Middleville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Middleville clear sky chart from 2005-11-06 to 2026-04-17.

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	17% 7% 3 7% 4 4 4 4 5% 7% 38%	131611
	Night	17% 8% 3 6% 4 4 4 3 5% 6% 40%	130500
Transparency	Day	44% 6% 12% 22% 14% 2	135125
	Night	43% 6% 12% 22% 15% 2	135073
Seeing	Day	24% 17% 29% 19% 9% 2	16703
	Night	22% 15% 29% 25% 8% 1	26027

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	12% 9% 3 8% 5% 4 5% 3 5% 5% 39%	4661
	11th to 20th	Day	14% 11% 4 9% 5% 5% 4 3 4 5% 37%	4650
	21st to end	Day	15% 7% 3 7% 4 4 4 4 5% 6% 39%	5702
February	1st to 10th	Day	15% 8% 3 9% 5% 5% 4 3 5% 6% 36%	1890
	11th to 20th	Day	15% 9% 4 8% 5% 4 4 3 6% 5% 37%	1998
	21st to end	Day	18% 9% 3 8% 4 5% 3 3 5% 5% 37%	1730
March	1st to 10th	Day	22% 9% 3 6% 4 3 3 3 4 5% 39%	4576
	11th to 20th	Day	12% 8% 3 7% 4 4 4 4 5% 7% 42%	5014
	21st to end	Day	18% 7% 2 6% 4 4 4 3 5% 6% 40%	5961
April	1st to 10th	Day	19% 9% 3 6% 4 4 4 4 5% 6% 36%	2520
	11th to 20th	Day	17% 7% 3 6% 4 4 5% 4 5% 6% 39%	2446
	21st to end	Day	17% 7% 2 6% 4 5% 5% 5% 6% 6% 38%	2400
May	1st to 10th	Day	28% 7% 2 6% 4 4 5% 4 5% 7% 28%	5971
	11th to 20th	Day	22% 9% 3 6% 5% 4 4 3 5% 6% 32%	6318
	21st to end	Day	21% 6% 2 5% 4 4 5% 4 7% 8% 33%	6949
June	1st to 10th	Day	15% 5% 3 6% 5% 5% 5% 5% 6% 8% 36%	2800
	11th to 20th	Day	17% 6% 3 6% 5% 5% 5% 4 7% 9% 33%	2800
	21st to end	Day	13% 6% 2 6% 5% 5% 4 4 6% 8% 40%	2800
July	1st to 10th	Day	9% 7% 3 8% 5% 5% 6% 5% 6% 10% 35%	6360
	11th to 20th	Day	10% 7% 3 7% 5% 5% 6% 6% 8% 12% 31%	6360
	21st to end	Day	13% 7% 2 7% 5% 4 5% 4 5% 9% 40%	6926
August	1st to 10th	Day	21% 6% 2 7% 4 5% 5% 4 7% 7% 31%	4283
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 4 6% 9% 40%	3859
	21st to end	Day	13% 6% 2 5% 3 4 4 4 5% 9% 45%	4312
September	1st to 10th	Day	15% 6% 2 6% 5% 4 4 4 5% 7% 43%	2400
	11th to 20th	Day	13% 5% 2 5% 4 4 4 3 5% 7% 50%	2351
	21st to end	Day	19% 6% 3 7% 4 4 4 4 5% 6% 38%	2200
October	1st to 10th	Day	19% 6% 2 6% 4 3 4 3 4 7% 42%	2025
	11th to 20th	Day	16% 6% 2 6% 4 4 4 3 4 7% 44%	2000
	21st to end	Day	21% 6% 2 5% 4 4 4 3 5% 6% 41%	2082
November	1st to 10th	Day	14% 7% 2 4 4 3 3 2 4 6% 51%	1851
	11th to 20th	Day	17% 7% 2 5% 3 4 4 3 5% 6% 43%	1890
	21st to end	Day	17% 8% 3 6% 4 4 5% 4 5% 6% 38%	1732
December	1st to 10th	Day	17% 8% 2 6% 4 4 5% 3 5% 5% 40%	2680
	11th to 20th	Day	21% 9% 3 6% 4 3 4 3 5% 5% 39%	3066
	21st to end	Day	18% 9% 4 9% 5% 4 4 3 5% 7% 30%	4048
January	1st to 10th	Night	13% 9% 3 9% 6% 5% 5% 4 5% 6% 35%	8234
	11th to 20th	Night	14% 10% 4 9% 5% 5% 5% 3 5% 6% 34%	8235
	21st to end	Night	14% 8% 2 7% 5% 5% 4 3 5% 6% 42%	8462
February	1st to 10th	Night	15% 9% 3 6% 5% 3 4 4 5% 6% 40%	2730
	11th to 20th	Night	16% 8% 4 7% 5% 5% 5% 3 5% 5% 38%	2506
	21st to end	Night	18% 7% 4 6% 5% 4 4 3 5% 5% 39%	2076
