 8% 15% 19% 13%	1859
	21st to end	Day	37% 6% 9% 17% 18% 13%	1570
March	1st to 10th	Day	43% 8% 9% 18% 15% 7%	3402
	11th to 20th	Day	53% 7% 7% 9% 16% 8%	3480
	21st to end	Day	29% 8% 10% 20% 17% 16%	3814
April	1st to 10th	Day	36% 7% 11% 16% 18% 13%	2090
	11th to 20th	Day	41% 6% 8% 17% 15% 13%	2066
	21st to end	Day	37% 7% 8% 18% 18% 12%	2334
May	1st to 10th	Day	42% 9% 12% 18% 12% 7%	4120
	11th to 20th	Day	35% 9% 10% 19% 17% 9%	4086
	21st to end	Day	27% 9% 12% 37% 13% 1	4489
June	1st to 10th	Day	24% 8% 17% 27% 21% 4	2470
	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	27% 8% 10% 19% 26% 10%	2090
	11th to 20th	Day	32% 6% 11% 19% 18% 15%	2000
	21st to end	Day	26% 4 7% 16% 26% 20%	2090
November	1st to 10th	Day	38% 6% 9% 19% 18% 11%	1868
	11th to 20th	Day	36% 5% 10% 16% 20% 13%	1824
	21st to end	Day	43% 4 7% 16% 17% 12%	1710
December	1st to 10th	Day	41% 5% 8% 18% 18% 9%	1710
	11th to 20th	Day	44% 5% 7% 10% 18% 15%	2159
	21st to end	Day	36% 5% 6% 19% 23% 11%	3135
January	1st to 10th	Night	35% 6% 7% 13% 17% 23%	4108
	11th to 20th	Night	27% 3 6% 19% 23% 22%	4120
	21st to end	Night	45% 5% 6% 12% 22% 10%	4198
February	1st to 10th	Night	39% 5% 9% 13% 15% 18%	2280
	11th to 20th	Night	37% 4 8% 18% 18% 15%	2218
	21st to end	Night	37% 6% 7% 18% 18% 13%	1884
March	1st to 10th	Night	44% 7% 10% 16% 15% 8%	3453
	11th to 20th	Night	52% 7% 9% 13% 10% 9%	3480
	21st to end	Night	28% 7% 14% 19% 20% 12%	3817
April	1st to 10th	Night	33% 8% 13% 19% 16% 11%	2090
	11th to 20th	Night	37% 7% 10% 17% 13% 16%	2063
	21st to end	Night	40% 7% 9% 18% 16% 10%	1839
May	1st to 10th	Night	38% 10% 12% 20% 13% 8%	2850
	11th to 20th	Night	34% 9% 12% 20% 18% 7%	2824
	21st to end	Night	30% 9% 17% 34% 10% 1	3099
June	1st to 10th	Night	16% 8% 20% 33% 21% 2	1710
	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	19% 7% 13% 28% 22% 13%	2090
	11th to 20th	Night	28% 5% 10% 22% 19% 16%	2157
	21st to end	Night	23% 4 8% 18% 26% 20%	2508
November	1st to 10th	Night	31% 7% 9% 19% 22% 11%	2244
	11th to 20th	Night	32% 6% 13% 17% 19% 14%	2351
	21st to end	Night	37% 5% 9% 20% 18% 12%	2470
December	1st to 10th	Night	37% 5% 9% 19% 20% 11%	2470
	11th to 20th	Night	40% 6% 6% 15% 16% 16%	3037
	21st to end	Night	35% 7% 8% 15% 23% 13%	4532

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	19% 9% 30% 30% 11% 1	270
	11th to 20th	Day	19% 9% 29% 30% 13% 1	270
	21st to end	Day	22% 8% 31% 26% 12% 1	297
February	1st to 10th	Day	20% 10% 30% 25% 13% 3	270
	11th to 20th	Day	21% 8% 37% 24% 9% 1	270
	21st to end	Day	20% 10% 35% 28% 7%	225
March	1st to 10th	Day	21% 7% 36% 27% 9%	270
	11th to 20th	Day	18% 10% 37% 27% 8%	270
	21st to end	Day	12% 11% 38% 32% 6% 1	297
April	1st to 10th	Day	16% 7% 35% 29% 12%	270
	11th to 20th	Day	14% 15% 32% 25% 13% 1	264
	21st to end	Day	12% 12% 39% 29% 7% 1	514
May	1st to 10th	Day	13% 11% 37% 30% 9%	653
	11th to 20th	Day	13% 9% 31% 32% 14% 2	675
	21st to end	Day	10% 4 28% 40% 18% 1	734
June	1st to 10th	Day	4 2 14% 40% 34% 5%	680
	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% 20% 28% 22% 9%	330
November	1st to 10th	Day	15% 3 18% 30% 29% 7%	273
	11th to 20th	Day	20% 4 16% 29% 24% 7%	270
	21st to end	Day	23% 9% 29% 23% 12% 4	270
December	1st to 10th	Day	19% 4 22% 27% 21% 7%	270
	11th to 20th	Day	25% 9% 24% 25% 17%	270
	21st to end	Day	18% 9% 25% 31% 14% 3	297
January	1st to 10th	Night	20% 7% 25% 37% 11% 1	950
	11th to 20th	Night	21% 7% 27% 36% 9%	950
	21st to end	Night	21% 7% 27% 38% 7%	841
February	1st to 10th	Night	19% 10% 33% 32% 6%	760
	11th to 20th	Night	22% 8% 35% 29% 6%	744
	21st to end	Night	20% 9% 41% 27% 3	628
March	1st to 10th	Night	20% 11% 41% 24% 4	593
	11th to 20th	Night	15% 13% 38% 31% 3	570
	21st to end	Night	13% 10% 46% 27% 3	627
April	1st to 10th	Night	12% 9% 49% 26% 4	570
	11th to 20th	Night	16% 8% 44% 28% 3	563
	21st to end	Night	13% 11% 45% 26% 5% 1	570
May	1st to 10th	Night	12% 8% 51% 27% 3	570
	11th to 20th	Night	12% 5% 41% 35% 7%	561
	21st to end	Night	7% 4 41% 41% 7%	617
June	1st to 10th	Night	4 2 24% 53% 17% 1	570
	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	10% 5% 26% 38% 20% 2	836
November	1st to 10th	Night	12% 5% 20% 41% 21% 1	748
	11th to 20th	Night	13% 5% 22% 43% 16% 1	831
	21st to end	Night	17% 6% 25% 36% 16% 1	950
December	1st to 10th	Night	20% 3 24% 37% 15% 1	950
	11th to 20th	Night	24% 7% 25% 35% 10%	950
	21st to end	Night	19% 6% 25% 39% 11%	1045

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