Springfield
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Springfield clear sky chart from 2005-11-06 to 2026-09-29.

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% 2 6% 4 4 4 4 5% 7% 39%	149017
	Night	18% 8% 3 6% 4 4 4 3 5% 6% 39%	142389
Transparency	Day	44% 4 12% 23% 15% 2	152539
	Night	45% 4 12% 22% 15% 2	146956
Seeing	Day	22% 14% 30% 21% 10% 3	17416
	Night	21% 11% 31% 29% 8% 1	26338

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	11% 9% 4 10% 5% 5% 4 3 5% 5% 39%	4661
	11th to 20th	Day	14% 9% 3 8% 4 4 3 3 5% 6% 42%	4650
	21st to end	Day	14% 8% 3 6% 3 4 4 4 5% 7% 43%	5161
February	1st to 10th	Day	16% 8% 2 6% 5% 4 4 4 6% 7% 36%	1960
	11th to 20th	Day	14% 8% 3 8% 5% 5% 4 3 5% 7% 38%	2048
	21st to end	Day	18% 9% 3 6% 5% 3 4 4 4 6% 37%	1730
March	1st to 10th	Day	21% 10% 4 7% 4 3 3 3 4 5% 36%	4576
	11th to 20th	Day	16% 8% 3 6% 4 4 4 4 6% 7% 38%	4749
	21st to end	Day	23% 8% 3 6% 4 3 4 3 5% 6% 36%	6101
April	1st to 10th	Day	20% 7% 3 6% 5% 4 3 3 5% 7% 37%	2520
	11th to 20th	Day	18% 7% 2 6% 4 4 4 3 5% 7% 40%	2494
	21st to end	Day	20% 7% 2 6% 4 4 4 3 5% 6% 39%	2667
May	1st to 10th	Day	28% 8% 2 6% 3 4 4 3 5% 7% 29%	7639
	11th to 20th	Day	19% 8% 3 7% 4 4 4 3 5% 6% 37%	8000
	21st to end	Day	21% 7% 3 7% 5% 4 4 4 6% 8% 30%	9060
June	1st to 10th	Day	16% 7% 2 6% 5% 4 6% 4 6% 9% 36%	2940
	11th to 20th	Day	16% 5% 2 6% 4 5% 4 5% 6% 10% 37%	2940
	21st to end	Day	15% 6% 3 6% 4 5% 5% 5% 6% 8% 37%	2940
July	1st to 10th	Day	15% 6% 2 6% 5% 5% 5% 4 7% 10% 36%	8280
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 4 7% 11% 42%	8280
	21st to end	Day	16% 7% 2 6% 4 4 4 3 4 7% 43%	8993
August	1st to 10th	Day	14% 6% 3 8% 6% 5% 5% 5% 7% 10% 30%	6253
	11th to 20th	Day	12% 5% 2 6% 4 5% 5% 4 6% 8% 44%	5627
	21st to end	Day	11% 5% 2 6% 4 5% 5% 4 7% 10% 41%	6080
September	1st to 10th	Day	13% 6% 2 6% 4 4 5% 4 6% 6% 44%	2520
	11th to 20th	Day	14% 6% 2 5% 3 3 3 3 4 6% 51%	2363
	21st to end	Day	18% 5% 2 6% 4 3 4 4 6% 7% 40%	2288
October	1st to 10th	Day	22% 6% 2 5% 4 3 4 3 4 5% 42%	2180
	11th to 20th	Day	15% 7% 2 5% 4 4 4 3 6% 6% 45%	1956
	21st to end	Day	21% 7% 2 6% 3 4 4 3 5% 5% 39%	1980
November	1st to 10th	Day	13% 8% 2 6% 4 3 5% 4 4 6% 47%	1851
	11th to 20th	Day	18% 7% 1 4 3 3 3 4 5% 7% 46%	1890
	21st to end	Day	19% 7% 2 5% 5% 3 4 4 4 6% 41%	1846
December	1st to 10th	Day	16% 7% 3 5% 4 4 4 4 5% 6% 42%	2680
	11th to 20th	Day	21% 6% 2 4 3 3 3 3 5% 5% 45%	3066
	21st to end	Day	20% 11% 2 7% 4 3 3 3 4 6% 37%	4048
January	1st to 10th	Night	15% 8% 3 8% 4 4 4 3 5% 6% 39%	8234
	11th to 20th	Night	14% 10% 4 9% 5% 4 4 3 5% 6% 37%	8235
	21st to end	Night	14% 9% 3 7% 4 4 4 3 5% 6% 41%	9017
February	1st to 10th	Night	16% 10% 3 6% 4 4 4 4 5% 5% 39%	2657
	11th to 20th	Night	13% 9% 3 8% 5% 4 4 3 6% 6% 38%	2458
	21st to end	Night	17% 9% 3 7% 5% 4 4 3 4 6% 37%	2076
