Bluerock Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bluerock Campground clear sky chart from 2005-11-06 to 2025-11-18.

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	6% 9% 3 8% 5% 5% 5% 4 7% 8% 38%	131157
	Night	3 8% 3 9% 5% 5% 5% 4 7% 9% 42%	127929
Transparency	Day	38% 10% 16% 22% 12% 2	130866
	Night	34% 10% 18% 23% 13% 2	127797
Seeing	Day	14% 22% 32% 21% 9% 2	16652
	Night	10% 23% 34% 23% 9% 2	25675

By Month

Percentage Cloud Cover NW (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	3 4 15% 7% 6% 6% 6% 8% 10% 36%	3179
	11th to 20th	Day	4 3 10% 6% 7% 8% 6% 8% 11% 38%	3365
	21st to end	Day	4 3 7% 4 5% 5% 5% 7% 9% 50%	4004
February	1st to 10th	Day	1 6% 3 11% 8% 8% 6% 7% 8% 9% 34%	1600
	11th to 20th	Day	1 7% 4 11% 8% 6% 7% 6% 8% 11% 31%	1725
	21st to end	Day	1 6% 5% 15% 9% 7% 6% 5% 7% 9% 30%	1650
March	1st to 10th	Day	1 7% 4 10% 6% 6% 4 4 6% 10% 42%	4518
	11th to 20th	Day	1 7% 6% 11% 6% 5% 6% 5% 7% 9% 38%	4899
	21st to end	Day	2 16% 7% 18% 7% 5% 5% 4 7% 7% 22%	5649
April	1st to 10th	Day	4 15% 6% 11% 6% 6% 6% 5% 8% 8% 26%	2421
	11th to 20th	Day	5% 18% 6% 12% 5% 5% 4 4 7% 8% 25%	2570
	21st to end	Day	7% 18% 6% 10% 5% 4 4 4 7% 7% 28%	2600
May	1st to 10th	Day	9% 19% 4 6% 4 4 4 3 5% 6% 36%	6137
	11th to 20th	Day	9% 16% 4 9% 6% 6% 6% 6% 7% 8% 23%	6706
	21st to end	Day	10% 11% 3 7% 5% 5% 5% 4 6% 8% 37%	7405
June	1st to 10th	Day	15% 12% 4 9% 6% 5% 5% 5% 5% 7% 28%	3000
	11th to 20th	Day	18% 12% 4 9% 6% 6% 5% 4 6% 7% 24%	3000
	21st to end	Day	10% 8% 3 8% 6% 6% 5% 5% 7% 8% 34%	3000
July	1st to 10th	Day	9% 6% 3 6% 5% 5% 5% 4 6% 8% 46%	6780
	11th to 20th	Day	11% 5% 2 6% 5% 5% 5% 4 7% 8% 42%	6780
	21st to end	Day	8% 6% 2 5% 4 5% 5% 4 5% 7% 48%	7041
August	1st to 10th	Day	12% 7% 3 7% 5% 5% 6% 4 7% 8% 37%	4541
	11th to 20th	Day	10% 5% 3 7% 5% 5% 5% 5% 6% 8% 41%	4227
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 6% 8% 48%	4664
September	1st to 10th	Day	10% 8% 2 5% 4 5% 4 3 6% 7% 46%	2450
	11th to 20th	Day	11% 8% 2 6% 4 4 5% 4 6% 7% 42%	2207
	21st to end	Day	7% 8% 2 5% 4 4 5% 4 7% 9% 44%	2200
October	1st to 10th	Day	4 8% 3 5% 4 3 5% 4 5% 8% 51%	3506
	11th to 20th	Day	3 8% 3 7% 5% 4 5% 4 7% 9% 46%	2964
	21st to end	Day	3 8% 3 7% 4 5% 5% 4 6% 9% 47%	3200
November	1st to 10th	Day	3 11% 4 10% 6% 6% 5% 5% 7% 10% 35%	1775
	11th to 20th	Day	1 8% 3 7% 5% 4 4 5% 9% 12% 43%	1564
	21st to end	Day	1 9% 3 9% 8% 6% 4 4 6% 11% 41%	1400
December	1st to 10th	Day	5% 4 8% 4 4 4 5% 9% 12% 46%	2290
	11th to 20th	Day	5% 3 9% 6% 6% 6% 5% 8% 10% 41%	2642
	21st to end	Day	6% 3 10% 6% 7% 6% 4 6% 9% 43%	3498
January	1st to 10th	Night	1 6% 5% 14% 7% 5% 6% 6% 8% 10% 33%	6766
	11th to 20th	Night	4 3 9% 6% 6% 6% 6% 9% 10% 40%	6574
	21st to end	Night	6% 3 8% 6% 4 5% 5% 7% 11% 45%	6952
February	1st to 10th	Night	7% 3 9% 8% 7% 7% 7% 7% 10% 36%	2800
	11th to 20th	Night	7% 4 12% 6% 6% 6% 6% 7% 10% 36%	2560
