KK's Hill
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the KK's Hill clear sky chart from 2005-11-06 to 2025-03-27.

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	17% 11% 4 8% 5% 4 4 3 5% 7% 32%	108910
	Night	18% 12% 4 9% 5% 4 4 3 5% 6% 32%	110396
Transparency	Day	50% 6% 11% 20% 11% 1	112560
	Night	52% 6% 10% 19% 11% 2	114885
Seeing	Day	25% 14% 24% 21% 12% 4	15247
	Night	24% 12% 23% 27% 12% 1	25236

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	17% 21% 8% 20% 5% 3 3 2 3 3 16%	4056
	11th to 20th	Day	16% 23% 9% 13% 9% 5% 4 2 2 3 14%	4060
	21st to end	Day	20% 19% 5% 10% 7% 4 4 3 4 4 20%	4466
February	1st to 10th	Day	23% 15% 6% 9% 6% 4 4 3 5% 5% 23%	1800
	11th to 20th	Day	21% 17% 5% 10% 5% 4 4 2 4 5% 23%	1754
	21st to end	Day	21% 17% 4 10% 4 3 3 3 4 5% 27%	1690
March	1st to 10th	Day	20% 16% 5% 8% 4 3 3 3 5% 6% 29%	3545
	11th to 20th	Day	15% 9% 4 7% 4 4 4 3 5% 7% 36%	3590
	21st to end	Day	21% 10% 3 8% 5% 4 4 3 5% 5% 31%	3881
April	1st to 10th	Day	18% 13% 3 8% 5% 5% 3 4 5% 7% 30%	2175
	11th to 20th	Day	17% 10% 2 6% 4 4 5% 3 5% 6% 37%	2264
	21st to end	Day	21% 8% 3 7% 4 4 4 4 6% 6% 32%	2470
May	1st to 10th	Day	23% 10% 3 8% 5% 5% 5% 3 5% 6% 26%	4082
	11th to 20th	Day	20% 9% 3 7% 5% 4 4 3 6% 7% 32%	4081
	21st to end	Day	13% 6% 2 6% 5% 5% 6% 4 6% 9% 37%	4539
June	1st to 10th	Day	14% 7% 2 6% 5% 4 5% 4 7% 9% 36%	2660
	11th to 20th	Day	14% 7% 2 6% 5% 5% 6% 5% 6% 8% 35%	2660
	21st to end	Day	14% 6% 3 6% 5% 4 5% 4 7% 9% 36%	2638
July	1st to 10th	Day	10% 5% 2 6% 5% 5% 6% 5% 7% 9% 40%	4120
	11th to 20th	Day	12% 6% 2 6% 5% 5% 5% 5% 7% 9% 39%	4120
	21st to end	Day	17% 9% 2 7% 6% 5% 6% 4 6% 8% 32%	4466
August	1st to 10th	Day	13% 8% 3 8% 5% 5% 6% 4 7% 9% 31%	4104
	11th to 20th	Day	12% 7% 3 7% 5% 5% 6% 4 6% 9% 37%	4044
	21st to end	Day	8% 3 1 5% 4 5% 5% 4 7% 9% 47%	4289
September	1st to 10th	Day	15% 5% 1 5% 3 4 4 3 5% 6% 47%	2266
	11th to 20th	Day	12% 7% 2 6% 4 4 4 4 5% 9% 44%	2090
	21st to end	Day	18% 8% 3 7% 4 4 5% 4 5% 7% 35%	2090
October	1st to 10th	Day	16% 7% 2 6% 3 4 4 3 6% 6% 43%	1908
	11th to 20th	Day	20% 8% 2 6% 3 4 4 3 4 6% 39%	1900
	21st to end	Day	23% 9% 2 5% 4 3 3 3 4 6% 38%	2090
November	1st to 10th	Day	14% 9% 2 6% 4 3 4 3 5% 5% 46%	1907
	11th to 20th	Day	16% 14% 4 6% 4 4 4 3 7% 6% 32%	1743
	21st to end	Day	20% 15% 5% 8% 4 3 4 3 5% 5% 28%	1600
December	1st to 10th	Day	20% 14% 6% 18% 5% 3 3 3 4 4 20%	2600
	11th to 20th	Day	24% 18% 5% 9% 3 2 3 2 4 4 24%	2990
	21st to end	Day	21% 18% 5% 10% 5% 5% 4 3 5% 6% 17%	4172
January	1st to 10th	Night	17% 19% 9% 18% 5% 3 3 2 3 3 18%	5889
	11th to 20th	Night	18% 18% 8% 14% 8% 5% 3 2 3 3 18%	5900
	21st to end	Night	21% 15% 6% 11% 5% 4 3 2 3 4 25%	6490
February	1st to 10th	Night	20% 16% 4 9% 5% 4 4 3 4 5% 26%	2600
	11th to 20th	Night	21% 15% 4 11% 5% 5% 4 3 4 4 24%	2528
