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 2026-10-29.

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	8% 4 1 4 3 3 3 3 5% 7% 59%	157415
	Night	8% 4 1 4 3 3 3 3 5% 7% 60%	152173
Transparency	Day	18% 33% 7% 16% 15% 11%	152519
	Night	17% 33% 7% 16% 16% 11%	148078
Seeing	Day	10% 6% 24% 36% 20% 4	17329
	Night	9% 6% 32% 41% 12%	27246

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	7% 5% 1 3 2 2 2 2 3 5% 67%	5403
	11th to 20th	Day	7% 5% 1 3 2 3 3 2 3 6% 65%	5910
	21st to end	Day	13% 7% 2 4 3 3 3 2 4 6% 53%	6468
February	1st to 10th	Day	9% 7% 2 5% 3 4 3 2 4 5% 56%	2100
	11th to 20th	Day	10% 6% 2 4 3 3 3 3 4 6% 56%	2049
	21st to end	Day	8% 5% 2 4 2 2 3 3 5% 7% 60%	1730
March	1st to 10th	Day	9% 5% 1 4 3 3 3 3 4 5% 60%	4600
	11th to 20th	Day	13% 4 2 3 2 2 3 2 3 5% 60%	4990
	21st to end	Day	8% 6% 2 5% 3 3 4 3 5% 6% 56%	5616
April	1st to 10th	Day	8% 4 1 6% 3 3 4 3 6% 7% 55%	2520
	11th to 20th	Day	12% 5% 1 4 3 3 3 3 5% 6% 55%	2491
	21st to end	Day	12% 5% 1 4 3 3 3 3 5% 7% 54%	2520
May	1st to 10th	Day	13% 5% 2 5% 3 3 3 4 5% 8% 49%	7226
	11th to 20th	Day	8% 4 2 5% 4 3 4 3 5% 9% 54%	7627
	21st to end	Day	11% 5% 2 5% 3 4 4 4 7% 9% 47%	8404
June	1st to 10th	Day	5% 3 1 4 2 4 4 3 6% 10% 59%	2730
	11th to 20th	Day	6% 4 2 4 2 3 3 3 5% 7% 60%	2730
	21st to end	Day	5% 4 1 3 4 3 3 4 6% 9% 56%	2730
July	1st to 10th	Day	8% 3 1 3 3 3 3 3 6% 9% 56%	7679
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 4 6% 8% 50%	7546
	21st to end	Day	3 3 1 3 2 3 3 3 4 7% 68%	7686
August	1st to 10th	Day	1 1 2 2 2 2 2 3 7% 79%	6988
	11th to 20th	Day	1 1 2 2 2 2 2 4 8% 75%	7003
	21st to end	Day	3 2 1 3 2 3 3 3 4 8% 68%	7751
September	1st to 10th	Day	9% 5% 2 5% 4 4 5% 4 5% 7% 50%	2420
	11th to 20th	Day	9% 6% 2 4 4 4 5% 4 6% 7% 49%	2310
	21st to end	Day	9% 3 1 4 3 4 4 3 6% 6% 56%	2310
October	1st to 10th	Day	4 2 1 2 2 2 2 2 4 5% 73%	3700
	11th to 20th	Day	12% 4 2 5% 4 3 2 2 3 4 58%	3678
	21st to end	Day	10% 4 1 3 2 2 2 2 2 4 69%	3769
November	1st to 10th	Day	12% 5% 1 4 2 2 2 2 4 7% 60%	1853
	11th to 20th	Day	9% 4 2 4 3 2 3 3 3 4 62%	1890
	21st to end	Day	12% 8% 2 4 3 3 3 2 4 6% 53%	1890
December	1st to 10th	Day	21% 10% 3 5% 3 2 3 2 4 5% 43%	3030
	11th to 20th	Day	12% 6% 2 5% 3 3 4 3 5% 6% 52%	3481
	21st to end	Day	8% 7% 2 4 2 2 2 1 3 4 66%	4587
January	1st to 10th	Night	6% 4 1 3 2 2 2 2 4 7% 66%	7574
	11th to 20th	Night	7% 5% 1 3 2 2 2 2 3 4 70%	7080
	21st to end	Night	15% 7% 2 5% 3 3 3 3 4 6% 50%	7746
February	1st to 10th	Night	7% 5% 2 4 3 3 2 3 5% 6% 61%	2520
	11th to 20th	Night	11% 5% 2 5% 3 3 4 2 5% 6% 56%	2458
	21st to end	Night	8% 4 2 4 3 3 3 3 5% 6% 59%	2076
March	1st to 10th	Night	5% 4 1 3 3 3 3 3 6% 7% 62%	5494
	11th to 20th	Night	12% 4 2 3 2 2 2 2 4 5% 62%	5190
