Munson Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Munson Observing Site clear sky chart from 2005-11-06 to 2026-01-02.

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	10% 6% 2 6% 5% 5% 5% 4 7% 9% 41%	126726
	Night	11% 6% 2 6% 4 4 4 4 6% 9% 44%	124649
Transparency	Day	37% 7% 13% 18% 17% 8%	130606
	Night	35% 7% 13% 18% 19% 9%	128842
Seeing	Day	13% 10% 22% 24% 19% 11%	16096
	Night	13% 8% 22% 29% 23% 6%	26051

By Month

Percentage Cloud Cover SE (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	12% 5% 2 5% 3 4 3 4 4 7% 52%	4129
	11th to 20th	Day	13% 5% 2 5% 3 3 4 3 5% 7% 50%	4520
	21st to end	Day	20% 7% 3 6% 4 3 4 3 4 6% 39%	4972
February	1st to 10th	Day	17% 6% 3 7% 5% 4 4 4 4 7% 41%	2000
	11th to 20th	Day	15% 6% 2 6% 4 4 4 4 5% 7% 43%	1948
	21st to end	Day	15% 7% 2 7% 4 5% 6% 4 5% 6% 39%	1650
March	1st to 10th	Day	16% 8% 2 7% 4 4 4 4 5% 7% 39%	4480
	11th to 20th	Day	8% 5% 2 5% 4 4 4 3 6% 6% 53%	4786
	21st to end	Day	15% 6% 2 6% 4 4 4 3 5% 6% 43%	5727
April	1st to 10th	Day	11% 7% 3 6% 5% 3 4 4 5% 7% 46%	2400
	11th to 20th	Day	12% 5% 2 6% 5% 5% 4 4 4 7% 46%	2374
	21st to end	Day	7% 4 2 5% 5% 5% 4 4 6% 7% 52%	2400
May	1st to 10th	Day	12% 6% 2 7% 5% 5% 4 4 6% 8% 39%	5515
	11th to 20th	Day	11% 5% 2 6% 4 5% 5% 5% 7% 9% 41%	5861
	21st to end	Day	6% 4 2 6% 5% 6% 6% 5% 7% 11% 43%	6433
June	1st to 10th	Day	7% 7% 3 8% 7% 6% 7% 6% 8% 10% 29%	2600
	11th to 20th	Day	5% 4 1 7% 7% 6% 7% 6% 10% 11% 34%	2600
	21st to end	Day	6% 5% 2 9% 7% 8% 9% 7% 9% 10% 29%	2600
July	1st to 10th	Day	6% 5% 3 9% 7% 8% 8% 7% 10% 13% 25%	5900
	11th to 20th	Day	3 4 2 7% 6% 7% 8% 7% 11% 14% 30%	5818
	21st to end	Day	4 5% 2 9% 8% 8% 9% 7% 10% 14% 24%	5922
August	1st to 10th	Day	4 4 1 6% 5% 7% 7% 6% 10% 13% 37%	3905
	11th to 20th	Day	5% 5% 1 7% 5% 6% 6% 4 7% 10% 44%	3849
	21st to end	Day	7% 5% 2 8% 7% 7% 7% 6% 8% 10% 34%	4312
September	1st to 10th	Day	9% 6% 3 9% 6% 7% 7% 6% 7% 7% 33%	2333
	11th to 20th	Day	11% 7% 3 9% 6% 5% 5% 4 6% 7% 38%	2200
	21st to end	Day	8% 5% 2 5% 5% 5% 5% 4 5% 7% 49%	2200
October	1st to 10th	Day	8% 5% 2 6% 4 4 4 4 5% 6% 52%	2200
	11th to 20th	Day	9% 4 1 4 3 3 3 3 5% 7% 58%	2200
	21st to end	Day	9% 5% 2 6% 4 4 3 2 4 5% 56%	2212
November	1st to 10th	Day	8% 6% 2 4 3 4 4 3 6% 6% 55%	1852
	11th to 20th	Day	10% 5% 2 4 3 4 3 3 5% 7% 54%	1890
	21st to end	Day	11% 5% 2 6% 3 4 4 4 6% 7% 48%	1890
December	1st to 10th	Day	16% 6% 2 5% 3 2 3 3 4 6% 50%	3020
	11th to 20th	Day	10% 7% 2 6% 4 3 4 2 4 5% 52%	3463
	21st to end	Day	17% 8% 3 6% 3 3 3 2 4 5% 46%	4565
January	1st to 10th	Night	14% 5% 2 6% 4 4 5% 3 4 5% 48%	5834
	11th to 20th	Night	16% 9% 3 6% 4 3 3 3 4 5% 44%	5440
	21st to end	Night	18% 9% 2 6% 4 3 4 3 5% 7% 39%	5984
February	1st to 10th	Night	14% 8% 2 6% 4 4 4 4 5% 7% 43%	2400
	11th to 20th	Night	17% 9% 2 6% 4 3 3 3 4 5% 44%	2338