	21st to end	Night	1 6% 3 11% 7% 7% 7% 6% 7% 8% 37%	1980
March	1st to 10th	Night	7% 4 11% 7% 5% 5% 5% 8% 9% 38%	5376
	11th to 20th	Night	1 6% 4 9% 5% 5% 5% 5% 8% 9% 43%	5100
	21st to end	Night	1 14% 7% 14% 5% 5% 4 4 7% 9% 29%	5324
April	1st to 10th	Night	4 13% 5% 10% 4 5% 5% 4 6% 7% 37%	1978
	11th to 20th	Night	4 12% 6% 11% 4 4 4 4 6% 9% 35%	1781
	21st to end	Night	4 12% 5% 11% 5% 5% 4 4 6% 7% 36%	1800
May	1st to 10th	Night	7% 16% 4 7% 4 4 3 3 4 6% 43%	3829
	11th to 20th	Night	7% 12% 4 10% 5% 5% 6% 5% 6% 8% 32%	3187
	21st to end	Night	8% 9% 3 7% 4 5% 4 4 5% 6% 44%	3470
June	1st to 10th	Night	11% 11% 4 7% 6% 5% 5% 4 6% 7% 35%	1400
	11th to 20th	Night	16% 11% 3 6% 6% 6% 5% 5% 6% 7% 32%	1400
	21st to end	Night	8% 6% 2 6% 4 3 5% 5% 7% 8% 47%	1400
July	1st to 10th	Night	6% 6% 2 6% 4 4 4 3 6% 7% 51%	3180
	11th to 20th	Night	9% 6% 2 5% 4 4 5% 3 6% 7% 49%	3180
	21st to end	Night	11% 6% 1 4 3 3 3 3 4 7% 54%	3786
August	1st to 10th	Night	10% 10% 3 6% 4 5% 5% 4 6% 9% 40%	2609
	11th to 20th	Night	5% 4 2 6% 4 4 5% 4 7% 9% 49%	2829
	21st to end	Night	7% 4 2 4 4 4 5% 4 7% 8% 51%	3245
September	1st to 10th	Night	9% 5% 2 5% 3 3 5% 3 6% 8% 52%	1949
	11th to 20th	Night	10% 8% 2 6% 3 4 4 4 5% 8% 47%	2192
	21st to end	Night	8% 8% 2 5% 3 3 4 4 5% 9% 50%	2200
October	1st to 10th	Night	4 7% 3 5% 3 3 4 3 6% 8% 53%	3690
	11th to 20th	Night	2 6% 2 5% 3 3 4 4 6% 11% 54%	4181
	21st to end	Night	2 6% 3 8% 4 4 4 4 7% 9% 48%	4600
November	1st to 10th	Night	2 9% 5% 10% 6% 4 5% 4 7% 9% 40%	2723
	11th to 20th	Night	1 6% 3 7% 5% 5% 4 5% 8% 12% 45%	2990
	21st to end	Night	1 7% 4 9% 6% 5% 5% 4 8% 10% 41%	3000
December	1st to 10th	Night	5% 2 7% 5% 4 4 4 7% 11% 48%	4890
	11th to 20th	Night	1 6% 4 10% 7% 6% 6% 5% 9% 11% 36%	5550
	21st to end	Night	1 8% 4 11% 6% 5% 5% 5% 7% 8% 40%	7458

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	38% 12% 15% 19% 13% 3	3179
	11th to 20th	Day	37% 9% 16% 20% 13% 4	3387
	21st to end	Day	23% 13% 18% 30% 15% 2	4004
February	1st to 10th	Day	39% 12% 20% 17% 9% 4	1600
	11th to 20th	Day	40% 11% 18% 21% 8% 2	1734
	21st to end	Day	45% 12% 14% 17% 11% 1	1650
March	1st to 10th	Day	32% 9% 19% 19% 19% 2	4518
	11th to 20th	Day	35% 8% 21% 21% 13% 1	4900
	21st to end	Day	53% 11% 16% 11% 8% 1	5649
April	1st to 10th	Day	50% 12% 18% 14% 6%	2421
	11th to 20th	Day	52% 9% 15% 17% 7% 1	2570
	21st to end	Day	50% 10% 16% 17% 6% 1	2600
May	1st to 10th	Day	46% 6% 11% 23% 12% 2	6137
	11th to 20th	Day	50% 11% 15% 20% 4	6710
	21st to end	Day	41% 9% 18% 22% 10%	7406
June	1st to 10th	Day	52% 9% 13% 16% 8% 1	3000
	11th to 20th	Day	57% 9% 11% 14% 7% 1	3000
	21st to end	Day	42% 12% 15% 19% 11% 1	3000
July	1st to 10th	Day	33% 8% 12% 23% 20% 4	6706
	11th to 20th	Day	34% 10% 14% 27% 14% 2	6699
	21st to end	Day	31% 8% 11% 24% 19% 7%	6844
August	1st to 10th	Day	39% 10% 13% 25% 11% 1	4524
	11th to 20th	Day	35% 11% 18% 26% 10% 1	4267