	21st to end	Night	7% 5% 2 4 2 3 3 3 4 5% 61%	5553
April	1st to 10th	Night	6% 5% 2 3 3 3 3 3 6% 8% 59%	2100
	11th to 20th	Night	12% 4 1 4 3 3 3 3 5% 6% 56%	2077
	21st to end	Night	12% 5% 1 3 3 3 3 2 4 5% 58%	2100
May	1st to 10th	Night	15% 6% 2 5% 3 3 3 3 4 5% 49%	5717
	11th to 20th	Night	6% 3 1 4 3 4 5% 4 6% 8% 56%	5265
	21st to end	Night	10% 5% 2 5% 3 4 5% 4 7% 9% 46%	5803
June	1st to 10th	Night	3 2 1 3 3 3 4 3 7% 10% 60%	1890
	11th to 20th	Night	3 3 1 2 3 3 4 3 6% 9% 62%	1890
	21st to end	Night	5% 3 1 3 3 3 4 4 7% 9% 57%	1890
July	1st to 10th	Night	6% 3 1 4 3 3 4 3 7% 14% 52%	5310
	11th to 20th	Night	7% 4 2 6% 4 4 4 4 6% 9% 51%	5424
	21st to end	Night	3 2 1 3 2 2 3 3 5% 7% 70%	6423
August	1st to 10th	Night	2 1 2 1 2 2 2 4 8% 77%	5834
	11th to 20th	Night	1 1 1 2 2 2 3 3 5% 11% 69%	5853
	21st to end	Night	4 2 1 4 3 3 3 3 5% 9% 63%	6465
September	1st to 10th	Night	6% 5% 2 5% 4 3 4 4 5% 8% 55%	2198
	11th to 20th	Night	8% 4 2 5% 4 3 5% 4 6% 9% 51%	2310
	21st to end	Night	7% 3 1 4 3 3 4 4 7% 7% 55%	2310
October	1st to 10th	Night	4 2 1 3 3 2 3 2 3 5% 72%	3700
	11th to 20th	Night	11% 4 1 5% 2 2 3 3 3 4 63%	3680
	21st to end	Night	6% 2 1 3 2 2 2 1 3 3 76%	4159
November	1st to 10th	Night	12% 3 1 3 2 2 2 2 4 4 65%	2665
	11th to 20th	Night	7% 3 1 3 2 2 3 3 4 6% 65%	2730
	21st to end	Night	10% 4 1 4 3 3 3 3 5% 6% 58%	2730
December	1st to 10th	Night	23% 7% 2 4 3 3 3 3 5% 6% 42%	4380
	11th to 20th	Night	9% 6% 2 5% 3 3 3 3 4 5% 58%	4946
	21st to end	Night	7% 5% 1 3 2 2 2 2 4 7% 65%	6633

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	17% 20% 5% 21% 19% 18%	5406
	11th to 20th	Day	19% 20% 4 16% 21% 20%	5910
	21st to end	Day	28% 22% 4 13% 21% 11%	6468
February	1st to 10th	Day	16% 59% 3 5% 8% 10%	2100
	11th to 20th	Day	12% 58% 4 12% 9% 6%	2059
	21st to end	Day	13% 59% 4 7% 11% 7%	1730
March	1st to 10th	Day	21% 28% 4 11% 12% 25%	4600
	11th to 20th	Day	20% 28% 4 5% 13% 31%	4990
	21st to end	Day	22% 29% 5% 11% 14% 19%	5616
April	1st to 10th	Day	12% 60% 4 8% 7% 9%	2520
	11th to 20th	Day	17% 60% 3 7% 7% 6%	2494
	21st to end	Day	11% 59% 5% 11% 6% 8%	2520
May	1st to 10th	Day	26% 24% 8% 12% 16% 13%	7226
	11th to 20th	Day	22% 23% 7% 15% 17% 15%	7631
	21st to end	Day	26% 25% 10% 20% 13% 7%	8405
June	1st to 10th	Day	10% 60% 5% 14% 9% 1	2730
	11th to 20th	Day	12% 60% 6% 8% 12% 2	2730
	21st to end	Day	8% 59% 8% 14% 9% 2	2730
July	1st to 10th	Day	17% 22% 15% 31% 14%	7616
	11th to 20th	Day	27% 24% 17% 24% 7% 1	7477
	21st to end	Day	12% 21% 10% 27% 27% 3	7516
August	1st to 10th	Day	6% 25% 8% 29% 26% 6%	5532
	11th to 20th	Day	6% 27% 15% 39% 13% 1	5519
	21st to end	Day	9% 28% 10% 25% 24% 5%	6078
September	1st to 10th	Day	15% 55% 5% 11% 9% 5%	2420
	11th to 20th	Day	14% 56% 8% 12% 8% 1	2310
