Seminole Canyon State Park & Historic Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Seminole Canyon State Park & Historic Site clear sky chart from 2005-11-06 to 2025-07-06.

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	9% 5% 2 4 3 3 3 3 4 7% 59%	124118
	Night	8% 4 1 4 3 3 3 3 5% 7% 60%	123501
Transparency	Day	16% 40% 6% 13% 14% 11%	123895
	Night	16% 39% 6% 14% 14% 11%	123312
Seeing	Day	10% 6% 25% 35% 20% 4	15585
	Night	10% 6% 32% 40% 12%	25596

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	9% 7% 1 3 2 2 2 2 3 5% 65%	4165
	11th to 20th	Day	7% 5% 1 2 2 2 3 2 3 7% 65%	4540
	21st to end	Day	13% 6% 2 4 3 3 3 2 4 6% 53%	4994
February	1st to 10th	Day	9% 7% 2 5% 3 4 3 2 4 5% 56%	2000
	11th to 20th	Day	11% 6% 3 4 3 3 3 2 4 6% 56%	1949
	21st to end	Day	9% 6% 2 4 2 2 3 3 5% 7% 59%	1650
March	1st to 10th	Day	9% 5% 1 4 3 3 3 3 4 5% 60%	4500
	11th to 20th	Day	14% 4 2 4 2 2 3 2 3 5% 59%	4882
	21st to end	Day	8% 6% 2 5% 3 3 4 3 5% 6% 55%	5495
April	1st to 10th	Day	8% 4 1 5% 3 2 4 3 6% 7% 56%	2400
	11th to 20th	Day	11% 5% 1 4 3 3 3 3 5% 6% 57%	2371
	21st to end	Day	12% 5% 1 4 2 3 3 3 5% 7% 55%	2400
May	1st to 10th	Day	13% 5% 2 5% 3 3 3 3 5% 7% 51%	5569
	11th to 20th	Day	9% 3 2 4 3 3 3 3 5% 8% 59%	5862
	21st to end	Day	11% 5% 2 4 3 4 4 4 6% 8% 49%	6446
June	1st to 10th	Day	4 3 1 3 2 4 4 3 6% 9% 61%	2600
	11th to 20th	Day	6% 4 2 4 2 3 3 3 5% 7% 61%	2600
	21st to end	Day	6% 4 1 3 4 3 3 4 6% 9% 56%	2600
July	1st to 10th	Day	8% 3 1 3 3 3 3 3 5% 7% 60%	4186
	11th to 20th	Day	3 2 1 3 3 3 3 3 5% 9% 64%	4042
	21st to end	Day	5% 3 1 4 3 3 3 3 5% 9% 60%	4118
August	1st to 10th	Day	1 1 2 2 2 2 2 4 7% 77%	3784
	11th to 20th	Day	2 2 1 2 2 2 2 3 4 8% 72%	3726
	21st to end	Day	4 3 1 4 3 3 4 4 5% 10% 59%	4180
September	1st to 10th	Day	9% 5% 2 6% 5% 4 5% 4 5% 7% 48%	2190
	11th to 20th	Day	10% 6% 2 4 4 4 5% 4 6% 7% 48%	2090
	21st to end	Day	9% 3 1 4 2 4 4 3 5% 6% 58%	2090
October	1st to 10th	Day	4 2 1 2 2 2 2 2 4 5% 73%	3480
	11th to 20th	Day	12% 4 2 5% 4 2 2 2 3 4 59%	3458
	21st to end	Day	10% 4 1 3 2 1 2 2 2 4 69%	3569
November	1st to 10th	Day	13% 5% 1 4 2 2 2 2 4 7% 58%	1763
	11th to 20th	Day	9% 4 2 4 3 2 3 3 4 5% 62%	1800
	21st to end	Day	11% 7% 2 4 3 3 3 2 4 6% 53%	1800
December	1st to 10th	Day	21% 10% 3 5% 3 2 3 2 4 5% 42%	2940
	11th to 20th	Day	12% 6% 2 5% 3 3 4 3 5% 6% 51%	3391
	21st to end	Day	8% 7% 2 3 2 2 2 1 3 4 66%	4488
January	1st to 10th	Night	7% 5% 2 4 3 2 2 2 4 7% 63%	5842
	11th to 20th	Night	7% 4 1 2 2 2 2 2 3 5% 70%	5440
	21st to end	Night	17% 7% 2 4 2 2 2 3 4 6% 51%	5984
February	1st to 10th	Night	7% 5% 2 5% 3 3 2 3 5% 6% 61%	2400
	11th to 20th	Night	11% 5% 2 5% 3 3 4 2 5% 6% 55%	2338
	21st to end	Night	8% 4 2 4 3 3 3 3 5% 7% 58%	1980
