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 2026-10-14.

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% 8% 20%	156507
	Night	5% 10% 5% 13% 9% 8% 8% 6% 8% 8% 22%	144078
Transparency	Day	50% 16% 16% 12% 6% 1	156153
	Night	44% 16% 15% 14% 9% 3	144016
Seeing	Day	14% 8% 21% 28% 21% 9%	20349
	Night	8% 4 20% 36% 25% 7%	24721

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% 4 12% 10% 8% 10% 6% 8% 10% 28%	2361
	11th to 20th	Day	2 5% 3 10% 9% 8% 10% 6% 8% 12% 27%	2931
	21st to end	Day	1 4 3 12% 7% 8% 10% 9% 12% 11% 23%	3871
February	1st to 10th	Day	1 8% 4 11% 9% 8% 8% 5% 8% 9% 29%	1400
	11th to 20th	Day	1 7% 5% 14% 10% 8% 8% 7% 10% 7% 22%	1639
	21st to end	Day	1 8% 4 15% 9% 9% 6% 6% 5% 8% 29%	1440
March	1st to 10th	Day	6% 7% 17% 13% 8% 8% 6% 6% 6% 22%	4574
	11th to 20th	Day	4 4 15% 13% 12% 9% 5% 6% 6% 25%	4732
	21st to end	Day	1 7% 6% 18% 10% 9% 7% 5% 8% 7% 23%	6091
April	1st to 10th	Day	1 11% 6% 12% 8% 8% 6% 7% 9% 9% 23%	2618
	11th to 20th	Day	2 11% 5% 12% 8% 5% 6% 5% 8% 8% 30%	2863
	21st to end	Day	3 11% 4 12% 7% 6% 6% 5% 8% 7% 31%	3055
May	1st to 10th	Day	3 15% 6% 14% 8% 7% 7% 6% 8% 7% 18%	9176
	11th to 20th	Day	5% 14% 5% 13% 7% 6% 6% 6% 7% 7% 22%	9624
	21st to end	Day	9% 16% 5% 13% 9% 8% 8% 6% 7% 6% 14%	11141
June	1st to 10th	Day	17% 12% 4 11% 8% 6% 6% 5% 6% 7% 18%	3780
	11th to 20th	Day	23% 12% 4 10% 7% 6% 5% 3 6% 6% 18%	3780
	21st to end	Day	25% 11% 3 10% 6% 6% 6% 5% 6% 6% 15%	3780
July	1st to 10th	Day	22% 11% 4 10% 7% 7% 7% 5% 7% 8% 13%	10620
	11th to 20th	Day	12% 13% 5% 13% 8% 8% 7% 6% 7% 7% 12%	10524
	21st to end	Day	18% 14% 4 11% 7% 6% 6% 4 6% 7% 18%	10348
August	1st to 10th	Day	13% 10% 4 9% 6% 5% 6% 5% 7% 9% 27%	7396
	11th to 20th	Day	12% 9% 3 8% 6% 6% 6% 6% 9% 9% 25%	6591
	21st to end	Day	16% 15% 4 11% 6% 6% 7% 5% 7% 7% 15%	7039
September	1st to 10th	Day	18% 13% 4 12% 6% 7% 6% 4 6% 7% 18%	2651
	11th to 20th	Day	12% 14% 5% 12% 7% 6% 6% 4 6% 7% 22%	2467
	21st to end	Day	11% 18% 6% 11% 7% 6% 5% 4 5% 6% 20%	2305
October	1st to 10th	Day	6% 14% 5% 13% 8% 7% 6% 5% 7% 7% 23%	3228
	11th to 20th	Day	3 10% 5% 14% 9% 6% 6% 5% 7% 8% 28%	2952
	21st to end	Day	3 12% 5% 12% 7% 6% 5% 5% 7% 9% 29%	2709
November	1st to 10th	Day	2 13% 6% 19% 14% 8% 6% 4 6% 5% 16%	1441
	11th to 20th	Day	2 11% 4 15% 10% 11% 10% 4 6% 8% 20%	1207
	21st to end	Day	1 8% 7% 18% 10% 11% 8% 5% 6% 7% 20%	1050
December	1st to 10th	Day	2 9% 5% 13% 8% 7% 8% 8% 11% 12% 18%	1520
	11th to 20th	Day	7% 6% 15% 11% 9% 10% 8% 10% 8% 16%	1557
	21st to end	Day	5% 4 13% 11% 9% 8% 8% 10% 14% 18%	2046
January	1st to 10th	Night	1 8% 4 12% 9% 10% 9% 5% 7% 9% 27%	10564
	11th to 20th	Night	1 5% 3 12% 9% 9% 9% 7% 9% 10% 26%	9976
	21st to end	Night	1 4 4 10% 8% 8% 10% 10% 13% 11% 22%	10342
February	1st to 10th	Night	1 8% 4 11% 8% 7% 7% 6% 7% 8% 32%	3218
	11th to 20th	Night	1 7% 5% 14% 11% 10% 8% 6% 7% 8% 25%	2868