	21st to end	Day	16% 56% 8% 10% 7% 3	2310
October	1st to 10th	Day	8% 35% 4 7% 15% 31%	3700
	11th to 20th	Day	21% 35% 4 8% 9% 22%	3678
	21st to end	Day	16% 34% 3 12% 29% 6%	3769
November	1st to 10th	Day	19% 54% 5% 7% 8% 8%	1853
	11th to 20th	Day	17% 55% 4 7% 9% 8%	1890
	21st to end	Day	18% 54% 3 7% 12% 5%	1890
December	1st to 10th	Day	34% 35% 3 11% 9% 8%	3030
	11th to 20th	Day	25% 32% 5% 14% 13% 10%	3479
	21st to end	Day	19% 25% 2 13% 18% 23%	4587
January	1st to 10th	Night	16% 20% 6% 19% 25% 14%	7575
	11th to 20th	Night	15% 20% 3 13% 23% 26%	7080
	21st to end	Night	29% 22% 5% 12% 19% 12%	7746
February	1st to 10th	Night	11% 59% 3 7% 8% 12%	2520
	11th to 20th	Night	12% 58% 4 11% 11% 5%	2458
	21st to end	Night	13% 59% 3 7% 11% 8%	2076
March	1st to 10th	Night	15% 28% 5% 15% 17% 19%	5494
	11th to 20th	Night	18% 28% 4 7% 13% 30%	5190
	21st to end	Night	18% 29% 6% 13% 16% 17%	5553
April	1st to 10th	Night	11% 59% 6% 9% 6% 10%	2100
	11th to 20th	Night	15% 61% 5% 7% 7% 6%	2077
	21st to end	Night	12% 59% 5% 10% 8% 5%	2100
May	1st to 10th	Night	30% 24% 8% 15% 12% 11%	5715
	11th to 20th	Night	19% 24% 9% 16% 19% 14%	5266
	21st to end	Night	27% 25% 13% 19% 10% 6%	5805
June	1st to 10th	Night	8% 61% 7% 15% 9% 1	1890
	11th to 20th	Night	10% 60% 7% 11% 10% 2	1890
	21st to end	Night	8% 59% 6% 15% 10% 2	1890
July	1st to 10th	Night	16% 22% 15% 36% 10%	5265
	11th to 20th	Night	25% 24% 16% 25% 9% 2	5370
	21st to end	Night	12% 21% 9% 27% 28% 3	6280
August	1st to 10th	Night	7% 25% 7% 29% 29% 4	4614
	11th to 20th	Night	6% 26% 16% 40% 10% 1	4613
	21st to end	Night	11% 27% 9% 23% 26% 4	5069
September	1st to 10th	Night	13% 55% 5% 11% 10% 6%	2198
	11th to 20th	Night	11% 56% 9% 13% 9% 2	2310
	21st to end	Night	15% 56% 7% 13% 5% 3	2310
October	1st to 10th	Night	10% 34% 4 7% 13% 32%	3700
	11th to 20th	Night	17% 35% 4 8% 13% 23%	3680
	21st to end	Night	11% 34% 4 15% 29% 7%	4159
November	1st to 10th	Night	17% 53% 5% 6% 11% 8%	2665
	11th to 20th	Night	14% 55% 5% 11% 8% 8%	2730
	21st to end	Night	15% 55% 3 8% 12% 7%	2730
December	1st to 10th	Night	34% 35% 4 10% 7% 10%	4380
	11th to 20th	Night	20% 31% 6% 14% 18% 11%	4947
	21st to end	Night	16% 26% 4 18% 19% 16%	6633

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% 8% 32% 32% 13% 2	330
	11th to 20th	Day	14% 9% 31% 33% 12% 2	330
	21st to end	Day	14% 8% 36% 31% 10% 1	363
February	1st to 10th	Day	15% 8% 27% 29% 16% 4	330
	11th to 20th	Day	17% 9% 34% 30% 8% 1	330
	21st to end	Day	12% 10% 40% 27% 10%	273
March	1st to 10th	Day	18% 10% 40% 25% 7%	330
	11th to 20th	Day	13% 13% 36% 27% 10% 1	330
	21st to end	Day	9% 13% 39% 28% 9% 1	369
April	1st to 10th	Day	9% 14% 41% 30% 6% 1	540
	11th to 20th	Day	12% 14% 45% 25% 4	532
