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 2025-10-19.

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	12% 7% 3 6% 4 4 4 3 5% 7% 44%	126087
	Night	12% 7% 3 6% 4 3 4 3 5% 6% 47%	123861
Transparency	Day	37% 6% 11% 25% 17% 4	129698
	Night	36% 5% 10% 25% 19% 4	128326
Seeing	Day	15% 10% 27% 27% 16% 4	16862
	Night	15% 11% 31% 30% 12% 1	26612

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	16% 11% 4 5% 5% 4 4 3 3 4 41%	4077
	11th to 20th	Day	7% 10% 4 7% 5% 5% 4 3 4 5% 45%	4080
	21st to end	Day	18% 10% 4 6% 3 3 3 3 4 5% 42%	4488
February	1st to 10th	Day	16% 12% 4 8% 5% 4 4 3 4 5% 36%	1800
	11th to 20th	Day	14% 9% 4 8% 5% 3 3 3 4 5% 41%	1779
	21st to end	Day	15% 9% 3 6% 5% 5% 4 3 4 6% 40%	1725
March	1st to 10th	Day	13% 9% 3 5% 3 3 4 3 4 5% 48%	4936
	11th to 20th	Day	9% 7% 2 5% 4 3 3 3 4 7% 54%	4980
	21st to end	Day	13% 9% 3 7% 6% 6% 5% 4 6% 7% 34%	5462
April	1st to 10th	Day	13% 8% 3 6% 4 3 4 4 5% 6% 44%	2370
	11th to 20th	Day	16% 9% 3 5% 4 3 4 4 5% 6% 40%	2374
	21st to end	Day	20% 8% 3 7% 4 5% 4 3 5% 7% 35%	2400
May	1st to 10th	Day	18% 8% 3 6% 4 5% 5% 4 6% 7% 35%	5766
	11th to 20th	Day	11% 6% 2 7% 5% 5% 5% 4 6% 8% 41%	5862
	21st to end	Day	20% 7% 2 5% 4 4 4 4 6% 7% 38%	6658
June	1st to 10th	Day	9% 4 2 6% 4 4 5% 4 6% 11% 46%	2800
	11th to 20th	Day	8% 4 1 5% 4 5% 6% 4 7% 10% 46%	2800
	21st to end	Day	5% 3 2 5% 4 4 4 4 7% 9% 54%	2800
July	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 4 7% 9% 44%	5907
	11th to 20th	Day	6% 5% 2 6% 5% 5% 5% 4 7% 10% 42%	5900
	21st to end	Day	6% 4 2 5% 4 4 6% 5% 8% 11% 46%	6422
August	1st to 10th	Day	5% 3 2 4 4 4 4 3 6% 9% 56%	4234
	11th to 20th	Day	9% 5% 2 6% 5% 4 5% 4 7% 9% 45%	4054
	21st to end	Day	6% 4 1 5% 4 4 4 4 6% 8% 53%	4312
September	1st to 10th	Day	11% 5% 2 5% 4 5% 5% 4 4 7% 50%	2400
	11th to 20th	Day	11% 5% 3 6% 4 5% 5% 4 5% 7% 45%	2333
	21st to end	Day	7% 5% 2 5% 4 4 5% 4 6% 7% 52%	2120
October	1st to 10th	Day	10% 4 2 5% 3 3 3 3 5% 6% 57%	2000
	11th to 20th	Day	12% 6% 2 5% 3 3 3 3 3 4 55%	1980
	21st to end	Day	18% 6% 2 5% 3 3 3 2 5% 5% 48%	2090
November	1st to 10th	Day	12% 6% 2 4 3 3 2 3 4 4 57%	1958
	11th to 20th	Day	13% 8% 3 5% 3 3 3 3 5% 6% 49%	1854
	21st to end	Day	15% 9% 3 5% 4 3 3 2 4 6% 48%	1600
December	1st to 10th	Day	10% 10% 2 6% 3 3 2 2 4 5% 53%	2610
	11th to 20th	Day	10% 10% 4 7% 4 3 3 3 3 5% 47%	3008
	21st to end	Day	18% 20% 6% 9% 4 3 3 3 4 4 26%	4148
January	1st to 10th	Night	14% 10% 4 11% 5% 5% 4 3 4 4 36%	5888
	11th to 20th	Night	9% 6% 3 10% 7% 4 5% 3 4 5% 45%	5900
	21st to end	Night	16% 11% 4 7% 3 3 3 2 3 5% 43%	6490
February	1st to 10th	Night	15% 10% 4 6% 4 3 4 3 4 6% 42%	2600
	11th to 20th	Night	15% 9% 3 7% 4 3 3 2 5% 6% 43%	2508
	21st to end	Night	14% 8% 4 6% 4 3 3 3 5% 5% 45%	1920
March	1st to 10th	Night	14% 11% 3 7% 4 3 3 2 4 4 45%	4919
