Pioneer Scout Reservation
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pioneer Scout Reservation 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	13% 9% 4 9% 5% 5% 5% 4 6% 7% 33%	126150
	Night	14% 10% 4 9% 5% 4 4 4 5% 7% 34%	123398
Transparency	Day	47% 6% 12% 21% 13% 1	129722
	Night	48% 5% 12% 21% 13% 1	127898
Seeing	Day	17% 9% 28% 24% 15% 7%	16937
	Night	18% 9% 29% 30% 13% 1	26712

By Month

Percentage Cloud Cover SE (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	12% 16% 8% 20% 6% 5% 5% 3 4 4 17%	3617
	11th to 20th	Day	13% 14% 7% 15% 10% 6% 6% 5% 6% 4 13%	3620
	21st to end	Day	19% 17% 8% 15% 6% 4 3 3 3 4 17%	4228
February	1st to 10th	Day	14% 16% 5% 12% 8% 6% 5% 4 4 6% 21%	1845
	11th to 20th	Day	15% 11% 4 13% 8% 6% 4 4 6% 5% 24%	1948
	21st to end	Day	16% 12% 5% 11% 6% 4 4 4 6% 7% 25%	1650
March	1st to 10th	Day	16% 12% 5% 13% 7% 5% 4 3 4 5% 27%	4480
	11th to 20th	Day	11% 10% 3 8% 5% 4 5% 4 6% 7% 37%	4968
	21st to end	Day	19% 14% 5% 9% 5% 5% 5% 3 5% 6% 24%	5494
April	1st to 10th	Day	17% 12% 4 7% 5% 5% 5% 4 6% 7% 28%	2400
	11th to 20th	Day	17% 9% 3 7% 5% 5% 5% 4 5% 6% 35%	2460
	21st to end	Day	17% 9% 3 7% 5% 5% 4 3 5% 8% 34%	2600
May	1st to 10th	Day	20% 9% 3 7% 5% 5% 5% 4 5% 6% 30%	5862
	11th to 20th	Day	16% 7% 3 6% 4 4 5% 4 6% 9% 36%	5861
	21st to end	Day	14% 6% 3 7% 4 4 5% 4 6% 8% 40%	6561
June	1st to 10th	Day	10% 7% 2 6% 5% 5% 6% 4 6% 8% 41%	2800
	11th to 20th	Day	9% 6% 2 6% 5% 5% 5% 4 6% 9% 43%	2800
	21st to end	Day	10% 5% 2 7% 5% 5% 6% 5% 8% 10% 38%	2800
July	1st to 10th	Day	9% 6% 2 7% 5% 4 5% 4 7% 11% 42%	6360
	11th to 20th	Day	6% 5% 2 6% 5% 5% 6% 5% 7% 11% 43%	6360
	21st to end	Day	8% 6% 3 7% 5% 5% 6% 4 7% 10% 41%	6662
August	1st to 10th	Day	10% 5% 2 6% 4 4 5% 4 7% 8% 46%	4234
	11th to 20th	Day	9% 6% 2 6% 4 5% 5% 4 6% 9% 43%	4174
	21st to end	Day	7% 4 3 6% 4 5% 4 4 6% 11% 45%	4426
September	1st to 10th	Day	11% 6% 2 5% 5% 4 4 4 6% 7% 44%	2311
	11th to 20th	Day	10% 4 2 5% 3 4 5% 4 7% 9% 47%	2200
	21st to end	Day	13% 8% 2 7% 4 4 5% 3 6% 8% 40%	2200
October	1st to 10th	Day	12% 7% 2 6% 5% 4 4 3 5% 7% 45%	2123
	11th to 20th	Day	16% 7% 3 7% 5% 4 5% 4 5% 7% 36%	1906
	21st to end	Day	18% 11% 3 7% 5% 5% 5% 4 7% 8% 29%	1881
November	1st to 10th	Day	12% 9% 3 7% 4 3 3 3 7% 7% 42%	1762
	11th to 20th	Day	16% 14% 4 9% 6% 5% 5% 3 4 7% 29%	1800
	21st to end	Day	20% 15% 5% 9% 6% 4 4 3 5% 6% 24%	1800
December	1st to 10th	Day	11% 14% 6% 13% 7% 5% 4 4 5% 6% 24%	2930
	11th to 20th	Day	19% 16% 7% 11% 7% 5% 5% 4 4 5% 17%	3045
	21st to end	Day	26% 21% 8% 10% 5% 4 4 2 4 5% 13%	3982
January	1st to 10th	Night	13% 14% 6% 18% 7% 5% 5% 4 4 6% 18%	6348
	11th to 20th	Night	12% 16% 8% 16% 8% 6% 5% 5% 5% 6% 14%	6360
	21st to end	Night	19% 14% 6% 11% 6% 5% 5% 4 4 5% 22%	6723
February	1st to 10th	Night	16% 15% 4 10% 7% 6% 4 3 5% 6% 24%	2555
	11th to 20th	Night	14% 12% 4 10% 7% 6% 5% 4 5% 6% 27%	2338