	21st to end	Night	15% 10% 3 6% 4 4 4 3 5% 6% 42%	1980
March	1st to 10th	Night	21% 11% 3 7% 3 3 3 3 4 6% 35%	5373
	11th to 20th	Night	12% 7% 2 5% 4 4 4 3 5% 7% 48%	5174
	21st to end	Night	13% 7% 2 6% 4 3 3 3 4 6% 48%	5243
April	1st to 10th	Night	13% 7% 2 6% 5% 4 4 3 6% 7% 44%	2000
	11th to 20th	Night	12% 5% 2 6% 2 3 4 4 5% 7% 48%	1975
	21st to end	Night	5% 4 2 5% 4 4 4 3 5% 7% 59%	2000
May	1st to 10th	Night	12% 7% 3 7% 4 5% 4 4 6% 10% 38%	4362
	11th to 20th	Night	12% 7% 2 6% 4 4 5% 3 6% 9% 43%	4032
	21st to end	Night	5% 4 2 5% 5% 4 5% 3 7% 12% 46%	4421
June	1st to 10th	Night	8% 5% 2 7% 4 5% 5% 5% 9% 12% 38%	1800
	11th to 20th	Night	4 4 1 5% 4 4 6% 7% 10% 12% 43%	1800
	21st to end	Night	4 4 2 7% 6% 6% 5% 6% 8% 15% 37%	1800
July	1st to 10th	Night	4 4 2 7% 6% 6% 7% 7% 11% 16% 28%	4058
	11th to 20th	Night	3 3 2 5% 4 5% 7% 6% 10% 17% 39%	4120
	21st to end	Night	3 3 2 6% 5% 6% 8% 7% 12% 16% 32%	4929
August	1st to 10th	Night	4 4 2 4 4 5% 6% 6% 9% 13% 44%	3244
	11th to 20th	Night	3 3 1 6% 4 5% 5% 5% 7% 13% 48%	3200
	21st to end	Night	4 6% 2 7% 6% 7% 7% 6% 9% 11% 36%	3586
September	1st to 10th	Night	9% 5% 2 7% 5% 5% 6% 5% 7% 11% 37%	2045
	11th to 20th	Night	10% 5% 3 7% 4 4 4 5% 6% 9% 42%	2200
	21st to end	Night	7% 5% 1 6% 5% 4 4 4 6% 7% 51%	2200
October	1st to 10th	Night	7% 6% 2 5% 3 3 4 4 7% 8% 52%	2200
	11th to 20th	Night	6% 5% 2 4 2 2 3 3 5% 6% 63%	2200
	21st to end	Night	9% 6% 2 4 3 3 3 3 4 6% 56%	2620
November	1st to 10th	Night	9% 4 2 5% 3 2 3 3 5% 7% 58%	2666
	11th to 20th	Night	11% 5% 2 4 3 3 3 3 4 6% 55%	2730
	21st to end	Night	12% 6% 2 5% 4 4 4 4 6% 7% 49%	2730
December	1st to 10th	Night	14% 6% 2 5% 3 3 2 3 5% 7% 49%	4380
	11th to 20th	Night	13% 6% 2 5% 3 3 3 3 5% 6% 51%	4952
	21st to end	Night	18% 8% 3 6% 4 3 3 2 3 4 47%	6633

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% 4 5% 18% 32% 9%	4130
	11th to 20th	Day	34% 4 5% 17% 30% 10%	4520
	21st to end	Day	46% 4 7% 14% 17% 13%	4972
February	1st to 10th	Day	44% 3 7% 16% 20% 10%	2000
	11th to 20th	Day	41% 4 5% 17% 22% 11%	1958
	21st to end	Day	43% 5% 7% 17% 17% 11%	1650
March	1st to 10th	Day	44% 4 7% 17% 18% 11%	4480
	11th to 20th	Day	31% 5% 8% 17% 20% 19%	4786
	21st to end	Day	41% 4 10% 17% 17% 10%	5729
April	1st to 10th	Day	38% 5% 10% 16% 20% 12%	2400
	11th to 20th	Day	38% 4 8% 18% 21% 11%	2374
	21st to end	Day	31% 5% 11% 21% 23% 10%	2400
May	1st to 10th	Day	40% 6% 12% 23% 15% 4	5550
	11th to 20th	Day	35% 7% 18% 26% 12% 2	5865
	21st to end	Day	32% 8% 14% 27% 17% 2	6447
June	1st to 10th	Day	45% 8% 16% 21% 9% 1	2600
	11th to 20th	Day	37% 11% 18% 21% 11% 2	2600
	21st to end	Day	43% 11% 19% 16% 9% 2	2600
July	1st to 10th	Day	42% 17% 26% 13% 2	5835
	11th to 20th	Day	35% 18% 33% 13% 1	5749
	21st to end	Day	42% 17% 24% 15% 2	5752
August	1st to 10th	Day	33% 11% 20% 22% 13% 2	3893
	11th to 20th	Day	33% 9% 19% 21% 17% 1	3885