March	1st to 10th	Night	23% 7% 3 6% 4 3 3 3 5% 6% 37%	5484
	11th to 20th	Night	18% 9% 3 5% 4 4 5% 3 5% 6% 39%	5414
	21st to end	Night	24% 8% 2 6% 3 3 4 3 5% 5% 36%	5072
April	1st to 10th	Night	20% 8% 3 7% 5% 4 4 3 4 6% 36%	2100
	11th to 20th	Night	21% 7% 2 6% 5% 4 3 3 4 5% 39%	2075
	21st to end	Night	22% 7% 3 5% 4 3 3 3 4 6% 40%	1951
May	1st to 10th	Night	28% 9% 3 6% 4 4 3 3 5% 6% 30%	5259
	11th to 20th	Night	19% 9% 3 7% 5% 5% 4 4 6% 7% 32%	4901
	21st to end	Night	23% 7% 3 7% 5% 5% 4 4 5% 7% 31%	5114
June	1st to 10th	Night	17% 5% 2 6% 5% 3 4 4 6% 6% 42%	1680
	11th to 20th	Night	18% 7% 3 4 4 4 4 4 6% 8% 37%	1680
	21st to end	Night	14% 6% 2 5% 5% 4 4 4 5% 9% 41%	1680
July	1st to 10th	Night	16% 6% 2 6% 4 4 5% 4 7% 9% 37%	4680
	11th to 20th	Night	11% 6% 2 7% 4 4 4 4 7% 9% 42%	4680
	21st to end	Night	14% 6% 2 6% 4 4 4 3 6% 7% 45%	5084
August	1st to 10th	Night	18% 6% 3 7% 5% 5% 5% 4 6% 8% 33%	3849
	11th to 20th	Night	13% 6% 3 7% 4 5% 5% 4 6% 7% 40%	4415
	21st to end	Night	13% 5% 2 6% 4 4 4 3 5% 8% 47%	5045
September	1st to 10th	Night	16% 6% 2 5% 5% 3 5% 3 4 7% 44%	2100
	11th to 20th	Night	12% 6% 2 5% 3 3 4 3 4 5% 53%	2256
	21st to end	Night	19% 7% 2 6% 4 3 3 3 5% 6% 42%	2289
October	1st to 10th	Night	21% 6% 2 5% 4 3 4 3 4 5% 43%	2215
	11th to 20th	Night	17% 5% 2 6% 3 3 4 3 4 6% 47%	2442
	21st to end	Night	23% 6% 2 6% 3 4 3 3 4 5% 40%	2860
November	1st to 10th	Night	14% 6% 2 5% 3 4 3 3 4 6% 49%	2667
	11th to 20th	Night	18% 7% 2 5% 3 4 3 3 4 5% 46%	2730
	21st to end	Night	16% 8% 2 5% 4 3 3 4 5% 6% 43%	2772
December	1st to 10th	Night	19% 8% 2 6% 4 4 3 3 4 6% 42%	4720
	11th to 20th	Night	25% 8% 2 4 3 3 3 3 5% 4 40%	5348
	21st to end	Night	21% 10% 3 7% 4 3 3 2 4 5% 38%	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	48% 3 11% 26% 12% 1	4662
	11th to 20th	Day	45% 3 9% 22% 17% 5%	4680
	21st to end	Day	41% 3 12% 24% 19% 1	5161
February	1st to 10th	Day	47% 3 14% 22% 14% 1	1960
	11th to 20th	Day	47% 4 9% 24% 14% 2	2057
	21st to end	Day	49% 3 11% 21% 15% 2	1730
March	1st to 10th	Day	52% 3 11% 17% 10% 7%	4579
	11th to 20th	Day	46% 3 13% 27% 9% 2	4749
	21st to end	Day	51% 3 5% 18% 19% 5%	6101
April	1st to 10th	Day	49% 3 9% 22% 14% 3	2520
	11th to 20th	Day	45% 3 10% 22% 18% 3	2494
	21st to end	Day	47% 3 8% 21% 18% 4	2667
May	1st to 10th	Day	55% 4 12% 17% 11% 1	7651
	11th to 20th	Day	49% 4 14% 21% 13% 1	8004
	21st to end	Day	52% 4 9% 22% 12% 1	9061
June	1st to 10th	Day	45% 5% 11% 24% 13% 1	2940
	11th to 20th	Day	43% 5% 14% 23% 14% 2	2940
	21st to end	Day	44% 5% 12% 22% 15% 1	2940
July	1st to 10th	Day	44% 7% 14% 21% 14% 1	8210
	11th to 20th	Day	35% 6% 16% 29% 13% 1	8205
	21st to end	Day	42% 4 11% 26% 16% 1	8795
August	1st to 10th	Day	47% 7% 17% 18% 10% 1	6239
	11th to 20th	Day	37% 5% 16% 33% 8%	5666