March	1st to 10th	Night	19% 9% 3 6% 4 3 3 3 5% 5% 40%	5484
	11th to 20th	Night	13% 9% 3 6% 3 4 4 3 4 6% 45%	5149
	21st to end	Night	16% 8% 3 8% 4 4 4 3 4 5% 41%	5199
April	1st to 10th	Night	19% 8% 2 7% 6% 5% 4 4 5% 6% 34%	2100
	11th to 20th	Night	18% 6% 3 6% 4 4 4 3 6% 8% 38%	2036
	21st to end	Night	18% 7% 2 5% 3 3 4 4 5% 7% 41%	2000
May	1st to 10th	Night	30% 9% 2 6% 4 3 4 3 5% 7% 27%	3997
	11th to 20th	Night	23% 10% 3 7% 4 4 4 3 4 6% 33%	3575
	21st to end	Night	22% 7% 2 6% 4 4 4 4 6% 7% 35%	3926
June	1st to 10th	Night	16% 6% 1 6% 4 5% 4 3 5% 6% 43%	1600
	11th to 20th	Night	14% 7% 2 6% 5% 4 4 4 6% 9% 40%	1600
	21st to end	Night	13% 4 2 5% 4 4 5% 4 6% 9% 44%	1600
July	1st to 10th	Night	12% 7% 2 7% 5% 5% 6% 3 6% 9% 39%	3600
	11th to 20th	Night	13% 8% 3 7% 4 5% 6% 5% 8% 10% 33%	3600
	21st to end	Night	12% 5% 2 5% 3 4 5% 4 6% 7% 47%	3926
August	1st to 10th	Night	21% 7% 3 7% 4 5% 5% 4 5% 8% 33%	2849
	11th to 20th	Night	15% 7% 3 6% 4 5% 4 3 5% 7% 42%	3157
	21st to end	Night	13% 4 2 4 3 3 4 3 5% 8% 51%	3586
September	1st to 10th	Night	15% 6% 2 5% 4 4 4 3 5% 6% 46%	2000
	11th to 20th	Night	12% 6% 2 5% 3 4 3 2 4 7% 53%	2048
	21st to end	Night	17% 7% 2 6% 4 3 3 3 5% 6% 44%	2200
October	1st to 10th	Night	21% 6% 2 5% 4 4 3 2 4 6% 43%	2371
	11th to 20th	Night	18% 6% 2 4 4 3 3 2 4 6% 48%	2400
	21st to end	Night	20% 7% 2 5% 3 3 2 3 5% 6% 44%	2756
November	1st to 10th	Night	13% 5% 2 6% 3 4 4 3 5% 6% 50%	2667
	11th to 20th	Night	18% 7% 3 5% 3 3 4 3 4 5% 45%	2730
	21st to end	Night	14% 7% 3 6% 4 3 4 4 5% 7% 42%	2883
December	1st to 10th	Night	13% 9% 3 7% 4 4 4 3 4 6% 43%	4720
	11th to 20th	Night	23% 9% 2 5% 3 4 4 3 4 5% 38%	5348
	21st to end	Night	19% 12% 4 8% 4 4 4 3 4 6% 33%	7150

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	45% 5% 11% 24% 14% 2	4662
	11th to 20th	Day	48% 5% 9% 20% 13% 5%	4680
	21st to end	Day	44% 5% 11% 23% 16% 1	5702
February	1st to 10th	Day	48% 6% 12% 21% 12% 2	1890
	11th to 20th	Day	47% 6% 8% 21% 15% 2	2007
	21st to end	Day	48% 5% 11% 22% 12% 3	1730
March	1st to 10th	Day	47% 5% 9% 21% 12% 7%	4579
	11th to 20th	Day	39% 7% 15% 27% 8% 4	5014
	21st to end	Day	43% 6% 10% 12% 23% 6%	5961
April	1st to 10th	Day	48% 6% 9% 19% 14% 4	2520
	11th to 20th	Day	44% 6% 13% 19% 16% 3	2446
	21st to end	Day	43% 8% 10% 21% 15% 4	2400
May	1st to 10th	Day	54% 7% 13% 15% 9% 1	5982
	11th to 20th	Day	52% 7% 8% 20% 12% 1	6322
	21st to end	Day	45% 8% 12% 21% 12% 2	6949
June	1st to 10th	Day	43% 10% 12% 20% 13% 1	2800
	11th to 20th	Day	45% 9% 13% 22% 10% 2	2800
	21st to end	Day	41% 8% 13% 23% 14% 1	2800
July	1st to 10th	Day	43% 10% 11% 21% 15% 1	6290
	11th to 20th	Day	42% 8% 18% 22% 10% 1	6285
	21st to end	Day	42% 6% 10% 21% 20% 1	6728
August	1st to 10th	Day	49% 8% 13% 20% 9%	4269
	11th to 20th	Day	39% 7% 15% 28% 11%	3895
	21st to end	Day	35% 7% 11% 31% 15% 2	4312
