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 2025-04-11.

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	14% 10% 4 9% 5% 5% 5% 4 5% 7% 33%	113298
	Night	15% 11% 4 9% 5% 4 4 3 5% 6% 33%	115127
Transparency	Day	49% 6% 12% 20% 12% 1	116900
	Night	50% 5% 11% 20% 12% 1	119654
Seeing	Day	18% 12% 29% 23% 13% 5%	16216
	Night	19% 10% 30% 28% 12% 1	26206

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% 16% 8% 18% 5% 5% 4 3 5% 5% 18%	3617
	11th to 20th	Day	14% 14% 6% 16% 11% 6% 9% 5% 4 5% 9%	3620
	21st to end	Day	21% 18% 7% 14% 4 4 4 2 3 4 18%	4220
February	1st to 10th	Day	14% 15% 5% 11% 8% 6% 6% 4 4 6% 20%	1810
	11th to 20th	Day	15% 11% 6% 13% 8% 6% 5% 4 4 5% 23%	1948
	21st to end	Day	15% 15% 5% 11% 5% 5% 4 4 5% 5% 24%	1650
March	1st to 10th	Day	15% 13% 5% 11% 6% 5% 4 4 4 5% 29%	4480
	11th to 20th	Day	11% 11% 4 8% 5% 4 4 4 5% 7% 36%	4979
	21st to end	Day	17% 15% 4 9% 6% 5% 4 4 5% 6% 26%	5465
April	1st to 10th	Day	18% 14% 3 8% 4 5% 4 3 4 6% 30%	2393
	11th to 20th	Day	17% 10% 3 7% 4 4 4 4 6% 6% 35%	2356
	21st to end	Day	17% 9% 3 8% 5% 4 4 4 5% 7% 34%	2470
May	1st to 10th	Day	18% 9% 3 6% 5% 4 5% 3 5% 7% 35%	4082
	11th to 20th	Day	15% 7% 3 6% 5% 4 5% 4 6% 9% 35%	4081
	21st to end	Day	10% 6% 2 6% 5% 4 4 4 6% 8% 45%	4590
June	1st to 10th	Day	11% 6% 2 6% 5% 5% 5% 3 7% 9% 42%	2660
	11th to 20th	Day	10% 5% 2 6% 5% 5% 5% 5% 7% 9% 42%	2660
	21st to end	Day	9% 6% 2 7% 5% 6% 6% 5% 7% 9% 38%	2660
July	1st to 10th	Day	11% 6% 2 7% 5% 5% 5% 6% 7% 9% 37%	4440
	11th to 20th	Day	8% 4 2 5% 4 4 5% 4 6% 10% 49%	4440
	21st to end	Day	7% 6% 2 6% 5% 6% 6% 5% 7% 9% 41%	4656
August	1st to 10th	Day	12% 5% 2 6% 4 4 5% 4 6% 9% 43%	4104
	11th to 20th	Day	11% 5% 2 6% 4 5% 5% 4 6% 9% 42%	4044
	21st to end	Day	9% 6% 2 7% 5% 5% 6% 4 6% 9% 43%	4350
September	1st to 10th	Day	11% 6% 2 6% 5% 5% 5% 4 5% 8% 42%	2190
	11th to 20th	Day	10% 5% 2 6% 3 4 5% 4 6% 9% 46%	2090
	21st to end	Day	14% 7% 3 6% 4 5% 5% 4 5% 7% 38%	2090
October	1st to 10th	Day	13% 7% 2 7% 5% 4 5% 4 5% 7% 42%	2085
	11th to 20th	Day	18% 10% 3 7% 5% 5% 5% 3 4 6% 34%	1898
	21st to end	Day	19% 10% 3 8% 5% 5% 4 4 5% 7% 30%	1881
November	1st to 10th	Day	11% 9% 4 8% 5% 4 4 3 5% 7% 40%	1762
	11th to 20th	Day	15% 15% 5% 9% 6% 5% 4 3 5% 6% 28%	1800
	21st to end	Day	19% 15% 5% 9% 5% 5% 4 3 4 6% 26%	1800
December	1st to 10th	Day	11% 16% 9% 14% 5% 5% 5% 4 5% 5% 20%	2930
	11th to 20th	Day	18% 20% 7% 11% 7% 5% 4 3 5% 5% 16%	3015
	21st to end	Day	24% 21% 7% 11% 5% 5% 3 3 3 5% 13%	3982
January	1st to 10th	Night	14% 15% 8% 16% 5% 5% 4 3 4 5% 20%	6348
	11th to 20th	Night	13% 15% 7% 16% 9% 6% 6% 5% 6% 5% 13%	6360
	21st to end	Night	19% 15% 8% 11% 5% 5% 5% 3 4 5% 21%	6743
February	1st to 10th	Night	15% 15% 5% 12% 7% 5% 5% 4 4 4 23%	2586
	11th to 20th	Night	13% 14% 5% 10% 7% 6% 5% 3 5% 5% 27%	2338
