GM Milford Proving Ground Softball Fields
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the GM Milford Proving Ground Softball Fields clear sky chart from 2005-11-06 to 2026-09-14.

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	13% 10% 4 8% 5% 5% 5% 4 5% 7% 34%	148013
	Night	14% 11% 4 9% 5% 4 4 3 5% 6% 34%	143233
Transparency	Day	47% 6% 12% 21% 13% 1	151570
	Night	48% 6% 11% 21% 13% 1	147738
Seeing	Day	18% 12% 29% 23% 13% 5%	18013
	Night	19% 10% 29% 29% 12% 1	28019

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% 18% 7% 17% 6% 4 4 3 4 4 20%	4691
	11th to 20th	Day	13% 16% 8% 18% 10% 10% 5% 3 3 4 11%	4710
	21st to end	Day	18% 17% 6% 13% 9% 5% 7% 4 4 4 16%	5589
February	1st to 10th	Day	13% 14% 6% 13% 8% 5% 5% 3 5% 6% 22%	1890
	11th to 20th	Day	14% 13% 6% 13% 9% 5% 4 3 4 5% 23%	2003
	21st to end	Day	13% 16% 6% 12% 5% 4 4 4 4 6% 25%	1730
March	1st to 10th	Day	15% 11% 5% 10% 6% 4 4 3 5% 6% 31%	4663
	11th to 20th	Day	13% 12% 4 8% 5% 4 4 4 5% 7% 33%	5090
	21st to end	Day	19% 14% 4 9% 5% 4 4 3 4 5% 29%	5586
April	1st to 10th	Day	17% 13% 4 8% 6% 4 5% 4 5% 6% 29%	2465
	11th to 20th	Day	16% 11% 4 7% 5% 5% 4 3 5% 7% 35%	2650
	21st to end	Day	16% 9% 3 8% 5% 4 5% 3 5% 7% 34%	2730
May	1st to 10th	Day	17% 9% 2 7% 5% 5% 5% 4 5% 7% 34%	7616
	11th to 20th	Day	14% 8% 2 8% 5% 5% 5% 4 6% 8% 35%	7626
	21st to end	Day	14% 7% 2 6% 4 4 4 3 5% 8% 44%	8468
June	1st to 10th	Day	9% 6% 2 7% 4 4 5% 4 6% 9% 42%	2940
	11th to 20th	Day	11% 6% 3 7% 5% 5% 5% 4 6% 9% 39%	2940
	21st to end	Day	10% 6% 2 6% 6% 5% 6% 5% 7% 10% 37%	2940
July	1st to 10th	Day	10% 5% 2 6% 5% 5% 5% 4 7% 10% 41%	8280
	11th to 20th	Day	6% 4 2 5% 4 4 5% 4 7% 10% 49%	8280
	21st to end	Day	8% 5% 2 5% 4 5% 4 4 6% 9% 47%	8575
August	1st to 10th	Day	15% 6% 2 6% 4 4 5% 4 5% 7% 41%	6014
	11th to 20th	Day	11% 7% 3 8% 5% 5% 5% 5% 7% 9% 36%	5951
	21st to end	Day	8% 5% 2 7% 5% 5% 6% 5% 7% 10% 39%	6480
September	1st to 10th	Day	11% 6% 3 7% 5% 5% 6% 4 6% 9% 40%	2389
	11th to 20th	Day	9% 5% 2 4 4 5% 4 4 6% 9% 48%	2233
	21st to end	Day	14% 7% 3 7% 5% 5% 5% 4 7% 7% 37%	2200
October	1st to 10th	Day	14% 6% 2 7% 4 4 4 4 4 6% 43%	2158
	11th to 20th	Day	16% 11% 3 8% 5% 5% 5% 3 5% 7% 34%	2000
	21st to end	Day	19% 12% 3 7% 5% 4 4 4 5% 7% 30%	2015
November	1st to 10th	Day	13% 10% 3 7% 6% 5% 5% 3 5% 7% 37%	1852
	11th to 20th	Day	16% 14% 5% 8% 5% 4 4 3 4 6% 30%	1890
	21st to end	Day	18% 15% 6% 10% 4 4 4 3 4 6% 26%	1823
December	1st to 10th	Day	12% 15% 8% 12% 7% 5% 5% 4 5% 5% 20%	2680
	11th to 20th	Day	18% 21% 7% 10% 6% 4 5% 3 4 5% 17%	2796
	21st to end	Day	25% 21% 7% 12% 4 3 3 3 3 4 14%	4070
January	1st to 10th	Night	14% 15% 6% 14% 6% 5% 4 3 4 5% 24%	8232
	11th to 20th	Night	9% 17% 8% 16% 9% 8% 6% 4 5% 5% 14%	8280
	21st to end	Night	14% 15% 8% 12% 6% 5% 6% 3 4 5% 21%	8599
February	1st to 10th	Night	16% 15% 5% 12% 7% 5% 5% 3 4 5% 24%	2730
