Knob Lakes
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Knob Lakes clear sky chart from 2005-11-06 to 2025-06-10.

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	9% 11% 5% 12% 8% 7% 7% 5% 7% 7% 20%	122942
	Night	4 10% 5% 13% 9% 8% 8% 6% 8% 8% 22%	123987
Transparency	Day	49% 16% 15% 13% 6% 1	122635
	Night	44% 16% 15% 14% 9% 2	123939
Seeing	Day	14% 7% 21% 27% 21% 9%	18412
	Night	8% 4 19% 36% 25% 8%	23146

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	5% 3 12% 9% 9% 11% 7% 9% 9% 25%	1819
	11th to 20th	Day	1 6% 4 10% 10% 9% 10% 7% 8% 10% 26%	2247
	21st to end	Day	1 4 3 12% 8% 9% 11% 9% 10% 10% 24%	2992
February	1st to 10th	Day	1 7% 4 11% 9% 8% 8% 5% 8% 9% 30%	1333
	11th to 20th	Day	1 8% 6% 15% 10% 8% 8% 6% 10% 7% 22%	1559
	21st to end	Day	1 8% 4 16% 9% 9% 6% 6% 5% 8% 28%	1373
March	1st to 10th	Day	6% 7% 18% 13% 9% 8% 6% 6% 6% 22%	4474
	11th to 20th	Day	4 4 15% 13% 12% 9% 5% 7% 6% 25%	4630
	21st to end	Day	1 7% 6% 18% 10% 8% 7% 5% 8% 7% 22%	5959
April	1st to 10th	Day	1 11% 6% 11% 8% 8% 6% 6% 10% 9% 23%	2493
	11th to 20th	Day	2 11% 5% 11% 8% 5% 6% 5% 8% 9% 31%	2725
	21st to end	Day	3 12% 4 12% 7% 6% 6% 5% 8% 7% 32%	2910
May	1st to 10th	Day	4 16% 5% 13% 8% 7% 7% 6% 7% 7% 20%	7071
	11th to 20th	Day	6% 14% 5% 12% 7% 6% 6% 6% 7% 7% 24%	7404
	21st to end	Day	10% 16% 5% 12% 8% 8% 8% 6% 7% 6% 15%	8547
June	1st to 10th	Day	17% 12% 4 11% 8% 6% 6% 5% 6% 6% 17%	3589
	11th to 20th	Day	25% 12% 4 10% 7% 6% 5% 3 5% 5% 16%	3420
	21st to end	Day	25% 11% 3 10% 6% 6% 6% 5% 6% 6% 16%	3420
July	1st to 10th	Day	17% 10% 4 10% 7% 7% 7% 6% 7% 8% 17%	5700
	11th to 20th	Day	16% 12% 5% 13% 9% 7% 7% 6% 7% 7% 12%	5646
	21st to end	Day	21% 13% 4 10% 7% 5% 6% 5% 6% 8% 15%	5545
August	1st to 10th	Day	17% 12% 4 11% 7% 6% 6% 4 5% 6% 19%	5046
	11th to 20th	Day	15% 10% 3 9% 6% 6% 6% 5% 9% 8% 24%	4478
	21st to end	Day	19% 16% 5% 11% 6% 5% 6% 5% 7% 6% 14%	4835
September	1st to 10th	Day	19% 14% 4 12% 7% 6% 6% 3 6% 7% 17%	2399
	11th to 20th	Day	13% 14% 5% 12% 7% 6% 5% 4 6% 7% 22%	2233
	21st to end	Day	11% 18% 6% 11% 6% 6% 5% 5% 5% 6% 20%	2085
October	1st to 10th	Day	6% 14% 5% 13% 8% 6% 6% 5% 7% 7% 22%	3036
	11th to 20th	Day	3 10% 5% 13% 9% 6% 6% 5% 7% 8% 29%	2834
	21st to end	Day	4 12% 5% 12% 7% 6% 5% 5% 7% 9% 30%	2625
November	1st to 10th	Day	2 14% 6% 19% 14% 9% 6% 4 5% 5% 16%	1371
