Fishers
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fishers clear sky chart from 2005-11-06 to 2025-09-19.

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% 4 8% 5% 4 4 4 5% 7% 35%	125890
	Night	15% 10% 4 8% 5% 4 4 3 5% 7% 36%	123343
Transparency	Day	46% 5% 12% 22% 13% 2	129487
	Night	47% 5% 10% 22% 14% 2	127818
Seeing	Day	17% 11% 26% 24% 16% 6%	16790
	Night	18% 9% 29% 29% 14% 1	26539

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	14% 16% 8% 14% 6% 4 3 3 4 5% 23%	3617
	11th to 20th	Day	12% 15% 8% 14% 7% 6% 6% 5% 4 3 20%	3620
	21st to end	Day	20% 17% 8% 12% 4 3 3 2 3 4 23%	4175
February	1st to 10th	Day	18% 14% 6% 9% 7% 5% 3 3 3 5% 25%	1985
	11th to 20th	Day	15% 12% 4 11% 6% 5% 4 3 4 5% 30%	1948
	21st to end	Day	16% 14% 5% 9% 5% 3 3 3 4 6% 32%	1650
March	1st to 10th	Day	19% 16% 5% 9% 4 3 3 2 4 4 31%	4480
	11th to 20th	Day	11% 10% 2 6% 4 3 4 3 5% 8% 43%	4832
	21st to end	Day	16% 11% 4 9% 5% 4 4 3 5% 6% 31%	5684
April	1st to 10th	Day	15% 10% 4 8% 6% 4 4 3 4 7% 34%	2400
	11th to 20th	Day	16% 9% 3 6% 5% 4 4 4 5% 7% 35%	2374
	21st to end	Day	19% 8% 3 7% 5% 4 4 3 4 7% 36%	2582
May	1st to 10th	Day	19% 9% 4 9% 5% 5% 5% 4 5% 7% 28%	5862
	11th to 20th	Day	18% 8% 2 7% 5% 5% 4 3 5% 7% 35%	5861
	21st to end	Day	12% 7% 3 7% 5% 5% 5% 5% 7% 8% 35%	6566
June	1st to 10th	Day	11% 6% 2 6% 5% 5% 6% 4 6% 8% 41%	2800
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 5% 7% 8% 43%	2800
	21st to end	Day	9% 6% 2 6% 6% 5% 5% 4 6% 9% 42%	2800
July	1st to 10th	Day	10% 6% 2 6% 4 5% 5% 4 7% 10% 39%	6360
	11th to 20th	Day	8% 6% 3 7% 6% 5% 5% 5% 7% 12% 37%	6360
	21st to end	Day	10% 7% 2 8% 5% 5% 6% 5% 7% 8% 36%	6708
August	1st to 10th	Day	8% 5% 2 5% 4 4 5% 4 7% 11% 46%	4234
	11th to 20th	Day	8% 6% 2 7% 4 5% 5% 4 7% 11% 41%	4019
	21st to end	Day	6% 4 2 6% 4 4 4 4 6% 9% 51%	4312
September	1st to 10th	Day	10% 6% 2 7% 4 4 4 3 6% 7% 47%	2360
	11th to 20th	Day	9% 5% 1 5% 4 4 4 4 6% 9% 48%	2178
	21st to end	Day	14% 6% 2 5% 4 4 4 3 4 7% 47%	2090
October	1st to 10th	Day	12% 5% 2 6% 4 4 4 3 5% 7% 48%	2090
	11th to 20th	Day	13% 7% 3 6% 3 4 4 4 5% 6% 44%	1938
	21st to end	Day	18% 9% 4 7% 4 4 4 4 6% 7% 34%	1881
November	1st to 10th	Day	9% 8% 2 5% 5% 5% 3 3 5% 7% 50%	1762
	11th to 20th	Day	15% 11% 4 8% 5% 4 4 3 5% 6% 34%	1800
	21st to end	Day	19% 11% 4 8% 4 4 3 3 5% 5% 34%	1800
December	1st to 10th	Day	13% 13% 4 9% 4 3 3 3 3 5% 41%	2930
	11th to 20th	Day	16% 16% 6% 11% 5% 5% 4 3 5% 5% 24%	3050
	21st to end	Day	25% 19% 7% 10% 5% 5% 4 3 4 5% 13%	3982
January	1st to 10th	Night	16% 15% 8% 14% 5% 4 3 3 5% 5% 21%	6348
	11th to 20th	Night	13% 20% 7% 14% 8% 6% 5% 4 3 3 18%	6360
	21st to end	Night	21% 14% 5% 8% 5% 4 3 3 4 4 27%	6790
February	1st to 10th	Night	19% 13% 4 10% 6% 4 4 3 5% 5% 27%	2410
	11th to 20th	Night	15% 13% 5% 11% 6% 4 3 3 4 6% 32%	2338
