Kevin's Cabin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kevin's Cabin clear sky chart from 2005-11-06 to 2025-10-19.

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	12% 10% 4 9% 5% 5% 5% 4 6% 7% 33%	127189
	Night	12% 11% 5% 11% 6% 5% 5% 4 5% 6% 30%	122791
Transparency	Day	48% 6% 14% 22% 9% 1	130640
	Night	53% 6% 12% 20% 8% 1	127430
Seeing	Day	18% 14% 34% 23% 9% 2	17569
	Night	18% 10% 33% 27% 10% 1	27406

By Month

Percentage Cloud Cover NE (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	6% 12% 8% 16% 7% 8% 7% 5% 6% 5% 21%	3178
	11th to 20th	Day	4 12% 6% 16% 8% 8% 8% 8% 11% 5% 13%	3152
	21st to end	Day	6% 16% 11% 20% 7% 5% 5% 3 5% 5% 16%	4060
February	1st to 10th	Day	8% 12% 6% 12% 7% 7% 8% 5% 7% 7% 20%	1800
	11th to 20th	Day	7% 11% 4 11% 8% 6% 6% 5% 6% 7% 30%	1754
	21st to end	Day	7% 12% 5% 14% 6% 6% 4 4 6% 6% 29%	1485
March	1st to 10th	Day	9% 11% 3 9% 5% 4 4 3 5% 7% 40%	4763
	11th to 20th	Day	10% 10% 4 12% 7% 5% 5% 3 6% 7% 30%	4980
	21st to end	Day	14% 14% 5% 9% 6% 4 4 2 4 5% 33%	5541
April	1st to 10th	Day	15% 13% 3 8% 4 4 5% 3 5% 6% 34%	2400
	11th to 20th	Day	15% 13% 3 8% 4 4 5% 4 6% 7% 32%	2510
	21st to end	Day	18% 12% 3 8% 5% 5% 4 3 4 6% 33%	2610
May	1st to 10th	Day	15% 8% 2 5% 3 3 4 3 5% 7% 44%	6348
	11th to 20th	Day	14% 9% 3 7% 5% 5% 5% 4 6% 7% 35%	6319
	21st to end	Day	15% 7% 2 5% 4 4 4 3 5% 7% 43%	7160
June	1st to 10th	Day	14% 7% 3 6% 5% 4 5% 4 6% 8% 38%	3000
	11th to 20th	Day	16% 6% 3 8% 5% 5% 5% 4 6% 7% 36%	3000
	21st to end	Day	15% 7% 3 8% 5% 5% 5% 4 7% 9% 31%	3000
July	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 5% 8% 11% 41%	6799
	11th to 20th	Day	12% 6% 2 5% 4 4 5% 4 6% 9% 42%	6800
	21st to end	Day	13% 7% 3 7% 5% 4 4 4 6% 8% 39%	7127
August	1st to 10th	Day	10% 7% 3 7% 5% 5% 5% 4 7% 9% 39%	4418
	11th to 20th	Day	12% 5% 2 5% 4 4 5% 4 7% 9% 43%	4171
	21st to end	Day	15% 7% 2 6% 4 4 4 4 5% 8% 39%	4616
September	1st to 10th	Day	13% 6% 2 7% 4 4 4 4 6% 8% 42%	2400
	11th to 20th	Day	17% 7% 2 7% 4 6% 4 4 5% 7% 36%	2351
	21st to end	Day	20% 7% 3 6% 4 3 3 3 4 7% 39%	2117
October	1st to 10th	Day	17% 13% 4 8% 4 5% 4 3 5% 6% 31%	2000
	11th to 20th	Day	19% 15% 5% 9% 4 4 4 3 5% 6% 26%	1980
	21st to end	Day	19% 20% 4 11% 4 4 3 2 4 5% 23%	1929
November	1st to 10th	Day	15% 19% 6% 11% 5% 4 4 3 5% 4 23%	1567
	11th to 20th	Day	14% 19% 6% 18% 6% 5% 4 3 4 4 17%	1600
	21st to end	Day	13% 18% 8% 18% 9% 6% 3 3 4 4 16%	1600
December	1st to 10th	Day	12% 15% 5% 22% 15% 7% 4 3 3 5% 10%	2517
	11th to 20th	Day	9% 17% 6% 15% 5% 5% 6% 4 6% 4 21%	2639
	21st to end	Day	13% 19% 8% 19% 9% 5% 5% 2 4 4 12%	3498
January	1st to 10th	Night	4 12% 6% 19% 9% 7% 6% 5% 6% 5% 21%	6787
	11th to 20th	Night	6% 11% 5% 14% 11% 12% 9% 7% 9% 3 12%	6753
	21st to end	Night	8% 17% 11% 16% 8% 5% 5% 4 6% 5% 14%	6900
February	1st to 10th	Night	7% 11% 5% 12% 8% 8% 7% 6% 7% 6% 23%	2600
