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 2025-05-11.

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 6% 4 4 4 4 5% 7% 39%	113510
	Night	18% 8% 3 6% 4 4 4 3 5% 6% 40%	115417
Transparency	Day	45% 4 11% 23% 15% 2	117078
	Night	45% 4 11% 22% 15% 2	120013
Seeing	Day	23% 14% 29% 21% 10% 3	15566
	Night	21% 11% 31% 29% 8% 1	24690

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% 8% 4 10% 5% 4 4 3 5% 5% 40%	3597
	11th to 20th	Day	13% 8% 3 8% 4 4 4 4 5% 5% 40%	3570
	21st to end	Day	17% 8% 3 6% 4 4 4 3 5% 7% 40%	3983
February	1st to 10th	Day	17% 8% 2 6% 5% 4 4 4 6% 7% 35%	1866
	11th to 20th	Day	14% 8% 3 8% 5% 5% 4 3 5% 7% 38%	1948
	21st to end	Day	19% 9% 3 6% 5% 3 3 4 4 6% 37%	1650
March	1st to 10th	Day	21% 10% 4 7% 4 3 3 3 4 5% 36%	4476
	11th to 20th	Day	15% 8% 3 6% 4 4 4 4 6% 7% 39%	4647
	21st to end	Day	23% 8% 3 6% 4 3 4 3 5% 6% 36%	5969
April	1st to 10th	Day	20% 7% 3 6% 5% 4 3 3 5% 7% 36%	2400
	11th to 20th	Day	18% 6% 2 6% 4 4 4 3 5% 7% 40%	2374
	21st to end	Day	20% 7% 2 6% 4 4 4 4 5% 6% 39%	2540
May	1st to 10th	Day	26% 8% 3 7% 4 5% 3 3 5% 7% 29%	4236
	11th to 20th	Day	21% 9% 3 7% 4 3 4 3 5% 6% 35%	4288
	21st to end	Day	13% 5% 2 5% 4 4 4 4 6% 8% 43%	4837
June	1st to 10th	Day	16% 7% 2 6% 5% 4 5% 4 6% 8% 36%	2660
	11th to 20th	Day	16% 5% 2 6% 4 5% 4 5% 6% 10% 37%	2660
	21st to end	Day	15% 6% 3 6% 4 4 5% 5% 6% 8% 36%	2660
July	1st to 10th	Day	10% 6% 2 7% 5% 6% 6% 4 7% 9% 37%	4440
	11th to 20th	Day	12% 5% 2 6% 5% 4 5% 4 7% 10% 38%	4440
	21st to end	Day	17% 8% 3 7% 5% 5% 4 4 5% 7% 36%	4814
August	1st to 10th	Day	16% 6% 3 8% 5% 5% 5% 4 7% 9% 32%	4268
	11th to 20th	Day	12% 6% 2 7% 5% 5% 5% 4 6% 8% 40%	3824
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 4 7% 9% 44%	4180
September	1st to 10th	Day	13% 6% 2 6% 4 4 5% 4 6% 6% 44%	2280
	11th to 20th	Day	14% 7% 2 5% 3 2 3 3 4 6% 50%	2138
	21st to end	Day	17% 5% 2 6% 4 3 4 4 6% 7% 41%	2090
October	1st to 10th	Day	23% 6% 2 6% 4 3 4 3 4 5% 40%	2071
	11th to 20th	Day	14% 7% 2 5% 4 3 4 3 6% 6% 45%	1858
	21st to end	Day	21% 7% 2 6% 3 4 4 3 5% 6% 39%	1881
November	1st to 10th	Day	14% 8% 2 5% 3 3 4 3 4 6% 48%	1761
	11th to 20th	Day	18% 7% 1 4 3 3 3 4 5% 6% 46%	1800
	21st to end	Day	19% 7% 2 5% 4 3 4 4 4 6% 41%	1758
December	1st to 10th	Day	16% 8% 3 5% 4 4 4 4 5% 6% 42%	2600
	11th to 20th	Day	21% 6% 2 4 3 3 3 3 5% 5% 45%	2986
	21st to end	Day	20% 11% 2 6% 4 3 3 3 4 6% 38%	3960
January	1st to 10th	Night	15% 7% 3 8% 4 4 4 3 5% 6% 41%	6349
	11th to 20th	Night	13% 9% 4 9% 5% 4 4 3 5% 6% 39%	6315
	21st to end	Night	16% 10% 3 7% 4 4 4 3 5% 6% 37%	6970
February	1st to 10th	Night	16% 10% 3 6% 4 4 4 4 5% 5% 38%	2531
	11th to 20th	Night	14% 9% 3 8% 4 4 4 3 6% 6% 39%	2338
	21st to end	Night	18% 8% 3 7% 5% 4 4 3 4 6% 37%	1980
March	1st to 10th	Night	23% 7% 3 6% 4 3 3 3 5% 6% 37%	5364
