Rainsburg Mountain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rainsburg Mountain clear sky chart from 2005-11-06 to 2026-03-18.

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	14% 8% 3 8% 5% 5% 5% 4 6% 7% 35%	131266
	Night	14% 8% 3 8% 5% 5% 4 4 5% 7% 37%	130230
Transparency	Day	45% 7% 12% 21% 12% 2	134865
	Night	44% 7% 12% 22% 13% 2	134702
Seeing	Day	23% 16% 26% 20% 11% 4	16511
	Night	20% 14% 25% 28% 12% 1	26222

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	13% 13% 4 14% 6% 5% 5% 3 5% 6% 28%	4997
	11th to 20th	Day	9% 13% 6% 13% 9% 7% 7% 4 5% 5% 24%	5280
	21st to end	Day	13% 9% 5% 10% 7% 6% 5% 4 5% 6% 31%	5780
February	1st to 10th	Day	13% 14% 3 8% 7% 4 5% 3 5% 6% 32%	1890
	11th to 20th	Day	14% 9% 5% 11% 6% 5% 5% 4 5% 5% 30%	1843
	21st to end	Day	15% 10% 4 11% 5% 4 3 3 4 6% 34%	1732
March	1st to 10th	Day	16% 13% 3 7% 4 4 4 3 4 5% 37%	5045
	11th to 20th	Day	12% 8% 3 7% 4 4 4 3 6% 7% 41%	5057
	21st to end	Day	13% 9% 3 9% 5% 5% 5% 3 4 6% 38%	5465
April	1st to 10th	Day	16% 11% 3 8% 5% 5% 4 3 5% 7% 33%	2374
	11th to 20th	Day	13% 9% 3 7% 5% 5% 5% 4 5% 6% 39%	2374
	21st to end	Day	19% 8% 3 6% 5% 4 4 4 6% 7% 35%	2499
May	1st to 10th	Day	22% 7% 3 7% 5% 5% 6% 4 6% 8% 28%	5862
	11th to 20th	Day	25% 7% 2 6% 4 4 5% 4 6% 8% 28%	5988
	21st to end	Day	17% 6% 3 7% 5% 5% 5% 5% 7% 9% 32%	6934
June	1st to 10th	Day	13% 6% 2 6% 5% 5% 5% 5% 7% 8% 39%	2800
	11th to 20th	Day	12% 6% 2 6% 5% 6% 6% 6% 7% 9% 35%	2800
	21st to end	Day	10% 5% 2 5% 5% 5% 5% 5% 7% 11% 39%	2800
July	1st to 10th	Day	6% 4 2 7% 5% 5% 6% 5% 6% 9% 45%	6360
	11th to 20th	Day	7% 5% 2 8% 6% 6% 7% 6% 8% 10% 33%	5975
	21st to end	Day	9% 6% 3 7% 5% 5% 5% 4 6% 9% 39%	6424
August	1st to 10th	Day	17% 6% 2 7% 4 5% 6% 5% 7% 9% 32%	4234
	11th to 20th	Day	10% 5% 2 7% 5% 5% 6% 6% 7% 9% 38%	4156
	21st to end	Day	12% 5% 2 5% 4 5% 5% 4 6% 9% 42%	4312
September	1st to 10th	Day	16% 5% 2 4 4 4 5% 4 5% 6% 45%	2400
	11th to 20th	Day	14% 6% 2 5% 4 3 4 3 6% 7% 47%	2325
	21st to end	Day	21% 8% 3 6% 4 5% 4 3 6% 6% 35%	2130
October	1st to 10th	Day	16% 6% 2 6% 4 4 4 3 4 7% 43%	2000
	11th to 20th	Day	16% 7% 2 8% 5% 4 4 3 5% 5% 41%	2000
	21st to end	Day	15% 7% 3 7% 5% 4 5% 3 5% 7% 40%	2200
November	1st to 10th	Day	10% 6% 3 6% 4 3 3 3 6% 7% 48%	2025
	11th to 20th	Day	13% 10% 3 7% 4 4 4 4 6% 7% 38%	1727
	21st to end	Day	15% 11% 3 8% 6% 5% 4 3 6% 6% 34%	1680
December	1st to 10th	Day	12% 9% 5% 12% 6% 5% 5% 4 6% 7% 30%	2680
	11th to 20th	Day	19% 14% 4 7% 5% 4 3 3 4 5% 31%	3070
	21st to end	Day	17% 12% 5% 11% 6% 6% 5% 4 5% 6% 22%	4048
January	1st to 10th	Night	9% 11% 5% 14% 7% 6% 6% 4 5% 6% 28%	7894
	11th to 20th	Night	8% 11% 5% 14% 6% 5% 5% 3 5% 6% 32%	7680
	21st to end	Night	12% 8% 4 8% 8% 6% 5% 4 5% 6% 35%	8401
February	1st to 10th	Night	13% 9% 3 7% 6% 5% 5% 4 5% 7% 35%	2730
	11th to 20th	Night	15% 10% 3 9% 5% 5% 5% 4 6% 6% 31%	2663