	11th to 20th	Night	8% 10% 3 10% 7% 6% 6% 6% 7% 6% 33%	2533
	21st to end	Night	7% 12% 6% 12% 7% 6% 6% 5% 6% 6% 27%	2145
March	1st to 10th	Night	10% 10% 5% 10% 5% 5% 5% 4 6% 7% 33%	5122
	11th to 20th	Night	7% 11% 5% 11% 9% 8% 6% 4 5% 7% 26%	4979
	21st to end	Night	17% 15% 4 9% 5% 4 3 2 4 5% 31%	5389
April	1st to 10th	Night	15% 11% 3 8% 5% 4 5% 3 5% 5% 35%	2000
	11th to 20th	Night	16% 13% 4 7% 4 3 4 3 4 6% 35%	1838
	21st to end	Night	17% 11% 4 8% 5% 4 5% 4 5% 5% 33%	1790
May	1st to 10th	Night	17% 8% 1 4 3 3 3 3 4 5% 49%	3613
	11th to 20th	Night	16% 8% 3 6% 4 3 4 4 6% 7% 40%	3596
	21st to end	Night	16% 6% 2 6% 4 3 4 4 5% 7% 43%	3735
June	1st to 10th	Night	15% 6% 2 5% 6% 3 4 3 6% 8% 42%	1400
	11th to 20th	Night	13% 5% 3 6% 5% 4 5% 4 5% 6% 44%	1400
	21st to end	Night	14% 5% 2 6% 4 4 4 4 5% 9% 43%	1400
July	1st to 10th	Night	10% 4 1 4 4 4 5% 4 6% 8% 48%	3180
	11th to 20th	Night	10% 4 2 5% 3 4 4 4 6% 10% 48%	3180
	21st to end	Night	10% 6% 2 5% 4 4 4 3 6% 9% 45%	3745
August	1st to 10th	Night	8% 6% 2 6% 4 5% 5% 5% 6% 8% 45%	2727
	11th to 20th	Night	12% 6% 2 5% 3 3 3 3 6% 9% 48%	2888
	21st to end	Night	14% 5% 2 6% 4 4 3 3 5% 8% 46%	3290
September	1st to 10th	Night	11% 5% 2 7% 4 4 4 3 4 7% 49%	2000
	11th to 20th	Night	16% 8% 2 6% 4 4 3 2 5% 7% 45%	2045
	21st to end	Night	18% 8% 3 6% 3 3 4 3 5% 7% 41%	2262
October	1st to 10th	Night	15% 12% 3 7% 5% 5% 5% 3 5% 7% 34%	2400
	11th to 20th	Night	19% 15% 4 7% 4 3 4 3 4 6% 32%	2377
	21st to end	Night	18% 15% 4 10% 5% 4 4 4 6% 5% 24%	2667
November	1st to 10th	Night	15% 19% 6% 11% 5% 4 4 4 4 5% 24%	2731
	11th to 20th	Night	14% 17% 6% 16% 8% 5% 4 3 4 5% 18%	2800
	21st to end	Night	13% 16% 7% 15% 9% 5% 5% 3 4 5% 18%	2800
December	1st to 10th	Night	9% 18% 8% 22% 11% 7% 5% 3 3 4 10%	4671
	11th to 20th	Night	9% 14% 6% 16% 8% 7% 6% 6% 6% 5% 17%	5568
	21st to end	Night	16% 16% 7% 19% 8% 6% 4 4 4 4 13%	7480

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	63% 5% 7% 14% 9% 1	3179
	11th to 20th	Day	64% 5% 8% 19% 4	3180
	21st to end	Day	69% 5% 9% 13% 5%	4060
February	1st to 10th	Day	60% 6% 10% 13% 9% 1	1800
	11th to 20th	Day	53% 5% 12% 22% 8% 1	1763
	21st to end	Day	53% 6% 12% 16% 12% 1	1485
March	1st to 10th	Day	43% 5% 14% 18% 14% 6%	4765
	11th to 20th	Day	51% 6% 12% 20% 10%	4980
	21st to end	Day	53% 5% 7% 21% 13% 1	5541
April	1st to 10th	Day	50% 5% 8% 21% 15% 1	2400
	11th to 20th	Day	51% 6% 11% 20% 12% 1	2510
	21st to end	Day	53% 4 10% 22% 11% 1	2610
May	1st to 10th	Day	38% 6% 13% 26% 16% 1	6357
	11th to 20th	Day	44% 8% 12% 19% 17% 1	6323
	21st to end	Day	39% 6% 9% 27% 16% 3	7160
June	1st to 10th	Day	42% 9% 14% 24% 11% 1	3000
	11th to 20th	Day	45% 7% 13% 24% 11%	3000
	21st to end	Day	46% 8% 16% 22% 7%	3000
July	1st to 10th	Day	32% 10% 21% 28% 8%	6726
	11th to 20th	Day	37% 7% 19% 31% 6%	6719
	21st to end	Day	42% 7% 15% 28% 7%	6923
