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 2024-03-08.

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	11% 11% 5% 10% 9% 5% 7% 7% 7% 7% 22%	76741
	Night	5% 9% 5% 11% 10% 6% 8% 7% 7% 8% 23%	82818
Transparency	Day	51% 16% 15% 11% 5% 1	76389
	Night	44% 17% 15% 12% 9% 3	82752
Seeing	Day	14% 7% 22% 27% 21% 9%	16638
	Night	8% 3 19% 36% 26% 8%	21633

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	1 6% 4 9% 11% 8% 11% 12% 11% 9% 18%	1269
	11th to 20th	Day	2 7% 4 9% 12% 8% 11% 9% 6% 6% 27%	1563
	21st to end	Day	1 5% 4 11% 12% 7% 10% 12% 10% 8% 20%	2090
February	1st to 10th	Day	1 7% 4 10% 11% 6% 9% 7% 8% 9% 29%	1265
	11th to 20th	Day	1 8% 5% 13% 10% 6% 9% 9% 9% 8% 22%	1479
	21st to end	Day	1 7% 5% 12% 12% 7% 8% 7% 5% 8% 29%	1306
March	1st to 10th	Day	1 7% 5% 13% 13% 4 7% 8% 6% 7% 30%	1873
	11th to 20th	Day	1 6% 4 12% 13% 7% 10% 6% 6% 7% 29%	1840
	21st to end	Day	1 6% 5% 15% 12% 5% 6% 7% 7% 7% 29%	2366
April	1st to 10th	Day	2 10% 7% 10% 10% 5% 8% 6% 9% 10% 24%	2243
	11th to 20th	Day	2 10% 7% 10% 9% 4 6% 6% 7% 9% 30%	2449
	21st to end	Day	3 11% 5% 10% 8% 4 6% 6% 8% 8% 32%	2618
May	1st to 10th	Day	5% 15% 5% 10% 9% 5% 7% 8% 7% 8% 23%	2803
	11th to 20th	Day	9% 12% 4 8% 7% 5% 7% 6% 7% 7% 30%	2907
	21st to end	Day	9% 12% 4 8% 8% 4 8% 7% 7% 7% 26%	3359
June	1st to 10th	Day	18% 11% 5% 9% 9% 5% 6% 6% 6% 6% 18%	3240
	11th to 20th	Day	25% 12% 4 9% 8% 4 6% 5% 5% 5% 16%	3240
	21st to end	Day	26% 11% 4 9% 8% 4 6% 6% 5% 6% 16%	3240
July	1st to 10th	Day	23% 9% 4 8% 8% 5% 7% 7% 5% 7% 19%	3240
	11th to 20th	Day	20% 10% 5% 10% 9% 5% 7% 6% 7% 6% 15%	3214
	21st to end	Day	22% 11% 5% 8% 8% 4 6% 6% 6% 7% 16%	3170
August	1st to 10th	Day	22% 12% 4 8% 8% 5% 6% 6% 6% 7% 17%	2865
	11th to 20th	Day	24% 11% 4 10% 8% 4 6% 6% 7% 6% 14%	2556
	21st to end	Day	22% 14% 6% 10% 7% 4 6% 6% 5% 6% 14%	2751
September	1st to 10th	Day	19% 13% 4 10% 8% 4 6% 5% 6% 6% 18%	2273
	11th to 20th	Day	12% 13% 5% 10% 9% 5% 5% 5% 6% 7% 22%	2116
	21st to end	Day	12% 17% 6% 10% 7% 4 6% 6% 5% 6% 21%	1976
October	1st to 10th	Day	11% 17% 5% 11% 8% 3 6% 5% 5% 6% 22%	1728
	11th to 20th	Day	5% 15% 7% 13% 11% 4 6% 6% 5% 6% 22%	1620
	21st to end	Day	4 14% 6% 14% 10% 4 5% 5% 6% 7% 25%	1514
November	1st to 10th	Day	2 14% 7% 15% 16% 7% 7% 5% 5% 5% 17%	1301
	11th to 20th	Day	2 11% 4 14% 11% 7% 11% 7% 5% 8% 20%	1093
	21st to end	Day	1 7% 7% 15% 13% 9% 9% 7% 6% 7% 21%	950
December	1st to 10th	Day	2 10% 6% 12% 12% 5% 7% 9% 9% 10% 18%	860
	11th to 20th	Day	1 8% 7% 13% 12% 6% 9% 11% 9% 8% 16%	967
	21st to end	Day	1 4 4 8% 11% 5% 9% 11% 10% 15% 21%	1397
January	1st to 10th	Night	1 9% 4 10% 12% 9% 11% 9% 8% 8% 19%	5686
	11th to 20th	Night	2 6% 5% 10% 10% 6% 10% 9% 7% 8% 28%	5341
	21st to end	Night	1 6% 4 10% 10% 6% 8% 10% 11% 10% 22%	5577
February	1st to 10th	Night	2 7% 5% 10% 9% 5% 8% 8% 7% 8% 32%	2913
	11th to 20th	Night	1 6% 6% 12% 12% 8% 8% 7% 7% 8% 25%	2588