	21st to end	Day	30% 7% 15% 33% 14% 1	4663
September	1st to 10th	Day	35% 8% 14% 24% 15% 3	2450
	11th to 20th	Day	36% 9% 16% 24% 13% 2	2207
	21st to end	Day	32% 10% 18% 26% 11% 2	2200
October	1st to 10th	Day	30% 8% 17% 35% 9%	3506
	11th to 20th	Day	29% 10% 22% 20% 15% 4	2964
	21st to end	Day	32% 7% 15% 27% 15% 3	3200
November	1st to 10th	Day	41% 12% 18% 18% 9% 2	1775
	11th to 20th	Day	32% 10% 24% 22% 10% 1	1564
	21st to end	Day	38% 11% 20% 21% 7% 3	1400
December	1st to 10th	Day	27% 10% 27% 23% 11% 2	2290
	11th to 20th	Day	33% 11% 22% 24% 8% 1	2644
	21st to end	Day	34% 8% 14% 24% 15% 5%	3498
January	1st to 10th	Night	41% 13% 18% 18% 8% 2	6766
	11th to 20th	Night	34% 11% 15% 20% 12% 8%	6614
	21st to end	Night	29% 12% 19% 22% 16% 2	6952
February	1st to 10th	Night	40% 11% 16% 17% 11% 4	2800
	11th to 20th	Night	40% 10% 20% 18% 10% 2	2561
	21st to end	Night	40% 11% 14% 20% 13% 2	1980
March	1st to 10th	Night	33% 12% 19% 19% 13% 4	5376
	11th to 20th	Night	31% 10% 21% 23% 14% 1	5100
	21st to end	Night	48% 8% 20% 15% 8% 1	5324
April	1st to 10th	Night	43% 9% 18% 20% 9% 1	1978
	11th to 20th	Night	44% 10% 16% 21% 8% 1	1781
	21st to end	Night	45% 10% 15% 21% 8% 2	1800
May	1st to 10th	Night	41% 8% 11% 25% 13% 2	3826
	11th to 20th	Night	43% 12% 12% 28% 4	3187
	21st to end	Night	37% 8% 19% 23% 11% 1	3470
June	1st to 10th	Night	44% 10% 15% 22% 9%	1400
	11th to 20th	Night	48% 10% 14% 18% 9% 1	1400
	21st to end	Night	30% 11% 19% 26% 12% 1	1400
July	1st to 10th	Night	29% 9% 14% 23% 20% 5%	3145
	11th to 20th	Night	30% 9% 18% 28% 14% 2	3138
	21st to end	Night	29% 7% 14% 25% 17% 8%	3678
August	1st to 10th	Night	35% 8% 16% 27% 12% 2	2601
	11th to 20th	Night	28% 9% 23% 29% 10% 1	2855
	21st to end	Night	25% 8% 22% 30% 15% 1	3245
September	1st to 10th	Night	29% 6% 19% 28% 15% 3	1949
	11th to 20th	Night	33% 8% 14% 27% 14% 3	2192
	21st to end	Night	31% 7% 20% 27% 13% 2	2200
October	1st to 10th	Night	27% 8% 14% 28% 22% 2	3690
	11th to 20th	Night	23% 8% 21% 27% 20% 2	4181
	21st to end	Night	29% 9% 15% 29% 18% 1	4600
November	1st to 10th	Night	39% 11% 18% 20% 9% 2	2723
	11th to 20th	Night	31% 13% 19% 23% 13% 1	2990
	21st to end	Night	34% 12% 21% 19% 10% 4	3000
December	1st to 10th	Night	28% 10% 26% 23% 10% 2	4890
	11th to 20th	Night	37% 13% 23% 18% 10%	5547
	21st to end	Night	36% 11% 14% 20% 14% 5%	7458

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	4 25% 35% 24% 8% 5%	200
	11th to 20th	Day	6% 25% 40% 23% 6% 1	200
	21st to end	Day	6% 33% 41% 12% 5% 2	220
February	1st to 10th	Day	8% 33% 36% 17% 5% 3	200
	11th to 20th	Day	5% 26% 40% 21% 7%	285
	21st to end	Day	11% 28% 29% 26% 5%	414
March	1st to 10th	Day	9% 33% 33% 18% 6% 2	500
	11th to 20th	Day	8% 27% 36% 21% 5% 2	500
	21st to end	Day	11% 31% 33% 16% 7% 2	550
April	1st to 10th	Day	12% 29% 34% 22% 4	500
	11th to 20th	Day	17% 23% 32% 20% 7% 1	492
