Whitefish
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Whitefish 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	16% 11% 4 8% 5% 4 4 3 5% 6% 35%	108621
	Night	15% 12% 4 9% 5% 4 4 3 5% 6% 33%	110801
Transparency	Day	29% 43% 6% 14% 7% 1	112166
	Night	32% 41% 7% 13% 7% 1	115420
Seeing	Day	23% 14% 32% 21% 8% 3	15712
	Night	22% 11% 29% 27% 10% 1	25127

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	13% 17% 7% 11% 4 3 4 2 4 5% 30%	3158
	11th to 20th	Day	10% 15% 7% 16% 7% 6% 6% 4 5% 5% 20%	3517
	21st to end	Day	12% 21% 8% 13% 6% 4 4 4 4 5% 19%	4221
February	1st to 10th	Day	11% 17% 5% 11% 7% 6% 4 4 4 6% 26%	1800
	11th to 20th	Day	12% 15% 4 11% 6% 4 4 4 4 6% 29%	1753
	21st to end	Day	13% 17% 6% 12% 7% 5% 5% 3 4 5% 25%	1612
March	1st to 10th	Day	17% 15% 3 7% 4 3 5% 4 5% 6% 32%	3373
	11th to 20th	Day	11% 14% 5% 10% 5% 5% 4 3 5% 7% 31%	3590
	21st to end	Day	13% 14% 6% 8% 4 4 3 3 4 5% 35%	3881
April	1st to 10th	Day	18% 13% 4 8% 4 4 4 4 5% 6% 30%	2237
	11th to 20th	Day	20% 11% 3 5% 4 4 4 3 5% 6% 35%	2442
	21st to end	Day	22% 9% 2 6% 4 3 3 2 5% 6% 37%	2470
May	1st to 10th	Day	17% 7% 2 7% 4 4 4 4 5% 6% 38%	4108
	11th to 20th	Day	13% 8% 3 7% 4 4 4 4 5% 7% 42%	4302
	21st to end	Day	17% 6% 2 5% 3 4 4 3 5% 7% 44%	5018
June	1st to 10th	Day	16% 7% 2 7% 5% 4 4 4 5% 8% 38%	2850
	11th to 20th	Day	13% 7% 2 6% 5% 4 4 4 6% 8% 41%	2850
	21st to end	Day	17% 6% 2 6% 5% 4 5% 4 6% 7% 38%	2850
July	1st to 10th	Day	17% 8% 3 6% 4 4 4 3 6% 8% 36%	4760
	11th to 20th	Day	11% 5% 2 5% 5% 5% 5% 4 5% 7% 46%	4746
	21st to end	Day	11% 5% 2 5% 4 3 4 3 5% 8% 50%	4668
August	1st to 10th	Day	11% 6% 2 6% 5% 5% 5% 4 6% 9% 41%	4104
	11th to 20th	Day	17% 6% 2 5% 4 4 4 3 6% 8% 42%	4044
	21st to end	Day	13% 5% 2 6% 4 4 5% 3 5% 7% 47%	4532
September	1st to 10th	Day	13% 7% 3 7% 5% 4 5% 3 5% 8% 41%	2265
	11th to 20th	Day	14% 5% 1 4 4 5% 4 4 5% 8% 45%	2090
	21st to end	Day	21% 7% 3 7% 4 3 4 3 4 6% 38%	2090
October	1st to 10th	Day	19% 7% 3 6% 4 4 4 3 5% 7% 38%	1943
	11th to 20th	Day	25% 9% 2 7% 6% 5% 5% 4 5% 7% 26%	1900
	21st to end	Day	27% 12% 3 8% 3 4 3 3 6% 6% 25%	1948
November	1st to 10th	Day	19% 13% 2 7% 5% 5% 4 4 6% 7% 30%	1698
	11th to 20th	Day	17% 16% 5% 9% 5% 5% 4 3 5% 5% 26%	1600
	21st to end	Day	22% 20% 4 9% 5% 5% 4 3 4 5% 19%	1600
December	1st to 10th	Day	13% 21% 5% 9% 5% 5% 5% 4 6% 6% 20%	2504
	11th to 20th	Day	18% 17% 7% 12% 5% 3 4 3 4 4 22%	2621
	21st to end	Day	28% 19% 6% 9% 4 3 2 2 3 4 18%	3476
January	1st to 10th	Night	11% 14% 7% 12% 5% 4 5% 4 5% 7% 27%	6808
	11th to 20th	Night	12% 16% 5% 12% 5% 5% 5% 4 5% 5% 25%	6385
	21st to end	Night	11% 18% 7% 13% 5% 5% 4 4 5% 5% 21%	6743
February	1st to 10th	Night	12% 15% 5% 12% 6% 5% 5% 4 5% 5% 26%	2600
	11th to 20th	Night	11% 14% 4 11% 7% 5% 4 5% 6% 6% 28%	2533
	21st to end	Night	12% 17% 5% 9% 6% 5% 5% 4 5% 6% 26%	2015