	21st to end	Day	36% 6% 15% 27% 14% 2	6080
September	1st to 10th	Day	39% 4 9% 27% 18% 1	2520
	11th to 20th	Day	35% 3 9% 27% 24% 3	2363
	21st to end	Day	42% 5% 9% 24% 19% 2	2288
October	1st to 10th	Day	40% 5% 8% 22% 23% 3	3557
	11th to 20th	Day	33% 3 8% 28% 25% 2	3159
	21st to end	Day	34% 4 12% 29% 17% 3	3180
November	1st to 10th	Day	40% 4 13% 25% 17% 2	1851
	11th to 20th	Day	40% 4 11% 24% 19% 3	1890
	21st to end	Day	46% 4 11% 27% 11% 2	1846
December	1st to 10th	Day	43% 4 15% 28% 10% 1	2680
	11th to 20th	Day	42% 2 14% 21% 18% 2	3066
	21st to end	Day	51% 2 8% 21% 15% 4	4048
January	1st to 10th	Night	46% 3 11% 25% 12% 2	8234
	11th to 20th	Night	49% 4 10% 20% 13% 5%	8280
	21st to end	Night	45% 2 10% 20% 20% 3	9017
February	1st to 10th	Night	47% 3 12% 23% 13% 2	2657
	11th to 20th	Night	47% 5% 9% 21% 15% 3	2460
	21st to end	Night	49% 3 7% 24% 13% 3	2076
March	1st to 10th	Night	50% 3 10% 18% 16% 4	5494
	11th to 20th	Night	47% 3 16% 21% 11% 3	5415
	21st to end	Night	51% 3 5% 14% 23% 4	5072
April	1st to 10th	Night	51% 2 9% 20% 15% 2	2100
	11th to 20th	Night	49% 3 9% 19% 19% 1	2075
	21st to end	Night	47% 3 8% 22% 16% 5%	1951
May	1st to 10th	Night	57% 3 14% 14% 11% 1	5265
	11th to 20th	Night	53% 5% 12% 20% 10% 2	4902
	21st to end	Night	53% 5% 12% 21% 9% 1	5115
June	1st to 10th	Night	44% 4 11% 26% 15% 1	1680
	11th to 20th	Night	45% 4 14% 23% 13%	1680
	21st to end	Night	40% 5% 14% 26% 14% 1	1680
July	1st to 10th	Night	43% 7% 15% 21% 14%	4640
	11th to 20th	Night	38% 6% 15% 24% 15% 1	4632
	21st to end	Night	38% 5% 12% 28% 15% 1	4967
August	1st to 10th	Night	48% 7% 15% 17% 12% 1	3839
	11th to 20th	Night	41% 6% 16% 28% 8%	4442
	21st to end	Night	34% 6% 16% 30% 13% 1	5045
September	1st to 10th	Night	41% 4 10% 26% 18% 1	2100
	11th to 20th	Night	34% 4 10% 25% 25% 2	2256
	21st to end	Night	44% 3 8% 22% 20% 2	2289
October	1st to 10th	Night	39% 5% 13% 24% 17% 2	3618
	11th to 20th	Night	30% 3 9% 28% 29% 1	3978
	21st to end	Night	35% 3 13% 31% 17% 1	4610
November	1st to 10th	Night	37% 4 11% 24% 20% 3	2667
	11th to 20th	Night	42% 3 11% 22% 19% 3	2730
	21st to end	Night	43% 4 14% 27% 11% 1	2772
December	1st to 10th	Night	45% 4 12% 30% 10%	4720
	11th to 20th	Night	49% 3 13% 16% 17% 2	5348
	21st to end	Night	51% 2 8% 22% 13% 4	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% 32% 17% 6%	220
	11th to 20th	Day	25% 27% 30% 14% 4	220
	21st to end	Day	21% 23% 33% 18% 4 2	248
February	1st to 10th	Day	27% 20% 33% 17% 4	400
	11th to 20th	Day	26% 21% 34% 16% 3	536
	21st to end	Day	27% 17% 35% 18% 3	446
March	1st to 10th	Day	27% 19% 29% 19% 5% 1	540
	11th to 20th	Day	29% 20% 29% 17% 4	540
	21st to end	Day	29% 21% 30% 13% 5% 3	594
April	1st to 10th	Day	32% 19% 28% 14% 6% 1	540
	11th to 20th	Day	30% 18% 29% 14% 8% 1	532
	21st to end	Day	30% 16% 29% 18% 6% 2	540
