Steamboat Lake State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Steamboat Lake State Park clear sky chart from 2005-11-06 to 2025-10-04.

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	4 10% 4 9% 5% 4 4 4 5% 7% 44%	135517
	Night	4 11% 4 9% 5% 4 4 3 5% 6% 45%	131342
Transparency	Day	38% 5% 10% 22% 19% 8%	130394
	Night	38% 5% 11% 23% 17% 6%	127470
Seeing	Day	14% 17% 31% 24% 11% 3	16885
	Night	12% 10% 27% 35% 15% 2	26880

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	2 15% 8% 18% 7% 4 2 2 4 5% 33%	3638
	11th to 20th	Day	2 14% 10% 18% 11% 6% 3 2 4 3 26%	3941
	21st to end	Day	2 17% 11% 14% 5% 3 2 2 4 4 37%	4510
February	1st to 10th	Day	4 23% 8% 15% 7% 4 3 2 4 5% 26%	1800
	11th to 20th	Day	5% 22% 10% 15% 6% 3 3 2 3 4 28%	1790
	21st to end	Day	2 19% 8% 18% 7% 4 4 3 4 4 27%	1650
March	1st to 10th	Day	2 14% 10% 15% 5% 3 3 3 4 4 37%	4730
	11th to 20th	Day	1 15% 7% 13% 5% 4 3 3 4 5% 40%	5000
	21st to end	Day	3 21% 8% 16% 5% 4 5% 3 4 6% 24%	5617
April	1st to 10th	Day	5% 19% 4 10% 4 4 5% 3 5% 7% 36%	2400
	11th to 20th	Day	6% 19% 5% 10% 5% 4 5% 4 5% 6% 32%	2371
	21st to end	Day	5% 16% 4 7% 5% 4 5% 5% 6% 8% 35%	2400
May	1st to 10th	Day	5% 15% 5% 8% 6% 4 6% 4 6% 8% 33%	5950
	11th to 20th	Day	4 9% 3 6% 5% 5% 6% 5% 8% 9% 40%	6298
	21st to end	Day	5% 7% 2 6% 5% 4 5% 5% 7% 8% 46%	6925
June	1st to 10th	Day	6% 5% 2 5% 4 4 4 5% 6% 8% 50%	2800
	11th to 20th	Day	5% 4 2 4 4 3 4 4 5% 8% 58%	2800
	21st to end	Day	3 3 1 4 4 4 5% 4 6% 7% 60%	2800
July	1st to 10th	Day	3 2 1 4 4 4 5% 4 7% 9% 58%	6339
	11th to 20th	Day	2 2 1 5% 4 5% 6% 5% 8% 10% 52%	6340
	21st to end	Day	3 3 2 4 4 5% 6% 4 8% 9% 52%	6524
August	1st to 10th	Day	3 3 2 5% 5% 5% 7% 5% 6% 8% 51%	5779
	11th to 20th	Day	4 4 1 5% 4 5% 5% 5% 6% 9% 53%	5671
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 4 6% 6% 48%	5984
September	1st to 10th	Day	5% 4 2 5% 3 3 5% 3 5% 6% 60%	2400
	11th to 20th	Day	7% 6% 2 5% 4 4 3 4 5% 5% 56%	2400
	21st to end	Day	7% 6% 2 5% 3 3 4 3 4 5% 60%	2128
October	1st to 10th	Day	5% 6% 1 3 2 2 2 2 3 4 68%	3200
	11th to 20th	Day	6% 7% 2 5% 4 4 4 4 6% 8% 52%	3150
	21st to end	Day	5% 15% 3 5% 2 2 3 3 4 6% 50%	3438
November	1st to 10th	Day	5% 13% 4 7% 3 3 3 4 5% 6% 47%	1779
	11th to 20th	Day	5% 18% 4 8% 5% 2 3 2 4 5% 43%	1715
	21st to end	Day	4 14% 5% 13% 3 3 2 2 4 6% 46%	1600
December	1st to 10th	Day	3 13% 5% 14% 4 3 2 2 2 4 50%	2620
	11th to 20th	Day	3 17% 7% 9% 4 3 2 2 4 6% 43%	3026
	21st to end	Day	3 21% 7% 15% 5% 4 3 4 4 6% 28%	4004
January	1st to 10th	Night	1 12% 8% 19% 8% 5% 3 3 5% 6% 30%	6327
	11th to 20th	Night	1 17% 8% 16% 11% 6% 2 2 3 4 29%	6082
	21st to end	Night	1 17% 8% 15% 6% 3 2 2 3 4 39%	6468
February	1st to 10th	Night	3 22% 8% 16% 7% 4 3 3 3 5% 26%	2600
	11th to 20th	Night	4 19% 8% 15% 5% 3 3 2 4 5% 30%	2497
	21st to end	Night	3 18% 8% 14% 6% 3 2 3 4 5% 33%	1980