	21st to end	Night	18% 11% 4 11% 4 5% 4 3 4 6% 28%	1980
March	1st to 10th	Night	15% 12% 5% 8% 4 4 3 3 5% 7% 36%	5373
	11th to 20th	Night	11% 8% 2 6% 4 4 4 4 6% 7% 44%	4981
	21st to end	Night	17% 11% 3 8% 5% 4 4 3 4 6% 35%	5467
April	1st to 10th	Night	16% 11% 3 6% 4 4 4 3 6% 6% 36%	2024
	11th to 20th	Night	19% 9% 3 6% 3 4 4 3 5% 5% 37%	1778
	21st to end	Night	16% 9% 3 7% 5% 4 4 3 4 8% 37%	1710
May	1st to 10th	Night	16% 9% 3 7% 5% 5% 5% 4 5% 8% 33%	2813
	11th to 20th	Night	17% 7% 2 7% 4 3 4 3 5% 7% 40%	2812
	21st to end	Night	11% 6% 2 5% 4 4 4 3 5% 9% 46%	2966
June	1st to 10th	Night	10% 4 2 5% 4 4 4 4 7% 8% 48%	1520
	11th to 20th	Night	11% 6% 2 6% 5% 4 4 4 6% 9% 43%	1520
	21st to end	Night	9% 5% 2 5% 4 3 4 4 8% 10% 46%	1520
July	1st to 10th	Night	9% 4 2 5% 4 4 4 4 6% 10% 48%	2530
	11th to 20th	Night	9% 4 1 4 3 3 4 3 6% 7% 56%	2530
	21st to end	Night	7% 5% 2 5% 4 5% 5% 4 7% 9% 48%	2902
August	1st to 10th	Night	11% 5% 2 6% 3 4 4 3 6% 8% 48%	2825
	11th to 20th	Night	11% 6% 2 5% 3 4 4 4 6% 7% 49%	2785
	21st to end	Night	10% 6% 2 7% 4 4 5% 4 5% 7% 46%	3302
September	1st to 10th	Night	10% 6% 2 6% 5% 4 4 4 5% 7% 49%	1971
	11th to 20th	Night	10% 5% 1 4 4 3 3 3 4 7% 56%	2090
	21st to end	Night	14% 7% 2 6% 3 5% 4 3 5% 6% 43%	2090
October	1st to 10th	Night	12% 7% 2 6% 3 4 4 3 5% 6% 47%	2095
	11th to 20th	Night	17% 11% 3 7% 5% 3 4 3 4 6% 37%	2280
	21st to end	Night	20% 10% 3 6% 5% 4 4 4 5% 6% 33%	2717
November	1st to 10th	Night	13% 11% 2 7% 5% 4 4 3 4 5% 42%	2536
	11th to 20th	Night	16% 12% 4 9% 4 5% 4 4 6% 6% 30%	2600
	21st to end	Night	17% 15% 5% 9% 5% 4 4 3 5% 6% 27%	2600
December	1st to 10th	Night	13% 14% 5% 15% 5% 5% 5% 4 5% 6% 22%	4250
	11th to 20th	Night	16% 20% 6% 13% 7% 5% 4 3 4 5% 17%	5189
	21st to end	Night	26% 21% 5% 11% 5% 4 3 3 4 5% 13%	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	68% 4 10% 15% 3	3618
	11th to 20th	Day	75% 6% 9% 7% 3	3620
	21st to end	Day	72% 3 9% 10% 6%	4220
February	1st to 10th	Day	64% 7% 10% 13% 6% 1	1810
	11th to 20th	Day	62% 6% 9% 15% 8% 1	1958
	21st to end	Day	61% 6% 11% 14% 6% 1	1650
March	1st to 10th	Day	57% 5% 11% 17% 9% 1	4480
	11th to 20th	Day	46% 5% 16% 23% 8% 2	4979
	21st to end	Day	59% 5% 9% 15% 11% 1	5465
April	1st to 10th	Day	55% 5% 10% 19% 11%	2393
	11th to 20th	Day	47% 7% 11% 20% 12% 2	2356
	21st to end	Day	49% 6% 13% 17% 14% 1	2470
May	1st to 10th	Day	46% 9% 12% 21% 12% 1	4120
	11th to 20th	Day	43% 9% 15% 23% 9% 1	4085
	21st to end	Day	36% 8% 12% 19% 22% 3	4603
June	1st to 10th	Day	38% 7% 13% 26% 14% 2	2660
	11th to 20th	Day	37% 8% 14% 23% 18% 2	2660
	21st to end	Day	39% 10% 13% 21% 15% 2	2660
July	1st to 10th	Day	43% 5% 14% 20% 15% 3	4371
	11th to 20th	Day	31% 5% 12% 33% 18% 1	4365
	21st to end	Day	38% 6% 15% 19% 21% 2	4509
August	1st to 10th	Day	37% 6% 14% 25% 17% 1	4091
	11th to 20th	Day	38% 6% 11% 31% 13% 1	4083