	11th to 20th	Night	14% 13% 5% 11% 7% 5% 4 4 5% 6% 27%	2500
	21st to end	Night	17% 13% 5% 10% 5% 5% 4 4 5% 6% 28%	2076
March	1st to 10th	Night	15% 11% 4 9% 4 4 4 3 5% 6% 35%	5410
	11th to 20th	Night	10% 9% 3 7% 5% 4 5% 4 5% 7% 41%	5090
	21st to end	Night	17% 10% 3 8% 5% 4 4 3 4 6% 36%	5588
April	1st to 10th	Night	17% 10% 3 7% 5% 4 4 4 5% 6% 35%	2174
	11th to 20th	Night	18% 9% 3 6% 4 4 4 3 6% 6% 36%	1917
	21st to end	Night	16% 8% 3 6% 4 4 4 5% 5% 7% 38%	1890
May	1st to 10th	Night	18% 10% 3 7% 5% 4 4 4 5% 7% 34%	5237
	11th to 20th	Night	16% 8% 2 7% 4 3 4 3 4 7% 41%	5234
	21st to end	Night	13% 7% 2 5% 4 4 4 3 5% 7% 44%	5671
June	1st to 10th	Night	11% 5% 2 6% 5% 4 3 3 5% 9% 48%	1680
	11th to 20th	Night	11% 6% 2 6% 4 3 4 5% 7% 8% 44%	1680
	21st to end	Night	10% 5% 2 5% 4 4 4 3 6% 9% 49%	1680
July	1st to 10th	Night	8% 5% 2 6% 4 4 4 4 6% 10% 47%	4708
	11th to 20th	Night	7% 4 1 5% 4 4 4 3 7% 9% 53%	4707
	21st to end	Night	9% 5% 2 6% 4 4 4 4 5% 7% 49%	5509
August	1st to 10th	Night	15% 6% 2 5% 4 3 3 3 5% 7% 45%	4135
	11th to 20th	Night	12% 7% 3 7% 4 4 4 4 5% 8% 42%	4095
	21st to end	Night	8% 6% 2 7% 4 4 5% 3 6% 7% 47%	4642
September	1st to 10th	Night	10% 6% 2 5% 4 3 4 4 5% 7% 49%	2210
	11th to 20th	Night	10% 4 2 4 4 3 3 4 4 7% 56%	2234
	21st to end	Night	14% 8% 2 6% 4 4 5% 3 5% 7% 43%	2200
October	1st to 10th	Night	13% 6% 2 5% 4 4 4 3 5% 6% 47%	2241
	11th to 20th	Night	18% 10% 3 7% 5% 4 4 3 4 5% 36%	2400
	21st to end	Night	20% 10% 3 7% 5% 4 4 3 5% 6% 33%	2820
November	1st to 10th	Night	13% 9% 3 7% 4 4 4 3 5% 6% 42%	2666
	11th to 20th	Night	15% 11% 4 8% 6% 5% 5% 4 5% 6% 31%	2730
	21st to end	Night	19% 15% 4 9% 4 4 4 4 4 6% 26%	2791
December	1st to 10th	Night	12% 14% 6% 16% 6% 5% 5% 4 5% 6% 21%	4720
	11th to 20th	Night	16% 20% 6% 12% 7% 5% 4 3 5% 4 19%	5607
	21st to end	Night	24% 23% 7% 10% 4 3 3 2 3 4 14%	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	66% 5% 11% 13% 4 1	4692
	11th to 20th	Day	76% 7% 7% 5% 5%	4710
	21st to end	Day	71% 5% 9% 10% 5%	5589
February	1st to 10th	Day	63% 6% 9% 15% 7%	1890
	11th to 20th	Day	62% 5% 9% 15% 8% 1	2013
	21st to end	Day	59% 5% 10% 17% 7% 2	1730
March	1st to 10th	Day	54% 5% 13% 17% 9% 2	4663
	11th to 20th	Day	47% 6% 15% 22% 8% 2	5090
	21st to end	Day	57% 5% 10% 15% 11% 1	5586
April	1st to 10th	Day	54% 5% 11% 18% 11%	2465
	11th to 20th	Day	49% 5% 12% 20% 12% 2	2650
	21st to end	Day	47% 7% 13% 18% 13% 2	2730
May	1st to 10th	Day	48% 6% 11% 21% 11% 2	7651
	11th to 20th	Day	45% 8% 12% 21% 13% 1	7630
	21st to end	Day	39% 5% 9% 20% 24% 4	8482
June	1st to 10th	Day	36% 7% 12% 27% 15% 2	2940
	11th to 20th	Day	40% 7% 12% 23% 16% 2	2940
	21st to end	Day	37% 9% 14% 23% 16% 1	2940
July	1st to 10th	Day	36% 8% 15% 25% 15% 1	8211
	11th to 20th	Day	27% 6% 13% 31% 20% 1	8205
	21st to end	Day	32% 7% 13% 23% 23% 1	8388
August	1st to 10th	Day	40% 7% 12% 21% 18% 2	6001
