Saginaw
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saginaw clear sky chart from 2005-11-06 to 2025-07-21.

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% 10% 3 8% 5% 5% 5% 4 5% 7% 34%	119304
	Night	14% 11% 4 9% 5% 4 4 3 5% 6% 34%	119908
Transparency	Day	48% 5% 12% 21% 12% 1	122900
	Night	49% 5% 11% 21% 12% 1	124450
Seeing	Day	18% 10% 28% 24% 14% 6%	16471
	Night	19% 8% 29% 31% 12% 1	26208

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	11% 15% 6% 15% 8% 5% 5% 3 5% 5% 22%	3617
	11th to 20th	Day	12% 16% 6% 15% 12% 8% 7% 4 4 4 11%	3620
	21st to end	Day	18% 19% 7% 13% 6% 5% 5% 3 4 5% 16%	4158
February	1st to 10th	Day	11% 15% 4 13% 7% 6% 6% 4 5% 7% 22%	1800
	11th to 20th	Day	13% 15% 5% 11% 8% 6% 5% 3 4 5% 24%	1898
	21st to end	Day	14% 14% 5% 11% 7% 5% 5% 3 5% 6% 26%	1650
March	1st to 10th	Day	14% 10% 3 9% 5% 6% 5% 3 5% 6% 35%	4518
	11th to 20th	Day	12% 12% 4 8% 5% 5% 5% 4 5% 8% 33%	4980
	21st to end	Day	18% 13% 5% 9% 5% 4 5% 3 5% 5% 28%	5465
April	1st to 10th	Day	19% 12% 4 7% 5% 4 5% 3 5% 6% 30%	2375
	11th to 20th	Day	17% 9% 3 7% 4 4 3 4 6% 6% 36%	2522
	21st to end	Day	16% 8% 3 8% 6% 5% 4 4 5% 7% 35%	2600
May	1st to 10th	Day	19% 9% 2 6% 4 4 5% 3 5% 8% 35%	5862
	11th to 20th	Day	15% 8% 3 7% 5% 4 5% 4 6% 7% 37%	5861
	21st to end	Day	14% 7% 2 7% 4 4 4 3 5% 7% 42%	6695
June	1st to 10th	Day	11% 7% 2 6% 4 5% 5% 4 7% 8% 43%	2905
	11th to 20th	Day	11% 6% 2 6% 5% 4 5% 4 6% 9% 43%	3000
	21st to end	Day	10% 5% 2 6% 5% 6% 5% 4 8% 9% 40%	2878
July	1st to 10th	Day	10% 6% 3 8% 6% 5% 5% 4 7% 9% 37%	4580
	11th to 20th	Day	7% 4 2 4 4 4 4 4 7% 10% 50%	4580
	21st to end	Day	7% 5% 2 6% 5% 5% 6% 4 7% 10% 44%	4698
August	1st to 10th	Day	11% 5% 2 7% 4 5% 6% 5% 6% 9% 41%	4104
	11th to 20th	Day	11% 6% 2 6% 5% 4 4 4 6% 7% 45%	4044
	21st to end	Day	8% 6% 2 7% 4 5% 5% 5% 7% 9% 42%	4449
September	1st to 10th	Day	10% 7% 2 8% 4 6% 5% 4 6% 8% 42%	2180
	11th to 20th	Day	11% 5% 2 5% 4 4 5% 4 5% 8% 47%	2090
	21st to end	Day	14% 7% 3 7% 5% 5% 5% 3 5% 8% 38%	2090
October	1st to 10th	Day	13% 7% 2 7% 5% 5% 5% 3 5% 6% 41%	2054
	11th to 20th	Day	19% 11% 3 6% 6% 5% 5% 3 5% 6% 31%	1900
	21st to end	Day	21% 9% 3 8% 5% 4 5% 5% 5% 8% 27%	1881
November	1st to 10th	Day	13% 11% 3 8% 5% 4 5% 4 5% 7% 35%	1762
	11th to 20th	Day	14% 13% 4 9% 6% 5% 6% 4 6% 7% 27%	1800
	21st to end	Day	18% 14% 5% 9% 6% 6% 5% 3 4 6% 24%	1680
December	1st to 10th	Day	14% 15% 6% 11% 7% 5% 6% 5% 6% 6% 19%	2522
	11th to 20th	Day	17% 20% 7% 11% 5% 4 4 3 4 5% 20%	2625
	21st to end	Day	26% 21% 6% 12% 5% 4 4 3 4 4 12%	3861
January	1st to 10th	Night	12% 13% 6% 14% 6% 5% 4 3 4 6% 26%	6348
	11th to 20th	Night	13% 14% 6% 18% 9% 8% 6% 3 4 5% 13%	6360
	21st to end	Night	15% 18% 7% 11% 5% 4 5% 4 6% 7% 19%	6797
February	1st to 10th	Night	14% 14% 4 12% 8% 6% 5% 4 5% 6% 24%	2600
	11th to 20th	Night	14% 13% 5% 11% 7% 5% 4 3 4 6% 27%	2383