	21st to end	Night	20% 11% 4 8% 5% 5% 5% 3 4 5% 30%	1980
March	1st to 10th	Night	15% 11% 4 8% 4 4 4 3 5% 7% 36%	5373
	11th to 20th	Night	10% 7% 3 6% 4 4 4 4 6% 8% 44%	4990
	21st to end	Night	17% 10% 4 9% 5% 4 4 3 5% 5% 35%	5467
April	1st to 10th	Night	15% 10% 3 7% 5% 4 3 4 5% 7% 37%	2010
	11th to 20th	Night	18% 8% 3 6% 5% 4 4 3 5% 6% 37%	1887
	21st to end	Night	17% 8% 3 7% 5% 3 4 4 5% 6% 38%	1800
May	1st to 10th	Night	20% 10% 4 8% 5% 5% 5% 3 5% 6% 30%	4033
	11th to 20th	Night	19% 8% 2 6% 3 3 3 3 4 6% 41%	4032
	21st to end	Night	15% 5% 2 6% 4 4 4 4 6% 8% 42%	4295
June	1st to 10th	Night	11% 5% 2 5% 4 4 4 4 6% 9% 46%	1600
	11th to 20th	Night	9% 5% 2 7% 5% 4 5% 4 7% 7% 45%	1600
	21st to end	Night	8% 5% 2 6% 5% 4 3 4 8% 9% 47%	1600
July	1st to 10th	Night	7% 4 2 5% 4 4 4 4 7% 10% 50%	3618
	11th to 20th	Night	6% 4 2 6% 4 4 5% 4 6% 8% 50%	3617
	21st to end	Night	9% 6% 2 6% 5% 4 4 3 6% 9% 47%	4196
August	1st to 10th	Night	10% 6% 2 6% 4 3 4 4 6% 9% 45%	2915
	11th to 20th	Night	8% 5% 1 5% 4 5% 5% 4 7% 8% 49%	2875
	21st to end	Night	8% 5% 2 6% 4 5% 4 4 5% 9% 48%	3468
September	1st to 10th	Night	10% 6% 2 5% 3 4 4 3 5% 6% 52%	2068
	11th to 20th	Night	8% 5% 1 4 4 2 4 3 4 7% 57%	2200
	21st to end	Night	14% 7% 2 7% 4 4 4 3 4 6% 45%	2200
October	1st to 10th	Night	11% 7% 2 5% 4 4 3 3 5% 7% 49%	2124
	11th to 20th	Night	17% 8% 3 6% 5% 4 4 3 5% 6% 37%	2271
	21st to end	Night	19% 9% 2 7% 4 4 4 3 5% 6% 37%	2717
November	1st to 10th	Night	12% 9% 3 7% 5% 4 4 3 5% 7% 42%	2536
	11th to 20th	Night	16% 11% 3 9% 5% 4 4 3 5% 6% 32%	2600
	21st to end	Night	18% 13% 5% 7% 5% 5% 4 4 5% 7% 27%	2600
December	1st to 10th	Night	13% 11% 5% 12% 6% 6% 5% 4 7% 8% 24%	4250
	11th to 20th	Night	18% 16% 7% 13% 7% 5% 4 3 4 5% 19%	5156
	21st to end	Night	27% 18% 6% 11% 5% 4 4 3 4 5% 13%	6996

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	69% 6% 9% 13% 4	3618
	11th to 20th	Day	69% 5% 10% 7% 9%	3620
	21st to end	Day	71% 4 8% 11% 5%	4228
February	1st to 10th	Day	64% 5% 10% 13% 7% 1	1845
	11th to 20th	Day	60% 5% 10% 16% 9% 1	1958
	21st to end	Day	57% 5% 13% 16% 7% 2	1650
March	1st to 10th	Day	60% 5% 9% 19% 7% 1	4480
	11th to 20th	Day	44% 5% 16% 25% 9% 2	4968
	21st to end	Day	60% 6% 10% 16% 8%	5496
April	1st to 10th	Day	53% 6% 11% 18% 11%	2400
	11th to 20th	Day	48% 6% 11% 22% 11% 2	2460
	21st to end	Day	48% 5% 13% 19% 12% 2	2600
May	1st to 10th	Day	52% 6% 11% 17% 14%	5897
	11th to 20th	Day	43% 7% 14% 22% 12% 2	5865
	21st to end	Day	41% 6% 10% 23% 18% 3	6575
June	1st to 10th	Day	39% 7% 11% 25% 16% 2	2800
	11th to 20th	Day	37% 7% 13% 25% 17% 2	2800
	21st to end	Day	39% 8% 13% 22% 15% 3	2800
July	1st to 10th	Day	35% 6% 13% 27% 16% 2	6291
	11th to 20th	Day	32% 8% 15% 28% 17% 1	6285
	21st to end	Day	36% 7% 14% 23% 19% 2	6472
August	1st to 10th	Day	33% 8% 16% 25% 17% 1	4221
