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 2026-07-16.

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% 5% 7% 9% 41%	138041
	Night	10% 5% 2 6% 4 4 4 4 6% 9% 45%	134633
Transparency	Day	35% 9% 15% 18% 15% 7%	141866
	Night	34% 7% 14% 19% 17% 9%	138867
Seeing	Day	11% 8% 23% 27% 21% 10%	17262
	Night	11% 6% 21% 31% 25% 6%	27239

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	11% 5% 2 6% 4 4 3 3 4 7% 49%	5258
	11th to 20th	Day	15% 6% 2 5% 4 4 4 4 6% 8% 43%	5377
	21st to end	Day	13% 5% 2 6% 3 4 5% 3 6% 9% 44%	6436
February	1st to 10th	Day	16% 7% 2 6% 4 3 4 3 4 6% 44%	2100
	11th to 20th	Day	17% 6% 2 5% 3 3 4 3 5% 6% 46%	2048
	21st to end	Day	15% 6% 2 5% 4 4 4 3 4 6% 48%	1730
March	1st to 10th	Day	21% 7% 2 5% 3 3 3 3 5% 8% 41%	4782
	11th to 20th	Day	8% 5% 2 5% 4 4 4 3 5% 8% 52%	5090
	21st to end	Day	15% 4 2 4 3 3 3 3 5% 7% 51%	5586
April	1st to 10th	Day	10% 4 2 5% 5% 4 5% 4 7% 8% 47%	2310
	11th to 20th	Day	11% 5% 1 6% 3 4 4 3 5% 6% 52%	2470
	21st to end	Day	6% 4 1 4 4 4 3 3 6% 8% 56%	2576
May	1st to 10th	Day	12% 7% 2 7% 4 4 5% 4 5% 8% 42%	7616
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 7% 10% 45%	7626
	21st to end	Day	4 4 2 6% 5% 6% 6% 5% 9% 12% 40%	8391
June	1st to 10th	Day	8% 6% 3 9% 6% 6% 7% 7% 9% 11% 28%	2730
	11th to 20th	Day	7% 5% 2 7% 6% 7% 8% 7% 9% 12% 29%	2730
	21st to end	Day	7% 5% 3 8% 8% 7% 8% 8% 9% 10% 28%	2730
July	1st to 10th	Day	7% 6% 3 10% 7% 7% 9% 8% 11% 13% 20%	6030
	11th to 20th	Day	5% 3 2 6% 5% 6% 7% 6% 10% 15% 36%	5965
	21st to end	Day	4 4 2 7% 7% 8% 9% 8% 11% 13% 27%	6424
August	1st to 10th	Day	8% 5% 2 9% 7% 7% 7% 7% 9% 11% 28%	3955
	11th to 20th	Day	7% 5% 2 7% 5% 6% 6% 6% 9% 11% 36%	3849
	21st to end	Day	8% 6% 3 8% 7% 7% 7% 6% 9% 11% 28%	4246
September	1st to 10th	Day	10% 8% 2 8% 7% 6% 7% 6% 8% 11% 27%	2200
	11th to 20th	Day	10% 6% 2 7% 5% 7% 7% 6% 7% 9% 33%	2200
	21st to end	Day	11% 5% 2 5% 4 5% 5% 3 6% 8% 45%	2200
October	1st to 10th	Day	10% 5% 3 6% 4 4 5% 4 6% 6% 46%	2200
	11th to 20th	Day	6% 3 1 3 3 3 3 3 4 7% 62%	2157
	21st to end	Day	8% 5% 2 5% 3 4 4 3 5% 6% 55%	2200
November	1st to 10th	Day	8% 4 1 4 3 3 3 3 5% 6% 58%	2001
	11th to 20th	Day	9% 4 1 5% 3 3 3 3 4 6% 58%	1890
	21st to end	Day	11% 4 2 7% 4 3 5% 4 5% 6% 49%	1890
December	1st to 10th	Day	11% 5% 2 6% 4 3 3 3 5% 6% 52%	3020
	11th to 20th	Day	12% 6% 2 5% 4 4 3 3 5% 6% 50%	3463
	21st to end	Day	19% 8% 2 5% 3 3 3 3 4 5% 44%	4565
January	1st to 10th	Night	10% 6% 2 5% 3 3 4 3 5% 7% 50%	7635
	11th to 20th	Night	15% 7% 3 7% 4 4 5% 4 6% 7% 40%	7580
	21st to end	Night	16% 8% 2 6% 4 3 4 3 6% 8% 40%	7745
February	1st to 10th	Night	15% 7% 2 6% 4 4 3 3 5% 6% 46%	2520
	11th to 20th	Night	16% 7% 2 6% 4 3 3 3 3 5% 47%	2458
	21st to end	Night	14% 8% 3 5% 4 3 4 3 4 6% 46%	2076
March	1st to 10th	Night	18% 9% 2 6% 4 4 3 3 5% 6% 40%	5288
