Jackson
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jackson clear sky chart from 2005-11-06 to 2026-08-15.

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	13% 9% 4 8% 5% 5% 5% 4 5% 7% 34%	143332
	Night	14% 11% 4 9% 5% 4 4 3 5% 6% 34%	138760
Transparency	Day	49% 5% 11% 21% 13% 1	146888
	Night	50% 4 11% 21% 13% 1	143266
Seeing	Day	18% 12% 29% 23% 13% 5%	18157
	Night	19% 10% 30% 28% 12% 1	27930

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	14% 16% 8% 17% 5% 5% 4 4 5% 5% 17%	4691
	11th to 20th	Day	12% 14% 7% 16% 12% 8% 7% 4 4 4 10%	4710
	21st to end	Day	17% 16% 6% 13% 9% 6% 6% 3 3 5% 17%	5470
February	1st to 10th	Day	13% 15% 6% 11% 8% 6% 6% 4 4 6% 20%	1901
	11th to 20th	Day	15% 11% 6% 13% 8% 6% 5% 4 4 5% 24%	2048
	21st to end	Day	15% 15% 6% 12% 5% 5% 4 4 5% 5% 24%	1730
March	1st to 10th	Day	15% 13% 5% 11% 6% 5% 4 3 4 5% 30%	4580
	11th to 20th	Day	11% 12% 4 8% 5% 4 4 4 5% 7% 36%	5089
	21st to end	Day	17% 15% 4 9% 6% 5% 5% 4 5% 6% 26%	5586
April	1st to 10th	Day	18% 15% 3 8% 4 5% 4 3 4 6% 29%	2513
	11th to 20th	Day	16% 10% 3 7% 4 4 4 4 6% 7% 35%	2607
	21st to end	Day	17% 9% 3 8% 5% 4 4 4 6% 7% 34%	2730
May	1st to 10th	Day	18% 9% 3 6% 4 4 5% 4 5% 7% 35%	7616
	11th to 20th	Day	14% 7% 3 7% 5% 5% 5% 4 6% 8% 35%	7626
	21st to end	Day	15% 6% 2 6% 5% 4 4 3 5% 7% 44%	8589
June	1st to 10th	Day	11% 6% 2 6% 5% 5% 5% 3 7% 8% 42%	2940
	11th to 20th	Day	11% 5% 2 6% 5% 5% 5% 5% 7% 9% 41%	2940
	21st to end	Day	9% 6% 2 7% 5% 6% 6% 5% 7% 9% 39%	2940
July	1st to 10th	Day	11% 5% 2 6% 5% 5% 5% 5% 7% 10% 40%	8280
	11th to 20th	Day	6% 4 2 6% 4 5% 5% 4 6% 11% 48%	8280
	21st to end	Day	8% 5% 2 6% 4 5% 5% 4 7% 9% 44%	8694
August	1st to 10th	Day	12% 4 2 6% 4 4 5% 4 6% 9% 44%	4364
	11th to 20th	Day	11% 5% 2 6% 4 5% 5% 4 6% 9% 42%	4226
	21st to end	Day	9% 5% 2 6% 5% 5% 6% 4 7% 9% 43%	4487
September	1st to 10th	Day	11% 6% 2 6% 4 5% 5% 4 5% 8% 43%	2305
	11th to 20th	Day	9% 4 2 6% 3 4 5% 4 6% 9% 48%	2200
	21st to end	Day	14% 7% 3 6% 4 5% 5% 4 5% 7% 39%	2200
October	1st to 10th	Day	12% 6% 2 7% 5% 4 5% 4 5% 6% 44%	2195
	11th to 20th	Day	17% 10% 3 7% 5% 5% 5% 3 4 6% 35%	1998
	21st to end	Day	18% 10% 3 8% 5% 5% 4 4 5% 7% 30%	1980
November	1st to 10th	Day	12% 9% 4 7% 5% 4 4 3 5% 7% 40%	1852
	11th to 20th	Day	15% 15% 4 9% 6% 5% 4 3 4 6% 29%	1890
	21st to end	Day	19% 15% 6% 9% 5% 5% 4 3 4 6% 26%	1890
December	1st to 10th	Day	11% 16% 10% 14% 5% 5% 5% 4 5% 5% 20%	3020
	11th to 20th	Day	18% 20% 7% 11% 6% 5% 4 3 5% 5% 16%	3095
	21st to end	Day	24% 21% 7% 12% 5% 5% 3 3 3 5% 13%	4070
January	1st to 10th	Night	14% 15% 8% 16% 6% 5% 4 3 4 5% 21%	8232
	11th to 20th	Night	10% 16% 8% 17% 9% 8% 5% 5% 5% 5% 13%	8280
	21st to end	Night	15% 14% 7% 12% 7% 6% 6% 3 5% 5% 20%	8723
February	1st to 10th	Night	15% 15% 5% 12% 7% 5% 5% 4 4 4 24%	2715
	11th to 20th	Night	13% 13% 5% 11% 7% 6% 5% 3 5% 5% 28%	2458