March	1st to 10th	Night	2 14% 8% 12% 4 3 4 3 4 5% 41%	5139
	11th to 20th	Night	1 10% 4 10% 4 4 4 3 5% 6% 49%	5000
	21st to end	Night	4 19% 7% 12% 5% 4 5% 4 4 6% 31%	5338
April	1st to 10th	Night	5% 15% 5% 7% 4 4 4 3 5% 5% 42%	2000
	11th to 20th	Night	7% 14% 4 8% 4 5% 4 4 5% 6% 40%	1977
	21st to end	Night	6% 14% 3 6% 5% 4 3 4 6% 8% 43%	2000
May	1st to 10th	Night	6% 11% 5% 6% 4 4 4 3 6% 7% 43%	4025
	11th to 20th	Night	6% 10% 3 7% 4 5% 5% 5% 6% 9% 40%	3617
	21st to end	Night	6% 8% 2 4 3 4 5% 4 6% 7% 51%	3972
June	1st to 10th	Night	5% 5% 2 3 4 3 4 4 7% 8% 54%	1600
	11th to 20th	Night	5% 4 1 5% 3 4 4 4 5% 6% 58%	1600
	21st to end	Night	3 3 1 3 3 3 3 3 6% 6% 66%	1600
July	1st to 10th	Night	4 3 1 5% 3 4 4 3 6% 7% 60%	3640
	11th to 20th	Night	2 2 1 4 4 4 6% 5% 8% 11% 54%	3640
	21st to end	Night	1 2 1 4 4 5% 5% 5% 7% 9% 56%	4332
August	1st to 10th	Night	3 3 1 5% 4 4 5% 5% 7% 9% 56%	4033
	11th to 20th	Night	3 3 2 5% 4 4 6% 4 7% 9% 55%	4178
	21st to end	Night	4 4 2 5% 4 5% 5% 5% 7% 8% 51%	4993
September	1st to 10th	Night	5% 3 1 3 2 3 3 3 5% 7% 64%	2000
	11th to 20th	Night	6% 6% 2 3 4 4 3 3 4 6% 59%	2000
	21st to end	Night	6% 4 1 4 2 3 3 3 4 5% 66%	2268
October	1st to 10th	Night	5% 4 1 3 2 2 2 2 3 4 71%	3836
	11th to 20th	Night	5% 7% 1 4 3 3 4 4 6% 7% 56%	3778
	21st to end	Night	5% 10% 4 6% 3 2 3 2 4 7% 55%	4120
November	1st to 10th	Night	6% 12% 3 7% 4 3 2 2 5% 6% 50%	2497
	11th to 20th	Night	5% 15% 4 8% 3 3 4 3 4 5% 45%	2680
	21st to end	Night	3 14% 5% 9% 4 3 3 3 4 7% 45%	2800
December	1st to 10th	Night	3 14% 4 10% 4 3 2 2 3 3 53%	4570
	11th to 20th	Night	2 12% 7% 12% 5% 3 4 4 7% 8% 36%	5181
	21st to end	Night	3 19% 8% 14% 6% 4 4 3 4 5% 28%	6974

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	51% 6% 12% 16% 12% 2	3639
	11th to 20th	Day	62% 4 10% 12% 8% 4	3941
	21st to end	Day	50% 6% 10% 14% 15% 5%	4510
February	1st to 10th	Day	60% 6% 10% 15% 8% 2	1800
	11th to 20th	Day	60% 4 10% 17% 7% 2	1799
	21st to end	Day	59% 5% 10% 14% 10% 1	1650
March	1st to 10th	Day	48% 5% 8% 20% 13% 6%	4730
	11th to 20th	Day	46% 3 13% 28% 9% 1	5000
	21st to end	Day	57% 6% 10% 20% 6% 1	5617
April	1st to 10th	Day	46% 6% 12% 19% 13% 4	2400
	11th to 20th	Day	50% 5% 10% 20% 13% 2	2374
	21st to end	Day	44% 6% 10% 29% 11%	2400
May	1st to 10th	Day	45% 6% 10% 19% 18% 1	5950
	11th to 20th	Day	34% 7% 12% 28% 18% 1	6302
	21st to end	Day	30% 7% 7% 30% 25% 1	6926
June	1st to 10th	Day	29% 6% 12% 25% 23% 6%	2800
	11th to 20th	Day	24% 4 7% 18% 30% 16%	2800
	21st to end	Day	22% 4 6% 20% 32% 16%	2800
July	1st to 10th	Day	20% 5% 5% 14% 25% 32%	6271
	11th to 20th	Day	22% 5% 7% 20% 29% 17%	6265
	21st to end	Day	24% 5% 9% 16% 27% 19%	6337
August	1st to 10th	Day	32% 5% 11% 21% 18% 14%	4208
	11th to 20th	Day	31% 4 11% 18% 25% 11%	4106
	21st to end	Day	26% 4 9% 21% 23% 16%	4311