	21st to end	Day	11% 14% 43% 26% 6%	540
May	1st to 10th	Day	11% 12% 38% 33% 7%	597
	11th to 20th	Day	14% 9% 37% 30% 9% 1	775
	21st to end	Day	14% 7% 35% 36% 7% 1	844
June	1st to 10th	Day	6% 3 27% 47% 15% 2	780
	11th to 20th	Day	7% 2 28% 44% 17% 2	780
	21st to end	Day	5% 2 16% 49% 23% 4	780
July	1st to 10th	Day	8% 2 11% 44% 30% 5%	771
	11th to 20th	Day	5% 1 7% 46% 36% 4	725
	21st to end	Day	2 5% 49% 37% 6%	619
August	1st to 10th	Day	2 1 6% 44% 40% 8%	567
	11th to 20th	Day	4 1 5% 41% 40% 8%	557
	21st to end	Day	4 1 5% 37% 43% 10%	627
September	1st to 10th	Day	9% 1 7% 33% 41% 9%	470
	11th to 20th	Day	6% 7% 36% 39% 12%	360
	21st to end	Day	9% 1 9% 36% 33% 11%	360
October	1st to 10th	Day	6% 3 14% 38% 34% 6%	360
	11th to 20th	Day	12% 3 19% 38% 25% 3	360
	21st to end	Day	15% 6% 24% 31% 21% 4	387
November	1st to 10th	Day	17% 5% 23% 30% 21% 2	330
	11th to 20th	Day	15% 9% 17% 31% 19% 8%	330
	21st to end	Day	19% 7% 31% 28% 12% 3	330
December	1st to 10th	Day	15% 6% 28% 29% 19% 3	330
	11th to 20th	Day	13% 9% 32% 25% 16% 5%	330
	21st to end	Day	18% 9% 23% 31% 18% 2	363
January	1st to 10th	Night	11% 5% 33% 42% 10%	1029
	11th to 20th	Night	14% 6% 31% 44% 6%	840
	21st to end	Night	14% 8% 36% 35% 6%	924
February	1st to 10th	Night	11% 7% 39% 36% 7%	840
	11th to 20th	Night	15% 10% 41% 29% 6%	824
	21st to end	Night	9% 10% 46% 34% 1	692
March	1st to 10th	Night	14% 12% 46% 26% 2	840
	11th to 20th	Night	12% 11% 44% 29% 4	678
	21st to end	Night	9% 11% 52% 24% 3	693
April	1st to 10th	Night	7% 13% 52% 26% 2	630
	11th to 20th	Night	13% 11% 52% 22% 1	623
	21st to end	Night	8% 14% 56% 18% 4	630
May	1st to 10th	Night	8% 10% 53% 26% 2	630
	11th to 20th	Night	9% 9% 43% 34% 5%	621
	21st to end	Night	9% 8% 49% 28% 5%	683
June	1st to 10th	Night	3 4 39% 50% 5%	630
	11th to 20th	Night	4 2 42% 45% 7%	630
	21st to end	Night	5% 2 31% 47% 14% 1	630
July	1st to 10th	Night	9% 2 15% 56% 16% 2	615
	11th to 20th	Night	3 1 16% 59% 20%	612
	21st to end	Night	3 1 13% 62% 21% 1	690
August	1st to 10th	Night	2 9% 63% 25% 1	627
	11th to 20th	Night	4 9% 55% 30% 1	624
	21st to end	Night	5% 9% 55% 29% 2	693
September	1st to 10th	Night	7% 1 9% 50% 30% 2	630
	11th to 20th	Night	8% 1 11% 49% 29% 1	630
	21st to end	Night	7% 1 17% 46% 28% 1	630
October	1st to 10th	Night	6% 2 21% 50% 20%	630
	11th to 20th	Night	10% 3 26% 49% 11% 1	630
	21st to end	Night	9% 6% 28% 41% 15% 1	788
November	1st to 10th	Night	12% 5% 26% 42% 15% 1	1025
	11th to 20th	Night	8% 5% 29% 42% 15% 1	1050
	21st to end	Night	13% 6% 32% 38% 11%	1050
December	1st to 10th	Night	15% 5% 25% 43% 11%	1050
	11th to 20th	Night	14% 7% 31% 38% 9%	1050
	21st to end	Night	12% 5% 33% 41% 9%	1155

Page generated at 2026-10-26 03:37:46. Version ac07

Copyright © 2026 Attilla Danko.