March	1st to 10th	Night	5% 4 1 3 3 3 3 3 6% 7% 62%	5374
	11th to 20th	Night	12% 4 2 3 2 2 2 2 4 5% 61%	5078
	21st to end	Night	7% 5% 2 4 2 3 3 3 5% 5% 61%	5433
April	1st to 10th	Night	6% 5% 2 3 3 3 3 3 5% 7% 60%	2000
	11th to 20th	Night	12% 4 1 4 2 3 3 3 5% 6% 57%	1977
	21st to end	Night	11% 5% 1 3 3 3 2 2 4 5% 59%	2000
May	1st to 10th	Night	16% 6% 2 5% 3 3 3 2 4 5% 50%	4407
	11th to 20th	Night	7% 3 1 4 3 3 4 4 5% 7% 59%	4053
	21st to end	Night	10% 4 2 5% 3 3 4 4 7% 9% 49%	4451
June	1st to 10th	Night	3 2 1 3 3 3 4 3 7% 10% 61%	1800
	11th to 20th	Night	3 2 1 2 3 3 4 3 6% 9% 64%	1800
	21st to end	Night	5% 3 1 3 3 4 4 4 7% 9% 57%	1800
July	1st to 10th	Night	5% 3 1 4 3 3 4 3 6% 10% 59%	2895
	11th to 20th	Night	2 2 1 3 2 3 3 4 6% 9% 64%	2908
	21st to end	Night	5% 3 1 3 3 3 3 3 5% 8% 62%	3445
August	1st to 10th	Night	1 1 2 2 2 2 2 4 8% 76%	3155
	11th to 20th	Night	3 1 1 2 2 2 3 3 5% 10% 66%	3113
	21st to end	Night	5% 3 2 4 3 3 4 4 6% 11% 54%	3487
September	1st to 10th	Night	6% 5% 2 5% 4 3 4 4 5% 8% 55%	1988
	11th to 20th	Night	9% 4 2 5% 4 3 5% 3 6% 9% 51%	2090
	21st to end	Night	8% 3 1 4 3 3 4 4 6% 7% 57%	2090
October	1st to 10th	Night	4 2 1 3 3 2 3 2 4 5% 72%	3480
	11th to 20th	Night	11% 4 1 5% 2 2 3 3 3 4 62%	3460
	21st to end	Night	6% 2 1 3 2 2 2 1 3 3 77%	3942
November	1st to 10th	Night	12% 4 2 3 2 2 2 2 4 4 63%	2535
	11th to 20th	Night	7% 3 1 3 2 3 3 3 4 6% 64%	2600
	21st to end	Night	10% 5% 1 4 3 3 3 3 5% 6% 59%	2600
December	1st to 10th	Night	23% 7% 2 4 3 3 3 4 5% 6% 41%	4250
	11th to 20th	Night	9% 6% 2 4 3 3 3 3 4 5% 58%	4816
	21st to end	Night	7% 5% 1 3 2 2 2 2 4 7% 65%	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	20% 25% 3 17% 17% 18%	4166
	11th to 20th	Day	15% 26% 4 17% 19% 18%	4540
	21st to end	Day	26% 28% 4 11% 18% 12%	4994
February	1st to 10th	Day	15% 62% 2 4 7% 9%	2000
	11th to 20th	Day	11% 60% 4 12% 8% 5%	1959
	21st to end	Day	13% 61% 4 5% 10% 7%	1650
March	1st to 10th	Day	20% 28% 4 11% 12% 26%	4500
	11th to 20th	Day	20% 29% 4 5% 12% 30%	4882
	21st to end	Day	22% 29% 5% 10% 14% 19%	5495
April	1st to 10th	Day	10% 63% 3 7% 7% 10%	2400
	11th to 20th	Day	14% 63% 2 7% 8% 6%	2374
	21st to end	Day	10% 62% 4 10% 6% 8%	2400
May	1st to 10th	Day	24% 30% 6% 11% 14% 16%	5569
	11th to 20th	Day	18% 29% 7% 12% 17% 18%	5866
	21st to end	Day	23% 31% 7% 17% 14% 9%	6447
June	1st to 10th	Day	8% 62% 5% 14% 9% 1	2600
	11th to 20th	Day	10% 63% 5% 8% 12% 2	2600
	21st to end	Day	8% 62% 8% 13% 8% 2	2600
July	1st to 10th	Day	10% 37% 13% 26% 14%	4122
	11th to 20th	Day	10% 37% 13% 26% 12% 2	3973
	21st to end	Day	13% 36% 8% 17% 22% 3	3988
August	1st to 10th	Day	5% 37% 5% 24% 27% 3	3772
	11th to 20th	Day	5% 38% 10% 33% 13% 1	3762
	21st to end	Day	11% 40% 12% 18% 16% 2	4179
September	1st to 10th	Day	14% 61% 4 9% 7% 5%	2190