September	1st to 10th	Day	41% 6% 12% 21% 18% 2	2400
	11th to 20th	Day	34% 6% 11% 23% 24% 3	2351
	21st to end	Day	45% 7% 11% 17% 18% 2	2200
October	1st to 10th	Day	41% 6% 7% 19% 23% 4	3298
	11th to 20th	Day	32% 5% 9% 28% 23% 4	3240
	21st to end	Day	29% 4 16% 26% 22% 3	3346
November	1st to 10th	Day	36% 5% 13% 24% 19% 3	1851
	11th to 20th	Day	40% 5% 10% 24% 17% 3	1890
	21st to end	Day	44% 6% 13% 25% 10% 2	1732
December	1st to 10th	Day	45% 5% 14% 25% 10% 1	2680
	11th to 20th	Day	46% 5% 14% 22% 12% 1	3066
	21st to end	Day	50% 8% 10% 18% 13% 1	4048
January	1st to 10th	Night	47% 6% 12% 21% 12% 2	8234
	11th to 20th	Night	49% 6% 12% 18% 12% 4	8280
	21st to end	Night	43% 5% 9% 21% 19% 3	8462
February	1st to 10th	Night	44% 5% 13% 23% 13% 2	2730
	11th to 20th	Night	47% 5% 10% 20% 14% 3	2508
	21st to end	Night	45% 6% 9% 23% 14% 3	2076
March	1st to 10th	Night	45% 5% 11% 20% 12% 6%	5494
	11th to 20th	Night	38% 6% 16% 25% 12% 4	5150
	21st to end	Night	44% 6% 7% 17% 22% 4	5199
April	1st to 10th	Night	49% 6% 11% 18% 12% 3	2100
	11th to 20th	Night	44% 7% 10% 20% 17% 1	2036
	21st to end	Night	41% 7% 10% 22% 16% 4	2000
May	1st to 10th	Night	56% 7% 12% 16% 10% 1	4003
	11th to 20th	Night	51% 8% 12% 14% 13% 1	3576
	21st to end	Night	46% 8% 13% 22% 9% 2	3927
June	1st to 10th	Night	40% 7% 11% 22% 18% 1	1600
	11th to 20th	Night	40% 9% 16% 24% 11% 1	1600
	21st to end	Night	34% 9% 17% 26% 13% 1	1600
July	1st to 10th	Night	41% 9% 14% 19% 15% 2	3560
	11th to 20th	Night	43% 9% 15% 21% 10%	3552
	21st to end	Night	35% 7% 13% 25% 19% 1	3809
August	1st to 10th	Night	49% 8% 16% 17% 9% 1	2839
	11th to 20th	Night	41% 7% 14% 27% 10%	3187
	21st to end	Night	32% 6% 11% 33% 17% 1	3586
September	1st to 10th	Night	38% 6% 11% 25% 19% 1	2000
	11th to 20th	Night	34% 4 10% 24% 25% 2	2048
	21st to end	Night	41% 6% 10% 21% 20% 1	2200
October	1st to 10th	Night	42% 5% 10% 23% 19% 1	3878
	11th to 20th	Night	30% 5% 10% 27% 26% 2	3899
	21st to end	Night	30% 5% 14% 31% 20% 1	4442
November	1st to 10th	Night	34% 6% 13% 24% 21% 3	2667
	11th to 20th	Night	41% 5% 11% 22% 18% 3	2730
	21st to end	Night	41% 5% 15% 26% 13% 1	2883
December	1st to 10th	Night	42% 5% 13% 30% 9% 1	4720
	11th to 20th	Night	47% 5% 12% 21% 14% 2	5348
	21st to end	Night	51% 6% 10% 18% 12% 2	7150

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	31% 29% 26% 12% 2	220
	11th to 20th	Day	40% 28% 25% 7% 1	220
	21st to end	Day	29% 32% 29% 7% 3 1	349
February	1st to 10th	Day	32% 29% 29% 8% 2	330
	11th to 20th	Day	37% 25% 29% 8% 1	486
	21st to end	Day	33% 24% 32% 10% 2	446
March	1st to 10th	Day	32% 22% 31% 13% 2	540
	11th to 20th	Day	32% 22% 29% 12% 4 1	540
	21st to end	Day	33% 24% 27% 11% 4 1	594
April	1st to 10th	Day	33% 22% 27% 12% 4 1	540
	11th to 20th	Day	29% 23% 28% 12% 7% 1	516
	21st to end	Day	29% 19% 32% 14% 4 1	500