	21st to end	Night	16% 14% 4 11% 6% 5% 4 3 5% 6% 27%	1980
March	1st to 10th	Night	15% 9% 3 8% 4 4 4 3 5% 6% 39%	5333
	11th to 20th	Night	11% 8% 3 7% 5% 4 4 4 7% 9% 39%	4980
	21st to end	Night	16% 11% 4 8% 4 4 4 3 5% 5% 34%	5467
April	1st to 10th	Night	18% 12% 3 6% 4 3 3 3 5% 6% 36%	2041
	11th to 20th	Night	19% 7% 2 6% 4 4 5% 3 5% 6% 38%	1826
	21st to end	Night	18% 8% 2 6% 4 4 5% 3 5% 7% 38%	1800
May	1st to 10th	Night	17% 9% 3 8% 4 4 5% 3 5% 7% 35%	4033
	11th to 20th	Night	16% 9% 4 8% 4 4 4 3 4 7% 39%	4032
	21st to end	Night	16% 6% 2 5% 4 4 4 3 5% 6% 47%	4168
June	1st to 10th	Night	11% 7% 2 5% 5% 3 4 3 7% 7% 45%	1485
	11th to 20th	Night	12% 5% 2 6% 4 4 4 4 6% 9% 44%	1400
	21st to end	Night	7% 5% 2 5% 5% 4 5% 4 6% 9% 47%	1512
July	1st to 10th	Night	8% 5% 2 7% 4 4 5% 4 7% 9% 44%	2610
	11th to 20th	Night	8% 3 1 4 4 4 4 3 5% 8% 55%	2610
	21st to end	Night	6% 4 2 6% 5% 5% 6% 4 7% 8% 47%	2862
August	1st to 10th	Night	10% 6% 2 5% 3 4 4 4 6% 8% 48%	2825
	11th to 20th	Night	11% 5% 2 6% 4 4 4 4 5% 7% 48%	2785
	21st to end	Night	8% 5% 2 6% 4 4 5% 4 6% 7% 49%	3204
September	1st to 10th	Night	8% 6% 2 6% 5% 5% 5% 3 5% 6% 48%	1981
	11th to 20th	Night	11% 4 2 4 3 2 4 3 5% 7% 54%	2090
	21st to end	Night	15% 7% 3 6% 4 4 4 3 5% 8% 43%	2090
October	1st to 10th	Night	16% 6% 2 6% 3 3 3 3 5% 6% 45%	2125
	11th to 20th	Night	18% 10% 4 8% 5% 5% 4 3 5% 6% 33%	2280
	21st to end	Night	22% 10% 3 8% 4 5% 4 3 5% 6% 31%	2712
November	1st to 10th	Night	14% 10% 3 6% 4 4 4 3 5% 6% 41%	2536
	11th to 20th	Night	15% 12% 4 8% 6% 5% 5% 5% 6% 6% 28%	2600
	21st to end	Night	18% 14% 4 9% 5% 5% 5% 3 5% 6% 25%	2715
December	1st to 10th	Night	13% 16% 5% 12% 6% 5% 5% 5% 5% 6% 23%	4645
	11th to 20th	Night	14% 18% 6% 12% 6% 5% 4 3 4 5% 23%	5582
	21st to end	Night	25% 21% 6% 9% 4 4 3 3 4 5% 17%	7111

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	63% 5% 13% 14% 5% 1	3618
	11th to 20th	Day	74% 5% 6% 8% 6%	3620
	21st to end	Day	71% 4 9% 10% 5% 1	4158
February	1st to 10th	Day	61% 6% 11% 16% 6%	1800
	11th to 20th	Day	62% 4 10% 16% 8% 1	1908
	21st to end	Day	57% 7% 11% 16% 8% 1	1650
March	1st to 10th	Day	50% 4 14% 20% 9% 3	4518
	11th to 20th	Day	50% 5% 14% 20% 10% 1	4980
	21st to end	Day	57% 4 12% 17% 9% 1	5465
April	1st to 10th	Day	55% 5% 10% 19% 11% 1	2375
	11th to 20th	Day	47% 4 11% 21% 14% 2	2522
	21st to end	Day	49% 5% 13% 20% 12% 2	2600
May	1st to 10th	Day	46% 6% 12% 19% 15% 3	5897
	11th to 20th	Day	45% 6% 11% 22% 14% 1	5865
	21st to end	Day	41% 5% 9% 22% 19% 4	6709
June	1st to 10th	Day	37% 6% 12% 29% 15% 2	2905
	11th to 20th	Day	38% 5% 12% 26% 17% 2	3000
	21st to end	Day	37% 7% 14% 25% 15% 2	2878
July	1st to 10th	Day	41% 8% 13% 22% 15% 2	4511
	11th to 20th	Day	28% 6% 14% 36% 15% 1	4505
	21st to end	Day	34% 7% 15% 21% 21% 2	4549
August	1st to 10th	Day	38% 6% 13% 26% 16% 1	4091
	11th to 20th	Day	36% 6% 12% 34% 11% 1	4083