	21st to end	Night	17% 12% 5% 11% 4 4 4 3 4 6% 29%	2076
March	1st to 10th	Night	15% 12% 5% 8% 4 4 3 3 5% 7% 35%	5493
	11th to 20th	Night	11% 8% 2 6% 4 4 4 4 6% 7% 43%	5091
	21st to end	Night	17% 11% 3 8% 5% 4 4 3 5% 6% 35%	5588
April	1st to 10th	Night	16% 11% 4 6% 5% 5% 4 4 6% 6% 35%	2125
	11th to 20th	Night	18% 9% 3 7% 4 5% 4 3 6% 5% 37%	1960
	21st to end	Night	16% 9% 3 7% 5% 4 4 3 4 8% 38%	1890
May	1st to 10th	Night	19% 10% 3 7% 4 4 5% 3 5% 7% 33%	5237
	11th to 20th	Night	16% 8% 2 7% 4 3 4 3 5% 7% 41%	5234
	21st to end	Night	14% 6% 2 5% 4 4 4 3 5% 8% 44%	5557
June	1st to 10th	Night	11% 4 2 5% 4 4 4 4 6% 9% 48%	1680
	11th to 20th	Night	11% 6% 2 6% 5% 4 5% 4 6% 9% 43%	1680
	21st to end	Night	9% 5% 2 5% 4 3 4 4 8% 10% 46%	1680
July	1st to 10th	Night	9% 5% 2 6% 4 4 4 4 5% 8% 49%	4708
	11th to 20th	Night	7% 4 2 5% 4 3 4 3 6% 9% 53%	4707
	21st to end	Night	10% 5% 2 6% 3 4 4 4 6% 8% 48%	5399
August	1st to 10th	Night	11% 5% 2 6% 3 4 3 3 5% 8% 48%	3005
	11th to 20th	Night	11% 6% 2 5% 3 4 4 4 6% 7% 48%	2911
	21st to end	Night	10% 6% 2 6% 4 4 5% 4 5% 7% 47%	3406
September	1st to 10th	Night	9% 6% 2 6% 5% 4 3 4 4 7% 50%	2075
	11th to 20th	Night	9% 5% 1 4 4 3 3 3 4 7% 57%	2200
	21st to end	Night	14% 7% 2 6% 3 4 4 3 5% 6% 44%	2200
October	1st to 10th	Night	12% 7% 2 6% 3 4 4 3 5% 6% 48%	2205
	11th to 20th	Night	17% 11% 3 7% 5% 3 4 3 4 6% 37%	2400
	21st to end	Night	19% 10% 3 6% 5% 4 4 4 5% 6% 34%	2860
November	1st to 10th	Night	13% 11% 2 7% 5% 4 4 3 4 5% 42%	2666
	11th to 20th	Night	16% 12% 4 9% 4 5% 4 4 6% 7% 31%	2730
	21st to end	Night	17% 16% 5% 9% 5% 4 4 3 4 6% 27%	2730
December	1st to 10th	Night	13% 14% 5% 15% 5% 5% 5% 4 5% 6% 22%	4380
	11th to 20th	Night	15% 19% 6% 13% 7% 5% 4 3 4 5% 17%	5329
	21st to end	Night	26% 21% 5% 11% 5% 4 3 3 4 5% 13%	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	70% 3 11% 13% 2	4692
	11th to 20th	Day	76% 5% 7% 7% 4	4710
	21st to end	Day	73% 2 7% 11% 6%	5470
February	1st to 10th	Day	64% 6% 10% 13% 6% 1	1901
	11th to 20th	Day	62% 5% 9% 14% 9% 1	2058
	21st to end	Day	61% 5% 11% 15% 6% 1	1730
March	1st to 10th	Day	57% 5% 10% 18% 9% 1	4580
	11th to 20th	Day	46% 5% 16% 23% 8% 2	5089
	21st to end	Day	59% 5% 9% 15% 11% 1	5586
April	1st to 10th	Day	55% 5% 10% 19% 11%	2513
	11th to 20th	Day	48% 6% 11% 21% 12% 2	2607
	21st to end	Day	48% 6% 13% 18% 13% 1	2730
May	1st to 10th	Day	48% 5% 10% 22% 14% 1	7651
	11th to 20th	Day	46% 5% 13% 22% 13% 1	7630
	21st to end	Day	40% 4 9% 21% 22% 4	8603
June	1st to 10th	Day	38% 7% 13% 25% 16% 2	2940
	11th to 20th	Day	38% 7% 13% 23% 17% 2	2940
	21st to end	Day	38% 9% 13% 22% 15% 2	2940
July	1st to 10th	Day	39% 3 14% 26% 16% 2	8211
	11th to 20th	Day	32% 3 12% 34% 18% 1	8205
	21st to end	Day	36% 3 13% 24% 23% 1	8503
August	1st to 10th	Day	37% 6% 14% 25% 18% 1	4351