	11th to 20th	Day	2 12% 4 16% 10% 10% 10% 4 5% 7% 20%	1150
	21st to end	Day	1 8% 6% 18% 10% 11% 9% 6% 6% 7% 21%	1000
December	1st to 10th	Day	2 8% 5% 13% 9% 7% 8% 8% 11% 13% 18%	1475
	11th to 20th	Day	7% 6% 16% 11% 9% 10% 8% 10% 8% 15%	1517
	21st to end	Day	6% 4 13% 11% 9% 8% 8% 10% 14% 17%	2002
January	1st to 10th	Night	1 8% 4 12% 9% 10% 9% 6% 8% 9% 24%	8146
	11th to 20th	Night	1 6% 4 12% 9% 8% 9% 7% 8% 9% 26%	7652
	21st to end	Night	1 5% 3 10% 8% 8% 9% 9% 12% 11% 24%	7986
February	1st to 10th	Night	1 8% 4 11% 8% 6% 7% 6% 7% 8% 34%	3065
	11th to 20th	Night	1 7% 5% 14% 11% 10% 8% 6% 6% 8% 25%	2728
	21st to end	Night	2 7% 4 14% 9% 8% 7% 6% 6% 8% 29%	2255
March	1st to 10th	Night	7% 5% 16% 9% 10% 8% 6% 7% 8% 24%	5380
	11th to 20th	Night	4 6% 18% 12% 9% 8% 6% 8% 9% 21%	5328
	21st to end	Night	7% 5% 18% 11% 8% 8% 6% 8% 9% 19%	4969
April	1st to 10th	Night	1 10% 6% 14% 8% 7% 7% 5% 7% 8% 25%	1907
	11th to 20th	Night	2 10% 5% 10% 7% 6% 7% 6% 7% 9% 32%	1623
	21st to end	Night	3 10% 3 11% 7% 6% 6% 6% 7% 8% 32%	1490
May	1st to 10th	Night	4 17% 6% 13% 9% 8% 7% 6% 8% 7% 16%	2909
	11th to 20th	Night	8% 18% 6% 12% 7% 6% 6% 4 6% 6% 19%	2502
	21st to end	Night	12% 14% 5% 11% 6% 6% 7% 6% 7% 6% 19%	2320
June	1st to 10th	Night	18% 9% 6% 9% 6% 6% 8% 4 7% 7% 21%	796
	11th to 20th	Night	23% 9% 5% 10% 4 4 5% 5% 6% 7% 22%	760
	21st to end	Night	19% 12% 4 9% 7% 7% 6% 4 6% 6% 20%	760
July	1st to 10th	Night	22% 11% 3 9% 6% 7% 7% 5% 7% 7% 16%	1270
	11th to 20th	Night	16% 14% 5% 12% 8% 6% 5% 5% 6% 6% 17%	1322
	21st to end	Night	25% 12% 4 10% 7% 5% 4 4 5% 5% 17%	2003
August	1st to 10th	Night	16% 15% 4 11% 7% 7% 5% 5% 4 6% 21%	1894
	11th to 20th	Night	13% 12% 4 12% 7% 6% 6% 4 7% 7% 23%	2356
	21st to end	Night	16% 16% 5% 12% 7% 7% 7% 5% 7% 5% 12%	2832
September	1st to 10th	Night	19% 16% 4 9% 5% 6% 6% 5% 7% 5% 19%	1778
	11th to 20th	Night	13% 16% 5% 9% 6% 5% 6% 5% 7% 6% 22%	1947
	21st to end	Night	13% 21% 5% 9% 6% 4 5% 5% 5% 7% 20%	2095
October	1st to 10th	Night	8% 17% 8% 14% 7% 6% 6% 6% 6% 6% 16%	3928
	11th to 20th	Night	3 12% 4 10% 8% 6% 4 4 7% 8% 33%	4094
	21st to end	Night	4 15% 6% 12% 8% 7% 7% 5% 7% 7% 22%	4931
November	1st to 10th	Night	3 14% 7% 17% 11% 9% 7% 4 5% 5% 19%	2927
	11th to 20th	Night	2 10% 5% 17% 11% 10% 7% 5% 5% 7% 21%	3250
	21st to end	Night	1 9% 5% 16% 10% 9% 8% 6% 6% 7% 22%	3400