	21st to end	Night	2 7% 4 14% 9% 8% 7% 6% 7% 8% 30%	2364
March	1st to 10th	Night	7% 5% 16% 9% 9% 8% 6% 7% 7% 25%	5500
	11th to 20th	Night	4 6% 18% 12% 9% 8% 6% 8% 9% 21%	5446
	21st to end	Night	7% 5% 18% 11% 8% 8% 6% 8% 9% 20%	5079
April	1st to 10th	Night	1 10% 6% 14% 8% 8% 7% 6% 7% 9% 24%	2002
	11th to 20th	Night	2 10% 5% 11% 7% 7% 7% 6% 7% 9% 30%	1705
	21st to end	Night	3 10% 3 11% 7% 7% 6% 6% 7% 8% 31%	1565
May	1st to 10th	Night	3 15% 6% 14% 10% 8% 7% 6% 8% 7% 16%	3773
	11th to 20th	Night	8% 16% 6% 13% 7% 6% 6% 5% 6% 7% 20%	3254
	21st to end	Night	11% 14% 5% 13% 7% 7% 7% 6% 7% 7% 17%	3025
June	1st to 10th	Night	18% 10% 5% 9% 5% 5% 8% 4 7% 7% 21%	840
	11th to 20th	Night	21% 9% 5% 10% 5% 4 5% 5% 6% 7% 23%	840
	21st to end	Night	20% 12% 4 9% 7% 7% 6% 4 6% 6% 19%	840
July	1st to 10th	Night	28% 13% 4 9% 6% 6% 5% 4 5% 6% 13%	2370
	11th to 20th	Night	13% 13% 6% 13% 8% 6% 6% 5% 6% 7% 17%	2461
	21st to end	Night	23% 14% 5% 12% 7% 6% 5% 4 5% 5% 14%	3734
August	1st to 10th	Night	12% 13% 4 10% 7% 6% 5% 5% 6% 8% 24%	2774
	11th to 20th	Night	11% 10% 3 11% 7% 7% 6% 5% 7% 9% 23%	3470
	21st to end	Night	15% 15% 5% 12% 7% 7% 6% 5% 7% 5% 16%	4109
September	1st to 10th	Night	18% 15% 4 9% 5% 6% 7% 5% 7% 5% 18%	1966
	11th to 20th	Night	13% 16% 5% 9% 6% 6% 6% 5% 7% 7% 21%	2153
	21st to end	Night	12% 21% 5% 9% 6% 4 5% 4 5% 7% 21%	2315
October	1st to 10th	Night	7% 17% 7% 14% 7% 6% 6% 6% 7% 6% 16%	4176
	11th to 20th	Night	3 13% 4 11% 8% 6% 4 4 7% 8% 32%	4263
	21st to end	Night	4 14% 6% 13% 8% 7% 7% 5% 7% 7% 22%	5089
November	1st to 10th	Night	3 14% 7% 17% 11% 9% 7% 4 4 5% 19%	3077
	11th to 20th	Night	2 10% 5% 17% 11% 9% 7% 5% 5% 7% 21%	3413
	21st to end	Night	1 9% 5% 16% 11% 10% 8% 6% 7% 7% 21%	3570
December	1st to 10th	Night	2 10% 5% 14% 8% 8% 8% 7% 9% 8% 21%	5883
	11th to 20th	Night	1 6% 6% 18% 11% 10% 10% 7% 9% 8% 16%	6880
	21st to end	Night	1 5% 4 16% 11% 10% 9% 7% 11% 11% 15%	9174

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	32% 14% 14% 14% 16% 11%	2361
	11th to 20th	Day	30% 16% 14% 19% 18% 2	2948
	21st to end	Day	30% 14% 19% 17% 15% 5%	3872
February	1st to 10th	Day	35% 13% 15% 15% 14% 7%	1400
	11th to 20th	Day	40% 18% 17% 13% 9% 3	1646
	21st to end	Day	40% 15% 13% 15% 15% 3	1440
March	1st to 10th	Day	41% 15% 16% 13% 12% 3	4574
	11th to 20th	Day	36% 17% 15% 13% 16% 2	4732
	21st to end	Day	39% 21% 16% 10% 11% 2	6091
April	1st to 10th	Day	47% 17% 15% 14% 5% 1	2618
	11th to 20th	Day	45% 13% 15% 17% 10%	2863
	21st to end	Day	44% 14% 16% 16% 8% 1	3055
May	1st to 10th	Day	49% 17% 13% 13% 8% 1	9176
	11th to 20th	Day	47% 13% 14% 21% 5%	9627
	21st to end	Day	57% 14% 13% 12% 3	11142
June	1st to 10th	Day	57% 16% 15% 11% 2	3780
	11th to 20th	Day	59% 14% 15% 11% 1	3780
	21st to end	Day	62% 17% 14% 6% 1	3780
July	1st to 10th	Day	61% 17% 16% 5%	10531
	11th to 20th	Day	58% 17% 17% 7% 1	10425
	21st to end	Day	59% 13% 16% 10% 1	10125