	21st to end	Day	18% 25% 28% 16% 11% 2	500
May	1st to 10th	Day	18% 20% 25% 21% 11% 4	503
	11th to 20th	Day	21% 12% 23% 24% 17% 4	710
	21st to end	Day	23% 13% 22% 23% 15% 4	789
June	1st to 10th	Day	18% 18% 33% 22% 8% 2	730
	11th to 20th	Day	24% 21% 29% 18% 7% 1	730
	21st to end	Day	17% 16% 28% 25% 12% 4	730
July	1st to 10th	Day	12% 12% 33% 24% 16% 3	721
	11th to 20th	Day	13% 16% 30% 27% 12% 2	718
	21st to end	Day	10% 14% 34% 27% 12% 3	651
August	1st to 10th	Day	16% 13% 30% 29% 10% 2	527
	11th to 20th	Day	13% 16% 35% 26% 9% 2	517
	21st to end	Day	13% 21% 30% 23% 10% 3	583
September	1st to 10th	Day	15% 22% 32% 19% 11% 3	530
	11th to 20th	Day	16% 19% 32% 24% 8% 1	530
	21st to end	Day	19% 31% 30% 14% 5% 1	530
October	1st to 10th	Day	15% 21% 35% 19% 10% 1	475
	11th to 20th	Day	14% 27% 33% 17% 7% 2	330
	21st to end	Day	16% 31% 33% 14% 4 2	363
November	1st to 10th	Day	17% 28% 38% 11% 5% 1	330
	11th to 20th	Day	16% 32% 35% 12% 4 1	274
	21st to end	Day	10% 29% 29% 19% 8% 6%	200
December	1st to 10th	Day	9% 28% 37% 19% 7% 2	200
	11th to 20th	Day	6% 33% 38% 20% 4 1	200
	21st to end	Day	9% 23% 40% 18% 8% 2	220
January	1st to 10th	Night	8% 32% 39% 16% 4 1	1000
	11th to 20th	Night	6% 32% 41% 17% 3 1	925
	21st to end	Night	6% 34% 36% 18% 5%	880
February	1st to 10th	Night	5% 28% 33% 22% 10% 3	800
	11th to 20th	Night	5% 26% 37% 25% 7%	784
	21st to end	Night	6% 23% 36% 22% 12% 1	660
March	1st to 10th	Night	5% 24% 42% 21% 7% 2	800
	11th to 20th	Night	6% 26% 39% 22% 6% 1	800
	21st to end	Night	7% 20% 35% 26% 9% 3	880
April	1st to 10th	Night	9% 24% 28% 29% 8% 1	778
	11th to 20th	Night	11% 19% 36% 26% 8% 1	593
	21st to end	Night	13% 18% 33% 25% 9% 2	600
May	1st to 10th	Night	13% 14% 28% 32% 12% 2	485
	11th to 20th	Night	14% 11% 26% 28% 18% 3	394
	21st to end	Night	22% 9% 22% 28% 17% 2	433
June	1st to 10th	Night	19% 13% 27% 28% 12% 2	400
	11th to 20th	Night	23% 13% 24% 28% 12%	400
	21st to end	Night	12% 10% 29% 29% 19% 1	400
July	1st to 10th	Night	12% 5% 26% 39% 17% 1	390
	11th to 20th	Night	12% 7% 29% 34% 16% 2	388
	21st to end	Night	9% 8% 22% 37% 22% 2	438
August	1st to 10th	Night	13% 5% 20% 36% 25% 2	398
	11th to 20th	Night	12% 7% 25% 35% 20% 2	546
	21st to end	Night	10% 14% 24% 35% 15% 2	660
September	1st to 10th	Night	13% 11% 26% 29% 16% 4	749
	11th to 20th	Night	15% 12% 27% 29% 13% 5%	800
	21st to end	Night	13% 21% 34% 21% 7% 4	800
October	1st to 10th	Night	13% 17% 33% 25% 10% 2	800
	11th to 20th	Night	11% 23% 34% 23% 7% 2	800
	21st to end	Night	10% 28% 35% 21% 4 1	880
November	1st to 10th	Night	11% 29% 40% 14% 5%	878
	11th to 20th	Night	10% 34% 39% 14% 2 1	1036
	21st to end	Night	7% 32% 37% 17% 5% 2	1000
December	1st to 10th	Night	6% 32% 36% 18% 7% 2	1000
	11th to 20th	Night	5% 32% 39% 19% 5% 1	1000
	21st to end	Night	6% 30% 39% 18% 6% 1	1100

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