August	1st to 10th	Day	39% 7% 16% 25% 12% 1	4403
	11th to 20th	Day	34% 8% 27% 26% 6%	4210
	21st to end	Day	40% 7% 21% 26% 6%	4615
September	1st to 10th	Day	39% 6% 16% 30% 8%	2400
	11th to 20th	Day	45% 7% 21% 22% 4	2351
	21st to end	Day	46% 5% 15% 28% 6%	2117
October	1st to 10th	Day	43% 6% 17% 26% 8%	3260
	11th to 20th	Day	47% 5% 15% 19% 13%	3220
	21st to end	Day	56% 5% 16% 18% 3	3161
November	1st to 10th	Day	64% 6% 12% 13% 4 1	1567
	11th to 20th	Day	71% 5% 9% 11% 4	1600
	21st to end	Day	72% 5% 10% 10% 3	1600
December	1st to 10th	Day	79% 6% 7% 6% 2	2517
	11th to 20th	Day	64% 4 9% 14% 9%	2640
	21st to end	Day	77% 3 6% 11% 4	3498
January	1st to 10th	Night	63% 5% 9% 13% 9% 1	6787
	11th to 20th	Night	68% 5% 8% 15% 4	6800
	21st to end	Night	70% 4 9% 13% 4	6900
February	1st to 10th	Night	57% 6% 13% 15% 9% 1	2600
	11th to 20th	Night	49% 6% 13% 21% 10% 1	2534
	21st to end	Night	54% 7% 11% 18% 9%	2145
March	1st to 10th	Night	48% 6% 13% 16% 13% 4	5133
	11th to 20th	Night	55% 7% 13% 16% 8%	4980
	21st to end	Night	56% 4 8% 18% 14% 1	5389
April	1st to 10th	Night	49% 5% 8% 20% 16% 1	2000
	11th to 20th	Night	50% 4 10% 21% 14% 2	1838
	21st to end	Night	52% 5% 9% 21% 12% 1	1790
May	1st to 10th	Night	37% 5% 9% 30% 19% 1	3620
	11th to 20th	Night	42% 7% 13% 20% 17% 1	3597
	21st to end	Night	38% 7% 10% 27% 16% 3	3736
June	1st to 10th	Night	38% 8% 17% 23% 14% 1	1400
	11th to 20th	Night	39% 6% 12% 27% 15% 1	1400
	21st to end	Night	38% 7% 19% 27% 8% 1	1400
July	1st to 10th	Night	30% 10% 22% 28% 9% 1	3145
	11th to 20th	Night	29% 7% 22% 32% 9%	3138
	21st to end	Night	34% 7% 18% 32% 8%	3635
August	1st to 10th	Night	35% 7% 16% 32% 10% 1	2718
	11th to 20th	Night	31% 8% 24% 32% 6%	2915
	21st to end	Night	36% 7% 22% 28% 7%	3290
September	1st to 10th	Night	35% 6% 17% 32% 10%	2000
	11th to 20th	Night	40% 7% 19% 27% 7%	2045
	21st to end	Night	44% 6% 14% 30% 7%	2262
October	1st to 10th	Night	40% 6% 13% 32% 7%	3920
	11th to 20th	Night	47% 4 15% 26% 8%	3876
	21st to end	Night	55% 6% 12% 21% 6%	4389
November	1st to 10th	Night	62% 5% 12% 15% 5% 1	2731
	11th to 20th	Night	70% 6% 9% 11% 4	2800
	21st to end	Night	68% 7% 12% 10% 3	2800
December	1st to 10th	Night	80% 5% 7% 7% 1	4671
	11th to 20th	Night	66% 5% 10% 11% 8%	5566
	21st to end	Night	75% 5% 6% 11% 3	7480

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	12% 19% 33% 26% 9% 1	300
	11th to 20th	Day	14% 12% 41% 27% 5% 1	300
	21st to end	Day	19% 9% 40% 22% 8% 1	330
February	1st to 10th	Day	18% 13% 42% 20% 5% 1	300
	11th to 20th	Day	12% 21% 36% 21% 7% 3	300
	21st to end	Day	20% 21% 42% 13% 4 1	249
March	1st to 10th	Day	16% 17% 39% 18% 10% 1	300
	11th to 20th	Day	15% 19% 36% 21% 8% 2	300
	21st to end	Day	18% 19% 37% 20% 6% 1	356
April	1st to 10th	Day	22% 15% 32% 24% 7%	500
	11th to 20th	Day	26% 16% 31% 21% 6% 1	628