September	1st to 10th	Day	25% 3 7% 19% 27% 19%	2400
	11th to 20th	Day	28% 4 8% 23% 25% 11%	2400
	21st to end	Day	27% 3 6% 29% 29% 6%	2128
October	1st to 10th	Day	22% 3 6% 23% 35% 11%	3200
	11th to 20th	Day	28% 4 8% 35% 21% 3	3150
	21st to end	Day	35% 2 11% 35% 15% 2	3438
November	1st to 10th	Day	37% 6% 11% 27% 18% 1	1779
	11th to 20th	Day	43% 4 14% 22% 15% 1	1715
	21st to end	Day	41% 3 14% 28% 13% 1	1600
December	1st to 10th	Day	41% 2 15% 32% 10% 1	2620
	11th to 20th	Day	43% 4 19% 28% 7%	3024
	21st to end	Day	56% 5% 9% 19% 11% 2	4004
January	1st to 10th	Night	53% 5% 10% 17% 11% 4	6327
	11th to 20th	Night	59% 4 11% 13% 11% 2	6082
	21st to end	Night	48% 6% 10% 15% 17% 5%	6468
February	1st to 10th	Night	59% 7% 9% 15% 8% 2	2600
	11th to 20th	Night	55% 4 11% 19% 9% 2	2498
	21st to end	Night	52% 5% 9% 18% 13% 3	1980
March	1st to 10th	Night	43% 5% 8% 22% 15% 6%	5139
	11th to 20th	Night	34% 3 14% 29% 18% 2	5000
	21st to end	Night	48% 7% 13% 25% 6% 1	5338
April	1st to 10th	Night	41% 6% 13% 20% 16% 4	2000
	11th to 20th	Night	42% 6% 12% 23% 16% 2	1977
	21st to end	Night	38% 5% 12% 28% 17% 1	2000
May	1st to 10th	Night	37% 7% 11% 27% 16% 2	4022
	11th to 20th	Night	34% 8% 13% 30% 12% 3	3618
	21st to end	Night	29% 6% 9% 33% 22% 1	3972
June	1st to 10th	Night	25% 5% 15% 27% 21% 7%	1600
	11th to 20th	Night	25% 5% 9% 18% 25% 18%	1600
	21st to end	Night	18% 4 5% 23% 31% 21%	1600
July	1st to 10th	Night	23% 5% 6% 14% 22% 31%	3600
	11th to 20th	Night	21% 5% 8% 29% 23% 14%	3592
	21st to end	Night	23% 5% 9% 21% 27% 16%	4208
August	1st to 10th	Night	25% 4 15% 23% 15% 18%	2928
	11th to 20th	Night	28% 7% 14% 15% 23% 13%	3019
	21st to end	Night	26% 4 11% 18% 26% 15%	3597
September	1st to 10th	Night	20% 4 9% 20% 27% 20%	2000
	11th to 20th	Night	26% 3 10% 23% 26% 13%	2000
	21st to end	Night	21% 3 6% 27% 35% 7%	2268
October	1st to 10th	Night	19% 3 5% 21% 40% 14%	3836
	11th to 20th	Night	26% 3 8% 36% 24% 3	3778
	21st to end	Night	31% 3 12% 36% 16% 3	4120
November	1st to 10th	Night	36% 5% 12% 26% 20% 2	2497
	11th to 20th	Night	40% 4 13% 27% 13% 3	2680
	21st to end	Night	39% 5% 10% 30% 15% 2	2800
December	1st to 10th	Night	38% 3 12% 33% 13% 1	4570
	11th to 20th	Night	43% 4 17% 28% 9%	5182
	21st to end	Night	56% 5% 9% 18% 11% 1	6974

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% 16% 32% 21% 10% 1	300
	11th to 20th	Day	15% 22% 34% 21% 7%	300
	21st to end	Day	12% 22% 39% 22% 5% 1	330
February	1st to 10th	Day	30% 24% 30% 13% 2	300
	11th to 20th	Day	22% 26% 32% 18% 2	300
	21st to end	Day	22% 28% 31% 16% 3	249
March	1st to 10th	Day	21% 24% 32% 18% 6%	400
	11th to 20th	Day	15% 23% 36% 19% 7%	500
	21st to end	Day	20% 27% 35% 14% 3 1	550
April	1st to 10th	Day	22% 25% 31% 17% 5%	500
	11th to 20th	Day	22% 28% 29% 17% 2 1	492
	21st to end	Day	17% 21% 35% 18% 7% 1	500
May	1st to 10th	Day	21% 21% 29% 18% 10% 1	533