December	1st to 10th	Night	2 10% 5% 14% 8% 8% 8% 7% 9% 9% 20%	5708
	11th to 20th	Night	1 7% 6% 18% 11% 10% 10% 7% 9% 8% 14%	6700
	21st to end	Night	1 5% 4 16% 11% 10% 9% 7% 11% 11% 15%	8976

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	29% 15% 18% 18% 14% 6%	1819
	11th to 20th	Day	31% 18% 16% 21% 13% 1	2264
	21st to end	Day	31% 14% 18% 12% 19% 6%	2992
February	1st to 10th	Day	34% 13% 15% 15% 14% 7%	1333
	11th to 20th	Day	41% 18% 18% 12% 8% 3	1566
	21st to end	Day	41% 15% 13% 15% 13% 3	1373
March	1st to 10th	Day	41% 16% 16% 13% 11% 3	4474
	11th to 20th	Day	36% 17% 15% 14% 16% 2	4630
	21st to end	Day	39% 22% 16% 10% 11% 2	5959
April	1st to 10th	Day	47% 17% 15% 14% 5% 1	2493
	11th to 20th	Day	43% 14% 16% 17% 10%	2725
	21st to end	Day	45% 14% 16% 16% 8% 1	2910
May	1st to 10th	Day	49% 17% 13% 13% 8% 1	7071
	11th to 20th	Day	45% 14% 14% 21% 5%	7407
	21st to end	Day	54% 15% 15% 13% 3	8548
June	1st to 10th	Day	57% 16% 15% 10% 2	3589
	11th to 20th	Day	61% 13% 13% 11% 1	3420
	21st to end	Day	61% 17% 15% 7% 1	3420
July	1st to 10th	Day	57% 19% 17% 7% 1	5611
	11th to 20th	Day	58% 19% 16% 6% 1	5547
	21st to end	Day	59% 17% 17% 7%	5370
August	1st to 10th	Day	59% 16% 14% 8% 3	5027
	11th to 20th	Day	49% 15% 18% 15% 2	4523
	21st to end	Day	62% 15% 11% 10% 1	4834
September	1st to 10th	Day	61% 16% 13% 8% 2	2399
	11th to 20th	Day	55% 18% 13% 11% 2	2233
	21st to end	Day	57% 17% 12% 11% 4	2085
October	1st to 10th	Day	51% 14% 12% 18% 5%	3036
	11th to 20th	Day	44% 15% 13% 21% 6%	2834
	21st to end	Day	40% 15% 17% 21% 7% 1	2625
November	1st to 10th	Day	53% 17% 14% 10% 6% 1	1371
	11th to 20th	Day	49% 16% 14% 13% 8%	1150
	21st to end	Day	43% 20% 16% 12% 10%	1000
December	1st to 10th	Day	40% 17% 19% 15% 9%	1475
	11th to 20th	Day	41% 20% 15% 15% 8%	1520
	21st to end	Day	35% 15% 15% 14% 14% 6%	2002
January	1st to 10th	Night	36% 14% 16% 12% 13% 8%	8146
	11th to 20th	Night	34% 15% 18% 17% 13% 3	7698
	21st to end	Night	29% 17% 15% 13% 18% 8%	7986
February	1st to 10th	Night	33% 13% 14% 18% 15% 8%	3065
	11th to 20th	Night	40% 17% 17% 13% 10% 3	2732
	21st to end	Night	40% 16% 16% 14% 11% 2	2255
March	1st to 10th	Night	38% 14% 12% 17% 14% 3	5380
	11th to 20th	Night	37% 16% 15% 13% 16% 2	5330
	21st to end	Night	36% 20% 17% 14% 11% 2	4969
