Colorado State Forest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Colorado State Forest clear sky chart from 2005-11-06 to 2024-04-03.

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	5% 11% 5% 9% 6% 3 4 4 5% 6% 40%	78904
	Night	3 10% 5% 9% 6% 3 4 4 4 6% 45%	81274
Transparency	Day	46% 5% 10% 21% 15% 4	78612
	Night	41% 4 12% 23% 15% 4	81088
Seeing	Day	14% 26% 30% 19% 9% 2	14723
	Night	10% 22% 29% 27% 12% 1	24953

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 10% 8% 17% 15% 5% 3 3 2 5% 31%	2538
	11th to 20th	Day	1 15% 10% 15% 12% 6% 3 3 3 4 27%	2650
	21st to end	Day	1 13% 12% 17% 6% 3 3 2 2 4 36%	3146
February	1st to 10th	Day	2 20% 10% 15% 8% 4 3 2 3 6% 28%	1710
	11th to 20th	Day	2 15% 10% 16% 8% 3 2 2 3 5% 32%	1756
	21st to end	Day	1 14% 10% 15% 11% 3 3 2 5% 5% 30%	1570
March	1st to 10th	Day	3 15% 8% 12% 9% 2 3 3 3 5% 37%	1929
	11th to 20th	Day	3 14% 8% 10% 5% 3 4 4 4 7% 39%	2090
	21st to end	Day	3 18% 10% 13% 6% 3 4 3 5% 6% 28%	2400
April	1st to 10th	Day	5% 16% 8% 9% 5% 3 4 4 5% 6% 36%	2185
	11th to 20th	Day	5% 19% 7% 11% 7% 3 3 5% 5% 6% 29%	2131
	21st to end	Day	7% 18% 7% 9% 6% 3 4 4 4 6% 31%	2160
May	1st to 10th	Day	10% 15% 5% 7% 6% 4 5% 5% 5% 7% 31%	2330
	11th to 20th	Day	10% 12% 3 7% 6% 4 6% 6% 5% 8% 32%	2478
	21st to end	Day	10% 11% 4 7% 5% 4 6% 7% 6% 8% 33%	2724
June	1st to 10th	Day	6% 6% 2 5% 5% 3 5% 6% 7% 8% 45%	2520
	11th to 20th	Day	7% 5% 2 4 4 3 4 5% 5% 7% 53%	2520
	21st to end	Day	4 4 2 4 5% 3 5% 6% 7% 8% 53%	2520
July	1st to 10th	Day	7% 4 2 5% 6% 3 6% 6% 7% 9% 45%	2520
	11th to 20th	Day	5% 4 2 5% 6% 3 5% 6% 7% 9% 46%	2520
	21st to end	Day	8% 5% 3 6% 7% 4 7% 7% 7% 8% 38%	2664
August	1st to 10th	Day	11% 6% 3 6% 7% 5% 6% 6% 7% 8% 35%	2328
	11th to 20th	Day	6% 5% 2 6% 6% 4 5% 6% 6% 6% 47%	2192
	21st to end	Day	7% 6% 2 6% 6% 4 6% 6% 5% 7% 44%	2376
September	1st to 10th	Day	7% 4 2 5% 4 3 4 3 4 6% 58%	2160
	11th to 20th	Day	9% 5% 3 5% 5% 3 4 5% 5% 5% 53%	2160
	21st to end	Day	9% 7% 2 3 3 2 3 3 3 5% 61%	1945
October	1st to 10th	Day	8% 12% 3 4 4 2 4 4 3 4 51%	1800
	11th to 20th	Day	8% 12% 3 4 3 2 2 3 5% 5% 53%	1800
	21st to end	Day	6% 14% 5% 6% 3 1 2 2 4 5% 49%	1944
November	1st to 10th	Day	3 11% 6% 7% 3 2 2 2 4 7% 52%	1673
	11th to 20th	Day	2 19% 6% 8% 5% 2 2 2 3 5% 45%	1705
	21st to end	Day	2 11% 5% 12% 6% 2 2 2 3 6% 49%	1520
December	1st to 10th	Day	2 17% 7% 15% 5% 4 3 3 3 5% 35%	1520
	11th to 20th	Day	1 16% 7% 12% 7% 3 2 3 4 7% 39%	1926
	21st to end	Day	1 14% 9% 15% 9% 4 4 3 4 6% 32%	2794
January	1st to 10th	Night	1 10% 8% 16% 13% 5% 5% 3 4 5% 31%	4417
	11th to 20th	Night	1 14% 11% 16% 9% 7% 3 2 3 4 30%	4335
	21st to end	Night	1 13% 10% 17% 9% 3 3 3 3 4 34%	4521
February	1st to 10th	Night	1 17% 8% 18% 9% 4 4 3 3 4 28%	2470
	11th to 20th	Night	2 13% 10% 16% 7% 3 4 2 4 5% 32%	2309