	21st to end	Night	2 7% 4 12% 11% 6% 7% 7% 6% 8% 30%	2146
March	1st to 10th	Night	1 6% 5% 9% 9% 7% 8% 9% 8% 8% 32%	2247
	11th to 20th	Night	1 5% 4 9% 10% 5% 8% 6% 8% 9% 35%	2118
	21st to end	Night	1 6% 7% 12% 12% 5% 6% 6% 7% 8% 31%	1987
April	1st to 10th	Night	2 9% 7% 13% 9% 5% 8% 7% 7% 8% 26%	1717
	11th to 20th	Night	2 8% 7% 9% 8% 5% 7% 8% 7% 8% 31%	1459
	21st to end	Night	4 10% 4 9% 8% 4 6% 7% 6% 8% 33%	1342
May	1st to 10th	Night	5% 13% 5% 11% 11% 6% 7% 8% 6% 6% 22%	1157
	11th to 20th	Night	12% 14% 3 6% 7% 5% 5% 6% 7% 8% 28%	988
	21st to end	Night	9% 11% 4 8% 7% 4 5% 6% 8% 8% 32%	915
June	1st to 10th	Night	19% 9% 6% 8% 6% 3 7% 7% 7% 7% 22%	720
	11th to 20th	Night	23% 8% 5% 8% 6% 3 5% 5% 6% 7% 23%	720
	21st to end	Night	20% 11% 5% 8% 8% 5% 7% 4 7% 7% 19%	720
July	1st to 10th	Night	22% 9% 4 6% 6% 4 6% 6% 6% 8% 23%	720
	11th to 20th	Night	20% 8% 4 8% 8% 5% 8% 5% 5% 7% 24%	746
	21st to end	Night	22% 8% 4 9% 8% 5% 5% 5% 5% 7% 22%	1147
August	1st to 10th	Night	18% 11% 4 9% 9% 5% 5% 7% 5% 6% 21%	1074
	11th to 20th	Night	18% 13% 4 10% 9% 5% 6% 6% 6% 6% 17%	1340
	21st to end	Night	20% 15% 4 7% 7% 5% 6% 5% 7% 6% 17%	1605
September	1st to 10th	Night	20% 15% 4 8% 6% 4 6% 6% 7% 6% 19%	1684
	11th to 20th	Night	13% 15% 5% 8% 7% 4 5% 6% 7% 6% 23%	1844
	21st to end	Night	13% 20% 5% 8% 7% 4 6% 6% 5% 6% 19%	1984
October	1st to 10th	Night	13% 19% 6% 10% 8% 5% 6% 6% 5% 5% 18%	2232
	11th to 20th	Night	5% 18% 7% 14% 9% 5% 4 5% 5% 6% 23%	2340
	21st to end	Night	5% 14% 8% 13% 9% 5% 5% 5% 7% 6% 23%	2839
November	1st to 10th	Night	3 13% 8% 15% 12% 7% 7% 6% 5% 5% 20%	2777
	11th to 20th	Night	2 10% 6% 15% 13% 7% 9% 6% 5% 7% 21%	3087
	21st to end	Night	2 8% 6% 14% 13% 7% 8% 8% 6% 7% 21%	3230
December	1st to 10th	Night	3 10% 6% 13% 11% 6% 8% 8% 8% 8% 20%	3318
	11th to 20th	Night	1 7% 6% 15% 14% 8% 9% 7% 7% 7% 18%	4240
	21st to end	Night	1 5% 5% 12% 10% 6% 9% 10% 9% 12% 20%	6270

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	30% 17% 22% 19% 9% 3	1269
	11th to 20th	Day	33% 17% 14% 19% 14% 2	1580
	21st to end	Day	32% 16% 16% 12% 16% 8%	2090
February	1st to 10th	Day	36% 14% 16% 14% 13% 8%	1265
	11th to 20th	Day	40% 19% 18% 13% 8% 3	1486
	21st to end	Day	40% 15% 14% 15% 13% 3	1306
March	1st to 10th	Day	43% 13% 16% 14% 12% 2	1873
	11th to 20th	Day	45% 12% 12% 15% 14% 2	1840
	21st to end	Day	47% 15% 15% 10% 8% 4	2366
April	1st to 10th	Day	49% 16% 15% 14% 5% 1	2243
	11th to 20th	Day	46% 14% 15% 16% 9%	2449
	21st to end	Day	46% 13% 16% 15% 8% 1	2618
May	1st to 10th	Day	52% 16% 16% 13% 3	2803
	11th to 20th	Day	45% 14% 16% 17% 7%	2910
	21st to end	Day	46% 18% 17% 14% 4	3360
June	1st to 10th	Day	58% 17% 15% 9% 1	3240
	11th to 20th	Day	62% 13% 13% 10% 2	3240
	21st to end	Day	62% 17% 15% 6%	3240
July	1st to 10th	Day	58% 16% 16% 9% 1 1	3151
	11th to 20th	Day	63% 18% 15% 3	3115
	21st to end	Day	58% 20% 17% 5%	2994