	21st to end	Night	18% 12% 4 9% 4 4 3 3 5% 5% 32%	1980
March	1st to 10th	Night	19% 12% 3 6% 4 3 3 3 4 5% 38%	5373
	11th to 20th	Night	12% 7% 2 6% 4 4 4 3 5% 7% 45%	5128
	21st to end	Night	17% 9% 4 8% 5% 4 4 3 5% 6% 34%	5288
April	1st to 10th	Night	15% 10% 2 7% 4 3 4 4 6% 7% 38%	2000
	11th to 20th	Night	17% 8% 2 6% 4 4 4 3 5% 7% 40%	1975
	21st to end	Night	16% 8% 3 7% 5% 5% 4 4 6% 8% 35%	1816
May	1st to 10th	Night	19% 11% 4 9% 5% 5% 4 3 6% 7% 28%	4033
	11th to 20th	Night	16% 7% 3 7% 4 4 4 3 6% 9% 38%	4032
	21st to end	Night	13% 7% 3 7% 5% 4 5% 4 6% 9% 37%	4290
June	1st to 10th	Night	9% 6% 3 6% 4 4 4 3 6% 7% 48%	1600
	11th to 20th	Night	10% 7% 2 6% 4 4 4 3 5% 10% 46%	1600
	21st to end	Night	6% 4 2 5% 5% 5% 4 5% 6% 11% 46%	1600
July	1st to 10th	Night	8% 5% 2 6% 4 4 4 4 7% 10% 46%	3618
	11th to 20th	Night	7% 5% 3 6% 4 4 5% 4 6% 10% 46%	3617
	21st to end	Night	9% 6% 3 8% 5% 5% 6% 4 6% 9% 40%	4155
August	1st to 10th	Night	10% 5% 2 6% 4 4 4 3 5% 9% 49%	2915
	11th to 20th	Night	7% 6% 2 7% 5% 5% 5% 4 6% 9% 44%	3026
	21st to end	Night	5% 4 2 6% 4 4 4 3 6% 8% 55%	3586
September	1st to 10th	Night	11% 6% 1 6% 4 3 4 3 4 7% 50%	2018
	11th to 20th	Night	7% 4 1 4 4 4 4 3 5% 8% 57%	2179
	21st to end	Night	12% 6% 2 5% 4 4 4 3 5% 6% 49%	2090
October	1st to 10th	Night	9% 4 2 6% 4 4 4 3 5% 7% 54%	2090
	11th to 20th	Night	18% 7% 2 5% 3 3 3 3 4 6% 46%	2238
	21st to end	Night	18% 7% 3 6% 4 4 4 4 4 6% 40%	2717
November	1st to 10th	Night	13% 7% 3 5% 3 3 4 3 5% 5% 49%	2536
	11th to 20th	Night	15% 9% 4 7% 4 4 4 3 5% 6% 39%	2600
	21st to end	Night	18% 13% 4 8% 5% 4 3 3 4 5% 31%	2600
December	1st to 10th	Night	15% 9% 5% 8% 5% 4 3 3 4 5% 39%	4250
	11th to 20th	Night	18% 15% 6% 10% 5% 4 4 3 4 5% 27%	5151
	21st to end	Night	26% 19% 6% 10% 5% 4 4 3 4 4 15%	6996

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	64% 3 7% 19% 6% 1	3618
	11th to 20th	Day	68% 4 9% 8% 8% 2	3620
	21st to end	Day	68% 3 7% 14% 6% 2	4175
February	1st to 10th	Day	61% 5% 9% 15% 9% 1	1985
	11th to 20th	Day	57% 4 9% 19% 9% 1	1958
	21st to end	Day	55% 5% 10% 20% 8% 2	1650
March	1st to 10th	Day	58% 4 5% 20% 11% 2	4480
	11th to 20th	Day	40% 4 10% 33% 11% 1	4832
	21st to end	Day	53% 6% 13% 18% 9% 1	5686
April	1st to 10th	Day	50% 7% 11% 19% 12% 1	2400
	11th to 20th	Day	47% 6% 12% 23% 9% 3	2374
	21st to end	Day	49% 5% 11% 22% 10% 3	2582
May	1st to 10th	Day	53% 7% 12% 18% 10%	5897
	11th to 20th	Day	48% 6% 11% 24% 10% 1	5865
	21st to end	Day	42% 9% 13% 23% 13% 1	6580
June	1st to 10th	Day	39% 7% 13% 23% 15% 3	2800
	11th to 20th	Day	36% 8% 12% 23% 19% 2	2800
	21st to end	Day	38% 7% 16% 19% 16% 4	2800
July	1st to 10th	Day	39% 5% 10% 26% 18% 2	6291
	11th to 20th	Day	38% 6% 17% 24% 14% 1	6285
	21st to end	Day	43% 6% 15% 21% 13% 2	6516
August	1st to 10th	Day	32% 6% 17% 29% 14% 1	4221
	11th to 20th	Day	35% 6% 13% 32% 13%	4058
