Crawfordville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Crawfordville clear sky chart from 2005-11-06 to 2025-03-12.

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	10% 5% 2 6% 5% 5% 5% 4 7% 9% 42%	109284
	Night	10% 5% 2 5% 4 4 4 4 6% 9% 46%	109716
Transparency	Day	35% 9% 15% 18% 16% 7%	113153
	Night	34% 7% 14% 18% 18% 9%	113973
Seeing	Day	11% 8% 22% 27% 21% 11%	15417
	Night	11% 6% 21% 31% 25% 6%	25512

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% 5% 1 5% 4 3 3 3 4 5% 55%	4056
	11th to 20th	Day	17% 6% 2 5% 4 4 3 3 5% 7% 43%	4129
	21st to end	Day	14% 5% 2 6% 3 4 4 3 5% 9% 45%	4972
February	1st to 10th	Day	16% 7% 2 6% 5% 4 4 4 4 6% 43%	2000
	11th to 20th	Day	18% 6% 2 5% 3 3 4 3 4 5% 47%	1948
	21st to end	Day	15% 6% 2 5% 4 4 4 3 4 6% 48%	1650
March	1st to 10th	Day	21% 7% 2 5% 3 3 4 3 5% 7% 39%	3366
	11th to 20th	Day	7% 5% 2 6% 4 5% 5% 4 6% 9% 47%	3491
	21st to end	Day	16% 4 2 4 3 3 3 3 5% 7% 51%	3815
April	1st to 10th	Day	10% 4 2 5% 5% 4 5% 4 7% 7% 47%	2090
	11th to 20th	Day	12% 5% 2 6% 3 4 4 3 5% 6% 49%	2232
	21st to end	Day	6% 4 1 4 4 4 3 3 6% 8% 57%	2330
May	1st to 10th	Day	7% 4 1 5% 4 4 4 4 6% 8% 53%	4082
	11th to 20th	Day	11% 6% 2 7% 4 5% 5% 4 7% 8% 40%	4081
	21st to end	Day	4 3 1 5% 5% 5% 4 5% 8% 11% 50%	4476
June	1st to 10th	Day	8% 6% 3 9% 7% 6% 6% 7% 9% 11% 28%	2470
	11th to 20th	Day	6% 5% 2 7% 6% 7% 8% 7% 9% 12% 30%	2470
	21st to end	Day	7% 5% 3 8% 7% 7% 8% 8% 10% 10% 27%	2470
July	1st to 10th	Day	7% 6% 3 9% 7% 7% 9% 8% 10% 13% 22%	4120
	11th to 20th	Day	5% 4 2 7% 5% 6% 6% 6% 11% 14% 34%	4120
	21st to end	Day	5% 5% 2 8% 8% 8% 10% 8% 11% 13% 21%	4466
August	1st to 10th	Day	8% 5% 2 9% 7% 7% 7% 7% 9% 11% 28%	3833
	11th to 20th	Day	7% 5% 2 7% 5% 6% 7% 6% 9% 11% 36%	3729
	21st to end	Day	8% 6% 3 8% 7% 7% 7% 6% 10% 11% 28%	4116
September	1st to 10th	Day	11% 8% 2 9% 7% 6% 7% 6% 9% 11% 26%	2090
	11th to 20th	Day	11% 7% 2 8% 6% 7% 7% 6% 7% 9% 31%	2090
	21st to end	Day	12% 5% 2 5% 4 4 5% 3 6% 8% 45%	2090
October	1st to 10th	Day	11% 5% 2 6% 4 4 5% 4 5% 6% 47%	2090
	11th to 20th	Day	6% 3 1 3 3 3 3 4 4 7% 62%	2049
	21st to end	Day	8% 5% 2 4 3 4 4 3 5% 6% 55%	2090
November	1st to 10th	Day	9% 4 1 4 3 3 3 3 5% 6% 58%	1904
	11th to 20th	Day	10% 5% 1 5% 4 3 3 3 4 6% 56%	1800
	21st to end	Day	12% 4 2 7% 4 3 5% 4 5% 6% 49%	1800
December	1st to 10th	Day	11% 5% 2 6% 4 3 3 3 5% 6% 53%	2930
	11th to 20th	Day	12% 6% 2 5% 4 4 3 3 5% 6% 49%	3373
	21st to end	Day	20% 8% 2 5% 3 3 3 3 4 5% 44%	4466
January	1st to 10th	Night	12% 6% 2 4 3 3 3 3 5% 7% 53%	5889
	11th to 20th	Night	15% 8% 3 7% 4 4 5% 4 5% 7% 38%	5828
	21st to end	Night	16% 8% 2 5% 4 3 3 3 6% 8% 41%	5984
February	1st to 10th	Night	15% 7% 2 6% 4 4 3 3 5% 6% 44%	2400
	11th to 20th	Night	16% 7% 2 6% 4 3 3 3 3 5% 47%	2338
	21st to end	Night	14% 7% 3 5% 4 3 4 3 4 6% 46%	1980
