Rooster Rock State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rooster Rock State Park clear sky chart from 2005-11-06 to 2026-08-15.

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	22% 11% 3 6% 3 3 3 3 4 5% 38%	153231
	Night	26% 12% 2 5% 3 3 3 2 4 5% 35%	145987
Transparency	Day	49% 5% 11% 18% 13% 5%	147990
	Night	53% 4 10% 16% 12% 4	142229
Seeing	Day	31% 10% 23% 24% 9% 2	16804
	Night	35% 7% 16% 26% 14% 2	25703

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	41% 22% 3 7% 4 3 3 2 3 3 9%	4722
	11th to 20th	Day	22% 14% 2 5% 2 2 2 2 3 5% 40%	4740
	21st to end	Day	33% 8% 2 6% 3 3 3 3 4 4 31%	5580
February	1st to 10th	Day	35% 16% 3 5% 5% 3 4 3 4 5% 17%	1890
	11th to 20th	Day	33% 20% 3 7% 5% 3 3 2 3 3 18%	1845
	21st to end	Day	33% 21% 4 6% 3 3 3 2 3 4 19%	1663
March	1st to 10th	Day	22% 18% 4 10% 5% 4 4 3 5% 5% 19%	4769
	11th to 20th	Day	31% 18% 4 7% 4 3 2 2 2 2 25%	5110
	21st to end	Day	33% 17% 4 9% 5% 5% 4 3 5% 4 12%	5779
April	1st to 10th	Day	33% 18% 3 7% 4 4 3 3 3 5% 17%	2520
	11th to 20th	Day	28% 18% 4 7% 4 4 3 2 4 4 23%	2489
	21st to end	Day	29% 13% 3 7% 4 4 4 3 4 5% 24%	2693
May	1st to 10th	Day	16% 11% 3 6% 4 3 3 3 4 7% 41%	8168
	11th to 20th	Day	22% 15% 4 8% 4 4 4 3 4 6% 26%	8160
	21st to end	Day	22% 9% 2 7% 4 4 4 3 5% 7% 33%	8992
June	1st to 10th	Day	28% 10% 3 5% 4 3 3 3 5% 5% 31%	2940
	11th to 20th	Day	27% 11% 3 6% 4 4 4 4 5% 6% 27%	2940
	21st to end	Day	15% 8% 2 5% 4 3 3 3 5% 6% 46%	2940
July	1st to 10th	Day	5% 5% 1 4 2 3 3 3 4 5% 66%	8219
	11th to 20th	Day	4 3 1 2 2 2 2 2 3 3 76%	8220
	21st to end	Day	6% 3 1 3 2 2 2 2 4 5% 70%	8922
August	1st to 10th	Day	7% 5% 1 5% 3 3 3 3 4 5% 61%	6049
	11th to 20th	Day	10% 5% 2 5% 3 4 4 3 5% 6% 53%	5849
	21st to end	Day	11% 6% 2 5% 4 3 4 4 6% 6% 50%	6116
September	1st to 10th	Day	12% 5% 1 4 2 3 3 2 4 7% 58%	2400
	11th to 20th	Day	17% 8% 3 5% 3 4 4 3 4 5% 44%	2400
	21st to end	Day	20% 7% 2 6% 2 3 3 2 4 7% 44%	2116
October	1st to 10th	Day	21% 6% 2 4 2 2 3 3 4 5% 48%	3280
	11th to 20th	Day	25% 8% 2 7% 4 3 4 3 5% 7% 32%	3261
	21st to end	Day	36% 12% 2 5% 4 3 3 3 5% 4 22%	3433
November	1st to 10th	Day	39% 12% 3 8% 4 3 3 2 4 6% 16%	1766
	11th to 20th	Day	40% 11% 3 6% 3 4 4 3 4 4 17%	1680
	21st to end	Day	34% 15% 2 6% 4 3 4 3 3 4 22%	1680
December	1st to 10th	Day	27% 11% 2 5% 3 3 3 2 3 4 37%	2700
	11th to 20th	Day	41% 15% 4 8% 4 3 3 3 3 4 12%	3108
	21st to end	Day	40% 17% 4 8% 4 3 3 2 3 3 13%	4092
January	1st to 10th	Night	41% 20% 2 6% 4 3 3 2 3 3 12%	8172
	11th to 20th	Night	23% 15% 2 4 2 2 2 2 3 6% 39%	8220
	21st to end	Night	31% 11% 3 6% 3 3 3 2 4 5% 32%	8616
February	1st to 10th	Night	32% 19% 4 6% 4 3 3 3 4 4 19%	2730
	11th to 20th	Night	35% 18% 3 5% 3 2 3 2 3 3 22%	2662
	21st to end	Night	34% 19% 3 5% 3 3 3 2 4 5% 20%	2142