	11th to 20th	Day	41% 8% 14% 27% 8% 1	5990
	21st to end	Day	37% 8% 17% 28% 10% 1	6479
September	1st to 10th	Day	39% 7% 14% 25% 13% 2	2389
	11th to 20th	Day	31% 8% 12% 32% 16% 1	2233
	21st to end	Day	44% 7% 12% 24% 14%	2200
October	1st to 10th	Day	31% 5% 11% 31% 21% 1	3509
	11th to 20th	Day	39% 6% 11% 25% 19%	3240
	21st to end	Day	45% 5% 14% 23% 12% 1	3227
November	1st to 10th	Day	46% 6% 12% 24% 12% 1	1852
	11th to 20th	Day	55% 5% 12% 19% 7% 2	1890
	21st to end	Day	59% 5% 11% 17% 6%	1823
December	1st to 10th	Day	63% 7% 15% 11% 3	2680
	11th to 20th	Day	69% 4 9% 12% 5%	2792
	21st to end	Day	76% 4 7% 8% 5%	4070
January	1st to 10th	Night	61% 6% 10% 16% 6% 1	8233
	11th to 20th	Night	68% 7% 10% 10% 5%	8280
	21st to end	Night	63% 5% 10% 15% 6%	8599
February	1st to 10th	Night	61% 6% 10% 15% 7% 1	2730
	11th to 20th	Night	57% 6% 10% 18% 9% 1	2501
	21st to end	Night	55% 5% 13% 17% 8% 1	2076
March	1st to 10th	Night	49% 5% 13% 22% 10% 1	5410
	11th to 20th	Night	38% 7% 14% 25% 15% 1	5090
	21st to end	Night	49% 6% 11% 20% 13% 2	5588
April	1st to 10th	Night	49% 5% 10% 21% 13% 2	2174
	11th to 20th	Night	45% 6% 11% 18% 18% 2	1917
	21st to end	Night	44% 6% 12% 19% 16% 2	1890
May	1st to 10th	Night	49% 6% 11% 17% 14% 4	5264
	11th to 20th	Night	43% 5% 11% 25% 13% 2	5235
	21st to end	Night	38% 6% 10% 22% 19% 5%	5681
June	1st to 10th	Night	34% 5% 11% 27% 21% 2	1680
	11th to 20th	Night	35% 7% 13% 26% 16% 2	1680
	21st to end	Night	32% 6% 14% 27% 20% 1	1680
July	1st to 10th	Night	32% 6% 13% 29% 16% 3	4670
	11th to 20th	Night	27% 5% 13% 31% 23% 1	4662
	21st to end	Night	33% 6% 12% 22% 25% 2	5384
August	1st to 10th	Night	38% 6% 12% 22% 21% 2	4124
	11th to 20th	Night	39% 7% 15% 30% 8% 1	4122
	21st to end	Night	34% 7% 16% 31% 12% 1	4642
September	1st to 10th	Night	33% 8% 11% 29% 17% 2	2210
	11th to 20th	Night	28% 5% 11% 32% 22% 2	2234
	21st to end	Night	40% 5% 13% 26% 15% 1	2200
October	1st to 10th	Night	26% 4 10% 33% 27% 1	3670
	11th to 20th	Night	43% 5% 11% 23% 18%	3899
	21st to end	Night	40% 5% 11% 30% 14% 1	4546
November	1st to 10th	Night	42% 5% 11% 26% 15% 1	2666
	11th to 20th	Night	52% 5% 14% 19% 9% 1	2730
	21st to end	Night	58% 5% 12% 18% 6%	2791
December	1st to 10th	Night	61% 6% 14% 14% 4	4720
	11th to 20th	Night	66% 6% 10% 13% 5% 1	5610
	21st to end	Night	74% 5% 8% 7% 6%	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	25% 18% 38% 14% 5% 1	330
	11th to 20th	Day	25% 18% 42% 12% 1 1	330
	21st to end	Day	28% 17% 35% 15% 4 1	363
February	1st to 10th	Day	24% 23% 35% 14% 3 1	330
	11th to 20th	Day	25% 21% 36% 15% 2	330
	21st to end	Day	27% 27% 34% 11% 1	273
March	1st to 10th	Day	26% 22% 35% 14% 2	361
	11th to 20th	Day	24% 14% 34% 20% 6%	540
	21st to end	Day	28% 14% 33% 19% 5% 1	594
April	1st to 10th	Day	23% 16% 36% 17% 8% 1	540
	11th to 20th	Day	25% 17% 32% 16% 6% 4	532