	21st to end	Day	38% 4 12% 32% 12% 2	4349
September	1st to 10th	Day	38% 8% 15% 21% 15% 2	2190
	11th to 20th	Day	32% 7% 12% 30% 18% 1	2090
	21st to end	Day	42% 7% 14% 21% 16%	2090
October	1st to 10th	Day	31% 4 10% 35% 19% 1	3462
	11th to 20th	Day	42% 3 9% 25% 19%	3126
	21st to end	Day	47% 4 13% 24% 11% 2	3081
November	1st to 10th	Day	44% 6% 11% 24% 14% 1	1762
	11th to 20th	Day	57% 6% 11% 18% 8% 2	1800
	21st to end	Day	60% 5% 14% 15% 6% 1	1800
December	1st to 10th	Day	67% 6% 14% 10% 3	2930
	11th to 20th	Day	70% 5% 10% 13% 2	3012
	21st to end	Day	76% 4 8% 9% 3	3982
January	1st to 10th	Night	65% 5% 8% 16% 6% 1	6348
	11th to 20th	Night	71% 4 10% 9% 6%	6360
	21st to end	Night	66% 4 12% 11% 7%	6743
February	1st to 10th	Night	64% 7% 10% 13% 6% 1	2586
	11th to 20th	Night	58% 5% 10% 18% 7% 1	2339
	21st to end	Night	57% 4 13% 17% 8% 2	1980
March	1st to 10th	Night	49% 4 13% 24% 10% 1	5373
	11th to 20th	Night	38% 6% 13% 27% 15% 1	4981
	21st to end	Night	50% 4 11% 19% 14% 1	5467
April	1st to 10th	Night	47% 6% 11% 20% 14% 2	2024
	11th to 20th	Night	46% 6% 12% 17% 17% 2	1778
	21st to end	Night	46% 6% 12% 19% 15% 3	1710
May	1st to 10th	Night	47% 8% 11% 21% 12% 2	2840
	11th to 20th	Night	41% 8% 11% 25% 14% 1	2813
	21st to end	Night	33% 9% 14% 22% 21% 3	2974
June	1st to 10th	Night	32% 6% 13% 29% 17% 2	1520
	11th to 20th	Night	36% 7% 13% 26% 16% 2	1520
	21st to end	Night	31% 8% 15% 25% 18% 2	1520
July	1st to 10th	Night	33% 4 12% 29% 15% 6%	2490
	11th to 20th	Night	27% 4 14% 31% 22% 2	2482
	21st to end	Night	32% 7% 18% 17% 24% 2	2810
August	1st to 10th	Night	36% 5% 13% 30% 15% 1	2814
	11th to 20th	Night	34% 5% 11% 34% 15% 2	2812
	21st to end	Night	38% 4 11% 30% 15% 2	3302
September	1st to 10th	Night	34% 6% 11% 26% 19% 3	1971
	11th to 20th	Night	29% 6% 9% 31% 22% 2	2090
	21st to end	Night	40% 6% 13% 26% 15% 1	2090
October	1st to 10th	Night	26% 3 10% 34% 26% 1	3498
	11th to 20th	Night	43% 4 10% 22% 21%	3779
	21st to end	Night	40% 4 9% 32% 15% 1	4467
November	1st to 10th	Night	45% 6% 11% 24% 15% 1	2536
	11th to 20th	Night	53% 6% 14% 17% 9% 2	2600
	21st to end	Night	57% 6% 12% 18% 6%	2600
December	1st to 10th	Night	63% 5% 14% 14% 4	4250
	11th to 20th	Night	69% 4 10% 12% 4	5191
	21st to end	Night	74% 5% 9% 8% 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	20% 19% 39% 17% 5% 1	300
	11th to 20th	Day	22% 20% 42% 13% 2 1	300
	21st to end	Day	27% 19% 34% 17% 4	330
February	1st to 10th	Day	26% 20% 35% 15% 3 1	300
	11th to 20th	Day	28% 17% 39% 14% 2	300
	21st to end	Day	27% 25% 35% 12% 2	249
March	1st to 10th	Day	22% 24% 39% 12% 3	300
	11th to 20th	Day	23% 14% 36% 20% 6% 1	499
	21st to end	Day	26% 17% 33% 17% 5% 1	550
April	1st to 10th	Day	23% 15% 36% 19% 7% 1	500
	11th to 20th	Day	24% 19% 31% 16% 6% 4	452
	21st to end	Day	21% 13% 33% 21% 9% 2	460