March	1st to 10th	Night	18% 11% 3 7% 4 4 4 3 5% 6% 35%	3704
	11th to 20th	Night	10% 5% 2 6% 4 4 4 3 7% 9% 46%	3498
	21st to end	Night	18% 5% 2 5% 3 3 4 3 4 7% 47%	3817
April	1st to 10th	Night	11% 4 2 5% 3 4 4 5% 6% 7% 49%	2090
	11th to 20th	Night	9% 5% 2 6% 4 4 4 4 5% 7% 50%	1909
	21st to end	Night	5% 4 2 3 3 4 3 3 6% 7% 58%	1848
May	1st to 10th	Night	6% 3 1 4 4 3 4 3 7% 10% 55%	2813
	11th to 20th	Night	10% 6% 1 6% 4 4 5% 3 6% 9% 46%	2812
	21st to end	Night	4 3 1 4 3 4 4 4 6% 10% 59%	3079
June	1st to 10th	Night	5% 6% 2 6% 4 4 5% 5% 8% 11% 41%	1710
	11th to 20th	Night	5% 4 2 5% 5% 4 4 5% 10% 13% 42%	1710
	21st to end	Night	6% 3 2 6% 5% 5% 7% 4 8% 12% 41%	1710
July	1st to 10th	Night	6% 5% 3 8% 6% 6% 8% 7% 10% 14% 26%	2840
	11th to 20th	Night	3 3 1 4 4 4 5% 6% 8% 13% 48%	2840
	21st to end	Night	3 4 2 7% 5% 5% 6% 6% 10% 15% 35%	3087
August	1st to 10th	Night	7% 4 2 5% 5% 5% 6% 5% 9% 13% 40%	3077
	11th to 20th	Night	4 3 1 4 4 5% 6% 5% 10% 16% 43%	3100
	21st to end	Night	7% 6% 3 8% 5% 7% 7% 7% 10% 11% 30%	3505
September	1st to 10th	Night	8% 7% 2 8% 6% 6% 7% 7% 9% 13% 28%	2090
	11th to 20th	Night	10% 6% 2 7% 5% 6% 7% 5% 8% 10% 35%	2090
	21st to end	Night	9% 4 1 5% 4 4 4 4 7% 10% 47%	2090
October	1st to 10th	Night	8% 4 3 8% 4 4 5% 4 4 7% 50%	2090
	11th to 20th	Night	6% 4 1 4 3 3 3 3 5% 7% 61%	2128
	21st to end	Night	7% 4 2 5% 4 4 5% 4 5% 6% 54%	2508
November	1st to 10th	Night	7% 5% 2 5% 4 4 4 4 6% 6% 53%	2390
	11th to 20th	Night	10% 5% 2 5% 4 4 4 3 4 6% 54%	2600
	21st to end	Night	12% 6% 2 5% 3 3 4 3 4 6% 51%	2600
December	1st to 10th	Night	10% 5% 2 4 4 3 4 3 5% 6% 54%	4250
	11th to 20th	Night	14% 6% 1 4 3 2 3 3 4 7% 53%	4822
	21st to end	Night	16% 7% 2 6% 4 4 3 3 4 6% 45%	6490

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	31% 5% 6% 15% 29% 13%	4057
	11th to 20th	Day	40% 4 6% 14% 22% 13%	4129
	21st to end	Day	36% 5% 10% 18% 20% 11%	4972
February	1st to 10th	Day	42% 5% 8% 15% 18% 11%	2000
	11th to 20th	Day	39% 5% 6% 15% 23% 12%	1958
	21st to end	Day	39% 5% 9% 15% 20% 12%	1650
March	1st to 10th	Day	43% 6% 10% 18% 16% 6%	3366
	11th to 20th	Day	31% 7% 16% 17% 20% 9%	3491
	21st to end	Day	33% 5% 14% 25% 14% 10%	3815
April	1st to 10th	Day	33% 7% 13% 17% 17% 13%	2090
	11th to 20th	Day	35% 5% 8% 22% 20% 10%	2232
	21st to end	Day	25% 5% 12% 25% 22% 11%	2330
May	1st to 10th	Day	25% 8% 17% 25% 19% 6%	4120
	11th to 20th	Day	38% 9% 13% 23% 15% 3	4085
	21st to end	Day	23% 9% 19% 28% 19% 2	4489
June	1st to 10th	Day	42% 11% 20% 21% 6% 1	2470
	11th to 20th	Day	37% 14% 22% 19% 7% 1	2470
	21st to end	Day	42% 14% 22% 14% 6% 1	2470
July	1st to 10th	Day	41% 19% 31% 8% 1	4055
	11th to 20th	Day	31% 16% 40% 11% 2	4051
	21st to end	Day	43% 22% 24% 10% 1	4324
August	1st to 10th	Day	40% 13% 22% 16% 7% 2	3820
	11th to 20th	Day	34% 13% 21% 23% 9%	3765
	21st to end	Day	41% 14% 24% 16% 5%	4116