	11th to 20th	Night	17% 9% 3 5% 4 4 5% 3 5% 6% 39%	5296
	21st to end	Night	24% 8% 2 6% 3 3 4 3 5% 5% 36%	4962
April	1st to 10th	Night	20% 8% 3 7% 6% 4 4 3 4 6% 35%	2000
	11th to 20th	Night	22% 7% 2 5% 5% 4 3 3 4 6% 39%	1975
	21st to end	Night	22% 8% 3 5% 3 3 3 3 4 6% 40%	1858
May	1st to 10th	Night	26% 8% 3 7% 4 4 4 3 5% 6% 29%	2924
	11th to 20th	Night	20% 9% 3 7% 5% 5% 5% 4 6% 6% 30%	2640
	21st to end	Night	16% 5% 2 5% 4 4 4 4 5% 9% 42%	2738
June	1st to 10th	Night	17% 5% 2 6% 5% 3 4 4 6% 6% 41%	1520
	11th to 20th	Night	18% 7% 3 4 4 4 4 4 6% 8% 38%	1520
	21st to end	Night	14% 7% 2 5% 5% 4 4 4 5% 9% 41%	1520
July	1st to 10th	Night	13% 5% 2 6% 4 5% 5% 5% 8% 9% 37%	2520
	11th to 20th	Night	15% 7% 2 7% 4 5% 4 3 6% 9% 37%	2520
	21st to end	Night	16% 9% 3 7% 5% 4 5% 4 6% 6% 36%	2739
August	1st to 10th	Night	21% 6% 3 7% 4 5% 4 4 6% 7% 31%	2629
	11th to 20th	Night	13% 7% 4 8% 5% 5% 5% 4 6% 7% 37%	3000
	21st to end	Night	9% 5% 2 5% 3 4 4 3 5% 8% 53%	3476
September	1st to 10th	Night	15% 6% 2 5% 5% 4 4 3 4 7% 45%	1900
	11th to 20th	Night	13% 6% 2 5% 3 3 3 3 3 5% 53%	2041
	21st to end	Night	17% 7% 2 6% 4 4 3 3 5% 6% 43%	2090
October	1st to 10th	Night	21% 6% 2 5% 4 4 4 3 4 5% 41%	2104
	11th to 20th	Night	16% 6% 1 6% 3 3 4 3 5% 6% 47%	2320
	21st to end	Night	24% 6% 2 6% 3 4 3 3 4 5% 39%	2717
November	1st to 10th	Night	14% 6% 2 5% 3 4 3 3 4 6% 49%	2537
	11th to 20th	Night	19% 7% 2 5% 3 4 4 3 4 4 46%	2600
	21st to end	Night	17% 8% 2 5% 4 3 3 4 4 6% 44%	2640
December	1st to 10th	Night	20% 7% 2 6% 4 4 3 3 4 6% 42%	4580
	11th to 20th	Night	25% 8% 2 4 3 3 3 3 5% 4 40%	5208
	21st to end	Night	21% 10% 3 7% 4 3 3 3 4 5% 38%	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	47% 3 9% 28% 12% 1	3598
	11th to 20th	Day	45% 4 10% 22% 15% 4	3600
	21st to end	Day	46% 3 11% 23% 17% 1	3983
February	1st to 10th	Day	48% 3 14% 21% 13% 1	1866
	11th to 20th	Day	47% 4 9% 23% 14% 2	1957
	21st to end	Day	49% 2 11% 21% 15% 2	1650
March	1st to 10th	Day	52% 3 11% 17% 11% 7%	4479
	11th to 20th	Day	46% 3 13% 27% 10% 2	4647
	21st to end	Day	51% 3 5% 18% 19% 5%	5969
April	1st to 10th	Day	49% 3 8% 22% 15% 3	2400
	11th to 20th	Day	45% 3 10% 22% 18% 3	2374
	21st to end	Day	47% 3 8% 21% 17% 4	2540
May	1st to 10th	Day	57% 3 12% 16% 12% 1	4250
	11th to 20th	Day	51% 2 14% 21% 10% 2	4292
	21st to end	Day	39% 3 10% 26% 19% 2	4837
June	1st to 10th	Day	46% 5% 12% 24% 13% 1	2660
	11th to 20th	Day	43% 4 14% 23% 14% 2	2660
	21st to end	Day	44% 5% 12% 22% 15% 1	2660
July	1st to 10th	Day	43% 6% 11% 22% 16% 2	4370
	11th to 20th	Day	41% 5% 15% 24% 13% 2	4365
	21st to end	Day	48% 5% 11% 20% 15% 2	4661
August	1st to 10th	Day	48% 6% 16% 21% 9% 1	4254
	11th to 20th	Day	41% 5% 13% 30% 10% 1	3863
	21st to end	Day	35% 6% 13% 29% 16% 2	4180