	11th to 20th	Day	35% 8% 12% 29% 15% 1	4213
	21st to end	Day	33% 6% 12% 34% 12% 3	4425
September	1st to 10th	Day	37% 7% 14% 23% 17% 2	2311
	11th to 20th	Day	31% 6% 11% 29% 20% 1	2200
	21st to end	Day	41% 5% 12% 23% 18%	2200
October	1st to 10th	Day	28% 4 12% 35% 20% 1	3513
	11th to 20th	Day	38% 5% 9% 26% 21%	3134
	21st to end	Day	43% 5% 13% 26% 12% 1	3081
November	1st to 10th	Day	40% 5% 13% 27% 15% 1	1762
	11th to 20th	Day	55% 5% 10% 18% 10% 1	1800
	21st to end	Day	61% 4 12% 16% 7%	1800
December	1st to 10th	Day	59% 7% 16% 15% 4	2930
	11th to 20th	Day	67% 6% 10% 14% 3	3042
	21st to end	Day	76% 4 7% 9% 4	3982
January	1st to 10th	Night	64% 6% 9% 15% 5%	6348
	11th to 20th	Night	70% 4 10% 9% 7%	6360
	21st to end	Night	63% 5% 13% 10% 8%	6723
February	1st to 10th	Night	61% 5% 11% 16% 7% 1	2555
	11th to 20th	Night	56% 5% 9% 20% 9% 1	2339
	21st to end	Night	56% 5% 11% 18% 9% 1	1980
March	1st to 10th	Night	47% 4 12% 24% 11% 1	5373
	11th to 20th	Night	37% 5% 15% 28% 15% 1	4990
	21st to end	Night	50% 5% 11% 20% 14% 1	5467
April	1st to 10th	Night	46% 6% 10% 23% 14% 2	2010
	11th to 20th	Night	46% 5% 10% 19% 18% 2	1887
	21st to end	Night	46% 5% 10% 21% 16% 2	1800
May	1st to 10th	Night	54% 6% 9% 15% 14% 2	4060
	11th to 20th	Night	44% 6% 10% 26% 13% 2	4033
	21st to end	Night	39% 5% 13% 23% 19% 2	4303
June	1st to 10th	Night	34% 5% 13% 26% 20% 3	1600
	11th to 20th	Night	36% 7% 13% 24% 18% 2	1600
	21st to end	Night	30% 8% 17% 25% 18% 2	1600
July	1st to 10th	Night	30% 6% 14% 26% 20% 5%	3580
	11th to 20th	Night	30% 7% 18% 24% 20% 2	3572
	21st to end	Night	33% 6% 14% 23% 21% 4	4073
August	1st to 10th	Night	34% 8% 15% 27% 15% 1	2904
	11th to 20th	Night	30% 7% 14% 32% 15% 2	2902
	21st to end	Night	33% 6% 12% 29% 18% 2	3468
September	1st to 10th	Night	32% 6% 11% 28% 19% 4	2068
	11th to 20th	Night	27% 6% 9% 31% 25% 2	2200
	21st to end	Night	40% 5% 10% 27% 17% 1	2200
October	1st to 10th	Night	23% 4 8% 34% 29% 1	3514
	11th to 20th	Night	39% 4 10% 23% 23% 1	3782
	21st to end	Night	36% 4 9% 33% 18% 1	4467
November	1st to 10th	Night	41% 5% 11% 25% 16% 1	2536
	11th to 20th	Night	51% 5% 12% 20% 10% 2	2600
	21st to end	Night	56% 5% 12% 20% 6%	2600
December	1st to 10th	Night	55% 6% 15% 17% 6%	4250
	11th to 20th	Night	67% 4 12% 12% 5% 1	5158
	21st to end	Night	73% 5% 10% 8% 4	6996

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	23% 16% 33% 22% 6% 1	300
	11th to 20th	Day	22% 14% 46% 14% 3 1	300
	21st to end	Day	25% 13% 34% 22% 6% 1	330
February	1st to 10th	Day	22% 16% 33% 23% 4 2	300
	11th to 20th	Day	22% 16% 38% 20% 4	300
	21st to end	Day	24% 17% 41% 16% 2	249
March	1st to 10th	Day	20% 17% 41% 18% 4	300
	11th to 20th	Day	20% 13% 35% 24% 6% 2	488
	21st to end	Day	30% 13% 32% 18% 6% 1	550
April	1st to 10th	Day	21% 15% 32% 21% 10%	500
	11th to 20th	Day	25% 15% 30% 18% 9% 3	492
	21st to end	Day	22% 12% 33% 19% 11% 3	500
