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 2024-01-13.

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% 10% 4 8% 6% 4 5% 5% 5% 7% 32%	74725
	Night	13% 11% 5% 9% 7% 4 5% 5% 5% 6% 31%	75015
Transparency	Day	51% 6% 13% 21% 8% 1	74415
	Night	53% 6% 12% 20% 8% 1	74859
Seeing	Day	18% 14% 34% 23% 9% 2	15014
	Night	18% 10% 33% 28% 10% 1	25066

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	12% 11% 8% 12% 7% 5% 5% 6% 8% 7% 20%	1328
	11th to 20th	Day	9% 15% 6% 11% 8% 5% 5% 7% 6% 7% 19%	1274
	21st to end	Day	11% 14% 8% 14% 10% 6% 7% 7% 8% 5% 10%	1614
February	1st to 10th	Day	8% 11% 7% 10% 8% 5% 9% 7% 7% 8% 21%	1620
	11th to 20th	Day	8% 11% 5% 9% 8% 5% 7% 5% 5% 6% 31%	1574
	21st to end	Day	7% 10% 6% 13% 7% 5% 4 6% 6% 6% 28%	1332
March	1st to 10th	Day	9% 13% 5% 8% 6% 4 6% 5% 5% 6% 32%	1900
	11th to 20th	Day	9% 14% 5% 9% 8% 3 4 4 5% 6% 32%	1980
	21st to end	Day	14% 11% 5% 7% 7% 3 4 4 5% 6% 33%	2200
April	1st to 10th	Day	15% 11% 4 7% 5% 3 5% 4 5% 6% 34%	2160
	11th to 20th	Day	15% 12% 3 7% 5% 3 5% 5% 5% 7% 33%	2256
	21st to end	Day	17% 11% 4 7% 6% 4 4 3 4 6% 34%	2348
May	1st to 10th	Day	17% 10% 4 6% 5% 3 4 3 4 7% 35%	2520
	11th to 20th	Day	16% 8% 4 6% 6% 3 5% 4 6% 7% 34%	2479
	21st to end	Day	20% 7% 2 5% 5% 2 4 4 5% 7% 38%	2806
June	1st to 10th	Day	14% 6% 3 6% 6% 3 5% 5% 6% 8% 37%	2700
	11th to 20th	Day	16% 6% 3 7% 6% 3 5% 5% 6% 6% 37%	2700
	21st to end	Day	15% 6% 4 7% 6% 3 6% 6% 7% 9% 32%	2700
July	1st to 10th	Day	9% 4 2 5% 5% 4 5% 6% 7% 10% 45%	2700
	11th to 20th	Day	14% 6% 2 4 5% 4 5% 6% 6% 8% 39%	2700
	21st to end	Day	11% 5% 3 5% 5% 3 4 5% 6% 8% 44%	2827
August	1st to 10th	Day	10% 5% 3 6% 5% 3 5% 5% 7% 8% 42%	2436
	11th to 20th	Day	13% 5% 2 4 5% 3 5% 5% 6% 8% 44%	2301
	21st to end	Day	14% 7% 2 5% 5% 3 4 5% 5% 8% 42%	2545
September	1st to 10th	Day	14% 6% 2 5% 5% 3 4 5% 5% 8% 42%	2160
	11th to 20th	Day	17% 7% 2 6% 5% 4 5% 5% 5% 7% 37%	2117
	21st to end	Day	22% 7% 3 6% 5% 3 3 4 4 7% 37%	1906
October	1st to 10th	Day	19% 14% 4 7% 6% 3 5% 4 5% 6% 28%	1800
	11th to 20th	Day	20% 14% 5% 8% 6% 3 4 5% 5% 5% 26%	1800
	21st to end	Day	20% 20% 5% 10% 5% 3 3 3 4 5% 22%	1828
November	1st to 10th	Day	16% 17% 8% 10% 6% 3 5% 4 5% 4 23%	1487
	11th to 20th	Day	14% 16% 8% 17% 8% 4 3 4 4 4 17%	1520
	21st to end	Day	13% 16% 8% 14% 12% 5% 5% 3 4 4 17%	1520
December	1st to 10th	Day	10% 13% 7% 17% 13% 6% 6% 7% 3 6% 14%	1466
	11th to 20th	Day	10% 19% 7% 13% 8% 4 6% 5% 4 4 20%	1679
	21st to end	Day	17% 16% 9% 13% 9% 4 4 3 5% 4 16%	2442
January	1st to 10th	Night	8% 12% 6% 12% 9% 5% 6% 8% 7% 5% 21%	2837
	11th to 20th	Night	12% 12% 6% 12% 9% 6% 7% 6% 6% 6% 17%	2731
	21st to end	Night	9% 14% 6% 12% 11% 4 7% 6% 9% 6% 15%	2738
February	1st to 10th	Night	7% 10% 6% 11% 9% 5% 8% 8% 7% 6% 23%	2340
	11th to 20th	Night	8% 10% 4 8% 8% 4 6% 6% 6% 6% 34%	2273