September	1st to 10th	Day	40% 4 10% 26% 19% 2	2280
	11th to 20th	Day	36% 3 8% 27% 24% 2	2138
	21st to end	Day	41% 4 9% 24% 19% 2	2090
October	1st to 10th	Day	41% 5% 8% 22% 22% 3	3448
	11th to 20th	Day	33% 4 8% 28% 26% 2	3061
	21st to end	Day	35% 4 12% 29% 17% 3	3081
November	1st to 10th	Day	39% 4 13% 25% 17% 2	1761
	11th to 20th	Day	40% 4 11% 23% 20% 3	1800
	21st to end	Day	45% 4 11% 27% 11% 2	1758
December	1st to 10th	Day	43% 5% 15% 28% 9% 1	2600
	11th to 20th	Day	43% 2 15% 21% 18% 2	2986
	21st to end	Day	51% 2 8% 20% 15% 4	3960
January	1st to 10th	Night	45% 3 10% 28% 13% 2	6349
	11th to 20th	Night	47% 4 12% 21% 13% 4	6360
	21st to end	Night	49% 2 10% 18% 17% 4	6970
February	1st to 10th	Night	47% 4 13% 23% 12% 2	2531
	11th to 20th	Night	47% 4 9% 21% 16% 3	2340
	21st to end	Night	49% 3 7% 24% 13% 4	1980
March	1st to 10th	Night	50% 3 10% 18% 15% 4	5374
	11th to 20th	Night	47% 3 16% 21% 11% 2	5297
	21st to end	Night	51% 3 5% 14% 23% 4	4962
April	1st to 10th	Night	51% 2 8% 21% 15% 3	2000
	11th to 20th	Night	49% 2 8% 19% 20% 1	1975
	21st to end	Night	47% 2 8% 22% 16% 5%	1858
May	1st to 10th	Night	57% 3 12% 16% 10% 2	2930
	11th to 20th	Night	56% 4 13% 18% 8% 2	2641
	21st to end	Night	41% 4 16% 24% 14% 1	2739
June	1st to 10th	Night	44% 4 12% 25% 14% 1	1520
	11th to 20th	Night	45% 4 15% 24% 13%	1520
	21st to end	Night	41% 5% 14% 25% 14% 1	1520
July	1st to 10th	Night	41% 8% 16% 20% 15% 1	2480
	11th to 20th	Night	44% 6% 14% 23% 12% 1	2472
	21st to end	Night	48% 5% 11% 19% 15% 1	2651
August	1st to 10th	Night	52% 7% 12% 20% 9% 1	2619
	11th to 20th	Night	44% 6% 14% 26% 9%	3027
	21st to end	Night	28% 6% 16% 33% 16% 1	3476
September	1st to 10th	Night	40% 4 11% 26% 19% 1	1900
	11th to 20th	Night	34% 4 9% 26% 25% 2	2041
	21st to end	Night	42% 3 8% 23% 21% 3	2090
October	1st to 10th	Night	40% 5% 13% 23% 17% 2	3507
	11th to 20th	Night	29% 3 9% 28% 29% 1	3856
	21st to end	Night	35% 3 13% 31% 17% 1	4467
November	1st to 10th	Night	37% 4 11% 24% 20% 3	2537
	11th to 20th	Night	42% 3 11% 21% 19% 3	2600
	21st to end	Night	43% 3 14% 27% 11% 1	2640
December	1st to 10th	Night	45% 4 12% 30% 9%	4580
	11th to 20th	Night	49% 3 13% 16% 17% 2	5208
	21st to end	Night	50% 2 8% 22% 14% 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	27% 19% 31% 18% 6% 1	200
	11th to 20th	Day	26% 25% 31% 15% 5%	200
	21st to end	Day	21% 23% 32% 18% 5% 2	225
February	1st to 10th	Day	30% 19% 31% 17% 3	366
	11th to 20th	Day	27% 22% 34% 15% 3	496
	21st to end	Day	28% 17% 34% 18% 4	414
March	1st to 10th	Day	27% 20% 29% 20% 4 1	500
	11th to 20th	Day	28% 21% 29% 17% 4	500
	21st to end	Day	29% 19% 31% 13% 5% 3	550
April	1st to 10th	Day	32% 19% 28% 14% 6% 1	500
	11th to 20th	Day	30% 17% 29% 14% 8% 1	492
	21st to end	Day	30% 16% 29% 18% 5% 2	500
May	1st to 10th	Day	34% 16% 25% 15% 8% 1	503