May	1st to 10th	Day	23% 11% 31% 20% 11% 3	503
	11th to 20th	Day	21% 8% 27% 22% 15% 6%	527
	21st to end	Day	12% 7% 26% 27% 18% 10%	623
June	1st to 10th	Day	12% 7% 28% 27% 20% 5%	730
	11th to 20th	Day	13% 6% 26% 30% 19% 6%	730
	21st to end	Day	12% 5% 29% 30% 18% 7%	730
July	1st to 10th	Day	9% 3 19% 30% 24% 14%	721
	11th to 20th	Day	10% 4 21% 30% 22% 13%	718
	21st to end	Day	7% 3 20% 29% 30% 10%	684
August	1st to 10th	Day	9% 2 15% 29% 25% 19%	526
	11th to 20th	Day	10% 5% 18% 28% 24% 15%	519
	21st to end	Day	8% 3 15% 29% 29% 16%	583
September	1st to 10th	Day	13% 5% 17% 28% 22% 15%	530
	11th to 20th	Day	9% 4 15% 22% 33% 19%	530
	21st to end	Day	17% 8% 19% 24% 22% 10%	530
October	1st to 10th	Day	12% 7% 23% 31% 19% 8%	502
	11th to 20th	Day	18% 14% 28% 29% 10% 2	482
	21st to end	Day	24% 13% 38% 18% 5% 1	330
November	1st to 10th	Day	15% 12% 34% 27% 9% 4	300
	11th to 20th	Day	21% 20% 32% 19% 7% 1	300
	21st to end	Day	26% 12% 41% 18% 3	300
December	1st to 10th	Day	21% 19% 36% 16% 9% 1	300
	11th to 20th	Day	23% 17% 37% 19% 4	300
	21st to end	Day	27% 19% 32% 20% 2	330
January	1st to 10th	Night	21% 16% 35% 22% 6% 1	1000
	11th to 20th	Night	23% 13% 37% 22% 4 1	1000
	21st to end	Night	22% 12% 35% 26% 5%	983
February	1st to 10th	Night	23% 11% 38% 23% 4	800
	11th to 20th	Night	21% 13% 35% 27% 3	783
	21st to end	Night	26% 11% 39% 21% 3	660
March	1st to 10th	Night	20% 11% 35% 27% 7% 1	800
	11th to 20th	Night	17% 14% 38% 24% 7% 1	800
	21st to end	Night	24% 10% 33% 26% 7% 1	880
April	1st to 10th	Night	20% 11% 35% 28% 6%	610
	11th to 20th	Night	22% 8% 35% 26% 9% 1	593
	21st to end	Night	22% 8% 33% 28% 9%	600
May	1st to 10th	Night	22% 7% 30% 32% 8% 1	600
	11th to 20th	Night	23% 5% 27% 28% 16% 1	591
	21st to end	Night	14% 3 24% 38% 18% 3	650
June	1st to 10th	Night	13% 2 25% 46% 15% 1	600
	11th to 20th	Night	10% 5% 23% 43% 18% 1	600
	21st to end	Night	9% 3 23% 41% 23% 2	600
July	1st to 10th	Night	8% 3 15% 42% 28% 5%	585
	11th to 20th	Night	9% 2 16% 40% 28% 4	582
	21st to end	Night	7% 2 16% 44% 31% 1	657
August	1st to 10th	Night	7% 2 15% 41% 31% 4	597
	11th to 20th	Night	9% 1 15% 41% 30% 4	594
	21st to end	Night	10% 2 15% 36% 34% 4	660
September	1st to 10th	Night	11% 3 17% 33% 31% 5%	668
	11th to 20th	Night	10% 3 14% 35% 35% 4	800
	21st to end	Night	17% 6% 20% 31% 22% 5%	800
October	1st to 10th	Night	13% 6% 25% 33% 21% 2	773
	11th to 20th	Night	22% 11% 29% 27% 10% 1	760
	21st to end	Night	22% 12% 33% 26% 8%	836
November	1st to 10th	Night	16% 11% 33% 27% 12% 1	780
	11th to 20th	Night	23% 13% 31% 28% 6% 1	800
	21st to end	Night	23% 11% 33% 27% 6%	800
December	1st to 10th	Night	24% 14% 34% 22% 7%	800
	11th to 20th	Night	24% 12% 35% 24% 4 1	970
	21st to end	Night	30% 11% 32% 24% 3	1100

Page generated at 2025-10-01 01:39:06. Version ac07

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