	21st to end	Day	37% 6% 15% 28% 13% 1	4448
September	1st to 10th	Day	40% 6% 14% 26% 13% 2	2180
	11th to 20th	Day	34% 5% 13% 31% 16% 1	2090
	21st to end	Day	44% 4 14% 25% 13%	2090
October	1st to 10th	Day	33% 4 9% 33% 18% 2	3418
	11th to 20th	Day	42% 4 13% 28% 14%	3140
	21st to end	Day	50% 5% 13% 24% 8% 1	3081
November	1st to 10th	Day	48% 6% 12% 22% 11% 1	1762
	11th to 20th	Day	54% 5% 13% 18% 9%	1800
	21st to end	Day	60% 5% 14% 15% 5% 1	1680
December	1st to 10th	Day	62% 7% 17% 10% 3	2522
	11th to 20th	Day	68% 4 9% 14% 4	2621
	21st to end	Day	76% 3 7% 9% 4	3861
January	1st to 10th	Night	59% 4 10% 18% 7% 2	6348
	11th to 20th	Night	72% 5% 8% 9% 6% 1	6360
	21st to end	Night	63% 5% 11% 13% 7%	6797
February	1st to 10th	Night	61% 6% 8% 17% 7% 1	2600
	11th to 20th	Night	59% 5% 8% 19% 8% 1	2384
	21st to end	Night	58% 4 11% 18% 9% 1	1980
March	1st to 10th	Night	46% 4 15% 24% 11% 1	5333
	11th to 20th	Night	41% 4 17% 23% 13% 1	4980
	21st to end	Night	51% 5% 11% 19% 12% 1	5467
April	1st to 10th	Night	48% 4 9% 22% 14% 2	2041
	11th to 20th	Night	46% 5% 9% 21% 17% 2	1826
	21st to end	Night	46% 6% 10% 20% 16% 3	1800
May	1st to 10th	Night	49% 5% 11% 16% 17% 3	4060
	11th to 20th	Night	46% 5% 9% 26% 12% 3	4033
	21st to end	Night	39% 4 8% 26% 18% 5%	4176
June	1st to 10th	Night	37% 5% 11% 25% 21% 2	1485
	11th to 20th	Night	36% 6% 13% 23% 21% 2	1400
	21st to end	Night	34% 6% 12% 28% 18% 2	1512
July	1st to 10th	Night	35% 6% 12% 26% 15% 6%	2570
	11th to 20th	Night	27% 5% 14% 35% 19% 1	2562
	21st to end	Night	33% 7% 17% 22% 19% 2	2771
August	1st to 10th	Night	33% 6% 13% 30% 16% 1	2814
	11th to 20th	Night	34% 5% 14% 31% 14% 1	2812
	21st to end	Night	33% 6% 12% 32% 15% 1	3204
September	1st to 10th	Night	36% 6% 11% 28% 18% 1	1981
	11th to 20th	Night	29% 6% 12% 32% 19% 1	2090
	21st to end	Night	41% 5% 13% 28% 12% 1	2090
October	1st to 10th	Night	27% 4 10% 34% 24% 1	3541
	11th to 20th	Night	45% 4 10% 25% 16%	3779
	21st to end	Night	44% 4 10% 30% 11%	4462
November	1st to 10th	Night	43% 6% 11% 26% 14% 1	2536
	11th to 20th	Night	53% 6% 12% 19% 9% 1	2600
	21st to end	Night	59% 4 15% 16% 5% 1	2715
December	1st to 10th	Night	60% 6% 17% 13% 3	4645
	11th to 20th	Night	63% 5% 10% 12% 9% 1	5585
	21st to end	Night	72% 4 9% 8% 7%	7111

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	20% 12% 38% 21% 8% 2	300
	11th to 20th	Day	23% 15% 38% 18% 6%	300
	21st to end	Day	25% 16% 31% 23% 5%	330
February	1st to 10th	Day	23% 22% 33% 19% 2 1	300
	11th to 20th	Day	21% 16% 36% 24% 3	300
	21st to end	Day	25% 24% 35% 12% 4	249
March	1st to 10th	Day	23% 16% 40% 16% 4 1	312
	11th to 20th	Day	22% 13% 30% 25% 10% 1	500
	21st to end	Day	29% 10% 30% 23% 7% 1	550
April	1st to 10th	Day	23% 14% 31% 23% 8% 1	500
	11th to 20th	Day	22% 18% 29% 21% 6% 4	492
	21st to end	Day	21% 9% 32% 23% 12% 2	500