	21st to end	Night	13% 10% 4 9% 6% 4 5% 4 6% 6% 33%	2067
March	1st to 10th	Night	17% 9% 3 6% 4 4 4 3 5% 6% 39%	5028
	11th to 20th	Night	10% 7% 4 7% 4 4 4 3 5% 6% 48%	5058
	21st to end	Night	10% 8% 3 8% 5% 5% 4 4 5% 6% 43%	5467
April	1st to 10th	Night	17% 11% 3 7% 5% 5% 4 4 5% 5% 35%	2025
	11th to 20th	Night	14% 8% 2 6% 5% 4 4 4 6% 9% 39%	1975
	21st to end	Night	17% 6% 2 5% 4 4 4 4 5% 8% 41%	1917
May	1st to 10th	Night	25% 9% 3 8% 4 4 4 4 5% 7% 27%	4033
	11th to 20th	Night	28% 7% 2 5% 4 4 4 4 6% 8% 30%	3905
	21st to end	Night	20% 6% 2 6% 4 4 4 4 6% 8% 35%	3920
June	1st to 10th	Night	12% 6% 2 5% 4 4 5% 4 6% 8% 45%	1600
	11th to 20th	Night	13% 5% 1 7% 4 4 5% 5% 5% 9% 42%	1600
	21st to end	Night	10% 4 2 5% 4 4 4 4 9% 11% 44%	1600
July	1st to 10th	Night	7% 5% 3 6% 4 6% 5% 4 7% 10% 43%	3598
	11th to 20th	Night	7% 7% 3 9% 6% 5% 6% 5% 7% 9% 35%	3964
	21st to end	Night	8% 6% 2 6% 5% 5% 5% 5% 7% 10% 42%	4427
August	1st to 10th	Night	15% 5% 2 7% 4 4 5% 4 6% 9% 38%	2915
	11th to 20th	Night	11% 6% 2 8% 4 4 5% 4 5% 7% 45%	2875
	21st to end	Night	15% 5% 2 4 4 4 4 4 6% 7% 47%	3571
September	1st to 10th	Night	15% 6% 2 5% 3 3 4 3 5% 5% 48%	2000
	11th to 20th	Night	13% 5% 2 5% 3 3 4 3 5% 6% 51%	2071
	21st to end	Night	22% 7% 2 5% 3 3 4 4 5% 6% 40%	2270
October	1st to 10th	Night	16% 6% 2 5% 4 4 4 4 5% 7% 45%	2400
	11th to 20th	Night	15% 4 2 5% 3 4 4 3 5% 7% 47%	2400
	21st to end	Night	17% 5% 2 5% 4 3 4 3 5% 6% 45%	2640
November	1st to 10th	Night	10% 7% 2 5% 4 4 4 3 5% 5% 50%	2491
	11th to 20th	Night	14% 9% 3 7% 5% 5% 4 4 5% 6% 39%	2890
	21st to end	Night	14% 9% 4 9% 5% 5% 5% 4 5% 6% 35%	2940
December	1st to 10th	Night	10% 9% 4 12% 5% 5% 4 4 6% 7% 35%	4720
	11th to 20th	Night	18% 11% 5% 9% 6% 5% 4 3 5% 6% 30%	5345
	21st to end	Night	16% 13% 5% 11% 6% 5% 5% 4 5% 6% 23%	7150

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	54% 6% 12% 19% 7% 2	4998
	11th to 20th	Day	59% 7% 8% 12% 10% 4	5280
	21st to end	Day	52% 6% 12% 21% 9% 1	5780
February	1st to 10th	Day	52% 6% 14% 18% 9% 1	1890
	11th to 20th	Day	54% 5% 13% 18% 9%	1852
	21st to end	Day	51% 5% 13% 18% 9% 3	1732
March	1st to 10th	Day	48% 6% 10% 21% 11% 4	5045
	11th to 20th	Day	40% 6% 14% 26% 11% 3	5057
	21st to end	Day	46% 6% 10% 19% 15% 3	5465
April	1st to 10th	Day	49% 7% 11% 17% 13% 3	2374
	11th to 20th	Day	45% 7% 10% 18% 16% 3	2374
	21st to end	Day	46% 6% 11% 22% 12% 2	2499
May	1st to 10th	Day	52% 8% 11% 18% 9% 2	5897
	11th to 20th	Day	51% 7% 10% 23% 7% 1	5992
	21st to end	Day	45% 9% 13% 18% 13% 2	6949
June	1st to 10th	Day	40% 9% 14% 21% 15% 1	2800
	11th to 20th	Day	42% 11% 14% 20% 13% 1	2800
	21st to end	Day	36% 9% 16% 24% 14% 1	2800
July	1st to 10th	Day	36% 9% 12% 26% 14% 3	6290
	11th to 20th	Day	41% 11% 17% 21% 10% 1	5904
	21st to end	Day	39% 7% 10% 24% 19% 1	6240
August	1st to 10th	Day	45% 11% 15% 21% 8%	4221
