Skunk Bay
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Skunk Bay clear sky chart from 2005-11-06 to 2025-12-18.

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	14% 9% 3 8% 5% 5% 5% 4 6% 7% 33%	131416
	Night	17% 10% 3 8% 5% 5% 5% 4 5% 6% 31%	128287
Transparency	Day	32% 39% 11% 13% 5% 1	131129
	Night	35% 39% 9% 12% 4 1	128151
Seeing	Day	18% 10% 21% 26% 19% 5%	16586
	Night	21% 10% 19% 26% 20% 4	24932

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	21% 16% 6% 14% 7% 6% 5% 4 5% 5% 11%	3179
	11th to 20th	Day	13% 9% 5% 13% 8% 5% 5% 4 8% 9% 22%	3476
	21st to end	Day	18% 13% 4 10% 7% 6% 5% 4 5% 6% 21%	4124
February	1st to 10th	Day	18% 15% 4 8% 6% 6% 5% 6% 6% 8% 19%	1800
	11th to 20th	Day	16% 14% 4 10% 7% 5% 4 5% 6% 7% 21%	1755
	21st to end	Day	17% 14% 3 10% 7% 5% 6% 4 5% 6% 23%	1535
March	1st to 10th	Day	13% 12% 4 10% 7% 7% 7% 5% 7% 8% 19%	4649
	11th to 20th	Day	14% 14% 4 9% 6% 5% 5% 4 5% 6% 28%	5000
	21st to end	Day	15% 11% 5% 13% 9% 8% 7% 5% 6% 7% 16%	5651
April	1st to 10th	Day	18% 13% 3 9% 7% 6% 6% 4 6% 8% 21%	2400
	11th to 20th	Day	17% 11% 4 7% 6% 5% 5% 4 6% 7% 29%	2420
	21st to end	Day	17% 10% 3 7% 5% 6% 5% 5% 6% 8% 27%	2640
May	1st to 10th	Day	15% 8% 3 6% 4 4 4 4 5% 7% 41%	6320
	11th to 20th	Day	16% 10% 4 8% 5% 5% 5% 5% 6% 7% 30%	6277
	21st to end	Day	20% 8% 3 7% 5% 5% 5% 5% 6% 9% 28%	6903
June	1st to 10th	Day	18% 7% 2 7% 5% 5% 5% 4 6% 7% 32%	2909
	11th to 20th	Day	18% 9% 4 9% 6% 6% 6% 5% 6% 7% 25%	3000
	21st to end	Day	12% 7% 3 7% 5% 4 5% 4 7% 8% 39%	3000
July	1st to 10th	Day	9% 4 2 4 2 3 3 2 4 7% 61%	6780
	11th to 20th	Day	5% 4 1 4 3 2 3 3 4 5% 67%	6606
	21st to end	Day	10% 6% 2 5% 3 3 3 3 5% 7% 54%	6874
August	1st to 10th	Day	6% 4 1 5% 3 3 4 3 5% 7% 59%	4455
	11th to 20th	Day	9% 8% 3 8% 4 4 4 4 6% 8% 42%	4156
	21st to end	Day	14% 8% 3 7% 4 4 4 3 4 5% 44%	4491
September	1st to 10th	Day	10% 5% 2 5% 3 3 4 3 5% 8% 51%	2400
	11th to 20th	Day	11% 8% 3 6% 5% 4 4 3 7% 6% 42%	2400
	21st to end	Day	13% 7% 2 7% 5% 5% 5% 4 6% 7% 40%	2109
October	1st to 10th	Day	12% 7% 3 8% 5% 5% 6% 5% 7% 9% 34%	3280
	11th to 20th	Day	21% 10% 4 10% 5% 5% 4 4 5% 6% 26%	3261
	21st to end	Day	16% 12% 5% 12% 7% 6% 6% 4 6% 7% 20%	3368
November	1st to 10th	Day	20% 12% 4 11% 6% 5% 5% 5% 7% 6% 18%	1668
	11th to 20th	Day	21% 11% 4 10% 6% 5% 5% 4 6% 6% 22%	1680
	21st to end	Day	23% 11% 4 9% 6% 4 5% 4 6% 8% 19%	1680
December	1st to 10th	Day	14% 10% 3 14% 8% 7% 7% 5% 7% 7% 17%	2700
	11th to 20th	Day	21% 14% 5% 14% 7% 7% 6% 4 5% 6% 12%	2972
	21st to end	Day	21% 15% 5% 12% 7% 7% 6% 3 6% 6% 12%	3498
January	1st to 10th	Night	20% 16% 5% 12% 8% 6% 6% 4 5% 5% 12%	6766
	11th to 20th	Night	14% 10% 4 10% 6% 5% 5% 4 7% 9% 27%	6405
	21st to end	Night	20% 11% 3 8% 6% 6% 6% 4 6% 6% 24%	6824
February	1st to 10th	Night	19% 15% 4 9% 6% 5% 5% 4 5% 6% 21%	2600