	11th to 20th	Day	13% 61% 6% 10% 8% 2	2090
	21st to end	Day	14% 61% 6% 8% 7% 3	2090
October	1st to 10th	Day	8% 37% 4 7% 13% 32%	3480
	11th to 20th	Day	21% 37% 4 7% 8% 23%	3458
	21st to end	Day	15% 36% 2 11% 30% 5%	3569
November	1st to 10th	Day	20% 56% 5% 7% 6% 6%	1763
	11th to 20th	Day	16% 57% 4 8% 8% 7%	1800
	21st to end	Day	17% 57% 3 7% 11% 5%	1800
December	1st to 10th	Day	35% 36% 3 11% 8% 8%	2940
	11th to 20th	Day	24% 33% 5% 15% 13% 10%	3389
	21st to end	Day	19% 26% 2 13% 17% 23%	4488
January	1st to 10th	Night	17% 26% 6% 16% 23% 13%	5842
	11th to 20th	Night	12% 26% 3 14% 20% 25%	5440
	21st to end	Night	27% 28% 4 12% 18% 12%	5984
February	1st to 10th	Night	11% 62% 3 7% 8% 11%	2400
	11th to 20th	Night	11% 61% 4 10% 10% 4	2338
	21st to end	Night	13% 62% 3 6% 9% 7%	1980
March	1st to 10th	Night	14% 29% 5% 15% 17% 20%	5374
	11th to 20th	Night	18% 29% 4 7% 12% 30%	5078
	21st to end	Night	18% 30% 6% 13% 16% 17%	5433
April	1st to 10th	Night	10% 61% 4 8% 6% 10%	2000
	11th to 20th	Night	13% 63% 4 7% 7% 6%	1977
	21st to end	Night	10% 62% 4 9% 9% 6%	2000
May	1st to 10th	Night	28% 30% 6% 12% 11% 13%	4404
	11th to 20th	Night	16% 29% 8% 12% 18% 17%	4054
	21st to end	Night	23% 30% 10% 17% 12% 8%	4452
June	1st to 10th	Night	6% 63% 6% 14% 9% 1	1800
	11th to 20th	Night	8% 62% 7% 11% 10% 2	1800
	21st to end	Night	7% 62% 6% 14% 9% 2	1800
July	1st to 10th	Night	9% 36% 14% 28% 12%	2850
	11th to 20th	Night	9% 37% 12% 24% 14% 3	2854
	21st to end	Night	13% 36% 8% 19% 22% 2	3336
August	1st to 10th	Night	6% 36% 6% 25% 26% 2	3144
	11th to 20th	Night	6% 38% 12% 34% 9% 1	3143
	21st to end	Night	13% 38% 11% 18% 18% 2	3487
September	1st to 10th	Night	12% 61% 4 9% 9% 6%	1988
	11th to 20th	Night	10% 61% 8% 11% 8% 2	2090
	21st to end	Night	13% 61% 6% 11% 5% 3	2090
October	1st to 10th	Night	9% 36% 4 7% 11% 33%	3480
	11th to 20th	Night	17% 37% 4 6% 13% 24%	3460
	21st to end	Night	11% 36% 4 14% 30% 6%	3942
November	1st to 10th	Night	18% 56% 5% 6% 8% 6%	2535
	11th to 20th	Night	14% 58% 5% 10% 7% 7%	2600
	21st to end	Night	14% 57% 3 8% 11% 7%	2600
December	1st to 10th	Night	34% 36% 4 10% 6% 10%	4250
	11th to 20th	Night	19% 32% 6% 15% 18% 10%	4817
	21st to end	Night	16% 27% 4 18% 19% 16%	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	15% 7% 33% 32% 12% 2	300
	11th to 20th	Day	15% 9% 30% 34% 11% 1	300
	21st to end	Day	14% 8% 37% 29% 11% 1	330
February	1st to 10th	Day	15% 9% 27% 29% 16% 4	300
	11th to 20th	Day	18% 10% 34% 29% 7% 1	300
	21st to end	Day	14% 11% 41% 27% 8%	249
March	1st to 10th	Day	18% 8% 42% 24% 8%	300
	11th to 20th	Day	14% 14% 36% 26% 10%	300
	21st to end	Day	10% 14% 42% 26% 7% 1	336
April	1st to 10th	Day	9% 15% 40% 30% 6% 1	500
	11th to 20th	Day	11% 13% 45% 26% 4	492