	11th to 20th	Day	39% 9% 11% 27% 13%	4195
	21st to end	Day	36% 7% 13% 27% 14% 2	4312
September	1st to 10th	Day	38% 7% 12% 20% 19% 3	2400
	11th to 20th	Day	36% 6% 11% 27% 19% 2	2325
	21st to end	Day	49% 6% 12% 16% 15% 1	2130
October	1st to 10th	Day	35% 4 9% 25% 22% 4	3260
	11th to 20th	Day	35% 5% 13% 25% 12% 10%	3240
	21st to end	Day	29% 4 14% 29% 23% 1	3538
November	1st to 10th	Day	35% 5% 13% 23% 20% 4	2025
	11th to 20th	Day	44% 6% 12% 19% 16% 2	1727
	21st to end	Day	49% 6% 14% 21% 9% 1	1680
December	1st to 10th	Day	52% 7% 15% 20% 3 3	2680
	11th to 20th	Day	54% 6% 13% 19% 7% 1	3066
	21st to end	Day	59% 8% 14% 10% 8%	4048
January	1st to 10th	Night	52% 7% 11% 19% 10% 1	7895
	11th to 20th	Night	50% 7% 10% 16% 14% 5%	7680
	21st to end	Night	49% 6% 11% 24% 9% 1	8401
February	1st to 10th	Night	48% 7% 13% 21% 10% 1	2730
	11th to 20th	Night	51% 6% 11% 19% 12% 1	2665
	21st to end	Night	50% 6% 11% 19% 10% 3	2067
March	1st to 10th	Night	44% 6% 12% 23% 11% 4	5028
	11th to 20th	Night	36% 5% 16% 29% 11% 4	5058
	21st to end	Night	40% 6% 13% 20% 18% 3	5467
April	1st to 10th	Night	49% 6% 11% 17% 14% 2	2025
	11th to 20th	Night	40% 8% 12% 21% 15% 3	1975
	21st to end	Night	39% 7% 13% 25% 12% 3	1917
May	1st to 10th	Night	56% 7% 10% 14% 9% 3	4060
	11th to 20th	Night	50% 8% 11% 22% 8% 1	3906
	21st to end	Night	43% 9% 15% 23% 7% 2	3927
June	1st to 10th	Night	36% 8% 12% 26% 17% 2	1600
	11th to 20th	Night	37% 10% 14% 25% 12% 2	1600
	21st to end	Night	32% 10% 17% 25% 16% 1	1600
July	1st to 10th	Night	36% 9% 14% 23% 13% 4	3560
	11th to 20th	Night	42% 10% 16% 20% 10% 1	3916
	21st to end	Night	35% 8% 12% 25% 19% 1	4297
August	1st to 10th	Night	42% 10% 17% 22% 9%	2904
	11th to 20th	Night	36% 8% 11% 28% 16% 1	2902
	21st to end	Night	35% 6% 13% 30% 14% 2	3571
September	1st to 10th	Night	37% 6% 12% 22% 20% 3	2000
	11th to 20th	Night	32% 6% 11% 29% 20% 2	2071
	21st to end	Night	44% 7% 11% 21% 16% 2	2270
October	1st to 10th	Night	36% 5% 9% 27% 23% 1	3920
	11th to 20th	Night	29% 6% 10% 25% 22% 8%	3899
	21st to end	Night	28% 4 12% 31% 23% 3	4252
November	1st to 10th	Night	35% 5% 13% 24% 20% 4	2491
	11th to 20th	Night	44% 6% 9% 23% 14% 3	2890
	21st to end	Night	47% 7% 13% 21% 10% 2	2940
December	1st to 10th	Night	46% 6% 16% 25% 6%	4720
	11th to 20th	Night	53% 6% 13% 19% 8% 1	5348
	21st to end	Night	57% 8% 14% 14% 7%	7150

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	35% 27% 24% 11% 3	281
	11th to 20th	Day	40% 26% 26% 6% 1	330
	21st to end	Day	32% 31% 24% 10% 2	363
February	1st to 10th	Day	33% 24% 32% 9% 2	330
	11th to 20th	Day	40% 28% 28% 3 1	330
	21st to end	Day	31% 26% 30% 11% 1	401
March	1st to 10th	Day	31% 21% 27% 18% 2	540
	11th to 20th	Day	32% 25% 25% 12% 4 1	528
	21st to end	Day	30% 21% 31% 13% 5% 1	550
April	1st to 10th	Day	30% 24% 24% 17% 4 1	500
	11th to 20th	Day	23% 23% 26% 17% 7% 4	492