	11th to 20th	Night	10% 7% 2 5% 3 3 4 3 5% 6% 53%	4980
	21st to end	Night	10% 7% 3 7% 5% 4 5% 4 6% 8% 41%	5467
April	1st to 10th	Night	11% 6% 2 4 4 3 3 3 5% 7% 51%	2030
	11th to 20th	Night	12% 8% 2 5% 3 3 3 2 6% 7% 47%	1975
	21st to end	Night	19% 7% 3 6% 4 3 3 4 6% 6% 39%	2000
May	1st to 10th	Night	15% 8% 3 6% 4 4 3 3 4 6% 44%	4140
	11th to 20th	Night	12% 8% 2 6% 4 4 4 4 6% 8% 42%	4053
	21st to end	Night	19% 7% 3 6% 4 4 4 3 5% 7% 39%	4214
June	1st to 10th	Night	8% 4 2 4 3 3 4 4 6% 9% 51%	1600
	11th to 20th	Night	5% 4 1 4 4 4 4 5% 7% 10% 53%	1600
	21st to end	Night	3 3 1 3 4 3 3 3 5% 9% 65%	1600
July	1st to 10th	Night	8% 5% 2 5% 4 4 5% 4 7% 9% 45%	4065
	11th to 20th	Night	4 3 2 4 4 3 4 4 6% 9% 56%	4077
	21st to end	Night	5% 4 1 4 3 4 5% 5% 7% 11% 52%	4449
August	1st to 10th	Night	4 2 1 4 3 3 4 3 5% 9% 62%	2926
	11th to 20th	Night	9% 4 3 6% 4 4 5% 3 6% 7% 50%	2998
	21st to end	Night	4 3 1 4 3 3 4 3 5% 9% 61%	3586
September	1st to 10th	Night	10% 4 2 5% 4 4 3 3 4 7% 54%	2000
	11th to 20th	Night	8% 5% 2 5% 4 4 4 3 6% 8% 51%	2062
	21st to end	Night	9% 5% 2 5% 3 2 3 3 4 6% 57%	2260
October	1st to 10th	Night	7% 4 2 3 3 3 3 3 5% 7% 62%	2400
	11th to 20th	Night	12% 6% 2 3 3 3 3 3 4 5% 56%	2377
	21st to end	Night	16% 8% 2 5% 3 3 3 3 4 5% 50%	2508
November	1st to 10th	Night	12% 6% 2 4 2 2 3 2 3 6% 58%	2340
	11th to 20th	Night	11% 7% 2 5% 3 3 3 3 4 6% 53%	2538
	21st to end	Night	14% 9% 3 5% 4 3 3 3 4 5% 49%	2800
December	1st to 10th	Night	10% 10% 2 6% 3 3 3 3 5% 6% 49%	4580
	11th to 20th	Night	14% 8% 4 7% 3 3 3 3 3 5% 47%	5199
	21st to end	Night	21% 18% 5% 7% 4 3 3 2 4 5% 28%	6812

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 8% 22% 16% 2	4078
	11th to 20th	Day	41% 4 7% 26% 17% 5%	4080
	21st to end	Day	46% 3 8% 18% 16% 9%	4488
February	1st to 10th	Day	51% 5% 10% 21% 11% 2	1800
	11th to 20th	Day	46% 4 10% 20% 16% 4	1788
	21st to end	Day	45% 4 7% 21% 16% 6%	1725
March	1st to 10th	Day	38% 4 7% 21% 17% 12%	4936
	11th to 20th	Day	32% 4 7% 22% 22% 12%	4980
	21st to end	Day	47% 7% 12% 24% 8% 1	5464
April	1st to 10th	Day	39% 6% 11% 22% 19% 2	2370
	11th to 20th	Day	44% 6% 13% 19% 16% 3	2374
	21st to end	Day	49% 6% 10% 23% 11% 1	2400
May	1st to 10th	Day	46% 8% 12% 20% 14% 1	5803
	11th to 20th	Day	40% 9% 13% 24% 14% 1	5866
	21st to end	Day	43% 8% 11% 23% 14% 1	6672
June	1st to 10th	Day	32% 9% 15% 27% 15% 1	2800
	11th to 20th	Day	31% 8% 15% 30% 14% 2	2800
	21st to end	Day	25% 8% 17% 30% 16% 4	2800
July	1st to 10th	Day	35% 8% 14% 24% 18% 2	5843
	11th to 20th	Day	35% 9% 14% 29% 12% 1	5831
	21st to end	Day	29% 8% 19% 33% 11%	6240
August	1st to 10th	Day	25% 7% 18% 29% 21% 1	4220
	11th to 20th	Day	35% 7% 15% 29% 13% 1	4093
	21st to end	Day	28% 6% 12% 34% 17% 4	4311
September	1st to 10th	Day	34% 6% 12% 25% 15% 9%	2400