	21st to end	Day	29% 5% 14% 31% 17% 4	4311
September	1st to 10th	Day	35% 7% 12% 24% 18% 4	2360
	11th to 20th	Day	31% 7% 12% 25% 21% 3	2178
	21st to end	Day	36% 5% 11% 25% 22% 1	2090
October	1st to 10th	Day	24% 4 9% 32% 30% 2	3480
	11th to 20th	Day	34% 4 9% 26% 25% 1	3193
	21st to end	Day	41% 4 10% 24% 20% 1	3081
November	1st to 10th	Day	35% 5% 13% 27% 17% 4	1762
	11th to 20th	Day	50% 5% 9% 20% 13% 3	1800
	21st to end	Day	53% 4 11% 21% 9% 2	1800
December	1st to 10th	Day	48% 3 10% 27% 11%	2930
	11th to 20th	Day	62% 5% 11% 17% 5%	3047
	21st to end	Day	73% 4 9% 10% 4	3982
January	1st to 10th	Night	64% 5% 8% 16% 7%	6348
	11th to 20th	Night	72% 4 6% 9% 7% 2	6360
	21st to end	Night	61% 3 10% 18% 8% 1	6790
February	1st to 10th	Night	59% 4 12% 16% 8% 1	2410
	11th to 20th	Night	54% 5% 11% 17% 12% 1	2339
	21st to end	Night	54% 5% 11% 17% 10% 2	1980
March	1st to 10th	Night	49% 4 7% 26% 12% 3	5373
	11th to 20th	Night	38% 5% 12% 27% 17% 2	5128
	21st to end	Night	50% 6% 9% 26% 8% 1	5288
April	1st to 10th	Night	44% 6% 12% 22% 14% 2	2000
	11th to 20th	Night	44% 5% 10% 21% 16% 4	1975
	21st to end	Night	45% 8% 10% 21% 12% 4	1816
May	1st to 10th	Night	55% 7% 9% 16% 11% 2	4060
	11th to 20th	Night	43% 6% 12% 25% 12% 1	4033
	21st to end	Night	41% 8% 16% 22% 12% 2	4298
June	1st to 10th	Night	34% 6% 11% 25% 21% 3	1600
	11th to 20th	Night	36% 6% 11% 23% 21% 4	1600
	21st to end	Night	30% 9% 17% 23% 17% 4	1600
July	1st to 10th	Night	34% 5% 11% 28% 18% 4	3580
	11th to 20th	Night	33% 6% 15% 29% 16% 1	3572
	21st to end	Night	40% 5% 14% 24% 13% 3	4034
August	1st to 10th	Night	32% 6% 14% 32% 14% 1	2904
	11th to 20th	Night	35% 6% 13% 28% 17% 1	3053
	21st to end	Night	27% 5% 13% 29% 22% 3	3586
September	1st to 10th	Night	32% 7% 11% 22% 21% 6%	2018
	11th to 20th	Night	27% 5% 10% 26% 27% 4	2179
	21st to end	Night	35% 6% 11% 23% 22% 3	2090
October	1st to 10th	Night	21% 4 7% 27% 39% 2	3480
	11th to 20th	Night	29% 3 9% 24% 33% 1	3722
	21st to end	Night	34% 3 8% 26% 24% 4	4467
November	1st to 10th	Night	36% 4 10% 24% 21% 3	2536
	11th to 20th	Night	45% 5% 9% 22% 16% 3	2600
	21st to end	Night	56% 4 9% 21% 9%	2600
December	1st to 10th	Night	48% 3 12% 26% 11%	4250
	11th to 20th	Night	61% 3 10% 16% 9% 1	5153
	21st to end	Night	73% 4 9% 10% 4	6996

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	24% 20% 31% 21% 3	300
	11th to 20th	Day	23% 20% 38% 14% 5%	300
	21st to end	Day	29% 18% 31% 19% 4	330
February	1st to 10th	Day	29% 15% 35% 18% 4	300
	11th to 20th	Day	23% 23% 35% 15% 5%	300
	21st to end	Day	25% 18% 41% 14% 2	249
March	1st to 10th	Day	22% 25% 32% 18% 2	300
	11th to 20th	Day	26% 17% 33% 16% 7% 1	430
	21st to end	Day	29% 16% 32% 17% 5% 1	550
April	1st to 10th	Day	16% 20% 35% 18% 8% 2	500
	11th to 20th	Day	20% 18% 28% 21% 11% 2	492
	21st to end	Day	23% 16% 33% 20% 7% 2	500