March	1st to 10th	Night	24% 20% 4 8% 4 4 5% 3 4 5% 20%	5331
	11th to 20th	Night	32% 18% 3 6% 3 2 2 2 2 3 27%	5110
	21st to end	Night	38% 18% 3 7% 4 4 3 3 4 4 12%	5437
April	1st to 10th	Night	31% 19% 3 7% 5% 4 3 2 3 4 20%	2100
	11th to 20th	Night	27% 15% 2 5% 4 3 4 2 4 6% 28%	2079
	21st to end	Night	31% 14% 2 4 3 3 4 2 4 4 27%	1925
May	1st to 10th	Night	20% 10% 2 5% 3 3 3 3 4 6% 44%	4749
	11th to 20th	Night	23% 15% 4 7% 4 3 3 3 3 4 30%	4700
	21st to end	Night	22% 9% 2 5% 3 3 4 3 6% 7% 36%	5181
June	1st to 10th	Night	27% 9% 3 5% 4 4 3 3 5% 4 35%	1680
	11th to 20th	Night	24% 11% 3 6% 4 2 3 3 4 5% 35%	1680
	21st to end	Night	15% 7% 2 4 3 3 3 3 4 6% 51%	1680
July	1st to 10th	Night	5% 4 1 3 2 2 3 3 4 4 70%	4740
	11th to 20th	Night	4 3 1 4 2 2 2 2 3 4 74%	4740
	21st to end	Night	5% 3 1 2 2 1 2 2 4 6% 71%	5153
August	1st to 10th	Night	8% 4 1 4 3 3 2 2 4 6% 63%	3974
	11th to 20th	Night	15% 6% 2 5% 3 3 2 3 4 5% 53%	4088
	21st to end	Night	12% 5% 2 5% 3 3 3 3 4 6% 55%	4877
September	1st to 10th	Night	12% 3 1 3 3 3 3 3 4 5% 61%	2000
	11th to 20th	Night	18% 7% 2 5% 4 3 3 2 4 5% 46%	2000
	21st to end	Night	18% 8% 1 4 3 3 3 3 4 6% 47%	2280
October	1st to 10th	Night	18% 7% 1 5% 2 3 3 2 4 6% 48%	3920
	11th to 20th	Night	23% 8% 2 5% 3 4 5% 3 5% 7% 34%	3897
	21st to end	Night	38% 11% 3 6% 3 3 3 3 3 5% 24%	4373
November	1st to 10th	Night	40% 12% 3 6% 4 3 3 3 3 5% 18%	2749
	11th to 20th	Night	43% 12% 3 5% 4 2 3 2 3 4 19%	2940
	21st to end	Night	33% 13% 2 5% 3 4 3 2 3 5% 26%	2940
December	1st to 10th	Night	26% 11% 2 5% 3 3 2 2 4 6% 37%	4700
	11th to 20th	Night	41% 16% 3 8% 4 3 3 2 3 4 12%	5316
	21st to end	Night	40% 18% 3 8% 4 4 3 2 2 2 13%	7106

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	82% 3 5% 6% 4	4723
	11th to 20th	Day	48% 3 5% 16% 15% 13%	4740
	21st to end	Day	58% 4 3 11% 18% 5%	5580
February	1st to 10th	Day	69% 6% 10% 9% 5%	1890
	11th to 20th	Day	72% 4 8% 11% 5% 2	1854
	21st to end	Day	70% 4 9% 8% 8% 2	1663
March	1st to 10th	Day	64% 6% 13% 11% 5% 1	4769
	11th to 20th	Day	66% 4 4 18% 6%	5110
	21st to end	Day	74% 7% 9% 6% 3	5779
April	1st to 10th	Day	70% 4 12% 11% 3	2520
	11th to 20th	Day	66% 4 9% 11% 8% 2	2492
	21st to end	Day	64% 5% 10% 12% 8% 2	2693
May	1st to 10th	Day	43% 5% 13% 24% 15%	8168
	11th to 20th	Day	54% 10% 15% 16% 5%	8163
	21st to end	Day	49% 8% 20% 19% 4	8994
June	1st to 10th	Day	55% 5% 14% 18% 7% 1	2940
	11th to 20th	Day	57% 6% 15% 14% 7% 1	2940
	21st to end	Day	39% 5% 16% 26% 10% 4	2940
July	1st to 10th	Day	20% 5% 11% 31% 17% 16%	8151
	11th to 20th	Day	15% 3 6% 20% 34% 22%	8145
	21st to end	Day	17% 4 15% 35% 26% 4	8723
August	1st to 10th	Day	23% 5% 9% 25% 25% 14%	4442
	11th to 20th	Day	30% 6% 15% 32% 11% 5%	4248
	21st to end	Day	34% 5% 10% 22% 18% 11%	4407