	21st to end	Day	11% 14% 43% 25% 7%	500
May	1st to 10th	Day	10% 11% 38% 33% 7%	554
	11th to 20th	Day	14% 8% 36% 31% 9% 1	725
	21st to end	Day	14% 6% 36% 35% 7% 1	789
June	1st to 10th	Day	5% 2 26% 48% 16% 2	730
	11th to 20th	Day	6% 2 30% 45% 16% 2	730
	21st to end	Day	6% 2 16% 48% 24% 4	730
July	1st to 10th	Day	9% 2 10% 41% 32% 6%	697
	11th to 20th	Day	3 6% 47% 38% 5%	629
	21st to end	Day	2 5% 46% 41% 6%	531
August	1st to 10th	Day	2 1 6% 44% 40% 8%	487
	11th to 20th	Day	5% 1 5% 39% 40% 9%	477
	21st to end	Day	4 1 5% 36% 42% 11%	539
September	1st to 10th	Day	9% 1 8% 33% 40% 9%	400
	11th to 20th	Day	7% 7% 32% 38% 15%	300
	21st to end	Day	11% 1 7% 34% 33% 14%	300
October	1st to 10th	Day	6% 3 16% 39% 31% 4	300
	11th to 20th	Day	13% 3 20% 36% 24% 3	300
	21st to end	Day	16% 6% 23% 30% 21% 4	330
November	1st to 10th	Day	19% 5% 24% 32% 18% 2	300
	11th to 20th	Day	16% 10% 18% 32% 17% 7%	300
	21st to end	Day	18% 8% 32% 28% 11% 3	300
December	1st to 10th	Day	16% 6% 26% 28% 20% 3	300
	11th to 20th	Day	13% 10% 32% 26% 16% 3	300
	21st to end	Day	17% 9% 25% 31% 18% 1	330
January	1st to 10th	Night	11% 5% 33% 41% 10%	980
	11th to 20th	Night	14% 6% 31% 43% 6%	800
	21st to end	Night	14% 8% 37% 35% 6%	880
February	1st to 10th	Night	11% 7% 38% 36% 7%	800
	11th to 20th	Night	15% 10% 40% 29% 5%	784
	21st to end	Night	10% 10% 47% 32% 1	660
March	1st to 10th	Night	14% 12% 46% 26% 2	800
	11th to 20th	Night	12% 12% 44% 29% 4	646
	21st to end	Night	9% 12% 53% 22% 3	660
April	1st to 10th	Night	7% 13% 52% 26% 2	600
	11th to 20th	Night	13% 11% 52% 23% 1	593
	21st to end	Night	8% 14% 56% 19% 4	600
May	1st to 10th	Night	8% 10% 54% 26% 2	600
	11th to 20th	Night	10% 7% 42% 35% 5%	591
	21st to end	Night	9% 8% 49% 28% 5%	650
June	1st to 10th	Night	2 4 38% 51% 5%	600
	11th to 20th	Night	4 2 43% 45% 7%	600
	21st to end	Night	5% 2 30% 48% 14% 1	600
July	1st to 10th	Night	9% 2 14% 56% 17% 2	570
	11th to 20th	Night	3 1 16% 60% 20% 1	552
	21st to end	Night	3 1 13% 62% 21% 1	624
August	1st to 10th	Night	2 1 8% 62% 26% 1	567
	11th to 20th	Night	5% 7% 55% 32% 1	564
	21st to end	Night	6% 9% 54% 30% 2	627
September	1st to 10th	Night	7% 1 8% 51% 31% 3	570
	11th to 20th	Night	9% 1 10% 46% 32% 2	570
	21st to end	Night	8% 1 16% 44% 31% 1	570
October	1st to 10th	Night	6% 2 23% 50% 19%	570
	11th to 20th	Night	11% 3 26% 48% 10% 1	570
	21st to end	Night	10% 6% 28% 40% 15% 1	723
November	1st to 10th	Night	13% 5% 26% 41% 15% 1	975
	11th to 20th	Night	9% 5% 30% 41% 15% 1	1000
	21st to end	Night	12% 6% 32% 39% 11%	1000
December	1st to 10th	Night	15% 5% 24% 44% 12% 1	1000
	11th to 20th	Night	15% 7% 31% 38% 9%	1000
	21st to end	Night	12% 5% 34% 41% 7%	1100

Page generated at 2025-07-03 00:30:15. Version ac07

Copyright © 2025 Attilla Danko.