	21st to end	Day	21% 15% 32% 23% 8% 1	700
May	1st to 10th	Day	22% 16% 37% 18% 6% 1	703
	11th to 20th	Day	20% 15% 35% 19% 8% 2	725
	21st to end	Day	22% 12% 32% 25% 7% 2	789
June	1st to 10th	Day	18% 14% 34% 23% 8% 3	730
	11th to 20th	Day	17% 16% 39% 18% 9% 1	730
	21st to end	Day	18% 11% 34% 25% 9% 4	730
July	1st to 10th	Day	11% 11% 30% 31% 13% 5%	721
	11th to 20th	Day	13% 13% 31% 26% 13% 4	718
	21st to end	Day	11% 11% 34% 26% 15% 5%	794
August	1st to 10th	Day	10% 10% 32% 31% 14% 3	726
	11th to 20th	Day	15% 8% 29% 27% 15% 6%	715
	21st to end	Day	17% 10% 30% 28% 13% 2	770
September	1st to 10th	Day	15% 10% 32% 29% 11% 2	530
	11th to 20th	Day	20% 16% 34% 22% 8% 1	481
	21st to end	Day	25% 15% 32% 19% 7% 2	330
October	1st to 10th	Day	23% 15% 33% 22% 7%	330
	11th to 20th	Day	23% 20% 35% 20% 2	324
	21st to end	Day	32% 18% 33% 14% 2 1	330
November	1st to 10th	Day	19% 21% 34% 21% 5%	300
	11th to 20th	Day	24% 19% 36% 18% 3	300
	21st to end	Day	27% 22% 36% 11% 3	300
December	1st to 10th	Day	20% 15% 35% 22% 6% 1	300
	11th to 20th	Day	20% 17% 42% 18% 3	300
	21st to end	Day	18% 15% 39% 19% 8% 1	330
January	1st to 10th	Night	13% 13% 39% 24% 10% 2	1000
	11th to 20th	Night	16% 10% 38% 27% 7% 1	1000
	21st to end	Night	16% 12% 38% 26% 7% 1	1100
February	1st to 10th	Night	14% 11% 35% 32% 8% 1	1000
	11th to 20th	Night	13% 12% 38% 24% 11% 2	979
	21st to end	Night	13% 11% 39% 25% 9% 3	825
March	1st to 10th	Night	14% 13% 38% 26% 9% 1	703
	11th to 20th	Night	15% 14% 38% 26% 7% 1	600
	21st to end	Night	21% 9% 32% 24% 12% 3	660
April	1st to 10th	Night	19% 11% 34% 28% 8% 1	600
	11th to 20th	Night	23% 11% 31% 27% 8%	593
	21st to end	Night	22% 10% 29% 30% 10%	600
May	1st to 10th	Night	22% 9% 30% 31% 7% 1	600
	11th to 20th	Night	21% 9% 35% 23% 10% 2	591
	21st to end	Night	20% 8% 28% 34% 10%	650
June	1st to 10th	Night	16% 9% 30% 33% 12% 1	600
	11th to 20th	Night	15% 9% 34% 30% 12% 1	600
	21st to end	Night	15% 6% 28% 34% 17% 1	600
July	1st to 10th	Night	9% 4 26% 39% 20% 2	585
	11th to 20th	Night	11% 7% 27% 36% 18% 1	582
	21st to end	Night	8% 5% 27% 37% 21% 2	657
August	1st to 10th	Night	9% 4 28% 40% 18% 2	597
	11th to 20th	Night	13% 5% 23% 34% 22% 3	594
	21st to end	Night	14% 6% 27% 32% 19% 1	660
September	1st to 10th	Night	13% 7% 31% 33% 15% 2	600
	11th to 20th	Night	18% 10% 28% 31% 13% 1	600
	21st to end	Night	22% 8% 32% 24% 13% 1	662
October	1st to 10th	Night	22% 13% 31% 29% 6%	800
	11th to 20th	Night	26% 12% 31% 23% 7% 1	793
	21st to end	Night	27% 13% 33% 21% 5% 1	900
November	1st to 10th	Night	22% 13% 34% 24% 5% 1	975
	11th to 20th	Night	23% 12% 34% 23% 6% 1	1000
	21st to end	Night	21% 16% 40% 18% 5%	1000
December	1st to 10th	Night	16% 10% 38% 26% 8% 2	1000
	11th to 20th	Night	19% 14% 38% 23% 5% 1	1000
	21st to end	Night	22% 11% 34% 24% 8% 1	1100

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