	21st to end	Day	31% 18% 28% 15% 7% 2	500
May	1st to 10th	Day	27% 21% 25% 16% 8% 3	503
	11th to 20th	Day	26% 17% 27% 18% 9% 3	527
	21st to end	Day	22% 11% 24% 23% 13% 6%	573
June	1st to 10th	Day	18% 15% 26% 21% 16% 4	530
	11th to 20th	Day	17% 12% 28% 25% 14% 4	530
	21st to end	Day	11% 13% 30% 26% 15% 5%	530
July	1st to 10th	Day	11% 7% 25% 30% 19% 9%	525
	11th to 20th	Day	7% 7% 26% 31% 20% 8%	524
	21st to end	Day	13% 7% 26% 31% 18% 5%	576
August	1st to 10th	Day	13% 7% 24% 29% 18% 9%	526
	11th to 20th	Day	15% 5% 23% 29% 19% 9%	519
	21st to end	Day	13% 6% 23% 27% 19% 11%	583
September	1st to 10th	Day	18% 9% 20% 23% 21% 8%	530
	11th to 20th	Day	15% 4 19% 31% 22% 9%	530
	21st to end	Day	28% 12% 24% 20% 13% 4	530
October	1st to 10th	Day	22% 8% 23% 25% 18% 5%	530
	11th to 20th	Day	21% 16% 27% 23% 11% 2	530
	21st to end	Day	20% 20% 30% 20% 8% 2	583
November	1st to 10th	Day	17% 18% 30% 23% 10% 2	518
	11th to 20th	Day	27% 21% 26% 21% 4	267
	21st to end	Day	30% 22% 28% 17% 2 1	220
December	1st to 10th	Day	30% 28% 29% 10% 4	220
	11th to 20th	Day	28% 26% 25% 16% 4	220
	21st to end	Day	31% 21% 26% 19% 4	242
January	1st to 10th	Night	22% 25% 33% 17% 3	840
	11th to 20th	Night	26% 21% 31% 20% 3	840
	21st to end	Night	23% 24% 31% 20% 2	924
February	1st to 10th	Night	23% 19% 31% 24% 2	840
	11th to 20th	Night	28% 26% 30% 15% 1	823
	21st to end	Night	25% 19% 33% 21% 2	692
March	1st to 10th	Night	25% 20% 32% 21% 3	840
	11th to 20th	Night	27% 21% 26% 20% 5%	829
	21st to end	Night	23% 18% 35% 18% 5% 1	880
April	1st to 10th	Night	26% 21% 28% 21% 5%	800
	11th to 20th	Night	19% 17% 28% 27% 8%	791
	21st to end	Night	21% 13% 27% 31% 8%	717
May	1st to 10th	Night	23% 12% 23% 30% 12% 1	600
	11th to 20th	Night	23% 10% 23% 33% 11%	542
	21st to end	Night	17% 7% 18% 34% 23% 1	433
June	1st to 10th	Night	13% 6% 24% 36% 21%	400
	11th to 20th	Night	15% 6% 21% 38% 20%	400
	21st to end	Night	10% 4 24% 39% 22% 1	400
July	1st to 10th	Night	10% 4 17% 38% 27% 3	390
	11th to 20th	Night	8% 3 14% 37% 34% 4	544
	21st to end	Night	10% 2 18% 37% 32% 2	657
August	1st to 10th	Night	10% 4 14% 41% 30% 2	597
	11th to 20th	Night	11% 5% 13% 41% 27% 4	594
	21st to end	Night	14% 3 16% 35% 28% 3	865
September	1st to 10th	Night	17% 4 17% 34% 24% 4	800
	11th to 20th	Night	15% 4 14% 36% 27% 4	800
	21st to end	Night	25% 7% 17% 30% 19% 3	800
October	1st to 10th	Night	19% 7% 21% 30% 22% 2	800
	11th to 20th	Night	18% 13% 27% 30% 11% 1	800
	21st to end	Night	21% 14% 24% 31% 9% 1	880
November	1st to 10th	Night	15% 11% 27% 36% 10%	820
	11th to 20th	Night	23% 18% 25% 26% 7% 1	840
	21st to end	Night	22% 18% 28% 26% 6%	840
December	1st to 10th	Night	25% 20% 28% 22% 5%	840
	11th to 20th	Night	24% 18% 30% 25% 3	840
	21st to end	Night	23% 18% 29% 29% 2	924

Page generated at 2026-03-15 02:23:52. Version ac07

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