	21st to end	Night	21% 15% 5% 8% 4 4 4 3 5% 5% 26%	1938
March	1st to 10th	Night	23% 12% 3 6% 5% 3 4 3 4 6% 30%	3528
	11th to 20th	Night	16% 15% 6% 7% 4 3 3 3 4 6% 34%	3590
	21st to end	Night	19% 10% 3 6% 4 3 4 3 4 6% 38%	3890
April	1st to 10th	Night	20% 12% 3 7% 4 4 5% 3 4 6% 32%	2005
	11th to 20th	Night	18% 8% 2 5% 4 4 4 4 5% 8% 37%	1875
	21st to end	Night	15% 8% 3 8% 6% 4 3 3 5% 6% 40%	1715
May	1st to 10th	Night	28% 12% 3 8% 4 4 3 3 4 6% 24%	2813
	11th to 20th	Night	20% 9% 3 7% 5% 4 4 3 4 7% 35%	2812
	21st to end	Night	14% 8% 3 7% 4 5% 5% 4 6% 8% 35%	2998
June	1st to 10th	Night	12% 6% 3 7% 5% 4 5% 4 5% 8% 42%	1520
	11th to 20th	Night	11% 6% 2 7% 6% 4 5% 5% 7% 9% 38%	1520
	21st to end	Night	12% 7% 2 5% 4 5% 5% 4 7% 9% 41%	1535
July	1st to 10th	Night	11% 7% 3 6% 5% 5% 5% 5% 7% 8% 37%	2840
	11th to 20th	Night	12% 7% 3 7% 5% 5% 5% 4 6% 9% 38%	2840
	21st to end	Night	13% 8% 3 7% 5% 5% 5% 4 6% 7% 37%	3087
August	1st to 10th	Night	13% 8% 3 8% 5% 5% 5% 5% 7% 10% 31%	2825
	11th to 20th	Night	15% 8% 2 7% 5% 4 4 3 6% 7% 38%	2785
	21st to end	Night	7% 5% 2 6% 4 4 4 4 7% 9% 47%	3334
September	1st to 10th	Night	13% 6% 2 6% 4 4 5% 3 5% 7% 46%	1909
	11th to 20th	Night	12% 5% 1 4 3 3 4 4 5% 8% 50%	2090
	21st to end	Night	16% 7% 2 7% 5% 4 4 3 5% 7% 41%	2090
October	1st to 10th	Night	16% 6% 2 5% 3 4 3 3 5% 6% 45%	2271
	11th to 20th	Night	16% 7% 2 6% 3 4 4 4 5% 7% 43%	2280
	21st to end	Night	24% 8% 2 4 3 3 4 2 4 5% 40%	2508
November	1st to 10th	Night	14% 9% 2 6% 4 4 4 3 4 5% 45%	2386
	11th to 20th	Night	20% 13% 3 7% 4 4 3 4 5% 5% 33%	2654
	21st to end	Night	20% 13% 4 9% 5% 4 4 3 4 4 30%	2800
December	1st to 10th	Night	19% 16% 5% 18% 4 3 3 2 4 5% 20%	4580
	11th to 20th	Night	23% 16% 7% 8% 4 3 4 3 4 5% 23%	5205
	21st to end	Night	20% 18% 5% 10% 6% 5% 4 3 5% 5% 21%	6766

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	76% 4 8% 8% 4	4057
	11th to 20th	Day	77% 3 5% 8% 5%	4060
	21st to end	Day	68% 3 8% 13% 7%	4466
February	1st to 10th	Day	64% 5% 9% 16% 6% 1	1800
	11th to 20th	Day	65% 4 10% 13% 8%	1763
	21st to end	Day	61% 5% 9% 14% 10% 1	1690
March	1st to 10th	Day	56% 6% 9% 19% 9% 1	3545
	11th to 20th	Day	45% 7% 10% 26% 10% 1	3590
	21st to end	Day	53% 7% 8% 19% 13% 1	3881
April	1st to 10th	Day	53% 7% 10% 17% 11% 3	2175
	11th to 20th	Day	47% 6% 11% 15% 18% 2	2264
	21st to end	Day	50% 7% 12% 20% 10% 2	2470
May	1st to 10th	Day	56% 9% 8% 19% 7% 1	4120
	11th to 20th	Day	49% 10% 11% 20% 9% 1	4085
	21st to end	Day	38% 11% 17% 20% 11% 3	4553
June	1st to 10th	Day	42% 10% 13% 21% 13% 1	2660
	11th to 20th	Day	45% 9% 12% 22% 11% 1	2660
	21st to end	Day	42% 9% 14% 22% 11% 1	2638
July	1st to 10th	Day	40% 7% 14% 22% 15% 2	4055
	11th to 20th	Day	40% 7% 12% 28% 13% 1	4051
	21st to end	Day	50% 6% 10% 20% 14% 1	4324
August	1st to 10th	Day	47% 7% 15% 23% 7%	4091
	11th to 20th	Day	42% 6% 11% 27% 12%	4083