September	1st to 10th	Day	45% 14% 18% 14% 7% 2	2090
	11th to 20th	Day	44% 13% 17% 15% 10% 2	2090
	21st to end	Day	35% 8% 13% 21% 15% 7%	2090
October	1st to 10th	Day	44% 5% 7% 11% 17% 15%	3480
	11th to 20th	Day	14% 3 5% 18% 31% 29%	3380
	21st to end	Day	18% 4 5% 18% 39% 15%	3428
November	1st to 10th	Day	27% 5% 9% 20% 23% 17%	1904
	11th to 20th	Day	31% 3 8% 17% 28% 14%	1800
	21st to end	Day	34% 5% 8% 21% 23% 9%	1800
December	1st to 10th	Day	33% 5% 8% 16% 26% 12%	2930
	11th to 20th	Day	34% 5% 9% 20% 23% 9%	3370
	21st to end	Day	44% 4 6% 17% 25% 4	4466
January	1st to 10th	Night	33% 3 6% 13% 30% 15%	5889
	11th to 20th	Night	45% 3 6% 15% 23% 8%	5828
	21st to end	Night	41% 4 8% 18% 20% 9%	5984
February	1st to 10th	Night	40% 5% 7% 15% 22% 11%	2400
	11th to 20th	Night	41% 5% 6% 13% 20% 14%	2339
	21st to end	Night	41% 5% 8% 16% 17% 14%	1980
March	1st to 10th	Night	49% 7% 9% 15% 14% 7%	3704
	11th to 20th	Night	32% 6% 13% 21% 19% 9%	3498
	21st to end	Night	37% 4 9% 21% 18% 10%	3817
April	1st to 10th	Night	33% 6% 12% 17% 18% 13%	2090
	11th to 20th	Night	34% 5% 8% 19% 23% 11%	1909
	21st to end	Night	23% 6% 10% 28% 22% 11%	1848
May	1st to 10th	Night	21% 9% 19% 25% 19% 6%	2840
	11th to 20th	Night	33% 8% 17% 24% 15% 3	2813
	21st to end	Night	19% 8% 17% 35% 19% 2	3087
June	1st to 10th	Night	34% 10% 23% 23% 10% 1	1710
	11th to 20th	Night	29% 11% 27% 22% 9% 1	1710
	21st to end	Night	32% 13% 25% 21% 9% 1	1710
July	1st to 10th	Night	42% 16% 29% 11% 1	2795
	11th to 20th	Night	24% 16% 43% 16% 2	2786
	21st to end	Night	34% 18% 35% 12% 2	2988
August	1st to 10th	Night	30% 12% 29% 19% 9%	3066
	11th to 20th	Night	25% 14% 28% 26% 7%	3130
	21st to end	Night	40% 16% 24% 14% 5%	3505
September	1st to 10th	Night	41% 15% 19% 15% 7% 2	2090
	11th to 20th	Night	41% 15% 17% 15% 11% 1	2090
	21st to end	Night	32% 9% 15% 21% 17% 6%	2090
October	1st to 10th	Night	43% 6% 9% 12% 17% 13%	3480
	11th to 20th	Night	16% 3 5% 19% 31% 26%	3523
	21st to end	Night	19% 4 6% 17% 38% 15%	4120
November	1st to 10th	Night	30% 6% 8% 21% 19% 16%	2390
	11th to 20th	Night	33% 4 7% 16% 24% 15%	2600
	21st to end	Night	35% 5% 9% 19% 21% 12%	2600
December	1st to 10th	Night	31% 4 9% 16% 23% 16%	4250
	11th to 20th	Night	31% 6% 10% 20% 22% 11%	4824
	21st to end	Night	41% 5% 7% 18% 24% 6%	6490

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	16% 21% 44% 15% 4 1	300
	11th to 20th	Day	14% 18% 35% 24% 7% 2	300
	21st to end	Day	22% 20% 42% 14% 2	330
February	1st to 10th	Day	18% 18% 36% 20% 7% 1	300
	11th to 20th	Day	26% 15% 32% 23% 4	300
	21st to end	Day	13% 18% 44% 20% 5%	249
March	1st to 10th	Day	14% 19% 36% 24% 6%	381
	11th to 20th	Day	12% 17% 36% 23% 10% 2	464
	21st to end	Day	14% 17% 31% 25% 11% 2	506
April	1st to 10th	Day	11% 16% 34% 25% 13% 2	460
	11th to 20th	Day	10% 15% 30% 30% 13% 2	452
	21st to end	Day	7% 9% 30% 33% 18% 4	460