August	1st to 10th	Day	48% 15% 25% 11% 2	7377
	11th to 20th	Day	46% 15% 24% 13% 3	6636
	21st to end	Day	60% 14% 14% 11% 1	7038
September	1st to 10th	Day	59% 16% 13% 9% 3	2651
	11th to 20th	Day	55% 18% 13% 12% 2	2467
	21st to end	Day	57% 17% 12% 11% 3	2305
October	1st to 10th	Day	51% 14% 12% 18% 5%	3228
	11th to 20th	Day	44% 15% 13% 21% 6%	2952
	21st to end	Day	40% 15% 17% 20% 6% 1	2709
November	1st to 10th	Day	53% 17% 13% 10% 6% 1	1441
	11th to 20th	Day	47% 15% 14% 14% 9%	1207
	21st to end	Day	43% 20% 16% 12% 10%	1050
December	1st to 10th	Day	41% 17% 18% 15% 9% 1	1520
	11th to 20th	Day	41% 20% 15% 14% 9% 1	1560
	21st to end	Day	36% 15% 15% 14% 15% 6%	2046
January	1st to 10th	Night	36% 13% 14% 12% 14% 12%	10564
	11th to 20th	Night	31% 15% 17% 16% 18% 3	10022
	21st to end	Night	29% 16% 16% 18% 15% 6%	10342
February	1st to 10th	Night	33% 14% 14% 17% 14% 7%	3218
	11th to 20th	Night	40% 17% 17% 13% 10% 3	2872
	21st to end	Night	39% 16% 16% 14% 12% 3	2364
March	1st to 10th	Night	38% 14% 12% 17% 15% 4	5500
	11th to 20th	Night	37% 16% 15% 13% 16% 2	5448
	21st to end	Night	36% 20% 17% 14% 12% 2	5079
April	1st to 10th	Night	45% 15% 19% 15% 7%	2002
	11th to 20th	Night	40% 16% 16% 17% 10%	1705
	21st to end	Night	43% 14% 18% 14% 10% 1	1565
May	1st to 10th	Night	48% 18% 12% 12% 9% 1	3770
	11th to 20th	Night	55% 12% 10% 15% 7%	3254
	21st to end	Night	50% 15% 13% 17% 5%	3029
June	1st to 10th	Night	55% 18% 14% 11% 2	840
	11th to 20th	Night	53% 17% 18% 11% 1	840
	21st to end	Night	61% 19% 11% 8% 1	840
July	1st to 10th	Night	65% 14% 15% 5%	2350
	11th to 20th	Night	56% 17% 15% 11% 1	2437
	21st to end	Night	65% 13% 15% 7%	3652
August	1st to 10th	Night	51% 16% 24% 8% 1	2768
	11th to 20th	Night	50% 14% 21% 12% 3	3491
	21st to end	Night	61% 14% 15% 10%	4109
September	1st to 10th	Night	58% 20% 13% 8% 2	1966
	11th to 20th	Night	56% 17% 14% 10% 3	2153
	21st to end	Night	58% 15% 14% 11% 2	2315
October	1st to 10th	Night	57% 14% 11% 13% 4	4176
	11th to 20th	Night	42% 13% 14% 22% 9%	4263
	21st to end	Night	47% 15% 14% 19% 5% 1	5089
November	1st to 10th	Night	51% 18% 14% 10% 6% 1	3077
	11th to 20th	Night	47% 14% 16% 15% 8%	3413
	21st to end	Night	42% 19% 17% 12% 9% 1	3570
December	1st to 10th	Night	42% 17% 17% 17% 7% 1	5883
	11th to 20th	Night	44% 18% 16% 12% 9% 1	6876
	21st to end	Night	39% 16% 13% 14% 13% 5%	9174

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	1 2 21% 36% 27% 13%	110
	11th to 20th	Day	4 4 16% 47% 18% 11%	194
	21st to end	Day	2 3 22% 37% 24% 13%	352
February	1st to 10th	Day	3 3 18% 35% 29% 13%	348
	11th to 20th	Day	2 3 27% 38% 21% 9%	425
	21st to end	Day	2 4 30% 37% 17% 11%	355
March	1st to 10th	Day	2 4 23% 34% 27% 10%	430
	11th to 20th	Day	1 4 24% 33% 26% 12%	430
	21st to end	Day	1 5% 25% 30% 26% 13%	694
April	1st to 10th	Day	3 7% 26% 30% 25% 9%	693
	11th to 20th	Day	3 6% 19% 34% 28% 11%	740