September	1st to 10th	Day	28% 4 12% 24% 19% 13%	2400
	11th to 20th	Day	41% 6% 11% 18% 16% 8%	2400
	21st to end	Day	42% 4 12% 19% 16% 6%	2116
October	1st to 10th	Day	39% 5% 6% 21% 25% 4	3280
	11th to 20th	Day	51% 6% 13% 16% 12% 2	3261
	21st to end	Day	63% 6% 6% 16% 9% 1	3433
November	1st to 10th	Day	71% 3 9% 12% 4 1	1766
	11th to 20th	Day	70% 5% 9% 9% 6% 1	1680
	21st to end	Day	66% 5% 7% 10% 11% 1	1680
December	1st to 10th	Day	52% 4 7% 11% 21% 5%	2700
	11th to 20th	Day	77% 3 9% 8% 3	3108
	21st to end	Day	78% 4 8% 9% 2	4092
January	1st to 10th	Night	79% 4 6% 7% 4 1	8172
	11th to 20th	Night	49% 3 5% 15% 17% 10%	8220
	21st to end	Night	57% 3 4 10% 18% 7%	8616
February	1st to 10th	Night	69% 5% 9% 10% 6% 1	2730
	11th to 20th	Night	68% 5% 9% 11% 5% 2	2664
	21st to end	Night	69% 4 8% 11% 8% 1	2142
March	1st to 10th	Night	63% 7% 11% 13% 3 2	5331
	11th to 20th	Night	64% 4 8% 15% 8% 1	5110
	21st to end	Night	75% 5% 9% 9% 2	5437
April	1st to 10th	Night	69% 4 12% 11% 3	2100
	11th to 20th	Night	59% 6% 12% 12% 7% 3	2079
	21st to end	Night	61% 5% 12% 13% 7% 2	1925
May	1st to 10th	Night	42% 5% 11% 25% 16% 1	4747
	11th to 20th	Night	55% 7% 15% 17% 5% 1	4700
	21st to end	Night	46% 8% 22% 19% 4	5182
June	1st to 10th	Night	52% 4 16% 20% 7%	1680
	11th to 20th	Night	52% 4 16% 21% 7%	1680
	21st to end	Night	36% 4 17% 27% 10% 5%	1680
July	1st to 10th	Night	17% 5% 11% 34% 19% 14%	4700
	11th to 20th	Night	17% 3 7% 19% 36% 17%	4692
	21st to end	Night	15% 3 20% 33% 26% 4	5040
August	1st to 10th	Night	18% 3 9% 30% 27% 14%	2907
	11th to 20th	Night	31% 5% 21% 27% 10% 6%	2965
	21st to end	Night	31% 4 11% 26% 13% 14%	3509
September	1st to 10th	Night	25% 4 14% 26% 19% 11%	2000
	11th to 20th	Night	41% 5% 10% 20% 13% 11%	2000
	21st to end	Night	38% 5% 14% 19% 15% 9%	2280
October	1st to 10th	Night	38% 4 8% 22% 26% 3	3920
	11th to 20th	Night	49% 5% 13% 17% 13% 2	3897
	21st to end	Night	64% 5% 6% 14% 9% 2	4373
November	1st to 10th	Night	70% 4 7% 12% 6% 1	2749
	11th to 20th	Night	71% 3 8% 10% 7% 1	2940
	21st to end	Night	62% 4 7% 12% 12% 2	2940
December	1st to 10th	Night	50% 4 8% 13% 21% 4	4700
	11th to 20th	Night	77% 4 8% 7% 4	5316
	21st to end	Night	78% 4 9% 7% 2	7106

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	58% 8% 20% 12% 2	220
	11th to 20th	Day	43% 14% 26% 12% 5%	220
	21st to end	Day	46% 12% 18% 18% 5%	379
February	1st to 10th	Day	47% 13% 19% 17% 4	430
	11th to 20th	Day	48% 10% 24% 14% 3 1	425
	21st to end	Day	47% 12% 21% 17% 3	411
March	1st to 10th	Day	44% 14% 24% 12% 5%	540
	11th to 20th	Day	43% 12% 22% 17% 4 1	540
	21st to end	Day	46% 12% 21% 17% 4	594
April	1st to 10th	Day	44% 11% 18% 20% 7% 1	540
	11th to 20th	Day	38% 16% 25% 15% 5% 2	532
	21st to end	Day	35% 14% 24% 19% 7% 1	540
May	1st to 10th	Day	26% 14% 29% 21% 9% 2	543