May	1st to 10th	Day	35% 19% 26% 12% 7% 1	503
	11th to 20th	Day	23% 20% 30% 18% 7% 2	527
	21st to end	Day	22% 10% 30% 24% 11% 2	573
June	1st to 10th	Day	19% 13% 32% 23% 11% 2	530
	11th to 20th	Day	22% 13% 28% 25% 10% 2	530
	21st to end	Day	16% 13% 33% 26% 11% 1	530
July	1st to 10th	Day	13% 9% 29% 27% 17% 4	525
	11th to 20th	Day	11% 6% 28% 33% 19% 3	524
	21st to end	Day	13% 11% 35% 27% 12% 3	576
August	1st to 10th	Day	13% 8% 29% 30% 14% 6%	526
	11th to 20th	Day	13% 7% 25% 34% 16% 6%	519
	21st to end	Day	13% 10% 33% 23% 14% 7%	583
September	1st to 10th	Day	18% 11% 27% 24% 14% 6%	530
	11th to 20th	Day	13% 9% 28% 24% 16% 10%	530
	21st to end	Day	24% 10% 29% 22% 12% 4	530
October	1st to 10th	Day	25% 10% 25% 21% 14% 5%	530
	11th to 20th	Day	23% 18% 29% 20% 8% 2	530
	21st to end	Day	26% 17% 30% 18% 7% 2	517
November	1st to 10th	Day	20% 20% 28% 20% 9% 2	425
	11th to 20th	Day	26% 21% 28% 19% 5%	430
	21st to end	Day	27% 25% 31% 13% 4	272
December	1st to 10th	Day	31% 28% 27% 8% 5%	220
	11th to 20th	Day	40% 20% 26% 10% 3	220
	21st to end	Day	34% 17% 34% 10% 5% 1	242
January	1st to 10th	Night	24% 22% 35% 17% 2	840
	11th to 20th	Night	28% 21% 29% 19% 3	840
	21st to end	Night	20% 23% 36% 19% 2	924
February	1st to 10th	Night	25% 19% 34% 20% 2	840
	11th to 20th	Night	29% 22% 36% 13%	823
	21st to end	Night	28% 19% 34% 17% 2	692
March	1st to 10th	Night	26% 21% 33% 18% 3	840
	11th to 20th	Night	27% 21% 30% 18% 4	840
	21st to end	Night	23% 22% 35% 15% 4 1	924
April	1st to 10th	Night	27% 21% 31% 18% 4	840
	11th to 20th	Night	22% 19% 32% 21% 5%	816
	21st to end	Night	24% 16% 31% 24% 5%	800
May	1st to 10th	Night	28% 13% 29% 24% 5%	582
	11th to 20th	Night	18% 13% 34% 28% 7% 1	394
	21st to end	Night	18% 7% 26% 37% 12%	433
June	1st to 10th	Night	17% 7% 27% 36% 14% 1	400
	11th to 20th	Night	14% 7% 31% 36% 13%	400
	21st to end	Night	14% 5% 24% 45% 12%	400
July	1st to 10th	Night	13% 5% 23% 38% 20% 1	390
	11th to 20th	Night	12% 4 20% 44% 18% 1	388
	21st to end	Night	11% 5% 22% 44% 18% 1	438
August	1st to 10th	Night	13% 2 20% 39% 24% 2	557
	11th to 20th	Night	13% 5% 19% 38% 24% 2	762
	21st to end	Night	14% 6% 21% 37% 20% 2	880
September	1st to 10th	Night	18% 6% 24% 35% 16% 2	800
	11th to 20th	Night	14% 7% 23% 32% 21% 5%	800
	21st to end	Night	20% 6% 25% 30% 17% 2	800
October	1st to 10th	Night	23% 10% 23% 28% 15% 2	800
	11th to 20th	Night	20% 13% 28% 31% 8% 1	800
	21st to end	Night	25% 14% 31% 23% 7%	880
November	1st to 10th	Night	18% 16% 30% 25% 10% 1	820
	11th to 20th	Night	24% 17% 29% 23% 6% 1	840
	21st to end	Night	20% 20% 31% 23% 5%	840
December	1st to 10th	Night	25% 18% 32% 20% 5%	840
	11th to 20th	Night	26% 19% 32% 21% 3	840
	21st to end	Night	26% 18% 33% 20% 2	924

Page generated at 2026-04-14 02:44:28. Version ac07

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