	21st to end	Day	5% 6% 18% 28% 30% 12%	750
May	1st to 10th	Day	10% 8% 26% 26% 22% 8%	753
	11th to 20th	Day	10% 8% 21% 28% 24% 10%	775
	21st to end	Day	14% 8% 22% 29% 20% 7%	908
June	1st to 10th	Day	19% 8% 20% 28% 19% 6%	990
	11th to 20th	Day	24% 7% 19% 25% 18% 8%	990
	21st to end	Day	24% 7% 16% 24% 21% 8%	990
July	1st to 10th	Day	22% 7% 19% 26% 19% 6%	976
	11th to 20th	Day	21% 10% 19% 24% 20% 6%	941
	21st to end	Day	23% 7% 22% 21% 17% 8%	849
August	1st to 10th	Day	20% 12% 22% 20% 17% 9%	776
	11th to 20th	Day	24% 13% 23% 21% 14% 5%	765
	21st to end	Day	24% 12% 21% 24% 15% 4	858
September	1st to 10th	Day	21% 14% 25% 20% 15% 5%	735
	11th to 20th	Day	20% 10% 22% 28% 15% 5%	607
	21st to end	Day	17% 11% 19% 23% 19% 11%	450
October	1st to 10th	Day	15% 10% 25% 22% 17% 11%	450
	11th to 20th	Day	10% 5% 18% 27% 29% 11%	430
	21st to end	Day	9% 5% 20% 30% 24% 13%	462
November	1st to 10th	Day	8% 3 20% 32% 28% 11%	425
	11th to 20th	Day	4 2 16% 38% 26% 14%	247
	21st to end	Day	5% 1 23% 30% 26% 15%	110
December	1st to 10th	Day	7% 3 22% 33% 25% 11%	110
	11th to 20th	Day	2 3 20% 45% 25% 6%	110
	21st to end	Day	2 2 24% 40% 21% 9%	121
January	1st to 10th	Night	3 2 19% 38% 29% 10%	1060
	11th to 20th	Night	3 2 21% 47% 21% 7%	995
	21st to end	Night	4 2 22% 42% 23% 8%	1045
February	1st to 10th	Night	2 2 19% 41% 27% 8%	950
	11th to 20th	Night	2 1 26% 45% 22% 3	934
	21st to end	Night	3 3 26% 40% 21% 7%	746
March	1st to 10th	Night	1 2 21% 41% 28% 7%	740
	11th to 20th	Night	2 1 18% 38% 30% 11%	715
	21st to end	Night	1 2 18% 32% 33% 14%	693
April	1st to 10th	Night	2 3 20% 35% 30% 9%	630
	11th to 20th	Night	3 3 20% 32% 33% 9%	623
	21st to end	Night	6% 3 16% 32% 36% 7%	630
May	1st to 10th	Night	11% 4 22% 31% 27% 6%	509
	11th to 20th	Night	13% 4 18% 32% 26% 6%	327
	21st to end	Night	7% 4 23% 32% 35%	228
June	1st to 10th	Night	19% 4 14% 33% 29% 1	210
	11th to 20th	Night	19% 3 12% 31% 32% 3	210
	21st to end	Night	20% 6% 18% 28% 25% 3	210
July	1st to 10th	Night	21% 4 16% 26% 29% 4	205
	11th to 20th	Night	20% 6% 16% 28% 27% 2	204
	21st to end	Night	22% 5% 14% 28% 25% 6%	419
August	1st to 10th	Night	18% 5% 22% 26% 25% 5%	418
	11th to 20th	Night	21% 9% 19% 29% 18% 4	616
	21st to end	Night	24% 6% 18% 28% 20% 4	693
September	1st to 10th	Night	23% 6% 18% 33% 17% 3	630
	11th to 20th	Night	18% 8% 18% 33% 18% 4	630
	21st to end	Night	20% 6% 17% 26% 22% 9%	633
October	1st to 10th	Night	17% 6% 21% 29% 19% 6%	834
	11th to 20th	Night	10% 4 16% 33% 29% 8%	925
	21st to end	Night	9% 4 17% 34% 28% 8%	1001
November	1st to 10th	Night	7% 5% 17% 39% 25% 7%	930
	11th to 20th	Night	5% 3 19% 40% 25% 9%	950
	21st to end	Night	3 3 22% 37% 25% 9%	950
December	1st to 10th	Night	5% 5% 21% 36% 24% 10%	1002
	11th to 20th	Night	3 3 21% 42% 23% 9%	1060
	21st to end	Night	3 4 23% 37% 23% 10%	1166

Page generated at 2026-10-11 01:06:31. Version ac07

Copyright © 2026 Attilla Danko.