	11th to 20th	Night	10% 4 1 5% 3 3 3 3 6% 9% 53%	5090
	21st to end	Night	15% 5% 2 5% 4 3 3 3 4 7% 49%	5588
April	1st to 10th	Night	10% 5% 2 5% 3 4 4 4 6% 6% 48%	2310
	11th to 20th	Night	8% 5% 2 5% 4 4 4 3 5% 6% 52%	2113
	21st to end	Night	5% 4 2 4 4 4 4 3 6% 8% 57%	2042
May	1st to 10th	Night	10% 6% 2 5% 3 4 4 3 5% 9% 48%	5237
	11th to 20th	Night	11% 5% 1 5% 3 4 4 3 6% 9% 47%	5234
	21st to end	Night	4 3 1 5% 4 4 5% 4 7% 13% 50%	5761
June	1st to 10th	Night	5% 6% 3 7% 4 4 5% 5% 8% 12% 40%	1890
	11th to 20th	Night	6% 4 2 5% 5% 4 4 5% 10% 13% 42%	1890
	21st to end	Night	6% 3 2 6% 5% 5% 7% 5% 8% 12% 41%	1890
July	1st to 10th	Night	5% 5% 2 8% 7% 7% 8% 8% 11% 14% 25%	4148
	11th to 20th	Night	2 3 1 4 4 5% 5% 6% 9% 15% 45%	4102
	21st to end	Night	4 4 2 6% 5% 5% 6% 6% 11% 16% 36%	4427
August	1st to 10th	Night	7% 4 2 5% 5% 5% 6% 5% 9% 13% 40%	3175
	11th to 20th	Night	4 3 1 4 4 5% 6% 5% 10% 16% 43%	3200
	21st to end	Night	7% 6% 3 8% 5% 7% 7% 6% 9% 11% 30%	3616
September	1st to 10th	Night	7% 6% 2 8% 6% 6% 7% 6% 9% 13% 30%	2200
	11th to 20th	Night	10% 6% 2 6% 5% 5% 6% 5% 8% 10% 37%	2200
	21st to end	Night	8% 4 1 5% 4 4 4 4 6% 10% 48%	2200
October	1st to 10th	Night	8% 4 3 8% 4 4 5% 4 5% 7% 49%	2200
	11th to 20th	Night	6% 4 1 4 3 3 3 3 4 7% 62%	2240
	21st to end	Night	7% 5% 2 5% 4 4 4 4 5% 6% 54%	2640
November	1st to 10th	Night	7% 5% 2 5% 4 4 4 4 6% 6% 54%	2513
	11th to 20th	Night	10% 5% 2 5% 4 3 4 3 4 6% 55%	2730
	21st to end	Night	12% 7% 2 6% 3 3 4 3 4 6% 50%	2730
December	1st to 10th	Night	11% 5% 2 5% 4 3 4 3 5% 6% 53%	4380
	11th to 20th	Night	13% 6% 1 4 3 2 3 3 4 7% 54%	4952
	21st to end	Night	16% 7% 2 5% 4 4 3 3 4 6% 45%	6633

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	35% 7% 7% 16% 25% 10%	5259
	11th to 20th	Day	39% 5% 6% 15% 21% 15%	5377
	21st to end	Day	37% 5% 10% 17% 19% 12%	6436
February	1st to 10th	Day	41% 5% 8% 16% 18% 12%	2100
	11th to 20th	Day	39% 5% 6% 16% 22% 12%	2058
	21st to end	Day	38% 5% 9% 16% 20% 12%	1730
March	1st to 10th	Day	40% 5% 10% 16% 19% 9%	4782
	11th to 20th	Day	28% 6% 12% 15% 21% 17%	5090
	21st to end	Day	33% 4 12% 24% 16% 10%	5586
April	1st to 10th	Day	33% 7% 13% 19% 16% 12%	2310
	11th to 20th	Day	33% 4 8% 22% 22% 12%	2470
	21st to end	Day	25% 5% 13% 26% 21% 10%	2576
May	1st to 10th	Day	38% 7% 15% 21% 14% 5%	7651
	11th to 20th	Day	31% 8% 17% 26% 14% 3	7630
	21st to end	Day	30% 13% 21% 21% 13% 2	8405
June	1st to 10th	Day	41% 12% 20% 20% 7% 1	2730
	11th to 20th	Day	38% 14% 23% 17% 7% 1	2730
	21st to end	Day	42% 14% 22% 15% 6% 1	2730
July	1st to 10th	Day	44% 19% 29% 7% 1	5965
	11th to 20th	Day	29% 16% 41% 13% 1	5896
	21st to end	Day	38% 19% 23% 19% 1	6240
August	1st to 10th	Day	41% 13% 22% 16% 7% 2	3942
	11th to 20th	Day	33% 13% 22% 23% 9%	3885
	21st to end	Day	41% 14% 24% 16% 5%	4246
September	1st to 10th	Day	44% 14% 18% 15% 7% 2	2200