August	1st to 10th	Day	59% 19% 15% 6% 1	2846
	11th to 20th	Day	66% 16% 11% 6% 1	2556
	21st to end	Day	69% 15% 10% 6% 1	2751
September	1st to 10th	Day	61% 16% 12% 8% 2	2273
	11th to 20th	Day	55% 19% 13% 11% 1	2116
	21st to end	Day	58% 17% 11% 10% 4	1976
October	1st to 10th	Day	57% 15% 13% 10% 5%	1728
	11th to 20th	Day	52% 20% 15% 9% 4	1620
	21st to end	Day	46% 20% 15% 12% 5% 2	1514
November	1st to 10th	Day	52% 17% 14% 10% 6% 1	1301
	11th to 20th	Day	48% 16% 14% 14% 8%	1093
	21st to end	Day	43% 20% 16% 12% 9%	950
December	1st to 10th	Day	45% 20% 19% 10% 7%	860
	11th to 20th	Day	41% 20% 14% 14% 11% 1	970
	21st to end	Day	29% 15% 18% 14% 14% 9%	1397
January	1st to 10th	Night	38% 15% 20% 15% 8% 4	5686
	11th to 20th	Night	34% 16% 17% 15% 14% 4	5387
	21st to end	Night	29% 18% 13% 14% 17% 9%	5577
February	1st to 10th	Night	35% 13% 14% 16% 14% 8%	2913
	11th to 20th	Night	40% 17% 18% 13% 9% 3	2592
	21st to end	Night	39% 16% 17% 14% 11% 3	2146
March	1st to 10th	Night	36% 15% 16% 16% 15% 2	2247
	11th to 20th	Night	36% 15% 13% 16% 17% 3	2120
	21st to end	Night	41% 17% 15% 14% 9% 4	1987
April	1st to 10th	Night	47% 14% 18% 15% 6%	1717
	11th to 20th	Night	41% 16% 17% 17% 9%	1459
	21st to end	Night	44% 15% 17% 13% 10% 1	1342
May	1st to 10th	Night	55% 15% 13% 15% 3 1	1157
	11th to 20th	Night	49% 14% 15% 16% 6%	988
	21st to end	Night	43% 20% 18% 15% 3	915
June	1st to 10th	Night	56% 19% 13% 11% 1	720
	11th to 20th	Night	56% 17% 17% 10% 1	720
	21st to end	Night	62% 19% 11% 7% 1	720
July	1st to 10th	Night	57% 15% 17% 10% 1	700
	11th to 20th	Night	62% 18% 16% 4	722
	21st to end	Night	58% 19% 18% 5%	1083
August	1st to 10th	Night	56% 21% 17% 5% 1	1068
	11th to 20th	Night	62% 19% 14% 6%	1340
	21st to end	Night	63% 19% 13% 5%	1605
September	1st to 10th	Night	58% 20% 13% 7% 1	1684
	11th to 20th	Night	55% 18% 14% 10% 3	1844
	21st to end	Night	59% 16% 13% 9% 2	1984
October	1st to 10th	Night	60% 16% 13% 6% 4	2232
	11th to 20th	Night	52% 18% 16% 9% 5%	2340
	21st to end	Night	51% 16% 14% 11% 7% 1	2839
November	1st to 10th	Night	50% 19% 14% 10% 6% 1	2777
	11th to 20th	Night	49% 15% 17% 14% 6%	3087
	21st to end	Night	43% 19% 17% 12% 9% 1	3230
December	1st to 10th	Night	45% 18% 17% 11% 8%	3318
	11th to 20th	Night	43% 18% 15% 12% 11% 1	4236
	21st to end	Night	34% 17% 14% 14% 14% 7%	6270

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 24% 34% 28% 12%	90
	11th to 20th	Day	4 4 15% 45% 19% 13%	166
	21st to end	Day	2 3 20% 38% 24% 13%	308
February	1st to 10th	Day	3 2 19% 35% 26% 14%	302
	11th to 20th	Day	3 2 26% 37% 21% 11%	365
	21st to end	Day	2 3 31% 37% 17% 10%	307
March	1st to 10th	Day	2 4 23% 34% 27% 10%	362
	11th to 20th	Day	2 4 24% 32% 25% 12%	340
	21st to end	Day	2 5% 25% 30% 25% 14%	562
April	1st to 10th	Day	3 6% 25% 29% 26% 11%	558
	11th to 20th	Day	3 5% 17% 32% 30% 13%	590
	21st to end	Day	6% 6% 18% 28% 31% 12%	600