	21st to end	Night	7% 10% 7% 11% 8% 4 6% 6% 6% 6% 27%	1924
March	1st to 10th	Night	10% 12% 6% 10% 6% 3 6% 5% 5% 7% 30%	2063
	11th to 20th	Night	11% 10% 4 7% 5% 3 5% 5% 4 7% 39%	1979
	21st to end	Night	15% 9% 5% 7% 6% 3 5% 3 5% 7% 35%	2155
April	1st to 10th	Night	15% 11% 4 6% 7% 4 5% 4 5% 6% 35%	1800
	11th to 20th	Night	16% 12% 4 6% 4 3 4 3 4 7% 37%	1652
	21st to end	Night	17% 10% 4 7% 6% 3 5% 4 4 6% 33%	1612
May	1st to 10th	Night	17% 9% 2 6% 5% 3 4 5% 6% 7% 36%	1440
	11th to 20th	Night	18% 7% 3 5% 4 3 3 5% 6% 8% 39%	1416
	21st to end	Night	18% 5% 2 5% 5% 2 4 5% 4 7% 43%	1467
June	1st to 10th	Night	16% 5% 2 4 7% 3 4 4 6% 9% 41%	1260
	11th to 20th	Night	14% 5% 3 5% 5% 3 4 5% 5% 6% 45%	1260
	21st to end	Night	13% 4 2 6% 5% 3 4 5% 5% 10% 43%	1260
July	1st to 10th	Night	7% 3 2 3 4 3 5% 5% 5% 9% 55%	1260
	11th to 20th	Night	9% 3 2 4 5% 3 5% 5% 6% 10% 47%	1260
	21st to end	Night	7% 4 2 4 4 3 3 4 6% 8% 56%	1489
August	1st to 10th	Night	8% 4 2 4 4 3 3 5% 6% 7% 54%	1502
	11th to 20th	Night	11% 6% 3 4 4 3 4 5% 6% 8% 48%	1600
	21st to end	Night	14% 5% 1 4 3 3 3 4 6% 7% 51%	1810
September	1st to 10th	Night	12% 5% 2 6% 5% 2 4 4 4 7% 49%	1800
	11th to 20th	Night	16% 7% 3 5% 4 2 4 3 5% 7% 45%	1840
	21st to end	Night	19% 8% 3 6% 4 2 4 4 5% 7% 38%	2035
October	1st to 10th	Night	15% 12% 4 6% 5% 4 5% 4 5% 7% 32%	2160
	11th to 20th	Night	19% 13% 5% 7% 4 3 5% 4 4 6% 31%	2160
	21st to end	Night	19% 15% 4 8% 7% 3 4 5% 6% 6% 24%	2526
November	1st to 10th	Night	15% 17% 8% 10% 6% 3 4 4 4 5% 24%	2591
	11th to 20th	Night	14% 15% 7% 14% 10% 4 5% 4 4 5% 18%	2660
	21st to end	Night	14% 15% 7% 12% 11% 5% 5% 4 5% 5% 19%	2660
December	1st to 10th	Night	8% 12% 7% 16% 14% 5% 7% 5% 4 6% 15%	2712
	11th to 20th	Night	11% 14% 7% 13% 10% 5% 7% 6% 6% 5% 17%	3518
	21st to end	Night	18% 15% 8% 13% 11% 4 4 5% 4 4 13%	5225

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	61% 6% 10% 17% 6%	1329
	11th to 20th	Day	62% 7% 11% 16% 5%	1274
	21st to end	Day	71% 6% 6% 10% 7%	1614
February	1st to 10th	Day	58% 6% 11% 14% 10% 1	1620
	11th to 20th	Day	54% 4 11% 20% 9% 1	1583
	21st to end	Day	54% 6% 11% 17% 12% 1	1332
March	1st to 10th	Day	52% 6% 13% 18% 9% 1	1902
	11th to 20th	Day	53% 5% 14% 18% 10% 1	1980
	21st to end	Day	52% 5% 12% 20% 9% 2	2200
April	1st to 10th	Day	50% 5% 9% 20% 15% 1	2160
	11th to 20th	Day	50% 6% 10% 20% 13% 1	2256
	21st to end	Day	52% 4 10% 22% 11% 1	2348
May	1st to 10th	Day	50% 5% 10% 22% 12% 1	2520
	11th to 20th	Day	48% 6% 12% 21% 11% 2	2483
	21st to end	Day	47% 5% 12% 21% 14% 1	2806
June	1st to 10th	Day	43% 9% 15% 23% 10% 1	2700
	11th to 20th	Day	46% 6% 13% 22% 12%	2700
	21st to end	Day	45% 9% 16% 23% 7%	2700
July	1st to 10th	Day	31% 9% 15% 32% 11% 1	2626
	11th to 20th	Day	39% 7% 16% 27% 10%	2619
	21st to end	Day	37% 8% 15% 30% 8% 1	2670
August	1st to 10th	Day	37% 8% 19% 27% 9% 1	2421