	11th to 20th	Day	39% 6% 11% 31% 13% 1	4265
	21st to end	Day	38% 4 12% 32% 12% 2	4486
September	1st to 10th	Day	38% 8% 14% 23% 15% 2	2305
	11th to 20th	Day	32% 7% 12% 30% 18% 1	2200
	21st to end	Day	42% 6% 13% 21% 17%	2200
October	1st to 10th	Day	31% 4 10% 35% 20% 1	3572
	11th to 20th	Day	42% 3 9% 26% 19%	3226
	21st to end	Day	47% 3 12% 24% 12% 2	3180
November	1st to 10th	Day	44% 6% 10% 25% 14% 1	1852
	11th to 20th	Day	57% 5% 11% 18% 8% 2	1890
	21st to end	Day	61% 4 13% 16% 6%	1890
December	1st to 10th	Day	67% 5% 13% 10% 3	3020
	11th to 20th	Day	70% 5% 10% 13% 2	3092
	21st to end	Day	76% 4 8% 9% 4	4070
January	1st to 10th	Night	67% 4 7% 15% 6% 1	8233
	11th to 20th	Night	72% 3 9% 10% 5%	8280
	21st to end	Night	66% 3 10% 13% 7%	8723
February	1st to 10th	Night	63% 6% 10% 14% 6% 2	2715
	11th to 20th	Night	58% 5% 10% 18% 8% 1	2459
	21st to end	Night	57% 4 13% 17% 8% 2	2076
March	1st to 10th	Night	49% 4 13% 24% 10% 1	5493
	11th to 20th	Night	38% 6% 13% 27% 15% 1	5091
	21st to end	Night	50% 4 11% 19% 14% 1	5588
April	1st to 10th	Night	49% 6% 10% 20% 13% 1	2125
	11th to 20th	Night	47% 6% 11% 17% 17% 2	1960
	21st to end	Night	45% 5% 12% 20% 14% 2	1890
May	1st to 10th	Night	51% 5% 10% 18% 14% 2	5264
	11th to 20th	Night	42% 5% 11% 26% 13% 2	5235
	21st to end	Night	39% 5% 11% 21% 21% 4	5567
June	1st to 10th	Night	33% 5% 12% 27% 20% 2	1680
	11th to 20th	Night	37% 7% 13% 25% 16% 2	1680
	21st to end	Night	31% 8% 16% 26% 18% 1	1680
July	1st to 10th	Night	35% 3 11% 29% 17% 4	4670
	11th to 20th	Night	29% 3 12% 31% 23% 2	4662
	21st to end	Night	34% 4 12% 22% 26% 2	5278
August	1st to 10th	Night	35% 5% 14% 29% 16% 1	2994
	11th to 20th	Night	34% 5% 12% 34% 14% 2	2938
	21st to end	Night	37% 4 11% 31% 15% 1	3406
September	1st to 10th	Night	34% 6% 11% 28% 19% 3	2075
	11th to 20th	Night	28% 6% 9% 32% 22% 2	2200
	21st to end	Night	40% 6% 13% 25% 16% 1	2200
October	1st to 10th	Night	26% 3 10% 34% 26% 1	3608
	11th to 20th	Night	43% 4 10% 23% 21% 1	3899
	21st to end	Night	40% 3 9% 32% 15% 1	4610
November	1st to 10th	Night	45% 5% 10% 23% 15% 1	2666
	11th to 20th	Night	52% 5% 14% 19% 8% 2	2730
	21st to end	Night	58% 5% 12% 18% 6%	2730
December	1st to 10th	Night	63% 5% 13% 14% 4	4380
	11th to 20th	Night	69% 4 10% 12% 4	5331
	21st to end	Night	74% 5% 8% 8% 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	21% 19% 38% 17% 5% 1	330
	11th to 20th	Day	24% 22% 39% 12% 2 1	330
	21st to end	Day	28% 18% 34% 16% 4	363
February	1st to 10th	Day	25% 20% 35% 15% 3 1	330
	11th to 20th	Day	27% 17% 39% 15% 2	330
	21st to end	Day	26% 26% 34% 11% 1	273
March	1st to 10th	Day	24% 23% 39% 11% 3	330
	11th to 20th	Day	25% 14% 36% 19% 5% 1	539
	21st to end	Day	26% 19% 34% 16% 5% 1	594
April	1st to 10th	Day	24% 16% 35% 18% 6% 1	540
	11th to 20th	Day	23% 21% 31% 15% 6% 3	532
	21st to end	Day	22% 13% 32% 21% 9% 2	540