May	1st to 10th	Day	24% 12% 30% 20% 11% 3	463
	11th to 20th	Day	20% 9% 29% 22% 13% 7%	487
	21st to end	Day	13% 9% 21% 29% 19% 8%	591
June	1st to 10th	Day	13% 7% 29% 31% 16% 5%	680
	11th to 20th	Day	13% 6% 30% 28% 18% 5%	680
	21st to end	Day	11% 9% 30% 29% 15% 5%	680
July	1st to 10th	Day	8% 5% 21% 30% 24% 12%	671
	11th to 20th	Day	11% 6% 24% 28% 20% 11%	668
	21st to end	Day	8% 3 26% 30% 24% 10%	644
August	1st to 10th	Day	11% 3 18% 29% 22% 17%	486
	11th to 20th	Day	13% 4 20% 27% 27% 10%	479
	21st to end	Day	11% 3 21% 30% 23% 12%	539
September	1st to 10th	Day	14% 6% 23% 22% 23% 12%	490
	11th to 20th	Day	9% 3 20% 22% 31% 14%	490
	21st to end	Day	18% 11% 21% 25% 17% 7%	490
October	1st to 10th	Day	15% 8% 29% 25% 16% 7%	490
	11th to 20th	Day	19% 16% 30% 26% 8% 2	488
	21st to end	Day	28% 15% 37% 15% 4 2	330
November	1st to 10th	Day	14% 17% 36% 24% 7% 2	300
	11th to 20th	Day	20% 25% 32% 17% 5% 1	300
	21st to end	Day	28% 14% 41% 14% 2	300
December	1st to 10th	Day	23% 27% 31% 12% 7%	300
	11th to 20th	Day	23% 24% 37% 13% 3	300
	21st to end	Day	26% 25% 31% 17% 1	330
January	1st to 10th	Night	22% 15% 38% 20% 5% 1	1000
	11th to 20th	Night	23% 14% 37% 20% 5% 1	1000
	21st to end	Night	20% 13% 37% 25% 5%	990
February	1st to 10th	Night	24% 14% 37% 21% 3	800
	11th to 20th	Night	22% 15% 36% 24% 3	783
	21st to end	Night	24% 15% 42% 17% 3	660
March	1st to 10th	Night	21% 13% 36% 24% 6%	800
	11th to 20th	Night	18% 16% 38% 22% 6% 1	800
	21st to end	Night	25% 12% 32% 24% 7%	880
April	1st to 10th	Night	20% 14% 37% 25% 4 1	624
	11th to 20th	Night	22% 11% 34% 24% 8% 1	565
	21st to end	Night	20% 8% 35% 29% 8% 1	570
May	1st to 10th	Night	20% 8% 29% 35% 7% 1	570
	11th to 20th	Night	23% 4 29% 29% 14% 1	561
	21st to end	Night	12% 4 24% 39% 19% 2	617
June	1st to 10th	Night	12% 3 25% 44% 16%	570
	11th to 20th	Night	11% 5% 24% 42% 17% 1	570
	21st to end	Night	10% 3 22% 42% 19% 3	570
July	1st to 10th	Night	8% 2 17% 42% 27% 4	555
	11th to 20th	Night	9% 3 17% 43% 26% 3	552
	21st to end	Night	7% 1 19% 44% 28% 1	624
August	1st to 10th	Night	9% 2 14% 44% 29% 3	567
	11th to 20th	Night	9% 2 16% 40% 29% 5%	564
	21st to end	Night	12% 1 15% 38% 29% 4	627
September	1st to 10th	Night	11% 4 18% 37% 25% 5%	641
	11th to 20th	Night	11% 4 16% 35% 30% 3	760
	21st to end	Night	17% 6% 22% 30% 20% 4	760
October	1st to 10th	Night	15% 7% 27% 31% 18% 2	760
	11th to 20th	Night	20% 15% 29% 26% 9% 1	760
	21st to end	Night	25% 12% 34% 23% 6%	836
November	1st to 10th	Night	19% 11% 31% 27% 10% 1	780
	11th to 20th	Night	23% 15% 34% 22% 6%	800
	21st to end	Night	25% 13% 33% 24% 4	800
December	1st to 10th	Night	23% 15% 37% 20% 5%	800
	11th to 20th	Night	24% 14% 37% 21% 4	990
	21st to end	Night	31% 13% 34% 19% 2	1100

Page generated at 2025-04-08 09:17:24. Version ac07

Copyright © 2025 Attilla Danko.