	21st to end	Night	2 12% 9% 17% 11% 3 2 2 4 5% 33%	1884
March	1st to 10th	Night	2 10% 7% 11% 8% 3 3 3 4 6% 42%	2247
	11th to 20th	Night	2 10% 5% 10% 5% 2 4 3 4 6% 49%	2090
	21st to end	Night	2 14% 8% 12% 5% 3 4 4 5% 6% 37%	2197
April	1st to 10th	Night	4 15% 5% 8% 5% 2 4 4 5% 6% 42%	1820
	11th to 20th	Night	4 15% 5% 8% 6% 3 4 4 5% 6% 39%	1777
	21st to end	Night	5% 15% 6% 6% 5% 2 4 4 4 5% 44%	1800
May	1st to 10th	Night	8% 11% 3 6% 5% 3 5% 4 5% 8% 40%	1623
	11th to 20th	Night	6% 9% 3 5% 6% 3 6% 5% 6% 8% 43%	1417
	21st to end	Night	5% 7% 2 4 5% 3 6% 6% 7% 8% 48%	1552
June	1st to 10th	Night	4 4 1 5% 3 2 3 5% 7% 10% 58%	1440
	11th to 20th	Night	5% 4 1 3 3 3 4 4 5% 7% 61%	1440
	21st to end	Night	4 2 1 2 3 1 3 4 6% 8% 64%	1440
July	1st to 10th	Night	4 2 1 3 4 2 5% 5% 8% 10% 56%	1440
	11th to 20th	Night	3 2 1 3 3 2 4 6% 7% 9% 60%	1440
	21st to end	Night	3 3 2 4 5% 4 6% 6% 7% 9% 52%	1651
August	1st to 10th	Night	5% 4 2 4 5% 4 4 5% 8% 8% 50%	1611
	11th to 20th	Night	3 3 2 4 4 3 4 6% 6% 9% 56%	1707
	21st to end	Night	4 4 2 3 5% 3 4 6% 6% 8% 56%	1980
September	1st to 10th	Night	5% 4 1 3 3 2 3 4 5% 7% 62%	1800
	11th to 20th	Night	6% 4 2 3 3 3 3 3 4 7% 63%	1800
	21st to end	Night	7% 5% 1 3 3 2 3 4 4 6% 63%	2012
October	1st to 10th	Night	5% 10% 3 4 3 3 4 3 4 7% 56%	2160
	11th to 20th	Night	5% 11% 3 3 2 2 2 2 3 5% 61%	2160
	21st to end	Night	6% 14% 4 6% 3 2 3 3 3 5% 51%	2391
November	1st to 10th	Night	3 13% 4 5% 2 2 2 3 4 6% 56%	2405
	11th to 20th	Night	3 16% 5% 9% 5% 2 2 3 3 5% 47%	2474
	21st to end	Night	2 11% 6% 9% 6% 2 3 3 4 7% 47%	2660
December	1st to 10th	Night	2 18% 6% 11% 8% 4 4 3 2 4 38%	2660
	11th to 20th	Night	2 11% 8% 12% 6% 3 4 3 5% 7% 39%	3271
	21st to end	Night	1 11% 8% 13% 10% 4 4 4 4 6% 34%	4873

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	58% 4 9% 14% 14% 1	2539
	11th to 20th	Day	63% 3 14% 12% 7% 1	2650
	21st to end	Day	54% 4 10% 18% 12% 2	3146
February	1st to 10th	Day	61% 5% 8% 13% 12% 1	1710
	11th to 20th	Day	57% 3 8% 20% 8% 4	1765
	21st to end	Day	58% 3 10% 12% 14% 3	1570
March	1st to 10th	Day	51% 4 10% 23% 12% 1	1929
	11th to 20th	Day	48% 4 11% 23% 11% 2	2090
	21st to end	Day	59% 5% 9% 19% 6% 2	2400
April	1st to 10th	Day	51% 5% 11% 17% 13% 3	2185
	11th to 20th	Day	57% 4 9% 17% 11% 2	2134
	21st to end	Day	56% 4 9% 24% 7%	2160
May	1st to 10th	Day	55% 5% 8% 22% 10%	2330
	11th to 20th	Day	52% 5% 14% 21% 7% 1	2482
	21st to end	Day	49% 6% 12% 21% 11% 2	2724
June	1st to 10th	Day	36% 7% 14% 23% 15% 5%	2520
	11th to 20th	Day	32% 4 10% 19% 24% 11%	2520
	21st to end	Day	30% 5% 8% 24% 24% 9%	2520
July	1st to 10th	Day	36% 7% 8% 19% 23% 7%	2451
	11th to 20th	Day	34% 7% 11% 23% 15% 9%	2445
	21st to end	Day	43% 7% 13% 18% 15% 4	2516
August	1st to 10th	Day	47% 7% 12% 17% 14% 4	2313
	11th to 20th	Day	40% 6% 8% 21% 18% 7%	2192
	21st to end	Day	42% 6% 8% 19% 18% 7%	2376