	11th to 20th	Day	36% 8% 20% 30% 6%	2301
	21st to end	Day	39% 7% 16% 29% 9%	2545
September	1st to 10th	Day	39% 6% 16% 29% 9%	2160
	11th to 20th	Day	45% 7% 20% 22% 5%	2117
	21st to end	Day	48% 6% 15% 27% 4	1906
October	1st to 10th	Day	57% 6% 15% 19% 4	1800
	11th to 20th	Day	59% 6% 11% 19% 6%	1800
	21st to end	Day	66% 5% 12% 14% 3	1828
November	1st to 10th	Day	64% 6% 12% 13% 4 1	1487
	11th to 20th	Day	71% 5% 9% 10% 4	1520
	21st to end	Day	71% 6% 11% 10% 3	1520
December	1st to 10th	Day	73% 6% 8% 10% 3 1	1466
	11th to 20th	Day	66% 5% 11% 15% 2	1680
	21st to end	Day	71% 4 7% 14% 5%	2442
January	1st to 10th	Night	60% 6% 11% 17% 6%	2837
	11th to 20th	Night	65% 6% 9% 16% 4	2731
	21st to end	Night	65% 6% 8% 16% 5%	2738
February	1st to 10th	Night	56% 6% 13% 14% 9% 1	2340
	11th to 20th	Night	48% 6% 14% 21% 11% 1	2274
	21st to end	Night	54% 7% 11% 18% 9%	1924
March	1st to 10th	Night	53% 5% 11% 18% 12% 1	2074
	11th to 20th	Night	45% 6% 12% 23% 13% 1	1980
	21st to end	Night	50% 4 12% 18% 12% 2	2155
April	1st to 10th	Night	50% 5% 8% 20% 16% 2	1800
	11th to 20th	Night	49% 3 10% 21% 15% 2	1652
	21st to end	Night	52% 5% 9% 20% 12% 1	1612
May	1st to 10th	Night	45% 6% 11% 23% 14% 1	1440
	11th to 20th	Night	43% 7% 11% 22% 15% 2	1417
	21st to end	Night	41% 6% 12% 23% 15% 2	1468
June	1st to 10th	Night	39% 8% 17% 23% 12% 1	1260
	11th to 20th	Night	39% 6% 12% 26% 16% 1	1260
	21st to end	Night	37% 8% 19% 27% 8% 1	1260
July	1st to 10th	Night	25% 9% 17% 35% 14% 1	1225
	11th to 20th	Night	29% 8% 19% 30% 13% 1	1218
	21st to end	Night	26% 8% 16% 36% 13% 1	1406
August	1st to 10th	Night	28% 7% 16% 35% 14% 1	1493
	11th to 20th	Night	33% 8% 18% 31% 10%	1600
	21st to end	Night	33% 6% 18% 32% 11%	1810
September	1st to 10th	Night	36% 6% 17% 31% 11%	1800
	11th to 20th	Night	40% 6% 18% 27% 8%	1840
	21st to end	Night	47% 6% 14% 29% 5%	2035
October	1st to 10th	Night	51% 8% 12% 22% 7%	2160
	11th to 20th	Night	55% 5% 12% 23% 4	2160
	21st to end	Night	60% 7% 12% 18% 3	2526
November	1st to 10th	Night	63% 5% 12% 15% 5% 1	2591
	11th to 20th	Night	70% 6% 9% 10% 4	2660
	21st to end	Night	67% 7% 12% 10% 3	2660
December	1st to 10th	Night	70% 6% 11% 11% 2	2712
	11th to 20th	Night	67% 6% 10% 12% 4	3516
	21st to end	Night	73% 6% 7% 11% 4	5225

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	13% 18% 34% 26% 9% 1	270
	11th to 20th	Day	16% 13% 37% 26% 6% 1	246
	21st to end	Day	19% 9% 38% 23% 9% 2	264
February	1st to 10th	Day	18% 12% 46% 19% 5%	240
	11th to 20th	Day	13% 23% 35% 20% 6% 4	240
	21st to end	Day	20% 17% 45% 13% 4 1	198
March	1st to 10th	Day	13% 15% 40% 20% 11% 1	240
	11th to 20th	Day	15% 18% 34% 22% 10% 2	240
	21st to end	Day	18% 20% 34% 21% 6% 1	286
April	1st to 10th	Day	22% 15% 31% 24% 8%	420
	11th to 20th	Day	25% 14% 30% 23% 7% 1	534