May	1st to 10th	Day	22% 13% 29% 21% 11% 4	503
	11th to 20th	Day	20% 9% 27% 22% 15% 7%	527
	21st to end	Day	15% 9% 24% 25% 19% 8%	679
June	1st to 10th	Day	13% 10% 29% 30% 12% 6%	730
	11th to 20th	Day	14% 8% 30% 27% 17% 5%	730
	21st to end	Day	13% 7% 28% 30% 16% 5%	730
July	1st to 10th	Day	8% 4 22% 32% 22% 12%	721
	11th to 20th	Day	12% 6% 23% 30% 19% 10%	718
	21st to end	Day	8% 4 25% 30% 25% 8%	673
August	1st to 10th	Day	11% 4 19% 25% 24% 17%	486
	11th to 20th	Day	12% 4 15% 25% 29% 14%	479
	21st to end	Day	13% 5% 19% 26% 25% 12%	539
September	1st to 10th	Day	12% 5% 25% 26% 21% 11%	490
	11th to 20th	Day	11% 5% 19% 22% 27% 17%	490
	21st to end	Day	18% 10% 21% 24% 18% 10%	490
October	1st to 10th	Day	16% 10% 29% 21% 17% 7%	490
	11th to 20th	Day	22% 14% 27% 28% 9% 1	490
	21st to end	Day	27% 13% 34% 19% 6% 2	330
November	1st to 10th	Day	19% 15% 34% 21% 10% 2	300
	11th to 20th	Day	21% 17% 39% 17% 5% 2	300
	21st to end	Day	24% 13% 37% 19% 7%	240
December	1st to 10th	Day	27% 15% 35% 17% 7% 1	200
	11th to 20th	Day	22% 20% 40% 15% 3 1	200
	21st to end	Day	30% 14% 33% 19% 3	303
January	1st to 10th	Night	21% 11% 36% 24% 7% 1	1000
	11th to 20th	Night	25% 13% 32% 25% 6% 1	1000
	21st to end	Night	20% 8% 33% 31% 8%	1018
February	1st to 10th	Night	21% 11% 36% 27% 5%	800
	11th to 20th	Night	20% 13% 35% 27% 5%	783
	21st to end	Night	24% 13% 38% 23% 3	660
March	1st to 10th	Night	21% 10% 33% 29% 8%	800
	11th to 20th	Night	17% 12% 36% 28% 7% 1	800
	21st to end	Night	24% 9% 30% 29% 7% 1	880
April	1st to 10th	Night	22% 12% 34% 24% 6% 1	641
	11th to 20th	Night	24% 8% 32% 25% 10% 1	593
	21st to end	Night	21% 9% 31% 31% 7% 1	600
May	1st to 10th	Night	18% 7% 33% 34% 8% 1	600
	11th to 20th	Night	20% 6% 27% 35% 11% 1	591
	21st to end	Night	14% 5% 25% 35% 18% 2	650
June	1st to 10th	Night	13% 5% 29% 40% 13%	485
	11th to 20th	Night	14% 5% 26% 41% 14%	400
	21st to end	Night	8% 5% 23% 43% 19% 1	512
July	1st to 10th	Night	9% 2 18% 44% 25% 3	585
	11th to 20th	Night	10% 1 18% 42% 26% 3	582
	21st to end	Night	9% 2 17% 47% 23% 1	624
August	1st to 10th	Night	9% 2 14% 44% 29% 2	567
	11th to 20th	Night	8% 1 17% 40% 30% 4	564
	21st to end	Night	12% 4 19% 34% 29% 3	627
September	1st to 10th	Night	9% 5% 23% 35% 23% 5%	651
	11th to 20th	Night	14% 3 15% 36% 29% 4	760
	21st to end	Night	17% 6% 20% 33% 20% 4	760
October	1st to 10th	Night	19% 7% 24% 32% 16% 2	760
	11th to 20th	Night	24% 10% 26% 30% 9%	760
	21st to end	Night	25% 9% 32% 27% 6%	836
November	1st to 10th	Night	20% 11% 31% 28% 10%	780
	11th to 20th	Night	20% 13% 35% 24% 8% 1	800
	21st to end	Night	26% 11% 35% 24% 4	800
December	1st to 10th	Night	26% 12% 33% 25% 5% 1	839
	11th to 20th	Night	23% 11% 38% 24% 5%	1000
	21st to end	Night	32% 10% 32% 23% 3	1100

Page generated at 2025-07-18 01:10:03. Version ac07

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