September	1st to 10th	Day	30% 4 7% 18% 28% 13%	2160
	11th to 20th	Day	36% 4 7% 23% 22% 8%	2160
	21st to end	Day	29% 3 7% 33% 24% 5%	1945
October	1st to 10th	Day	39% 4 8% 25% 19% 5%	1800
	11th to 20th	Day	34% 3 8% 34% 16% 5%	1800
	21st to end	Day	40% 4 12% 27% 15% 3	1944
November	1st to 10th	Day	36% 4 12% 25% 21% 2	1673
	11th to 20th	Day	43% 3 13% 22% 15% 4	1705
	21st to end	Day	40% 3 11% 28% 13% 4	1520
December	1st to 10th	Day	54% 3 16% 14% 10% 2	1520
	11th to 20th	Day	46% 4 10% 28% 11% 1	1924
	21st to end	Day	55% 5% 4 18% 15% 4	2794
January	1st to 10th	Night	56% 4 9% 19% 11% 2	4417
	11th to 20th	Night	60% 3 12% 12% 8% 4	4335
	21st to end	Night	56% 4 10% 16% 10% 4	4521
February	1st to 10th	Night	59% 6% 9% 15% 10% 2	2470
	11th to 20th	Night	54% 3 9% 20% 11% 2	2310
	21st to end	Night	55% 4 8% 15% 14% 4	1884
March	1st to 10th	Night	45% 3 10% 25% 15% 1	2247
	11th to 20th	Night	38% 3 15% 27% 13% 4	2090
	21st to end	Night	49% 6% 13% 23% 8% 1	2197
April	1st to 10th	Night	44% 5% 12% 20% 15% 3	1820
	11th to 20th	Night	47% 3 13% 24% 12% 1	1777
	21st to end	Night	44% 4 11% 29% 12%	1800
May	1st to 10th	Night	43% 7% 12% 28% 10%	1623
	11th to 20th	Night	39% 5% 20% 27% 8%	1418
	21st to end	Night	34% 6% 14% 29% 16% 2	1552
June	1st to 10th	Night	23% 4 23% 31% 15% 4	1440
	11th to 20th	Night	24% 4 13% 22% 27% 10%	1440
	21st to end	Night	19% 4 10% 28% 26% 12%	1440
July	1st to 10th	Night	23% 8% 15% 25% 21% 9%	1400
	11th to 20th	Night	19% 7% 18% 26% 18% 11%	1392
	21st to end	Night	28% 7% 20% 22% 18% 4	1559
August	1st to 10th	Night	29% 7% 21% 22% 16% 5%	1602
	11th to 20th	Night	25% 6% 13% 23% 23% 10%	1707
	21st to end	Night	27% 4 12% 25% 24% 7%	1980
September	1st to 10th	Night	24% 4 12% 18% 30% 12%	1800
	11th to 20th	Night	24% 4 13% 25% 25% 10%	1800
	21st to end	Night	24% 4 8% 33% 26% 4	2012
October	1st to 10th	Night	32% 4 10% 30% 18% 7%	2160
	11th to 20th	Night	29% 2 10% 34% 20% 5%	2160
	21st to end	Night	38% 3 13% 28% 15% 3	2391
November	1st to 10th	Night	32% 5% 12% 28% 21% 3	2405
	11th to 20th	Night	40% 4 13% 26% 14% 4	2474
	21st to end	Night	40% 4 10% 28% 13% 4	2660
December	1st to 10th	Night	51% 5% 13% 15% 12% 3	2660
	11th to 20th	Night	46% 3 11% 27% 13% 1	3272
	21st to end	Night	50% 5% 8% 18% 15% 4	4873

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	17% 32% 25% 15% 9% 1	270
	11th to 20th	Day	19% 41% 22% 14% 3 1	270
	21st to end	Day	8% 42% 31% 14% 6%	297
February	1st to 10th	Day	22% 50% 19% 7% 1 1	270
	11th to 20th	Day	23% 37% 28% 11% 1	270
	21st to end	Day	28% 41% 24% 6% 1	225
March	1st to 10th	Day	19% 45% 22% 10% 3	299
	11th to 20th	Day	18% 35% 30% 14% 3	460
	21st to end	Day	18% 46% 27% 8% 1	506
April	1st to 10th	Day	22% 40% 30% 6% 2	429
	11th to 20th	Day	26% 42% 25% 5% 2	412
	21st to end	Day	24% 34% 27% 11% 4 1	420