	21st to end	Day	32% 7% 16% 27% 17% 2	4289
September	1st to 10th	Day	37% 6% 11% 21% 21% 3	2266
	11th to 20th	Day	37% 6% 11% 26% 16% 3	2090
	21st to end	Day	48% 6% 12% 18% 16% 1	2090
October	1st to 10th	Day	33% 4 9% 27% 24% 3	3168
	11th to 20th	Day	41% 4 11% 23% 14% 7%	3140
	21st to end	Day	35% 3 10% 29% 22% 2	3428
November	1st to 10th	Day	41% 5% 9% 24% 17% 4	1907
	11th to 20th	Day	51% 5% 10% 16% 15% 3	1743
	21st to end	Day	58% 5% 10% 15% 12%	1600
December	1st to 10th	Day	70% 3 11% 13% 3 1	2600
	11th to 20th	Day	64% 3 11% 16% 4 1	2986
	21st to end	Day	67% 5% 10% 13% 5%	4172
January	1st to 10th	Night	73% 3 7% 11% 4 1	5889
	11th to 20th	Night	72% 4 7% 10% 5% 2	5900
	21st to end	Night	65% 3 9% 15% 7% 1	6490
February	1st to 10th	Night	61% 5% 10% 16% 8%	2600
	11th to 20th	Night	64% 5% 9% 14% 8%	2530
	21st to end	Night	60% 5% 9% 15% 9% 2	1938
March	1st to 10th	Night	54% 6% 8% 22% 9% 1	3528
	11th to 20th	Night	51% 7% 8% 25% 8% 1	3590
	21st to end	Night	46% 7% 9% 24% 13% 2	3890
April	1st to 10th	Night	54% 6% 8% 17% 13% 2	2005
	11th to 20th	Night	44% 6% 13% 19% 14% 4	1875
	21st to end	Night	44% 7% 12% 21% 13% 3	1715
May	1st to 10th	Night	60% 8% 8% 15% 9% 2	2840
	11th to 20th	Night	48% 9% 12% 21% 9% 1	2813
	21st to end	Night	41% 11% 15% 20% 9% 3	3005
June	1st to 10th	Night	38% 9% 13% 24% 15% 1	1520
	11th to 20th	Night	40% 11% 13% 21% 13% 2	1520
	21st to end	Night	38% 9% 16% 20% 15% 1	1535
July	1st to 10th	Night	43% 7% 12% 20% 14% 3	2795
	11th to 20th	Night	42% 7% 12% 26% 12% 1	2786
	21st to end	Night	45% 8% 11% 18% 17% 2	2988
August	1st to 10th	Night	47% 8% 16% 22% 7% 1	2814
	11th to 20th	Night	44% 6% 10% 21% 18% 1	2812
	21st to end	Night	31% 7% 12% 33% 15% 2	3334
September	1st to 10th	Night	37% 7% 12% 20% 18% 5%	1909
	11th to 20th	Night	31% 7% 13% 25% 22% 2	2090
	21st to end	Night	43% 8% 11% 21% 17% 1	2090
October	1st to 10th	Night	35% 5% 9% 27% 21% 4	3791
	11th to 20th	Night	38% 4 9% 23% 17% 8%	3779
	21st to end	Night	36% 3 6% 27% 25% 3	4120
November	1st to 10th	Night	41% 5% 11% 19% 18% 5%	2386
	11th to 20th	Night	53% 5% 9% 17% 13% 3	2654
	21st to end	Night	59% 4 8% 18% 10% 1	2800
December	1st to 10th	Night	68% 3 10% 15% 3 1	4580
	11th to 20th	Night	65% 4 12% 15% 4	5208
	21st to end	Night	66% 5% 10% 14% 6%	6766

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	33% 33% 20% 10% 4 1	300
	11th to 20th	Day	43% 23% 27% 6%	300
	21st to end	Day	39% 27% 25% 6% 3	330
February	1st to 10th	Day	37% 27% 26% 8% 2	300
	11th to 20th	Day	49% 25% 22% 4 1	300
	21st to end	Day	43% 22% 28% 6% 1	289
March	1st to 10th	Day	34% 21% 26% 16% 3	500
	11th to 20th	Day	34% 22% 26% 13% 4 1	500
	21st to end	Day	32% 19% 29% 15% 4	530
April	1st to 10th	Day	33% 20% 22% 19% 5% 1	460
	11th to 20th	Day	27% 19% 26% 17% 7% 4	452
	21st to end	Day	29% 19% 25% 18% 6% 2	460