March	1st to 10th	Night	16% 10% 4 8% 5% 4 3 3 5% 6% 37%	3686
	11th to 20th	Night	10% 11% 5% 9% 5% 5% 4 4 5% 6% 36%	3589
	21st to end	Night	14% 9% 6% 8% 5% 4 4 3 4 6% 37%	3890
April	1st to 10th	Night	19% 10% 3 7% 4 5% 4 4 5% 6% 33%	1957
	11th to 20th	Night	19% 9% 3 6% 4 3 4 3 5% 6% 39%	1687
	21st to end	Night	20% 9% 3 10% 4 5% 4 4 3 5% 34%	1710
May	1st to 10th	Night	16% 8% 2 8% 6% 5% 4 4 4 6% 37%	2833
	11th to 20th	Night	9% 8% 3 6% 5% 5% 5% 4 6% 8% 39%	2575
	21st to end	Night	13% 7% 3 7% 4 4 5% 3 4 7% 43%	2560
June	1st to 10th	Night	13% 6% 3 7% 4 5% 5% 5% 7% 7% 38%	1330
	11th to 20th	Night	11% 6% 2 6% 3 5% 6% 4 6% 8% 43%	1330
	21st to end	Night	14% 5% 2 7% 5% 5% 4 4 6% 7% 42%	1330
July	1st to 10th	Night	14% 7% 2 5% 4 4 3 3 6% 8% 44%	2210
	11th to 20th	Night	12% 5% 1 5% 4 3 4 4 5% 7% 50%	2210
	21st to end	Night	10% 4 2 5% 4 4 3 3 5% 7% 52%	2886
August	1st to 10th	Night	10% 6% 2 6% 3 5% 5% 4 6% 8% 44%	2825
	11th to 20th	Night	14% 5% 2 6% 4 3 4 3 5% 8% 46%	2785
	21st to end	Night	11% 4 2 5% 3 4 4 3 4 7% 51%	3124
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 7% 46%	1894
	11th to 20th	Night	13% 4 1 4 3 3 4 3 5% 8% 53%	2090
	21st to end	Night	17% 8% 3 7% 4 4 3 3 5% 7% 40%	2090
October	1st to 10th	Night	20% 8% 2 6% 3 4 3 3 5% 7% 39%	2237
	11th to 20th	Night	24% 9% 3 6% 5% 4 4 3 4 6% 32%	2280
	21st to end	Night	26% 10% 3 8% 4 5% 4 3 5% 5% 28%	2648
November	1st to 10th	Night	19% 11% 3 6% 4 3 4 4 5% 7% 33%	2598
	11th to 20th	Night	18% 14% 4 9% 5% 5% 5% 3 5% 7% 26%	2800
	21st to end	Night	20% 17% 5% 8% 5% 5% 4 3 5% 5% 23%	2800
December	1st to 10th	Night	16% 19% 4 9% 5% 5% 5% 4 5% 5% 23%	4675
	11th to 20th	Night	17% 15% 5% 12% 5% 4 4 3 4 5% 25%	5586
	21st to end	Night	25% 21% 6% 10% 4 3 3 2 3 4 18%	7502

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	43% 26% 7% 16% 6% 2	3159
	11th to 20th	Day	52% 26% 7% 9% 6% 1	3548
	21st to end	Day	52% 28% 4 8% 7%	4221
February	1st to 10th	Day	24% 62% 4 8% 3	1800
	11th to 20th	Day	23% 61% 3 8% 5%	1762
	21st to end	Day	24% 62% 2 8% 4	1612
March	1st to 10th	Day	36% 38% 8% 8% 8% 1	3376
	11th to 20th	Day	37% 37% 7% 13% 6% 1	3590
	21st to end	Day	35% 38% 7% 9% 8% 3	3881
April	1st to 10th	Day	19% 64% 3 8% 5%	2237
	11th to 20th	Day	19% 64% 2 9% 5% 1	2442
	21st to end	Day	18% 64% 4 9% 5% 1	2470
May	1st to 10th	Day	30% 39% 4 18% 9% 1	4120
	11th to 20th	Day	26% 38% 6% 21% 8% 1	4306
	21st to end	Day	28% 38% 7% 10% 13% 3	5018
June	1st to 10th	Day	15% 65% 3 10% 6% 1	2850
	11th to 20th	Day	15% 65% 3 9% 7% 1	2850
	21st to end	Day	17% 63% 3 9% 7% 1	2850
July	1st to 10th	Day	33% 37% 9% 14% 7% 1	4686
	11th to 20th	Day	22% 37% 9% 25% 6% 1	4665
	21st to end	Day	19% 36% 5% 24% 15%	4520
August	1st to 10th	Day	22% 39% 7% 22% 8% 1	4091
	11th to 20th	Day	27% 38% 10% 17% 8%	4083