	11th to 20th	Night	16% 14% 4 10% 6% 5% 5% 4 5% 5% 26%	2532
	21st to end	Night	17% 15% 3 9% 6% 4 5% 4 6% 7% 25%	2095
March	1st to 10th	Night	12% 12% 4 10% 7% 6% 7% 5% 7% 8% 21%	5231
	11th to 20th	Night	13% 12% 4 9% 5% 5% 4 4 6% 6% 32%	4999
	21st to end	Night	20% 14% 5% 10% 6% 6% 6% 4 6% 6% 18%	5324
April	1st to 10th	Night	18% 13% 4 9% 6% 6% 6% 6% 5% 7% 21%	2000
	11th to 20th	Night	17% 10% 3 7% 5% 5% 5% 4 5% 6% 33%	1929
	21st to end	Night	19% 10% 3 8% 5% 5% 4 4 6% 8% 28%	1760
May	1st to 10th	Night	14% 8% 3 6% 3 4 4 3 4 5% 45%	3640
	11th to 20th	Night	20% 9% 3 8% 5% 4 3 3 5% 6% 35%	3616
	21st to end	Night	23% 9% 3 6% 5% 5% 5% 4 6% 7% 29%	3972
June	1st to 10th	Night	20% 6% 2 7% 6% 4 5% 4 6% 6% 35%	1488
	11th to 20th	Night	22% 9% 3 9% 5% 5% 5% 3 5% 7% 28%	1400
	21st to end	Night	12% 6% 1 6% 4 4 5% 4 7% 7% 44%	1400
July	1st to 10th	Night	15% 4 2 4 2 2 2 2 4 5% 59%	3180
	11th to 20th	Night	5% 2 1 2 2 2 2 2 3 5% 73%	3354
	21st to end	Night	12% 4 1 4 4 3 3 3 5% 7% 53%	3969
August	1st to 10th	Night	5% 3 1 3 3 3 3 3 4 5% 66%	2696
	11th to 20th	Night	13% 6% 3 7% 4 3 3 3 4 6% 49%	2902
	21st to end	Night	15% 7% 2 6% 3 3 3 3 5% 5% 49%	3410
September	1st to 10th	Night	8% 6% 2 5% 3 3 4 3 5% 6% 56%	2000
	11th to 20th	Night	14% 7% 3 7% 5% 4 4 3 6% 6% 43%	2000
	21st to end	Night	13% 7% 3 7% 4 4 4 3 6% 6% 43%	2289
October	1st to 10th	Night	12% 7% 3 7% 4 5% 5% 4 6% 8% 38%	3920
	11th to 20th	Night	20% 10% 3 7% 4 5% 4 4 5% 7% 32%	3897
	21st to end	Night	20% 11% 3 10% 5% 5% 5% 3 5% 6% 27%	4437
November	1st to 10th	Night	22% 11% 3 8% 5% 5% 5% 4 6% 6% 25%	2848
	11th to 20th	Night	22% 12% 4 9% 6% 5% 4 4 5% 6% 23%	2940
	21st to end	Night	17% 14% 4 9% 7% 6% 6% 4 6% 6% 22%	2940
December	1st to 10th	Night	15% 11% 4 10% 7% 6% 7% 5% 5% 7% 22%	4700
	11th to 20th	Night	23% 14% 4 12% 6% 6% 6% 4 5% 6% 14%	5366
	21st to end	Night	21% 15% 5% 11% 7% 6% 5% 4 6% 6% 14%	7458

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	58% 27% 6% 7% 2	3179
	11th to 20th	Day	41% 30% 9% 17% 3	3500
	21st to end	Day	48% 30% 7% 12% 3	4124
February	1st to 10th	Day	26% 64% 3 3 2 1	1800
	11th to 20th	Day	28% 63% 3 4 2	1764
	21st to end	Day	24% 64% 4 5% 3	1535
March	1st to 10th	Day	45% 31% 11% 10% 3	4649
	11th to 20th	Day	40% 31% 10% 17% 2	5000
	21st to end	Day	50% 31% 10% 8% 1	5651
April	1st to 10th	Day	23% 64% 7% 5%	2400
	11th to 20th	Day	18% 65% 6% 7% 3 1	2420
	21st to end	Day	20% 63% 6% 7% 2	2640
May	1st to 10th	Day	29% 30% 12% 21% 8% 1	6320
	11th to 20th	Day	40% 31% 16% 11% 2	6280
	21st to end	Day	37% 31% 18% 13% 1	6904
June	1st to 10th	Day	15% 64% 9% 9% 3	2909
	11th to 20th	Day	20% 63% 6% 8% 3	3000
	21st to end	Day	17% 62% 9% 9% 2	3000
July	1st to 10th	Day	17% 26% 15% 16% 17% 8%	6706
	11th to 20th	Day	12% 27% 12% 22% 25% 2	6525
	21st to end	Day	24% 26% 22% 21% 6%	6681
August	1st to 10th	Day	13% 36% 7% 28% 14% 1	4438