	11th to 20th	Day	14% 15% 29% 26% 14% 2	725
	21st to end	Day	15% 16% 26% 24% 16% 2	789
June	1st to 10th	Day	9% 12% 27% 29% 18% 5%	730
	11th to 20th	Day	8% 16% 34% 28% 11% 2	730
	21st to end	Day	6% 13% 32% 31% 15% 3	730
July	1st to 10th	Day	7% 6% 24% 35% 23% 5%	721
	11th to 20th	Day	5% 5% 27% 35% 22% 6%	718
	21st to end	Day	6% 9% 26% 33% 22% 5%	633
August	1st to 10th	Day	10% 8% 36% 31% 11% 4	527
	11th to 20th	Day	6% 9% 34% 31% 14% 5%	517
	21st to end	Day	8% 11% 33% 28% 17% 4	583
September	1st to 10th	Day	7% 12% 30% 28% 18% 5%	530
	11th to 20th	Day	10% 14% 38% 23% 12% 5%	530
	21st to end	Day	10% 15% 28% 26% 15% 6%	399
October	1st to 10th	Day	14% 15% 27% 26% 13% 6%	309
	11th to 20th	Day	16% 17% 31% 23% 10% 3	300
	21st to end	Day	19% 23% 31% 21% 6%	330
November	1st to 10th	Day	19% 22% 30% 22% 8%	300
	11th to 20th	Day	18% 24% 30% 24% 4 1	300
	21st to end	Day	12% 21% 38% 24% 4 1	300
December	1st to 10th	Day	18% 24% 30% 20% 6% 2	300
	11th to 20th	Day	16% 20% 42% 17% 4	300
	21st to end	Day	25% 19% 34% 16% 5% 1	330
January	1st to 10th	Night	14% 14% 30% 31% 10% 1	1000
	11th to 20th	Night	15% 16% 33% 29% 6% 1	885
	21st to end	Night	13% 10% 37% 32% 7% 1	880
February	1st to 10th	Night	18% 13% 40% 23% 6%	800
	11th to 20th	Night	14% 16% 32% 32% 5%	784
	21st to end	Night	14% 18% 37% 27% 3	660
March	1st to 10th	Night	14% 12% 34% 30% 10% 1	800
	11th to 20th	Night	10% 10% 29% 40% 10% 1	800
	21st to end	Night	12% 12% 34% 32% 9% 1	819
April	1st to 10th	Night	15% 12% 32% 35% 6%	600
	11th to 20th	Night	15% 12% 33% 30% 9% 1	593
	21st to end	Night	13% 11% 26% 36% 13% 1	600
May	1st to 10th	Night	15% 7% 31% 32% 14% 2	600
	11th to 20th	Night	12% 5% 20% 44% 17% 2	591
	21st to end	Night	11% 6% 25% 38% 19% 2	650
June	1st to 10th	Night	7% 6% 24% 39% 23% 2	600
	11th to 20th	Night	8% 7% 26% 44% 14% 1	600
	21st to end	Night	4 4 19% 45% 26% 2	600
July	1st to 10th	Night	5% 3 14% 39% 37% 3	585
	11th to 20th	Night	4 2 10% 47% 34% 3	582
	21st to end	Night	2 3 8% 44% 40% 4	657
August	1st to 10th	Night	6% 2 9% 48% 34% 2	597
	11th to 20th	Night	5% 2 9% 51% 30% 4	594
	21st to end	Night	4 2 10% 45% 33% 6%	660
September	1st to 10th	Night	6% 2 14% 44% 29% 5%	600
	11th to 20th	Night	9% 3 16% 45% 25% 4	600
	21st to end	Night	9% 3 21% 36% 25% 6%	738
October	1st to 10th	Night	11% 6% 25% 35% 20% 3	772
	11th to 20th	Night	12% 9% 24% 39% 14% 2	760
	21st to end	Night	14% 10% 30% 33% 11% 2	836
November	1st to 10th	Night	13% 12% 31% 32% 11% 1	937
	11th to 20th	Night	16% 15% 33% 29% 6% 1	1000
	21st to end	Night	12% 11% 34% 35% 8%	1000
December	1st to 10th	Night	17% 12% 34% 29% 8% 1	1000
	11th to 20th	Night	14% 14% 37% 30% 5%	1000
	21st to end	Night	18% 17% 36% 23% 6% 1	1100

Page generated at 2025-09-30 23:39:06. Version ac07

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