May	1st to 10th	Day	28% 18% 27% 15% 7% 5%	463
	11th to 20th	Day	24% 15% 27% 19% 11% 3	487
	21st to end	Day	15% 9% 30% 22% 16% 8%	529
June	1st to 10th	Day	15% 11% 27% 24% 16% 6%	490
	11th to 20th	Day	18% 8% 23% 28% 17% 5%	490
	21st to end	Day	14% 10% 29% 27% 16% 4	490
July	1st to 10th	Day	15% 6% 21% 26% 20% 12%	485
	11th to 20th	Day	13% 7% 23% 29% 20% 8%	484
	21st to end	Day	20% 6% 23% 26% 19% 8%	532
August	1st to 10th	Day	15% 6% 19% 32% 17% 10%	486
	11th to 20th	Day	16% 7% 20% 28% 19% 9%	479
	21st to end	Day	12% 6% 20% 29% 21% 12%	539
September	1st to 10th	Day	18% 7% 19% 27% 20% 9%	490
	11th to 20th	Day	13% 3 18% 30% 24% 12%	490
	21st to end	Day	23% 9% 24% 26% 14% 3	490
October	1st to 10th	Day	18% 9% 22% 27% 19% 4	490
	11th to 20th	Day	26% 10% 27% 24% 10% 3	490
	21st to end	Day	29% 15% 26% 19% 11% 1	539
November	1st to 10th	Day	22% 12% 27% 25% 9% 4	445
	11th to 20th	Day	32% 18% 26% 18% 5% 1	271
	21st to end	Day	32% 22% 33% 12% 2 1	200
December	1st to 10th	Day	32% 25% 27% 12% 3 2	200
	11th to 20th	Day	40% 22% 21% 14% 4	200
	21st to end	Day	40% 19% 21% 15% 4	267
January	1st to 10th	Night	33% 23% 26% 15% 3	800
	11th to 20th	Night	38% 18% 27% 16% 2	800
	21st to end	Night	30% 22% 29% 18% 1	880
February	1st to 10th	Night	31% 18% 26% 22% 2	800
	11th to 20th	Night	33% 23% 30% 14% 1	783
	21st to end	Night	32% 19% 29% 19% 1	660
March	1st to 10th	Night	29% 18% 27% 23% 3	800
	11th to 20th	Night	32% 17% 25% 20% 6% 1	800
	21st to end	Night	29% 17% 28% 22% 4 1	863
April	1st to 10th	Night	27% 18% 28% 22% 5%	760
	11th to 20th	Night	21% 15% 30% 24% 10%	751
	21st to end	Night	19% 12% 30% 31% 8%	575
May	1st to 10th	Night	23% 9% 28% 29% 10% 1	570
	11th to 20th	Night	22% 9% 24% 31% 13% 1	561
	21st to end	Night	14% 5% 20% 30% 27% 4	574
June	1st to 10th	Night	11% 7% 24% 39% 20% 1	380
	11th to 20th	Night	15% 3 23% 37% 21% 2	380
	21st to end	Night	14% 3 21% 42% 20% 1	395
July	1st to 10th	Night	13% 3 15% 37% 27% 4	555
	11th to 20th	Night	12% 4 13% 37% 31% 4	552
	21st to end	Night	16% 3 13% 37% 30% 2	624
August	1st to 10th	Night	11% 3 12% 42% 28% 3	567
	11th to 20th	Night	15% 4 12% 37% 29% 3	564
	21st to end	Night	13% 3 12% 36% 30% 5%	746
September	1st to 10th	Night	15% 3 16% 35% 26% 4	760
	11th to 20th	Night	15% 4 15% 34% 29% 3	760
	21st to end	Night	19% 8% 20% 32% 19% 2	760
October	1st to 10th	Night	20% 6% 19% 33% 19% 3	760
	11th to 20th	Night	21% 10% 25% 30% 13% 1	760
	21st to end	Night	29% 11% 21% 28% 11% 1	836
November	1st to 10th	Night	19% 10% 26% 32% 13% 1	780
	11th to 20th	Night	31% 13% 24% 25% 7% 1	800
	21st to end	Night	28% 15% 27% 23% 6% 1	800
December	1st to 10th	Night	33% 18% 26% 19% 5%	800
	11th to 20th	Night	32% 18% 24% 22% 5%	800
	21st to end	Night	33% 14% 27% 24% 2	880

Page generated at 2025-03-24 09:04:29. Version ac07

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