	11th to 20th	Day	30% 37% 15% 13% 4 1	4195
	21st to end	Day	31% 37% 6% 19% 8%	4490
September	1st to 10th	Day	19% 58% 9% 8% 5% 1	2400
	11th to 20th	Day	20% 60% 6% 7% 7%	2400
	21st to end	Day	19% 59% 9% 9% 3	2109
October	1st to 10th	Day	30% 38% 15% 15% 1	3280
	11th to 20th	Day	42% 37% 7% 10% 5%	3261
	21st to end	Day	43% 37% 8% 8% 4 1	3368
November	1st to 10th	Day	32% 56% 8% 4 1	1668
	11th to 20th	Day	28% 56% 6% 6% 3 1	1680
	21st to end	Day	28% 56% 5% 6% 4	1680
December	1st to 10th	Day	45% 37% 5% 9% 4	2700
	11th to 20th	Day	53% 33% 7% 6% 1	2975
	21st to end	Day	58% 27% 10% 4 1	3498
January	1st to 10th	Night	57% 29% 6% 6% 2	6766
	11th to 20th	Night	35% 33% 10% 19% 3	6443
	21st to end	Night	45% 30% 9% 12% 4	6824
February	1st to 10th	Night	24% 64% 4 3 4 1	2600
	11th to 20th	Night	27% 62% 4 5% 2 1	2534
	21st to end	Night	22% 63% 5% 6% 3	2095
March	1st to 10th	Night	46% 31% 9% 10% 5%	5231
	11th to 20th	Night	37% 30% 12% 19% 1	5000
	21st to end	Night	50% 30% 11% 8% 1	5324
April	1st to 10th	Night	23% 64% 6% 7%	2000
	11th to 20th	Night	20% 63% 6% 6% 3 1	1929
	21st to end	Night	23% 63% 5% 6% 3	1760
May	1st to 10th	Night	30% 29% 7% 25% 8% 1	3637
	11th to 20th	Night	40% 29% 14% 14% 3	3616
	21st to end	Night	40% 34% 17% 8% 1	3972
June	1st to 10th	Night	17% 64% 9% 8% 2	1488
	11th to 20th	Night	21% 63% 6% 8% 3	1400
	21st to end	Night	17% 62% 10% 9% 2	1400
July	1st to 10th	Night	22% 26% 12% 16% 15% 9%	3145
	11th to 20th	Night	10% 26% 12% 22% 29% 2	3312
	21st to end	Night	25% 27% 18% 21% 8% 1	3857
August	1st to 10th	Night	12% 35% 7% 29% 15% 1	2688
	11th to 20th	Night	31% 37% 14% 13% 4 1	2929
	21st to end	Night	28% 36% 8% 19% 9% 1	3410
September	1st to 10th	Night	18% 58% 9% 9% 5% 1	2000
	11th to 20th	Night	22% 58% 5% 8% 6% 1	2000
	21st to end	Night	20% 59% 6% 12% 3	2289
October	1st to 10th	Night	29% 37% 13% 19% 2	3920
	11th to 20th	Night	38% 37% 8% 14% 3	3897
	21st to end	Night	42% 37% 8% 8% 4 1	4437
November	1st to 10th	Night	30% 55% 8% 7% 1	2848
	11th to 20th	Night	30% 55% 4 5% 3 2	2940
	21st to end	Night	28% 57% 4 5% 5%	2940
December	1st to 10th	Night	42% 38% 6% 11% 3	4700
	11th to 20th	Night	51% 33% 8% 5% 2	5362
	21st to end	Night	55% 28% 9% 7% 1	7458

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	29% 15% 25% 19% 10% 3	200
	11th to 20th	Day	25% 18% 28% 11% 18% 2	200
	21st to end	Day	31% 15% 25% 16% 11% 3	275
February	1st to 10th	Day	27% 20% 25% 18% 10% 1	400
	11th to 20th	Day	30% 14% 26% 20% 8% 2	395
	21st to end	Day	23% 20% 25% 18% 12% 1	357
March	1st to 10th	Day	23% 17% 25% 23% 11% 2	500
	11th to 20th	Day	24% 18% 19% 21% 13% 5%	500
	21st to end	Day	22% 16% 29% 21% 10% 2	550
April	1st to 10th	Day	23% 16% 22% 23% 13% 3	500
	11th to 20th	Day	17% 17% 29% 21% 11% 4	492
	21st to end	Day	19% 12% 25% 27% 14% 3	500
May	1st to 10th	Day	14% 7% 26% 33% 17% 3	503