	21st to end	Day	23% 38% 9% 22% 8%	4531
September	1st to 10th	Day	17% 61% 6% 11% 5%	2265
	11th to 20th	Day	12% 60% 6% 15% 8%	2090
	21st to end	Day	17% 59% 8% 11% 4 1	2090
October	1st to 10th	Day	23% 36% 5% 22% 14%	3229
	11th to 20th	Day	25% 38% 10% 22% 5%	3140
	21st to end	Day	38% 37% 8% 11% 5%	3185
November	1st to 10th	Day	28% 55% 5% 9% 3	1698
	11th to 20th	Day	27% 57% 5% 7% 3	1600
	21st to end	Day	28% 56% 5% 6% 4	1600
December	1st to 10th	Day	42% 38% 12% 7% 2	2504
	11th to 20th	Day	48% 31% 4 9% 7% 1	2621
	21st to end	Day	56% 26% 2 9% 6%	3476
January	1st to 10th	Night	42% 27% 8% 15% 7% 1	6808
	11th to 20th	Night	46% 25% 11% 11% 7%	6429
	21st to end	Night	49% 29% 5% 9% 7% 1	6743
February	1st to 10th	Night	22% 62% 3 9% 4	2600
	11th to 20th	Night	22% 60% 4 10% 5%	2535
	21st to end	Night	23% 62% 2 7% 5%	2015
March	1st to 10th	Night	32% 39% 6% 13% 9% 1	3696
	11th to 20th	Night	32% 38% 8% 15% 6% 1	3590
	21st to end	Night	33% 38% 3 14% 10% 2	3890
April	1st to 10th	Night	20% 64% 2 7% 6%	1957
	11th to 20th	Night	17% 64% 2 8% 7% 1	1687
	21st to end	Night	20% 64% 3 7% 5% 1	1710
May	1st to 10th	Night	33% 39% 3 17% 7%	2840
	11th to 20th	Night	27% 38% 6% 18% 11%	2576
	21st to end	Night	30% 38% 5% 16% 7% 4	2561
June	1st to 10th	Night	14% 64% 2 11% 6% 2	1330
	11th to 20th	Night	14% 64% 4 8% 8% 1	1330
	21st to end	Night	14% 63% 4 11% 8% 1	1330
July	1st to 10th	Night	29% 38% 8% 15% 9% 2	2175
	11th to 20th	Night	22% 36% 9% 27% 6%	2168
	21st to end	Night	18% 35% 7% 22% 17%	2795
August	1st to 10th	Night	24% 37% 8% 21% 9%	2814
	11th to 20th	Night	25% 38% 13% 17% 6%	2812
	21st to end	Night	20% 38% 8% 25% 10%	3124
September	1st to 10th	Night	16% 60% 6% 13% 5%	1894
	11th to 20th	Night	11% 59% 6% 17% 7%	2090
	21st to end	Night	17% 60% 6% 10% 6%	2090
October	1st to 10th	Night	24% 36% 6% 22% 12%	3731
	11th to 20th	Night	23% 37% 9% 24% 6%	3779
	21st to end	Night	31% 38% 14% 12% 4	4361
November	1st to 10th	Night	25% 55% 6% 9% 4	2598
	11th to 20th	Night	25% 56% 6% 8% 4	2800
	21st to end	Night	29% 57% 4 6% 4	2800
December	1st to 10th	Night	42% 37% 10% 9% 3	4675
	11th to 20th	Night	44% 32% 5% 8% 10% 1	5585
	21st to end	Night	55% 25% 5% 9% 6%	7502

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	22% 15% 34% 23% 8%	200
	11th to 20th	Day	22% 16% 36% 20% 6% 1	285
	21st to end	Day	27% 11% 32% 22% 7% 1	330
February	1st to 10th	Day	27% 21% 35% 12% 4	300
	11th to 20th	Day	23% 22% 40% 12% 2	300
	21st to end	Day	32% 24% 33% 10% 1	249
March	1st to 10th	Day	26% 20% 32% 17% 4	391
	11th to 20th	Day	26% 13% 34% 19% 6% 1	500
	21st to end	Day	28% 16% 31% 19% 5% 1	530
April	1st to 10th	Day	27% 15% 29% 21% 8% 1	460
	11th to 20th	Day	33% 18% 22% 17% 9% 2	452
	21st to end	Day	32% 14% 29% 15% 8% 2	460
May	1st to 10th	Day	21% 13% 35% 21% 6% 3	463