	21st to end	Day	40% 12% 21% 16% 10% 1	4311
September	1st to 10th	Day	45% 8% 17% 14% 12% 4	2333
	11th to 20th	Day	45% 7% 11% 17% 14% 6%	2200
	21st to end	Day	35% 6% 9% 20% 21% 9%	2200
October	1st to 10th	Day	34% 4 7% 11% 16% 28%	3590
	11th to 20th	Day	17% 3 5% 18% 22% 35%	3568
	21st to end	Day	22% 3 3 13% 38% 21%	3552
November	1st to 10th	Day	29% 4 8% 19% 23% 17%	1852
	11th to 20th	Day	30% 3 7% 17% 27% 15%	1890
	21st to end	Day	35% 4 8% 18% 22% 13%	1890
December	1st to 10th	Day	37% 3 8% 17% 24% 10%	3020
	11th to 20th	Day	35% 3 5% 23% 23% 10%	3460
	21st to end	Day	42% 3 4 17% 29% 5%	4565
January	1st to 10th	Night	37% 4 5% 13% 30% 11%	5834
	11th to 20th	Night	43% 3 4 12% 30% 9%	5440
	21st to end	Night	45% 4 7% 16% 20% 9%	5984
February	1st to 10th	Night	41% 3 6% 17% 21% 11%	2400
	11th to 20th	Night	42% 4 7% 13% 20% 14%	2339
	21st to end	Night	44% 5% 7% 15% 16% 13%	1980
March	1st to 10th	Night	50% 3 5% 14% 19% 8%	5373
	11th to 20th	Night	36% 4 8% 14% 21% 17%	5174
	21st to end	Night	38% 4 10% 22% 14% 12%	5243
April	1st to 10th	Night	39% 5% 11% 13% 19% 13%	2000
	11th to 20th	Night	34% 5% 9% 19% 22% 11%	1975
	21st to end	Night	25% 4 12% 27% 23% 9%	2000
May	1st to 10th	Night	40% 7% 19% 18% 12% 4	4392
	11th to 20th	Night	36% 7% 17% 24% 14% 2	4033
	21st to end	Night	28% 8% 19% 31% 13% 2	4429
June	1st to 10th	Night	35% 9% 20% 23% 10% 2	1800
	11th to 20th	Night	27% 12% 26% 22% 11% 2	1800
	21st to end	Night	32% 12% 27% 18% 9% 2	1800
July	1st to 10th	Night	36% 17% 31% 13% 2	4015
	11th to 20th	Night	26% 18% 41% 13% 1	4069
	21st to end	Night	33% 21% 26% 18% 1	4785
August	1st to 10th	Night	27% 12% 25% 22% 12% 1	3232
	11th to 20th	Night	25% 11% 25% 24% 15%	3230
	21st to end	Night	37% 13% 21% 18% 10% 2	3586
September	1st to 10th	Night	35% 11% 22% 17% 11% 4	2045
	11th to 20th	Night	36% 9% 16% 18% 16% 5%	2200
	21st to end	Night	30% 7% 14% 20% 20% 9%	2200
October	1st to 10th	Night	35% 5% 8% 12% 20% 20%	3590
	11th to 20th	Night	14% 2 5% 18% 28% 33%	3571
	21st to end	Night	21% 3 4 14% 40% 19%	4230
November	1st to 10th	Night	27% 4 8% 18% 25% 18%	2666
	11th to 20th	Night	31% 4 5% 17% 28% 14%	2730
	21st to end	Night	34% 5% 9% 18% 21% 14%	2730
December	1st to 10th	Night	36% 3 7% 19% 24% 12%	4380
	11th to 20th	Night	34% 4 7% 23% 23% 10%	4954
	21st to end	Night	43% 3 5% 18% 27% 4	6633

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	19% 21% 39% 16% 3 1	303
	11th to 20th	Day	19% 21% 33% 18% 8% 1	300
	21st to end	Day	25% 25% 37% 10% 3	330
February	1st to 10th	Day	23% 22% 31% 18% 5% 1	300
	11th to 20th	Day	26% 24% 33% 15% 1	300
	21st to end	Day	17% 31% 35% 15% 2	249
March	1st to 10th	Day	19% 25% 39% 12% 4	300
	11th to 20th	Day	20% 22% 31% 18% 7% 1	410
	21st to end	Day	19% 18% 33% 21% 10% 1	550
April	1st to 10th	Day	20% 16% 33% 19% 9% 3	500
	11th to 20th	Day	15% 15% 33% 23% 11% 2	492