April	1st to 10th	Night	45% 15% 19% 14% 6%	1907
	11th to 20th	Night	39% 16% 16% 18% 10%	1623
	21st to end	Night	43% 15% 18% 14% 9% 1	1490
May	1st to 10th	Night	49% 19% 11% 11% 9%	2906
	11th to 20th	Night	55% 13% 11% 15% 5%	2502
	21st to end	Night	48% 16% 15% 17% 3	2320
June	1st to 10th	Night	56% 18% 13% 11% 2	796
	11th to 20th	Night	55% 17% 17% 10% 1	760
	21st to end	Night	61% 19% 11% 8% 1	760
July	1st to 10th	Night	62% 17% 14% 6% 1	1250
	11th to 20th	Night	60% 17% 13% 9%	1298
	21st to end	Night	63% 15% 15% 7%	1939
August	1st to 10th	Night	59% 16% 17% 7% 1	1888
	11th to 20th	Night	54% 15% 15% 13% 3	2377
	21st to end	Night	66% 16% 12% 7%	2832
September	1st to 10th	Night	58% 20% 13% 7% 1	1778
	11th to 20th	Night	56% 18% 14% 10% 3	1947
	21st to end	Night	58% 16% 14% 10% 2	2095
October	1st to 10th	Night	58% 14% 11% 12% 4	3928
	11th to 20th	Night	42% 13% 14% 22% 10%	4094
	21st to end	Night	47% 14% 13% 19% 5% 1	4931
November	1st to 10th	Night	51% 18% 14% 10% 6% 1	2927
	11th to 20th	Night	49% 15% 16% 14% 6%	3250
	21st to end	Night	42% 19% 17% 12% 9% 1	3400
December	1st to 10th	Night	41% 17% 17% 18% 7%	5708
	11th to 20th	Night	44% 18% 16% 12% 9% 1	6696
	21st to end	Night	38% 17% 13% 14% 13% 5%	8976

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	2 23% 36% 26% 13%	100
	11th to 20th	Day	4 4 15% 47% 18% 12%	180
	21st to end	Day	2 3 21% 38% 24% 12%	330
February	1st to 10th	Day	2 2 18% 35% 29% 14%	325
	11th to 20th	Day	3 2 25% 37% 23% 10%	395
	21st to end	Day	2 3 29% 37% 18% 11%	331
March	1st to 10th	Day	2 4 24% 33% 27% 11%	400
	11th to 20th	Day	2 4 24% 32% 27% 12%	400
	21st to end	Day	2 5% 25% 30% 26% 14%	650
April	1st to 10th	Day	3 7% 28% 29% 24% 9%	648
	11th to 20th	Day	3 6% 18% 33% 29% 11%	690
	21st to end	Day	6% 6% 16% 28% 32% 13%	700
May	1st to 10th	Day	10% 8% 25% 26% 23% 8%	703
	11th to 20th	Day	10% 8% 20% 28% 24% 10%	725
	21st to end	Day	14% 9% 23% 28% 20% 7%	850
June	1st to 10th	Day	19% 9% 21% 27% 17% 6%	927
	11th to 20th	Day	25% 6% 20% 24% 17% 7%	870
	21st to end	Day	23% 7% 17% 23% 21% 8%	870
July	1st to 10th	Day	21% 7% 20% 27% 19% 7%	856
	11th to 20th	Day	22% 10% 19% 23% 21% 6%	824
	21st to end	Day	25% 7% 22% 21% 17% 8%	739
August	1st to 10th	Day	22% 13% 23% 20% 15% 7%	676
	11th to 20th	Day	25% 14% 25% 20% 13% 4	665
	21st to end	Day	26% 12% 21% 23% 15% 4	748