	11th to 20th	Day	38% 5% 10% 22% 23% 2	2333
	21st to end	Day	30% 7% 10% 25% 25% 4	2120
October	1st to 10th	Day	17% 3 6% 18% 37% 18%	3260
	11th to 20th	Day	22% 2 5% 24% 33% 13%	3220
	21st to end	Day	28% 3 8% 32% 24% 4	3428
November	1st to 10th	Day	32% 5% 9% 27% 23% 5%	1958
	11th to 20th	Day	36% 4 7% 22% 23% 7%	1854
	21st to end	Day	40% 4 9% 24% 21% 2	1600
December	1st to 10th	Day	36% 3 8% 34% 18% 1	2610
	11th to 20th	Day	41% 4 6% 26% 21% 2	3005
	21st to end	Day	62% 4 7% 17% 9% 1	4148
January	1st to 10th	Night	52% 4 10% 20% 13% 2	5888
	11th to 20th	Night	42% 5% 8% 23% 21% 2	5900
	21st to end	Night	46% 3 7% 20% 19% 5%	6490
February	1st to 10th	Night	44% 5% 11% 23% 14% 3	2600
	11th to 20th	Night	43% 4 10% 21% 17% 4	2509
	21st to end	Night	42% 4 10% 21% 18% 6%	1920
March	1st to 10th	Night	44% 4 7% 17% 22% 6%	4919
	11th to 20th	Night	33% 5% 8% 23% 21% 10%	4980
	21st to end	Night	39% 7% 14% 25% 14% 1	5467
April	1st to 10th	Night	32% 6% 12% 25% 21% 4	2030
	11th to 20th	Night	35% 6% 12% 23% 19% 6%	1975
	21st to end	Night	44% 6% 11% 23% 15% 1	2000
May	1st to 10th	Night	41% 6% 13% 24% 13% 2	4168
	11th to 20th	Night	39% 8% 11% 24% 14% 4	4054
	21st to end	Night	44% 8% 12% 23% 11% 3	4222
June	1st to 10th	Night	27% 7% 16% 29% 18% 3	1600
	11th to 20th	Night	24% 8% 14% 30% 21% 3	1600
	21st to end	Night	17% 5% 20% 31% 21% 6%	1600
July	1st to 10th	Night	34% 7% 14% 23% 19% 4	4022
	11th to 20th	Night	24% 7% 13% 39% 17% 1	4026
	21st to end	Night	24% 7% 19% 36% 15%	4320
August	1st to 10th	Night	19% 7% 15% 33% 24% 2	2916
	11th to 20th	Night	32% 6% 15% 29% 17% 1	3025
	21st to end	Night	21% 5% 14% 37% 19% 4	3586
September	1st to 10th	Night	30% 5% 13% 27% 19% 7%	2000
	11th to 20th	Night	31% 6% 11% 24% 25% 3	2062
	21st to end	Night	29% 5% 9% 24% 30% 3	2260
October	1st to 10th	Night	14% 4 6% 17% 41% 18%	3920
	11th to 20th	Night	22% 3 6% 21% 30% 19%	3876
	21st to end	Night	30% 3 6% 31% 25% 5%	4120
November	1st to 10th	Night	29% 4 9% 26% 24% 7%	2340
	11th to 20th	Night	33% 4 7% 24% 25% 7%	2538
	21st to end	Night	39% 4 8% 24% 22% 3	2800
December	1st to 10th	Night	37% 4 9% 33% 17% 1	4580
	11th to 20th	Night	42% 3 7% 23% 22% 2	5201
	21st to end	Night	60% 5% 9% 18% 7% 2	6812

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	21% 18% 41% 17% 3	300
	11th to 20th	Day	23% 23% 39% 13% 1	300
	21st to end	Day	18% 21% 43% 16% 2	330
February	1st to 10th	Day	24% 19% 42% 14% 2	300
	11th to 20th	Day	25% 26% 32% 15% 2	300
	21st to end	Day	25% 23% 37% 12% 2	249
March	1st to 10th	Day	22% 23% 33% 19% 3	300
	11th to 20th	Day	28% 18% 34% 18% 3	300
	21st to end	Day	27% 21% 38% 11% 2 1	330
April	1st to 10th	Day	23% 16% 37% 19% 4	470
	11th to 20th	Day	23% 19% 36% 17% 4	492
	21st to end	Day	24% 16% 32% 22% 6% 1	500