	21st to end	Day	9% 13% 29% 28% 16% 4	500
May	1st to 10th	Day	11% 12% 26% 27% 18% 6%	503
	11th to 20th	Day	8% 5% 28% 29% 18% 12%	527
	21st to end	Day	8% 3 22% 32% 19% 16%	573
June	1st to 10th	Day	11% 3 16% 32% 25% 14%	530
	11th to 20th	Day	7% 5% 12% 32% 25% 20%	530
	21st to end	Day	7% 2 12% 26% 28% 24%	530
July	1st to 10th	Day	8% 3 7% 20% 34% 28%	525
	11th to 20th	Day	6% 2 4 22% 37% 30%	524
	21st to end	Day	6% 1 8% 21% 37% 26%	576
August	1st to 10th	Day	8% 5% 24% 30% 33%	526
	11th to 20th	Day	9% 3 3 19% 34% 31%	519
	21st to end	Day	11% 2 10% 29% 30% 17%	583
September	1st to 10th	Day	11% 3 11% 28% 29% 19%	530
	11th to 20th	Day	14% 6% 8% 31% 30% 11%	530
	21st to end	Day	10% 4 16% 29% 29% 12%	530
October	1st to 10th	Day	12% 5% 31% 28% 18% 5%	530
	11th to 20th	Day	9% 6% 23% 32% 22% 8%	530
	21st to end	Day	12% 11% 25% 33% 17% 2	453
November	1st to 10th	Day	15% 8% 30% 31% 15% 2	330
	11th to 20th	Day	13% 13% 34% 29% 10% 1	330
	21st to end	Day	15% 17% 36% 22% 10% 1	330
December	1st to 10th	Day	20% 20% 33% 19% 7% 1	330
	11th to 20th	Day	22% 15% 38% 20% 5%	330
	21st to end	Day	24% 16% 32% 19% 8% 1	363
January	1st to 10th	Night	18% 16% 34% 26% 6%	805
	11th to 20th	Night	18% 16% 26% 31% 9%	800
	21st to end	Night	22% 15% 32% 26% 4	880
February	1st to 10th	Night	19% 13% 35% 27% 7%	800
	11th to 20th	Night	21% 15% 33% 23% 8%	783
	21st to end	Night	20% 14% 37% 26% 3	660
March	1st to 10th	Night	17% 15% 32% 29% 7%	800
	11th to 20th	Night	14% 16% 33% 27% 10%	800
	21st to end	Night	13% 13% 31% 31% 11% 1	785
April	1st to 10th	Night	17% 11% 27% 34% 11% 1	600
	11th to 20th	Night	14% 9% 29% 29% 18% 1	593
	21st to end	Night	7% 6% 26% 39% 22% 1	600
May	1st to 10th	Night	10% 7% 22% 38% 21% 3	600
	11th to 20th	Night	9% 4 18% 36% 27% 5%	591
	21st to end	Night	8% 2 14% 35% 36% 6%	650
June	1st to 10th	Night	10% 2 12% 32% 35% 9%	600
	11th to 20th	Night	4 3 8% 32% 42% 12%	600
	21st to end	Night	5% 1 8% 24% 48% 14%	600
July	1st to 10th	Night	5% 1 3 23% 48% 20%	585
	11th to 20th	Night	6% 1 3 17% 43% 30%	582
	21st to end	Night	4 1 3 25% 51% 17%	657
August	1st to 10th	Night	5% 1 4 18% 48% 24%	597
	11th to 20th	Night	5% 2 2 21% 46% 24%	594
	21st to end	Night	8% 3 7% 25% 42% 17%	660
September	1st to 10th	Night	10% 3 7% 25% 40% 15%	645
	11th to 20th	Night	12% 3 11% 29% 38% 8%	800
	21st to end	Night	10% 2 15% 30% 36% 7%	800
October	1st to 10th	Night	9% 3 26% 35% 24% 3	800
	11th to 20th	Night	8% 6% 23% 32% 28% 3	800
	21st to end	Night	13% 7% 24% 34% 22% 2	880
November	1st to 10th	Night	10% 7% 24% 38% 19% 2	820
	11th to 20th	Night	13% 10% 26% 34% 15% 1	840
	21st to end	Night	14% 10% 29% 32% 14% 1	840
December	1st to 10th	Night	17% 12% 29% 28% 13% 1	840
	11th to 20th	Night	18% 10% 28% 31% 13%	840
	21st to end	Night	25% 13% 26% 27% 9% 1	924

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