May	1st to 10th	Day	34% 17% 26% 14% 8% 1	543
	11th to 20th	Day	22% 14% 39% 16% 6% 2	567
	21st to end	Day	21% 12% 33% 22% 9% 3	617
June	1st to 10th	Day	16% 13% 31% 24% 12% 4	570
	11th to 20th	Day	18% 12% 33% 25% 9% 3	570
	21st to end	Day	15% 14% 30% 26% 12% 3	570
July	1st to 10th	Day	16% 7% 29% 30% 15% 3	565
	11th to 20th	Day	12% 7% 28% 30% 18% 5%	564
	21st to end	Day	15% 6% 29% 31% 15% 4	620
August	1st to 10th	Day	12% 8% 24% 31% 17% 7%	566
	11th to 20th	Day	14% 6% 28% 28% 17% 6%	559
	21st to end	Day	11% 9% 28% 28% 18% 6%	627
September	1st to 10th	Day	19% 8% 24% 25% 16% 8%	570
	11th to 20th	Day	16% 9% 24% 22% 17% 12%	570
	21st to end	Day	21% 9% 30% 22% 13% 6%	562
October	1st to 10th	Day	26% 10% 23% 19% 13% 8%	530
	11th to 20th	Day	20% 14% 29% 22% 12% 3	505
	21st to end	Day	27% 12% 27% 23% 10% 2	462
November	1st to 10th	Day	21% 15% 30% 23% 9% 3	425
	11th to 20th	Day	27% 14% 30% 20% 7% 1	430
	21st to end	Day	28% 12% 32% 19% 7% 1	386
December	1st to 10th	Day	20% 22% 30% 20% 8%	220
	11th to 20th	Day	29% 23% 33% 12% 4	220
	21st to end	Day	25% 18% 35% 17% 5% 1	242
January	1st to 10th	Night	22% 13% 38% 24% 3	840
	11th to 20th	Night	28% 13% 31% 25% 3	840
	21st to end	Night	19% 13% 38% 27% 3	924
February	1st to 10th	Night	22% 13% 36% 26% 2	840
	11th to 20th	Night	21% 16% 40% 21% 1	823
	21st to end	Night	24% 16% 34% 23% 2	692
March	1st to 10th	Night	23% 17% 34% 24% 2	840
	11th to 20th	Night	23% 16% 36% 22% 3	840
	21st to end	Night	25% 14% 34% 21% 5%	924
April	1st to 10th	Night	26% 15% 33% 23% 4	840
	11th to 20th	Night	25% 16% 32% 21% 6%	831
	21st to end	Night	25% 16% 31% 23% 4	691
May	1st to 10th	Night	28% 13% 33% 21% 5%	630
	11th to 20th	Night	20% 14% 38% 25% 4	509
	21st to end	Night	21% 7% 31% 35% 5% 1	455
June	1st to 10th	Night	19% 5% 28% 40% 8% 1	420
	11th to 20th	Night	20% 8% 33% 31% 9%	420
	21st to end	Night	16% 3 30% 39% 10%	420
July	1st to 10th	Night	14% 4 27% 42% 12%	410
	11th to 20th	Night	14% 4 20% 45% 15%	408
	21st to end	Night	11% 4 25% 47% 13%	460
August	1st to 10th	Night	12% 3 25% 44% 14%	497
	11th to 20th	Night	13% 4 22% 40% 19% 2	763
	21st to end	Night	15% 4 21% 40% 18% 2	924
September	1st to 10th	Night	18% 5% 26% 36% 14% 1	840
	11th to 20th	Night	14% 6% 21% 35% 21% 2	840
	21st to end	Night	21% 6% 25% 33% 13% 2	833
October	1st to 10th	Night	23% 6% 23% 32% 14% 2	800
	11th to 20th	Night	20% 9% 29% 31% 10% 1	800
	21st to end	Night	27% 10% 29% 27% 7%	880
November	1st to 10th	Night	20% 9% 32% 30% 8% 1	820
	11th to 20th	Night	22% 11% 35% 25% 7%	840
	21st to end	Night	22% 14% 30% 29% 5%	840
December	1st to 10th	Night	24% 12% 35% 22% 5%	840
	11th to 20th	Night	24% 13% 33% 28% 3	840
	21st to end	Night	27% 12% 34% 24% 3	924

Page generated at 2026-09-26 04:18:44. Version ac07

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