	11th to 20th	Day	42% 12% 16% 16% 11% 2	2200
	21st to end	Day	35% 8% 13% 22% 15% 7%	2200
October	1st to 10th	Day	44% 5% 8% 12% 17% 15%	3590
	11th to 20th	Day	14% 3 5% 18% 31% 29%	3488
	21st to end	Day	19% 4 5% 18% 39% 15%	3538
November	1st to 10th	Day	26% 5% 9% 20% 23% 17%	2001
	11th to 20th	Day	29% 3 8% 17% 28% 14%	1890
	21st to end	Day	34% 5% 8% 21% 23% 10%	1890
December	1st to 10th	Day	34% 5% 8% 16% 25% 12%	3020
	11th to 20th	Day	34% 5% 8% 20% 23% 10%	3460
	21st to end	Day	43% 4 6% 17% 25% 5%	4565
January	1st to 10th	Night	34% 4 9% 15% 26% 12%	7636
	11th to 20th	Night	43% 4 6% 16% 21% 11%	7580
	21st to end	Night	42% 4 8% 18% 20% 9%	7745
February	1st to 10th	Night	39% 5% 7% 15% 22% 12%	2520
	11th to 20th	Night	41% 5% 7% 14% 19% 14%	2459
	21st to end	Night	41% 5% 8% 16% 17% 14%	2076
March	1st to 10th	Night	44% 6% 9% 15% 19% 9%	5288
	11th to 20th	Night	27% 5% 10% 20% 20% 18%	5090
	21st to end	Night	35% 4 8% 22% 18% 12%	5588
April	1st to 10th	Night	34% 6% 12% 18% 18% 12%	2310
	11th to 20th	Night	31% 5% 7% 19% 25% 13%	2113
	21st to end	Night	24% 6% 11% 28% 21% 10%	2042
May	1st to 10th	Night	32% 7% 16% 25% 13% 6%	5264
	11th to 20th	Night	31% 7% 17% 25% 16% 3	5235
	21st to end	Night	24% 10% 25% 27% 13% 1	5771
June	1st to 10th	Night	34% 10% 23% 21% 11% 1	1890
	11th to 20th	Night	30% 11% 28% 21% 9% 1	1890
	21st to end	Night	32% 13% 24% 22% 8% 1	1890
July	1st to 10th	Night	44% 18% 28% 9% 1	4105
	11th to 20th	Night	24% 16% 42% 16% 2	4051
	21st to end	Night	32% 15% 34% 17% 1	4297
August	1st to 10th	Night	31% 12% 28% 19% 9%	3164
	11th to 20th	Night	25% 14% 28% 26% 7%	3230
	21st to end	Night	40% 16% 24% 15% 5%	3616
September	1st to 10th	Night	40% 15% 19% 16% 7% 2	2200
	11th to 20th	Night	39% 14% 16% 17% 13% 1	2200
	21st to end	Night	31% 9% 16% 22% 17% 6%	2200
October	1st to 10th	Night	43% 6% 9% 13% 17% 13%	3590
	11th to 20th	Night	16% 3 5% 19% 32% 26%	3635
	21st to end	Night	19% 4 6% 17% 38% 16%	4252
November	1st to 10th	Night	29% 6% 8% 20% 20% 17%	2513
	11th to 20th	Night	32% 4 7% 17% 25% 16%	2730
	21st to end	Night	35% 5% 9% 19% 20% 12%	2730
December	1st to 10th	Night	32% 4 8% 16% 23% 16%	4380
	11th to 20th	Night	31% 6% 10% 20% 22% 11%	4954
	21st to end	Night	40% 5% 7% 18% 24% 6%	6633

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% 20% 44% 16% 4 1	330
	11th to 20th	Day	14% 19% 35% 23% 7% 2	330
	21st to end	Day	22% 20% 42% 14% 2	363
February	1st to 10th	Day	18% 18% 37% 18% 7% 1	330
	11th to 20th	Day	25% 17% 33% 22% 4	330
	21st to end	Day	14% 19% 43% 18% 5%	273
March	1st to 10th	Day	14% 19% 33% 28% 6%	415
	11th to 20th	Day	14% 17% 35% 24% 9% 1	540
	21st to end	Day	13% 17% 31% 26% 11% 2	594
April	1st to 10th	Day	11% 16% 35% 24% 12% 1	540
	11th to 20th	Day	9% 15% 31% 30% 13% 2	532
	21st to end	Day	6% 9% 31% 33% 17% 4	540