September	1st to 10th	Day	23% 14% 24% 18% 16% 6%	643
	11th to 20th	Day	21% 9% 23% 27% 16% 5%	533
	21st to end	Day	18% 11% 19% 24% 18% 10%	390
October	1st to 10th	Day	17% 9% 24% 21% 18% 11%	390
	11th to 20th	Day	10% 5% 17% 26% 30% 11%	390
	21st to end	Day	9% 4 21% 30% 24% 12%	429
November	1st to 10th	Day	8% 3 21% 30% 28% 11%	395
	11th to 20th	Day	4 2 17% 37% 26% 13%	230
	21st to end	Day	4 1 24% 31% 27% 13%	100
December	1st to 10th	Day	6% 3 22% 33% 24% 12%	100
	11th to 20th	Day	2 2 18% 46% 25% 7%	100
	21st to end	Day	3 3 23% 39% 24% 9%	110
January	1st to 10th	Night	3 2 19% 37% 29% 10%	1000
	11th to 20th	Night	3 2 20% 47% 21% 7%	941
	21st to end	Night	4 2 22% 43% 22% 7%	990
February	1st to 10th	Night	2 2 19% 41% 27% 8%	900
	11th to 20th	Night	2 1 24% 46% 23% 4	884
	21st to end	Night	3 2 24% 41% 22% 8%	708
March	1st to 10th	Night	1 2 20% 42% 28% 7%	700
	11th to 20th	Night	2 1 18% 39% 29% 11%	677
	21st to end	Night	1 2 19% 32% 33% 14%	660
April	1st to 10th	Night	3 3 21% 36% 29% 9%	600
	11th to 20th	Night	2 2 20% 32% 34% 9%	593
	21st to end	Night	6% 2 15% 32% 38% 7%	600
May	1st to 10th	Night	11% 4 21% 30% 28% 6%	485
	11th to 20th	Night	13% 4 18% 32% 27% 6%	311
	21st to end	Night	7% 3 24% 31% 35%	217
June	1st to 10th	Night	18% 5% 15% 33% 28% 2	199
	11th to 20th	Night	21% 3 12% 31% 32% 3	190
	21st to end	Night	20% 5% 17% 28% 26% 4	190
July	1st to 10th	Night	21% 4 16% 25% 30% 4	185
	11th to 20th	Night	21% 5% 15% 27% 29% 3	184
	21st to end	Night	22% 4 13% 28% 26% 6%	379
August	1st to 10th	Night	19% 5% 23% 27% 21% 4	378
	11th to 20th	Night	21% 9% 19% 29% 17% 4	556
	21st to end	Night	24% 6% 17% 27% 21% 4	627
September	1st to 10th	Night	23% 5% 18% 32% 18% 4	570
	11th to 20th	Night	18% 8% 18% 33% 18% 5%	570
	21st to end	Night	20% 6% 17% 26% 21% 9%	573
October	1st to 10th	Night	18% 7% 21% 28% 20% 7%	746
	11th to 20th	Night	10% 4 15% 33% 29% 9%	860
	21st to end	Night	9% 4 17% 35% 27% 8%	946
November	1st to 10th	Night	7% 5% 18% 38% 25% 7%	880
	11th to 20th	Night	5% 3 19% 40% 25% 9%	900
	21st to end	Night	3 3 23% 37% 25% 9%	900
December	1st to 10th	Night	5% 4 20% 36% 24% 10%	947
	11th to 20th	Night	3 2 20% 41% 24% 10%	1000
	21st to end	Night	3 4 21% 37% 24% 11%	1100

Page generated at 2025-06-07 06:28:19. Version ac07

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