May	1st to 10th	Day	21% 13% 33% 25% 7% 1	658
	11th to 20th	Day	16% 12% 30% 26% 13% 3	725
	21st to end	Day	14% 8% 32% 26% 15% 6%	789
June	1st to 10th	Day	10% 4 21% 31% 25% 8%	730
	11th to 20th	Day	8% 3 18% 37% 28% 5%	730
	21st to end	Day	6% 2 29% 37% 22% 5%	730
July	1st to 10th	Day	10% 3 16% 30% 30% 11%	721
	11th to 20th	Day	6% 4 15% 37% 30% 8%	718
	21st to end	Day	8% 2 11% 35% 30% 13%	794
August	1st to 10th	Day	8% 4 13% 42% 29% 5%	726
	11th to 20th	Day	10% 2 15% 36% 31% 7%	650
	21st to end	Day	11% 2 12% 29% 35% 11%	583
September	1st to 10th	Day	12% 2 11% 37% 29% 9%	530
	11th to 20th	Day	9% 2 17% 37% 25% 10%	463
	21st to end	Day	10% 5% 25% 31% 21% 7%	330
October	1st to 10th	Day	9% 8% 28% 33% 18% 4	330
	11th to 20th	Day	15% 14% 34% 27% 10% 1	324
	21st to end	Day	26% 15% 30% 25% 3 1	330
November	1st to 10th	Day	16% 13% 38% 23% 9% 2	300
	11th to 20th	Day	17% 22% 31% 23% 7% 1	300
	21st to end	Day	22% 17% 34% 20% 5% 1	300
December	1st to 10th	Day	17% 16% 44% 16% 5% 2	300
	11th to 20th	Day	20% 20% 38% 17% 5%	300
	21st to end	Day	21% 26% 37% 14% 2	330
January	1st to 10th	Night	17% 19% 38% 22% 5%	1000
	11th to 20th	Night	19% 19% 41% 17% 4	1000
	21st to end	Night	17% 19% 42% 21% 2	1100
February	1st to 10th	Night	20% 16% 43% 18% 2	1000
	11th to 20th	Night	22% 17% 40% 19% 2	954
	21st to end	Night	20% 21% 39% 18% 2	600
March	1st to 10th	Night	20% 17% 36% 24% 3	600
	11th to 20th	Night	23% 15% 33% 24% 5%	600
	21st to end	Night	21% 17% 38% 20% 4	660
April	1st to 10th	Night	15% 16% 39% 27% 3	600
	11th to 20th	Night	17% 14% 38% 25% 5%	593
	21st to end	Night	22% 12% 36% 22% 7%	600
May	1st to 10th	Night	16% 6% 37% 33% 8%	600
	11th to 20th	Night	14% 7% 30% 32% 17% 1	591
	21st to end	Night	13% 5% 31% 32% 18% 2	650
June	1st to 10th	Night	8% 5% 18% 41% 27% 1	600
	11th to 20th	Night	6% 2 23% 46% 22% 1	600
	21st to end	Night	2 2 22% 50% 23% 1	600
July	1st to 10th	Night	8% 1 11% 40% 34% 5%	585
	11th to 20th	Night	3 2 11% 46% 35% 3	582
	21st to end	Night	6% 2 9% 47% 32% 4	657
August	1st to 10th	Night	6% 2 12% 49% 29% 3	597
	11th to 20th	Night	9% 2 13% 48% 26% 3	594
	21st to end	Night	5% 1 14% 41% 35% 4	660
September	1st to 10th	Night	10% 2 15% 41% 30% 3	600
	11th to 20th	Night	10% 2 13% 43% 28% 4	600
	21st to end	Night	12% 4 22% 40% 20% 3	660
October	1st to 10th	Night	8% 4 28% 36% 20% 3	800
	11th to 20th	Night	16% 8% 36% 32% 8%	793
	21st to end	Night	21% 11% 31% 28% 9%	836
November	1st to 10th	Night	14% 11% 38% 27% 9%	780
	11th to 20th	Night	15% 15% 38% 25% 7%	820
	21st to end	Night	19% 14% 36% 23% 8%	1000
December	1st to 10th	Night	21% 13% 39% 23% 4	1000
	11th to 20th	Night	21% 15% 37% 25% 3	1000
	21st to end	Night	21% 18% 39% 21% 2	1100

Page generated at 2025-10-16 00:50:23. Version ac07

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