	11th to 20th	Day	38% 11% 19% 19% 9% 3	568
	21st to end	Day	29% 10% 21% 26% 11% 3	617
June	1st to 10th	Day	29% 9% 21% 25% 14% 3	570
	11th to 20th	Day	28% 11% 31% 21% 8% 1	570
	21st to end	Day	16% 8% 26% 30% 15% 4	570
July	1st to 10th	Day	11% 7% 25% 41% 13% 3	566
	11th to 20th	Day	8% 9% 26% 39% 15% 4	564
	21st to end	Day	6% 5% 24% 40% 19% 6%	619
August	1st to 10th	Day	10% 4 21% 44% 14% 8%	567
	11th to 20th	Day	8% 5% 24% 38% 19% 6%	534
	21st to end	Day	11% 9% 28% 34% 14% 4	583
September	1st to 10th	Day	14% 5% 29% 33% 14% 4	530
	11th to 20th	Day	20% 7% 26% 30% 15% 2	530
	21st to end	Day	22% 8% 26% 32% 10% 2	530
October	1st to 10th	Day	27% 9% 25% 24% 13% 2	530
	11th to 20th	Day	36% 6% 22% 25% 10% 2	530
	21st to end	Day	42% 10% 20% 18% 8% 1	507
November	1st to 10th	Day	49% 10% 16% 19% 5% 1	283
	11th to 20th	Day	43% 12% 25% 15% 4 1	220
	21st to end	Day	45% 10% 19% 21% 4	220
December	1st to 10th	Day	46% 11% 20% 19% 3 1	220
	11th to 20th	Day	61% 11% 14% 12% 1	220
	21st to end	Day	56% 10% 21% 9% 5% 1	242
January	1st to 10th	Night	52% 12% 19% 13% 4 1	840
	11th to 20th	Night	45% 9% 23% 18% 5%	840
	21st to end	Night	43% 8% 24% 18% 6% 1	924
February	1st to 10th	Night	43% 9% 21% 21% 5% 1	840
	11th to 20th	Night	46% 10% 15% 22% 7%	824
	21st to end	Night	47% 10% 17% 21% 5%	692
March	1st to 10th	Night	42% 9% 17% 22% 10% 1	840
	11th to 20th	Night	41% 7% 19% 23% 9%	840
	21st to end	Night	47% 9% 13% 22% 8% 1	924
April	1st to 10th	Night	42% 8% 14% 25% 11% 1	840
	11th to 20th	Night	35% 8% 19% 25% 12% 2	831
	21st to end	Night	40% 6% 13% 27% 12% 1	665
May	1st to 10th	Night	30% 5% 16% 30% 18% 2	433
	11th to 20th	Night	30% 7% 9% 28% 23% 3	414
	21st to end	Night	30% 5% 12% 29% 23% 2	455
June	1st to 10th	Night	30% 5% 13% 31% 19% 3	420
	11th to 20th	Night	27% 8% 17% 32% 15%	420
	21st to end	Night	18% 5% 11% 41% 24% 1	420
July	1st to 10th	Night	11% 2 10% 42% 35% 1	410
	11th to 20th	Night	9% 2 14% 47% 26% 2	408
	21st to end	Night	5% 2 10% 43% 37% 3	460
August	1st to 10th	Night	10% 3 8% 35% 39% 5%	553
	11th to 20th	Night	9% 2 8% 35% 36% 9%	606
	21st to end	Night	12% 3 12% 41% 27% 4	820
September	1st to 10th	Night	15% 3 16% 34% 30% 3	800
	11th to 20th	Night	20% 4 12% 31% 28% 5%	800
	21st to end	Night	22% 4 15% 34% 21% 4	800
October	1st to 10th	Night	26% 6% 16% 30% 20% 3	800
	11th to 20th	Night	31% 6% 13% 30% 18% 3	800
	21st to end	Night	40% 6% 20% 23% 10% 3	880
November	1st to 10th	Night	48% 6% 16% 22% 7%	820
	11th to 20th	Night	51% 7% 20% 18% 4	840
	21st to end	Night	41% 8% 23% 24% 4	840
December	1st to 10th	Night	42% 10% 25% 18% 4 1	840
	11th to 20th	Night	52% 8% 18% 18% 4	840
	21st to end	Night	55% 9% 17% 14% 4	924

Page generated at 2026-08-12 00:37:15. Version ac07

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