May	1st to 10th	Day	24% 14% 30% 20% 10% 2	543
	11th to 20th	Day	21% 10% 30% 21% 12% 6%	567
	21st to end	Day	14% 10% 23% 28% 18% 7%	685
June	1st to 10th	Day	13% 7% 29% 31% 15% 4	780
	11th to 20th	Day	14% 8% 31% 27% 16% 5%	780
	21st to end	Day	11% 9% 30% 32% 15% 4	780
July	1st to 10th	Day	9% 4 22% 31% 23% 11%	771
	11th to 20th	Day	11% 6% 25% 29% 20% 10%	768
	21st to end	Day	9% 4 25% 30% 23% 9%	744
August	1st to 10th	Day	11% 3 18% 29% 23% 15%	566
	11th to 20th	Day	13% 4 20% 28% 25% 10%	535
	21st to end	Day	10% 3 22% 30% 22% 13%	583
September	1st to 10th	Day	14% 6% 23% 21% 22% 13%	530
	11th to 20th	Day	8% 3 19% 23% 31% 16%	530
	21st to end	Day	18% 10% 21% 25% 18% 8%	530
October	1st to 10th	Day	14% 8% 28% 25% 18% 7%	530
	11th to 20th	Day	19% 14% 30% 27% 8% 2	528
	21st to end	Day	26% 15% 38% 16% 4 1	363
November	1st to 10th	Day	17% 15% 37% 22% 7% 2	330
	11th to 20th	Day	22% 24% 32% 17% 5% 1	330
	21st to end	Day	28% 16% 40% 14% 2	330
December	1st to 10th	Day	22% 26% 31% 12% 8%	330
	11th to 20th	Day	25% 23% 36% 13% 3	330
	21st to end	Day	27% 25% 31% 15% 1	363
January	1st to 10th	Night	22% 16% 38% 20% 4	1050
	11th to 20th	Night	24% 15% 37% 19% 4	1050
	21st to end	Night	20% 14% 37% 25% 5%	1039
February	1st to 10th	Night	24% 14% 37% 22% 3	840
	11th to 20th	Night	22% 16% 36% 24% 3	823
	21st to end	Night	24% 15% 41% 17% 2	692
March	1st to 10th	Night	22% 13% 36% 23% 6%	840
	11th to 20th	Night	19% 15% 38% 22% 6% 1	840
	21st to end	Night	24% 12% 33% 24% 7%	924
April	1st to 10th	Night	21% 14% 36% 24% 4 1	655
	11th to 20th	Night	22% 13% 34% 22% 9% 1	623
	21st to end	Night	20% 9% 34% 29% 8%	630
May	1st to 10th	Night	20% 9% 30% 33% 7% 1	630
	11th to 20th	Night	23% 5% 31% 28% 13% 1	621
	21st to end	Night	13% 4 25% 39% 17% 2	683
June	1st to 10th	Night	13% 3 25% 44% 15%	630
	11th to 20th	Night	13% 5% 25% 40% 16% 1	630
	21st to end	Night	10% 3 23% 41% 19% 3	630
July	1st to 10th	Night	8% 2 16% 44% 26% 4	615
	11th to 20th	Night	8% 3 18% 43% 25% 3	612
	21st to end	Night	8% 2 19% 45% 27% 1	690
August	1st to 10th	Night	10% 2 14% 43% 29% 3	627
	11th to 20th	Night	10% 2 16% 40% 28% 4	606
	21st to end	Night	12% 1 15% 38% 29% 4	660
September	1st to 10th	Night	11% 4 19% 36% 25% 5%	675
	11th to 20th	Night	10% 4 16% 35% 32% 4	800
	21st to end	Night	17% 6% 22% 31% 21% 5%	800
October	1st to 10th	Night	15% 6% 26% 32% 19% 2	800
	11th to 20th	Night	20% 14% 29% 26% 9% 1	800
	21st to end	Night	25% 12% 34% 23% 6%	880
November	1st to 10th	Night	19% 12% 32% 27% 10% 1	820
	11th to 20th	Night	23% 15% 34% 23% 6%	840
	21st to end	Night	26% 13% 33% 24% 4	840
December	1st to 10th	Night	23% 15% 36% 21% 5%	840
	11th to 20th	Night	24% 15% 37% 21% 4	1040
	21st to end	Night	32% 13% 35% 19% 2	1155

Page generated at 2026-08-12 03:37:17. Version ac07

Copyright © 2026 Attilla Danko.