	21st to end	Day	23% 15% 29% 19% 12% 2	540
May	1st to 10th	Day	25% 13% 27% 22% 10% 3	543
	11th to 20th	Day	20% 12% 27% 21% 13% 6%	567
	21st to end	Day	15% 8% 24% 27% 17% 9%	642
June	1st to 10th	Day	11% 8% 31% 29% 17% 4	780
	11th to 20th	Day	13% 10% 31% 27% 16% 4	780
	21st to end	Day	11% 8% 28% 30% 17% 4	780
July	1st to 10th	Day	9% 5% 24% 28% 24% 11%	771
	11th to 20th	Day	9% 6% 28% 29% 20% 8%	768
	21st to end	Day	8% 4 26% 31% 22% 9%	702
August	1st to 10th	Day	8% 4 18% 31% 24% 15%	566
	11th to 20th	Day	12% 5% 18% 30% 23% 11%	559
	21st to end	Day	10% 4 22% 28% 23% 13%	627
September	1st to 10th	Day	12% 7% 23% 25% 20% 12%	570
	11th to 20th	Day	10% 3 18% 25% 28% 17%	542
	21st to end	Day	17% 9% 23% 23% 19% 9%	530
October	1st to 10th	Day	18% 6% 26% 23% 18% 8%	530
	11th to 20th	Day	19% 16% 27% 28% 8% 2	530
	21st to end	Day	27% 15% 36% 17% 5%	398
November	1st to 10th	Day	18% 18% 36% 18% 9% 1	330
	11th to 20th	Day	25% 21% 30% 17% 6% 1	330
	21st to end	Day	28% 19% 34% 16% 3	294
December	1st to 10th	Day	24% 18% 36% 13% 9%	220
	11th to 20th	Day	29% 22% 36% 9% 4	228
	21st to end	Day	28% 20% 37% 13% 1	363
January	1st to 10th	Night	21% 15% 37% 21% 5% 1	1050
	11th to 20th	Night	24% 15% 36% 21% 4 1	1050
	21st to end	Night	21% 13% 35% 27% 4	992
February	1st to 10th	Night	24% 12% 37% 24% 3	840
	11th to 20th	Night	22% 15% 34% 24% 4	823
	21st to end	Night	25% 14% 38% 20% 2	692
March	1st to 10th	Night	22% 13% 35% 25% 5% 1	840
	11th to 20th	Night	19% 16% 36% 24% 5% 1	840
	21st to end	Night	22% 12% 32% 27% 7% 1	924
April	1st to 10th	Night	22% 14% 34% 26% 4	704
	11th to 20th	Night	22% 10% 33% 26% 7% 1	623
	21st to end	Night	20% 9% 31% 31% 8%	630
May	1st to 10th	Night	19% 10% 31% 31% 8% 1	630
	11th to 20th	Night	20% 6% 29% 32% 12% 1	621
	21st to end	Night	13% 4 25% 38% 19% 2	683
June	1st to 10th	Night	12% 3 24% 45% 14% 1	630
	11th to 20th	Night	13% 4 25% 41% 17%	630
	21st to end	Night	12% 4 20% 45% 18% 1	630
July	1st to 10th	Night	9% 2 16% 41% 29% 4	615
	11th to 20th	Night	9% 3 19% 41% 24% 4	612
	21st to end	Night	6% 3 18% 48% 24% 2	690
August	1st to 10th	Night	8% 3 16% 42% 28% 3	627
	11th to 20th	Night	9% 2 20% 38% 29% 3	624
	21st to end	Night	9% 3 16% 39% 30% 3	693
September	1st to 10th	Night	12% 4 20% 34% 25% 4	740
	11th to 20th	Night	11% 3 16% 33% 32% 5%	813
	21st to end	Night	15% 7% 20% 31% 21% 5%	800
October	1st to 10th	Night	17% 6% 26% 31% 18% 3	800
	11th to 20th	Night	22% 12% 29% 27% 9% 2	800
	21st to end	Night	25% 10% 34% 25% 5%	880
November	1st to 10th	Night	18% 12% 31% 28% 10% 1	820
	11th to 20th	Night	21% 15% 35% 22% 6% 1	840
	21st to end	Night	27% 12% 34% 20% 6%	840
December	1st to 10th	Night	23% 17% 33% 22% 6%	840
	11th to 20th	Night	23% 16% 37% 22% 3	998
	21st to end	Night	32% 12% 36% 18% 2	1155

Page generated at 2026-09-11 04:11:57. Version ac07

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