	11th to 20th	Day	22% 15% 29% 22% 8% 4	487
	21st to end	Day	19% 12% 34% 24% 8% 2	632
June	1st to 10th	Day	18% 16% 38% 21% 6% 1	680
	11th to 20th	Day	19% 15% 36% 21% 8% 2	680
	21st to end	Day	23% 15% 31% 22% 7% 2	680
July	1st to 10th	Day	13% 14% 35% 27% 9% 2	671
	11th to 20th	Day	13% 12% 34% 29% 9% 4	668
	21st to end	Day	13% 7% 38% 27% 10% 5%	656
August	1st to 10th	Day	17% 8% 27% 28% 15% 5%	486
	11th to 20th	Day	16% 6% 27% 27% 15% 9%	479
	21st to end	Day	17% 10% 31% 23% 14% 6%	539
September	1st to 10th	Day	16% 10% 28% 28% 12% 6%	490
	11th to 20th	Day	17% 7% 26% 30% 13% 7%	490
	21st to end	Day	26% 11% 23% 24% 11% 4	490
October	1st to 10th	Day	27% 11% 28% 21% 11% 2	490
	11th to 20th	Day	31% 13% 33% 17% 5% 1	490
	21st to end	Day	35% 16% 32% 15% 2 1	397
November	1st to 10th	Day	32% 15% 36% 12% 4 1	267
	11th to 20th	Day	26% 19% 33% 20% 3	200
	21st to end	Day	30% 21% 28% 16% 6% 1	200
December	1st to 10th	Day	27% 11% 35% 20% 6% 2	200
	11th to 20th	Day	31% 17% 37% 13% 3	200
	21st to end	Day	37% 17% 28% 12% 5% 1	220
January	1st to 10th	Night	23% 13% 31% 26% 7% 1	1000
	11th to 20th	Night	26% 15% 25% 26% 7% 1	1000
	21st to end	Night	21% 10% 30% 28% 10% 1	990
February	1st to 10th	Night	19% 16% 35% 25% 5%	800
	11th to 20th	Night	21% 14% 34% 24% 6% 1	783
	21st to end	Night	22% 16% 33% 23% 6%	660
March	1st to 10th	Night	19% 16% 35% 25% 5%	800
	11th to 20th	Night	20% 13% 36% 24% 7% 1	800
	21st to end	Night	22% 12% 32% 26% 7% 1	863
April	1st to 10th	Night	24% 12% 31% 26% 6% 1	708
	11th to 20th	Night	26% 12% 26% 25% 10% 1	563
	21st to end	Night	24% 12% 26% 27% 11%	570
May	1st to 10th	Night	16% 8% 30% 34% 11% 1	570
	11th to 20th	Night	16% 8% 29% 35% 12%	428
	21st to end	Night	15% 8% 32% 32% 13%	411
June	1st to 10th	Night	17% 7% 34% 34% 8%	380
	11th to 20th	Night	15% 6% 30% 37% 11%	380
	21st to end	Night	18% 5% 28% 34% 14% 1	380
July	1st to 10th	Night	11% 5% 28% 43% 12% 1	370
	11th to 20th	Night	10% 4 26% 45% 15%	368
	21st to end	Night	12% 5% 25% 36% 20% 2	621
August	1st to 10th	Night	14% 3 22% 39% 20% 1	567
	11th to 20th	Night	14% 2 20% 37% 24% 3	564
	21st to end	Night	16% 5% 23% 31% 22% 2	627
September	1st to 10th	Night	16% 8% 25% 32% 17% 2	712
	11th to 20th	Night	15% 8% 25% 29% 19% 4	760
	21st to end	Night	21% 7% 24% 28% 18% 2	760
October	1st to 10th	Night	24% 8% 26% 30% 10% 2	760
	11th to 20th	Night	30% 10% 27% 23% 9% 1	760
	21st to end	Night	31% 12% 28% 23% 5% 1	836
November	1st to 10th	Night	27% 11% 28% 25% 8%	780
	11th to 20th	Night	28% 14% 26% 24% 8%	800
	21st to end	Night	32% 13% 29% 21% 5% 1	800
December	1st to 10th	Night	28% 14% 30% 21% 7%	856
	11th to 20th	Night	28% 15% 31% 20% 6% 1	1000
	21st to end	Night	33% 13% 26% 20% 7%	1100

Page generated at 2025-03-24 09:04:25. Version ac07

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