May	1st to 10th	Day	7% 10% 30% 31% 16% 6%	543
	11th to 20th	Day	9% 5% 23% 35% 20% 8%	567
	21st to end	Day	8% 3 18% 33% 25% 13%	617
June	1st to 10th	Day	10% 2 16% 35% 25% 12%	570
	11th to 20th	Day	8% 4 14% 28% 28% 18%	570
	21st to end	Day	6% 1 7% 32% 31% 22%	570
July	1st to 10th	Day	7% 3 6% 24% 29% 31%	565
	11th to 20th	Day	6% 1 6% 21% 36% 30%	544
	21st to end	Day	6% 1 6% 25% 36% 27%	576
August	1st to 10th	Day	10% 2 7% 20% 37% 24%	526
	11th to 20th	Day	9% 1 6% 19% 37% 29%	519
	21st to end	Day	11% 2 11% 25% 33% 19%	583
September	1st to 10th	Day	11% 3 11% 25% 28% 21%	530
	11th to 20th	Day	13% 2 12% 32% 29% 13%	530
	21st to end	Day	11% 2 14% 25% 35% 13%	530
October	1st to 10th	Day	12% 5% 23% 35% 21% 4	530
	11th to 20th	Day	5% 6% 20% 35% 28% 6%	530
	21st to end	Day	9% 7% 26% 38% 19% 2	583
November	1st to 10th	Day	10% 7% 26% 37% 17% 4	479
	11th to 20th	Day	10% 11% 36% 32% 9% 2	330
	21st to end	Day	11% 13% 37% 28% 11% 1	330
December	1st to 10th	Day	19% 15% 33% 22% 8% 3	330
	11th to 20th	Day	17% 11% 38% 28% 6% 1	330
	21st to end	Day	20% 12% 32% 23% 12% 1	363
January	1st to 10th	Night	17% 12% 35% 27% 8% 1	840
	11th to 20th	Night	14% 11% 30% 33% 11% 1	840
	21st to end	Night	20% 12% 33% 29% 6%	924
February	1st to 10th	Night	18% 9% 30% 33% 10% 1	840
	11th to 20th	Night	20% 12% 27% 32% 8%	823
	21st to end	Night	17% 12% 33% 32% 6%	692
March	1st to 10th	Night	14% 8% 31% 35% 11%	840
	11th to 20th	Night	13% 10% 29% 32% 16%	840
	21st to end	Night	12% 10% 28% 35% 15% 1	924
April	1st to 10th	Night	12% 8% 29% 35% 17%	840
	11th to 20th	Night	10% 7% 26% 36% 19% 2	661
	21st to end	Night	7% 5% 24% 37% 25% 2	630
May	1st to 10th	Night	8% 4 22% 38% 25% 3	630
	11th to 20th	Night	7% 2 19% 39% 27% 5%	621
	21st to end	Night	5% 1 11% 36% 39% 7%	683
June	1st to 10th	Night	8% 2 10% 33% 40% 7%	630
	11th to 20th	Night	5% 3 8% 29% 40% 15%	630
	21st to end	Night	5% 2 6% 26% 46% 15%	630
July	1st to 10th	Night	6% 2 6% 16% 46% 25%	615
	11th to 20th	Night	6% 1 3 13% 49% 28%	597
	21st to end	Night	4 1 3 17% 53% 23%	657
August	1st to 10th	Night	6% 1 4 18% 48% 23%	597
	11th to 20th	Night	5% 1 4 15% 52% 24%	594
	21st to end	Night	8% 1 8% 26% 39% 19%	677
September	1st to 10th	Night	9% 2 10% 26% 38% 15%	800
	11th to 20th	Night	10% 2 11% 32% 36% 9%	800
	21st to end	Night	9% 2 13% 31% 38% 8%	800
October	1st to 10th	Night	9% 3 26% 31% 27% 4	800
	11th to 20th	Night	6% 4 23% 35% 29% 4	800
	21st to end	Night	9% 5% 22% 40% 21% 2	880
November	1st to 10th	Night	9% 5% 24% 40% 20% 1	820
	11th to 20th	Night	12% 9% 27% 35% 17% 1	840
	21st to end	Night	14% 9% 26% 35% 15% 1	840
December	1st to 10th	Night	16% 9% 28% 30% 16% 2	840
	11th to 20th	Night	15% 9% 28% 32% 15%	840
	21st to end	Night	19% 9% 28% 30% 13% 1	924

Page generated at 2026-07-13 03:14:48. Version ac07

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