	11th to 20th	Day	23% 13% 39% 16% 7% 2	487
	21st to end	Day	19% 11% 31% 24% 11% 4	529
June	1st to 10th	Day	17% 14% 31% 23% 12% 3	490
	11th to 20th	Day	17% 11% 33% 26% 10% 3	490
	21st to end	Day	15% 14% 31% 25% 11% 3	490
July	1st to 10th	Day	16% 7% 29% 29% 15% 4	485
	11th to 20th	Day	13% 6% 27% 31% 18% 5%	484
	21st to end	Day	15% 6% 30% 32% 15% 2	532
August	1st to 10th	Day	13% 9% 25% 33% 15% 5%	486
	11th to 20th	Day	15% 7% 29% 28% 15% 7%	479
	21st to end	Day	11% 8% 26% 28% 20% 7%	539
September	1st to 10th	Day	19% 8% 23% 25% 17% 9%	490
	11th to 20th	Day	17% 9% 24% 21% 16% 13%	490
	21st to end	Day	20% 9% 30% 22% 14% 6%	490
October	1st to 10th	Day	28% 10% 24% 19% 12% 8%	490
	11th to 20th	Day	18% 14% 29% 22% 13% 3	467
	21st to end	Day	28% 11% 26% 24% 9% 2	429
November	1st to 10th	Day	21% 13% 29% 24% 10% 3	395
	11th to 20th	Day	29% 14% 30% 20% 7% 1	400
	21st to end	Day	28% 12% 32% 20% 8% 1	358
December	1st to 10th	Day	21% 21% 31% 20% 8% 1	200
	11th to 20th	Day	30% 22% 33% 11% 4	200
	21st to end	Day	23% 18% 35% 18% 5% 1	220
January	1st to 10th	Night	22% 14% 38% 24% 3	800
	11th to 20th	Night	27% 13% 31% 26% 3	800
	21st to end	Night	19% 12% 38% 28% 3	880
February	1st to 10th	Night	23% 14% 36% 26% 2	800
	11th to 20th	Night	22% 16% 41% 19% 2	783
	21st to end	Night	24% 15% 35% 23% 3	660
March	1st to 10th	Night	23% 17% 34% 23% 3	800
	11th to 20th	Night	23% 15% 37% 22% 3	800
	21st to end	Night	25% 14% 34% 22% 6%	880
April	1st to 10th	Night	25% 15% 33% 24% 4	800
	11th to 20th	Night	25% 16% 32% 21% 6%	791
	21st to end	Night	26% 17% 31% 23% 4	658
May	1st to 10th	Night	28% 13% 33% 22% 5% 1	600
	11th to 20th	Night	21% 13% 37% 24% 5%	463
	21st to end	Night	20% 8% 32% 34% 6% 1	411
June	1st to 10th	Night	20% 4 29% 38% 8% 1	380
	11th to 20th	Night	20% 8% 32% 31% 10%	380
	21st to end	Night	16% 3 31% 39% 10% 1	380
July	1st to 10th	Night	14% 4 27% 41% 13% 1	370
	11th to 20th	Night	15% 4 19% 45% 16%	368
	21st to end	Night	11% 5% 24% 47% 13%	416
August	1st to 10th	Night	12% 3 27% 44% 13%	449
	11th to 20th	Night	13% 4 23% 39% 19% 2	689
	21st to end	Night	14% 4 19% 41% 19% 2	836
September	1st to 10th	Night	18% 4 26% 36% 15% 1	760
	11th to 20th	Night	15% 6% 21% 34% 21% 3	760
	21st to end	Night	20% 6% 24% 34% 13% 2	760
October	1st to 10th	Night	24% 6% 23% 32% 13% 2	760
	11th to 20th	Night	19% 9% 29% 32% 11% 1	760
	21st to end	Night	28% 10% 29% 26% 7%	836
November	1st to 10th	Night	18% 9% 33% 31% 9% 1	780
	11th to 20th	Night	22% 10% 34% 25% 8% 1	800
	21st to end	Night	22% 14% 30% 28% 5% 1	800
December	1st to 10th	Night	25% 12% 35% 22% 6% 1	800
	11th to 20th	Night	25% 12% 32% 28% 4	800
	21st to end	Night	27% 11% 34% 24% 3	880

Page generated at 2025-05-08 09:33:54. Version ac07

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