May	1st to 10th	Day	22% 13% 32% 23% 8% 2	503
	11th to 20th	Day	23% 7% 28% 23% 13% 7%	527
	21st to end	Day	12% 8% 28% 24% 19% 9%	628
June	1st to 10th	Day	11% 7% 30% 29% 18% 6%	730
	11th to 20th	Day	12% 5% 24% 34% 20% 6%	730
	21st to end	Day	12% 6% 26% 28% 20% 8%	730
July	1st to 10th	Day	13% 2 17% 27% 26% 16%	721
	11th to 20th	Day	7% 5% 19% 34% 23% 11%	718
	21st to end	Day	10% 2 15% 32% 29% 12%	704
August	1st to 10th	Day	10% 4 14% 26% 30% 16%	526
	11th to 20th	Day	11% 4 18% 29% 25% 13%	519
	21st to end	Day	7% 3 14% 32% 30% 15%	583
September	1st to 10th	Day	11% 4 16% 30% 28% 12%	530
	11th to 20th	Day	8% 2 14% 28% 29% 18%	522
	21st to end	Day	17% 9% 22% 22% 21% 10%	490
October	1st to 10th	Day	10% 9% 23% 33% 18% 7%	490
	11th to 20th	Day	14% 17% 31% 23% 12% 3	428
	21st to end	Day	25% 17% 34% 19% 5%	330
November	1st to 10th	Day	11% 19% 32% 22% 14% 2	300
	11th to 20th	Day	22% 19% 32% 16% 8% 2	300
	21st to end	Day	26% 12% 38% 21% 3	300
December	1st to 10th	Day	18% 25% 35% 17% 4 1	300
	11th to 20th	Day	21% 18% 36% 17% 6% 1	300
	21st to end	Day	30% 19% 30% 16% 4	330
January	1st to 10th	Night	24% 16% 33% 23% 4	1000
	11th to 20th	Night	27% 13% 37% 19% 4	1000
	21st to end	Night	24% 15% 35% 24% 3	1011
February	1st to 10th	Night	26% 12% 34% 25% 2	800
	11th to 20th	Night	21% 15% 38% 23% 3	783
	21st to end	Night	26% 12% 39% 21% 2	660
March	1st to 10th	Night	20% 16% 34% 24% 6%	800
	11th to 20th	Night	20% 14% 37% 23% 6% 1	800
	21st to end	Night	25% 11% 32% 27% 5%	804
April	1st to 10th	Night	19% 12% 36% 25% 7% 1	600
	11th to 20th	Night	19% 12% 31% 29% 8% 1	593
	21st to end	Night	22% 9% 39% 23% 7% 1	600
May	1st to 10th	Night	19% 9% 35% 27% 10%	600
	11th to 20th	Night	20% 6% 24% 32% 17% 1	591
	21st to end	Night	11% 4 26% 37% 21% 2	650
June	1st to 10th	Night	12% 4 25% 44% 15% 1	600
	11th to 20th	Night	12% 4 22% 40% 21% 1	600
	21st to end	Night	7% 3 23% 40% 26% 2	600
July	1st to 10th	Night	10% 2 13% 36% 33% 6%	585
	11th to 20th	Night	7% 3 16% 38% 32% 4	582
	21st to end	Night	7% 2 15% 41% 32% 3	657
August	1st to 10th	Night	9% 2 13% 40% 34% 4	597
	11th to 20th	Night	7% 2 13% 42% 32% 5%	594
	21st to end	Night	7% 1 14% 36% 37% 5%	660
September	1st to 10th	Night	13% 4 13% 34% 31% 5%	618
	11th to 20th	Night	8% 3 16% 34% 35% 4	793
	21st to end	Night	15% 5% 21% 32% 24% 2	760
October	1st to 10th	Night	11% 5% 24% 35% 20% 5%	760
	11th to 20th	Night	20% 10% 29% 26% 14%	760
	21st to end	Night	22% 10% 36% 25% 7%	836
November	1st to 10th	Night	17% 9% 33% 27% 12% 1	780
	11th to 20th	Night	18% 16% 32% 27% 7% 1	800
	21st to end	Night	26% 12% 29% 26% 7%	800
December	1st to 10th	Night	22% 13% 37% 23% 5%	800
	11th to 20th	Night	25% 11% 34% 23% 6%	965
	21st to end	Night	31% 14% 32% 19% 4	1100

Page generated at 2025-09-16 01:49:14. Version ac07

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