May	1st to 10th	Day	6% 8% 28% 33% 17% 7%	463
	11th to 20th	Day	9% 6% 19% 35% 22% 10%	487
	21st to end	Day	9% 2 16% 33% 27% 14%	529
June	1st to 10th	Day	11% 2 13% 33% 28% 13%	490
	11th to 20th	Day	8% 3 14% 27% 29% 19%	490
	21st to end	Day	7% 1 7% 32% 31% 22%	490
July	1st to 10th	Day	8% 2 6% 21% 30% 33%	485
	11th to 20th	Day	6% 1 5% 19% 36% 31%	484
	21st to end	Day	6% 1 5% 24% 35% 28%	532
August	1st to 10th	Day	11% 2 7% 20% 36% 24%	486
	11th to 20th	Day	9% 1 5% 19% 37% 29%	479
	21st to end	Day	10% 1 10% 25% 33% 19%	539
September	1st to 10th	Day	12% 3 10% 23% 30% 22%	490
	11th to 20th	Day	14% 2 12% 30% 29% 13%	490
	21st to end	Day	11% 3 13% 24% 35% 13%	490
October	1st to 10th	Day	12% 6% 22% 35% 21% 5%	490
	11th to 20th	Day	5% 6% 20% 35% 28% 7%	490
	21st to end	Day	8% 6% 26% 38% 20% 2	539
November	1st to 10th	Day	10% 7% 26% 36% 18% 4	442
	11th to 20th	Day	11% 12% 37% 30% 9% 2	300
	21st to end	Day	11% 13% 35% 28% 11% 1	300
December	1st to 10th	Day	17% 15% 33% 23% 8% 3	300
	11th to 20th	Day	18% 11% 38% 26% 6% 1	300
	21st to end	Day	21% 11% 33% 22% 11% 2	330
January	1st to 10th	Night	18% 13% 36% 25% 8% 1	800
	11th to 20th	Night	14% 11% 28% 34% 11% 1	800
	21st to end	Night	20% 12% 33% 29% 6%	880
February	1st to 10th	Night	18% 9% 29% 33% 11% 1	800
	11th to 20th	Night	20% 12% 27% 32% 8%	783
	21st to end	Night	17% 11% 33% 33% 6%	660
March	1st to 10th	Night	15% 9% 32% 34% 11%	800
	11th to 20th	Night	13% 9% 28% 33% 16%	767
	21st to end	Night	12% 11% 28% 34% 15% 1	836
April	1st to 10th	Night	12% 8% 28% 36% 17%	760
	11th to 20th	Night	11% 7% 27% 35% 18% 2	597
	21st to end	Night	7% 5% 25% 36% 24% 2	570
May	1st to 10th	Night	6% 4 22% 38% 27% 3	570
	11th to 20th	Night	7% 2 19% 39% 28% 6%	561
	21st to end	Night	5% 1 10% 37% 39% 7%	617
June	1st to 10th	Night	9% 1 8% 32% 42% 8%	570
	11th to 20th	Night	5% 3 8% 30% 39% 15%	570
	21st to end	Night	5% 2 6% 26% 45% 15%	570
July	1st to 10th	Night	6% 2 6% 16% 45% 26%	555
	11th to 20th	Night	6% 4 12% 48% 30%	552
	21st to end	Night	3 1 3 16% 53% 24%	624
August	1st to 10th	Night	6% 1 4 17% 49% 23%	567
	11th to 20th	Night	5% 1 4 15% 51% 25%	564
	21st to end	Night	9% 1 8% 24% 39% 19%	643
September	1st to 10th	Night	9% 2 9% 24% 39% 16%	760
	11th to 20th	Night	11% 3 11% 30% 36% 9%	760
	21st to end	Night	9% 2 13% 30% 38% 8%	760
October	1st to 10th	Night	9% 2 26% 31% 28% 4	760
	11th to 20th	Night	6% 4 23% 34% 28% 4	760
	21st to end	Night	8% 5% 22% 41% 22% 2	836
November	1st to 10th	Night	9% 5% 24% 40% 19% 2	780
	11th to 20th	Night	13% 9% 27% 34% 17% 1	800
	21st to end	Night	15% 9% 26% 35% 15% 1	800
December	1st to 10th	Night	15% 8% 27% 31% 17% 2	800
	11th to 20th	Night	16% 9% 28% 32% 16%	800
	21st to end	Night	20% 9% 28% 29% 12% 1	880

Page generated at 2025-03-09 08:08:44. Version ac07

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