May	1st to 10th	Day	10% 6% 25% 25% 24% 9%	603
	11th to 20th	Day	10% 8% 20% 30% 22% 9%	625
	21st to end	Day	14% 9% 23% 29% 19% 6%	734
June	1st to 10th	Day	20% 8% 20% 27% 19% 7%	810
	11th to 20th	Day	25% 7% 21% 24% 17% 7%	810
	21st to end	Day	25% 7% 18% 22% 20% 8%	810
July	1st to 10th	Day	21% 7% 18% 27% 19% 8%	796
	11th to 20th	Day	22% 9% 19% 22% 21% 6%	766
	21st to end	Day	24% 6% 22% 21% 18% 9%	684
August	1st to 10th	Day	23% 12% 23% 20% 15% 7%	626
	11th to 20th	Day	26% 13% 25% 19% 13% 4	615
	21st to end	Day	25% 12% 20% 23% 15% 4	693
September	1st to 10th	Day	23% 13% 25% 18% 15% 6%	597
	11th to 20th	Day	20% 8% 23% 27% 16% 6%	496
	21st to end	Day	19% 11% 21% 25% 18% 8%	360
October	1st to 10th	Day	18% 10% 25% 21% 17% 9%	360
	11th to 20th	Day	10% 5% 17% 26% 30% 12%	360
	21st to end	Day	9% 5% 20% 29% 25% 13%	396
November	1st to 10th	Day	8% 3 21% 29% 28% 11%	365
	11th to 20th	Day	5% 2 18% 38% 25% 13%	213
	21st to end	Day	4 1 24% 29% 27% 14%	90
December	1st to 10th	Day	7% 2 23% 32% 23% 12%	90
	11th to 20th	Day	2 2 19% 44% 24% 8%	90
	21st to end	Day	3 3 24% 41% 20% 8%	99
January	1st to 10th	Night	2 1 19% 37% 30% 10%	940
	11th to 20th	Night	3 2 19% 47% 22% 8%	887
	21st to end	Night	4 1 21% 43% 23% 8%	935
February	1st to 10th	Night	2 2 20% 40% 27% 9%	850
	11th to 20th	Night	2 1 26% 45% 22% 4	834
	21st to end	Night	3 3 25% 41% 21% 7%	670
March	1st to 10th	Night	1 2 21% 41% 27% 8%	649
	11th to 20th	Night	2 1 17% 39% 30% 11%	602
	21st to end	Night	1 2 19% 31% 34% 14%	594
April	1st to 10th	Night	3 3 17% 36% 31% 10%	540
	11th to 20th	Night	2 2 18% 31% 36% 11%	533
	21st to end	Night	7% 2 16% 31% 36% 7%	540
May	1st to 10th	Night	11% 2 21% 30% 30% 7%	437
	11th to 20th	Night	14% 4 19% 31% 26% 6%	280
	21st to end	Night	8% 3 22% 31% 36% 1	195
June	1st to 10th	Night	19% 4 13% 32% 30% 2	180
	11th to 20th	Night	21% 3 13% 29% 32% 3	180
	21st to end	Night	20% 6% 17% 27% 27% 4	180
July	1st to 10th	Night	21% 3 15% 24% 31% 5%	175
	11th to 20th	Night	21% 5% 15% 27% 30% 3	174
	21st to end	Night	21% 4 13% 28% 27% 7%	359
August	1st to 10th	Night	18% 5% 24% 28% 22% 4	358
	11th to 20th	Night	21% 9% 19% 29% 18% 4	526
	21st to end	Night	24% 6% 17% 28% 21% 5%	594
September	1st to 10th	Night	23% 5% 18% 32% 18% 4	540
	11th to 20th	Night	17% 8% 19% 32% 19% 5%	540
	21st to end	Night	20% 6% 18% 27% 20% 8%	542
October	1st to 10th	Night	20% 7% 21% 29% 19% 6%	702
	11th to 20th	Night	10% 4 15% 32% 30% 9%	810
	21st to end	Night	9% 3 16% 36% 27% 8%	891
November	1st to 10th	Night	7% 4 18% 38% 26% 7%	830
	11th to 20th	Night	5% 3 19% 40% 24% 9%	850
	21st to end	Night	4 3 24% 36% 25% 9%	850
December	1st to 10th	Night	5% 4 20% 35% 25% 11%	892
	11th to 20th	Night	3 2 20% 41% 24% 10%	940
	21st to end	Night	4 4 22% 36% 24% 11%	1034

Page generated at 2024-03-05 03:24:02. Version ac07

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