	11th to 20th	Day	18% 7% 20% 30% 17% 9%	528
	21st to end	Day	20% 8% 17% 28% 18% 9%	573
June	1st to 10th	Day	17% 8% 23% 30% 18% 4	639
	11th to 20th	Day	17% 7% 23% 31% 18% 4	730
	21st to end	Day	13% 5% 19% 35% 23% 6%	730
July	1st to 10th	Day	10% 4 18% 33% 28% 7%	721
	11th to 20th	Day	6% 5% 16% 33% 32% 9%	648
	21st to end	Day	8% 3 10% 31% 36% 12%	575
August	1st to 10th	Day	8% 3 9% 31% 35% 14%	527
	11th to 20th	Day	7% 3 11% 34% 33% 12%	517
	21st to end	Day	12% 4 16% 34% 26% 7%	583
September	1st to 10th	Day	13% 6% 17% 33% 26% 6%	530
	11th to 20th	Day	15% 6% 18% 29% 28% 4	530
	21st to end	Day	16% 8% 24% 30% 20% 2	530
October	1st to 10th	Day	19% 9% 22% 23% 21% 6%	530
	11th to 20th	Day	23% 12% 22% 22% 17% 5%	530
	21st to end	Day	25% 19% 20% 23% 12% 2	468
November	1st to 10th	Day	33% 12% 24% 19% 10%	231
	11th to 20th	Day	29% 18% 23% 13% 10% 6%	220
	21st to end	Day	30% 14% 25% 15% 9% 7%	220
December	1st to 10th	Day	30% 15% 18% 14% 17% 7%	220
	11th to 20th	Day	31% 19% 30% 13% 5% 1	214
	21st to end	Day	30% 18% 25% 19% 6% 2	220
January	1st to 10th	Night	29% 14% 24% 19% 11% 3	900
	11th to 20th	Night	25% 14% 18% 22% 19% 2	828
	21st to end	Night	25% 12% 20% 23% 16% 4	880
February	1st to 10th	Night	27% 14% 23% 23% 11% 3	800
	11th to 20th	Night	23% 12% 22% 25% 17% 1	784
	21st to end	Night	25% 14% 24% 22% 13% 2	660
March	1st to 10th	Night	21% 14% 24% 25% 14% 2	800
	11th to 20th	Night	23% 16% 21% 24% 15% 2	800
	21st to end	Night	23% 12% 26% 26% 11% 1	880
April	1st to 10th	Night	24% 8% 21% 29% 16% 2	800
	11th to 20th	Night	21% 9% 24% 28% 16% 3	741
	21st to end	Night	22% 6% 21% 32% 15% 3	560
May	1st to 10th	Night	16% 7% 21% 34% 19% 4	400
	11th to 20th	Night	20% 3 16% 28% 30% 3	394
	21st to end	Night	21% 6% 14% 30% 23% 5%	433
June	1st to 10th	Night	20% 5% 20% 32% 22% 2	400
	11th to 20th	Night	19% 10% 18% 33% 20% 2	400
	21st to end	Night	15% 3 14% 38% 27% 3	400
July	1st to 10th	Night	13% 3 10% 30% 39% 5%	390
	11th to 20th	Night	7% 3 13% 34% 39% 4	388
	21st to end	Night	8% 3 6% 32% 44% 6%	438
August	1st to 10th	Night	10% 2 5% 27% 46% 9%	446
	11th to 20th	Night	10% 2 6% 27% 45% 10%	594
	21st to end	Night	11% 4 12% 33% 36% 5%	760
September	1st to 10th	Night	11% 2 10% 37% 33% 8%	800
	11th to 20th	Night	16% 3 13% 24% 33% 11%	800
	21st to end	Night	15% 6% 19% 30% 26% 5%	800
October	1st to 10th	Night	14% 8% 18% 29% 25% 6%	800
	11th to 20th	Night	21% 10% 18% 26% 21% 5%	800
	21st to end	Night	23% 10% 21% 27% 16% 3	880
November	1st to 10th	Night	28% 13% 21% 25% 12%	820
	11th to 20th	Night	28% 13% 23% 21% 13% 3	840
	21st to end	Night	25% 14% 22% 21% 14% 4	840
December	1st to 10th	Night	25% 11% 20% 24% 17% 3	840
	11th to 20th	Night	27% 17% 24% 20% 11% 2	846
	21st to end	Night	31% 16% 25% 18% 8% 1	990

Page generated at 2025-12-14 22:13:55. Version ac07

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