	21st to end	Day	21% 15% 32% 24% 8% 1	600
May	1st to 10th	Day	22% 15% 37% 18% 6% 1	603
	11th to 20th	Day	21% 13% 34% 20% 9% 2	625
	21st to end	Day	23% 12% 32% 26% 7% 1	679
June	1st to 10th	Day	18% 13% 33% 24% 8% 3	630
	11th to 20th	Day	18% 15% 37% 19% 10% 1	630
	21st to end	Day	16% 10% 33% 26% 10% 4	630
July	1st to 10th	Day	11% 11% 30% 31% 12% 5%	621
	11th to 20th	Day	14% 12% 31% 26% 13% 4	618
	21st to end	Day	10% 10% 33% 26% 16% 5%	684
August	1st to 10th	Day	10% 9% 32% 31% 15% 4	626
	11th to 20th	Day	14% 8% 30% 27% 15% 6%	615
	21st to end	Day	17% 9% 29% 28% 14% 2	664
September	1st to 10th	Day	16% 10% 33% 28% 11% 2	450
	11th to 20th	Day	20% 16% 33% 22% 9%	407
	21st to end	Day	29% 14% 32% 18% 7%	270
October	1st to 10th	Day	23% 13% 34% 22% 8%	270
	11th to 20th	Day	20% 20% 37% 20% 3	270
	21st to end	Day	32% 19% 32% 14% 3 1	297
November	1st to 10th	Day	19% 20% 36% 20% 5%	270
	11th to 20th	Day	23% 18% 37% 19% 3	270
	21st to end	Day	29% 21% 38% 10% 2	270
December	1st to 10th	Day	20% 13% 37% 22% 7% 1	270
	11th to 20th	Day	21% 17% 39% 20% 3	270
	21st to end	Day	19% 14% 40% 20% 6% 1	297
January	1st to 10th	Night	14% 12% 39% 23% 10% 2	950
	11th to 20th	Night	17% 10% 37% 28% 7% 1	911
	21st to end	Night	16% 12% 37% 27% 7% 1	990
February	1st to 10th	Night	13% 11% 36% 33% 7% 1	900
	11th to 20th	Night	15% 12% 37% 24% 11% 3	879
	21st to end	Night	12% 11% 39% 25% 9% 3	740
March	1st to 10th	Night	13% 14% 37% 26% 10% 1	634
	11th to 20th	Night	15% 12% 38% 26% 8% 1	540
	21st to end	Night	21% 8% 32% 24% 12% 3	594
April	1st to 10th	Night	19% 11% 32% 27% 9% 1	540
	11th to 20th	Night	23% 9% 32% 27% 9%	533
	21st to end	Night	22% 9% 29% 30% 10%	540
May	1st to 10th	Night	22% 8% 30% 31% 7% 1	540
	11th to 20th	Night	21% 9% 35% 23% 11% 2	531
	21st to end	Night	20% 8% 29% 33% 10% 1	584
June	1st to 10th	Night	16% 8% 29% 33% 13% 1	540
	11th to 20th	Night	15% 9% 34% 29% 13% 1	540
	21st to end	Night	14% 5% 27% 34% 19% 1	540
July	1st to 10th	Night	9% 5% 26% 40% 20% 1	525
	11th to 20th	Night	12% 8% 27% 35% 17% 1	522
	21st to end	Night	8% 4 28% 36% 22% 2	591
August	1st to 10th	Night	9% 4 28% 39% 19% 2	537
	11th to 20th	Night	13% 4 23% 34% 22% 4	534
	21st to end	Night	15% 6% 26% 31% 21% 2	594
September	1st to 10th	Night	14% 6% 31% 32% 15% 2	540
	11th to 20th	Night	18% 8% 28% 31% 14% 1	540
	21st to end	Night	24% 8% 32% 24% 12% 1	595
October	1st to 10th	Night	22% 12% 29% 30% 6%	720
	11th to 20th	Night	26% 11% 31% 24% 7% 1	720
	21st to end	Night	27% 13% 33% 21% 6% 1	852
November	1st to 10th	Night	22% 13% 34% 24% 6% 1	925
	11th to 20th	Night	22% 12% 35% 24% 6% 1	950
	21st to end	Night	22% 16% 40% 18% 4	950
December	1st to 10th	Night	15% 10% 38% 26% 9% 2	950
	11th to 20th	Night	19% 13% 37% 24% 6% 1	950
	21st to end	Night	22% 11% 34% 24% 8% 1	1045

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