May	1st to 10th	Day	19% 31% 29% 14% 7%	503
	11th to 20th	Day	18% 17% 30% 22% 11% 2	625
	21st to end	Day	16% 20% 29% 21% 11% 2	679
June	1st to 10th	Day	9% 16% 30% 24% 18% 4	630
	11th to 20th	Day	10% 22% 34% 23% 10% 1	630
	21st to end	Day	5% 17% 34% 27% 14% 3	630
July	1st to 10th	Day	7% 8% 29% 32% 22% 4	621
	11th to 20th	Day	6% 8% 31% 30% 20% 4	618
	21st to end	Day	7% 6% 32% 30% 21% 4	606
August	1st to 10th	Day	10% 14% 38% 28% 9% 2	447
	11th to 20th	Day	7% 11% 38% 29% 12% 3	437
	21st to end	Day	8% 15% 33% 29% 13% 2	495
September	1st to 10th	Day	9% 20% 33% 23% 11% 3	450
	11th to 20th	Day	10% 20% 38% 20% 10% 2	450
	21st to end	Day	11% 27% 26% 20% 13% 4	290
October	1st to 10th	Day	16% 24% 26% 18% 13% 4	270
	11th to 20th	Day	14% 37% 27% 15% 5% 2	270
	21st to end	Day	19% 34% 28% 14% 3 1	297
November	1st to 10th	Day	21% 39% 23% 10% 7% 1	270
	11th to 20th	Day	18% 39% 27% 12% 3 1	270
	21st to end	Day	14% 35% 31% 17% 3	270
December	1st to 10th	Day	20% 36% 26% 11% 5% 1	270
	11th to 20th	Day	10% 41% 32% 12% 4	270
	21st to end	Day	18% 38% 31% 11% 2	297
January	1st to 10th	Night	11% 29% 29% 21% 9% 1	950
	11th to 20th	Night	11% 37% 27% 19% 5% 1	894
	21st to end	Night	7% 32% 33% 22% 5% 1	836
February	1st to 10th	Night	11% 38% 31% 15% 5%	760
	11th to 20th	Night	9% 38% 29% 21% 3	744
	21st to end	Night	13% 34% 37% 13% 2	628
March	1st to 10th	Night	9% 34% 31% 20% 6%	760
	11th to 20th	Night	8% 21% 39% 24% 8% 1	760
	21st to end	Night	9% 27% 40% 19% 5% 1	734
April	1st to 10th	Night	14% 26% 37% 20% 3	546
	11th to 20th	Night	14% 23% 37% 20% 5% 1	533
	21st to end	Night	12% 20% 32% 26% 9% 1	540
May	1st to 10th	Night	13% 14% 36% 27% 9% 1	540
	11th to 20th	Night	11% 9% 27% 37% 16% 1	531
	21st to end	Night	8% 13% 28% 32% 18% 1	584
June	1st to 10th	Night	6% 8% 27% 38% 20% 1	540
	11th to 20th	Night	7% 12% 31% 36% 14%	540
	21st to end	Night	6% 5% 23% 45% 20% 1	540
July	1st to 10th	Night	4 2 16% 41% 35% 2	525
	11th to 20th	Night	3 2 18% 39% 34% 3	522
	21st to end	Night	4 2 10% 47% 35% 3	591
August	1st to 10th	Night	6% 2 15% 47% 28% 2	537
	11th to 20th	Night	3 3 18% 43% 31% 3	534
	21st to end	Night	5% 3 16% 40% 32% 3	594
September	1st to 10th	Night	6% 5% 22% 41% 24% 3	540
	11th to 20th	Night	6% 5% 24% 43% 18% 4	540
	21st to end	Night	9% 8% 28% 32% 18% 4	593
October	1st to 10th	Night	10% 17% 30% 26% 15% 3	720
	11th to 20th	Night	11% 24% 26% 29% 9% 2	720
	21st to end	Night	15% 22% 32% 21% 8% 2	807
November	1st to 10th	Night	12% 29% 32% 20% 7% 1	925
	11th to 20th	Night	14% 33% 30% 18% 5% 1	950
	21st to end	Night	9% 29% 34% 22% 6% 1	950
December	1st to 10th	Night	16% 32% 30% 17% 5%	950
	11th to 20th	Night	10% 33% 33% 20% 4	950
	21st to end	Night	10% 36% 31% 17% 5%	1045

Page generated at 2024-03-31 04:08:55. Version ac07

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