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 2024-10-24.

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% 3 8% 5% 5% 5% 4 5% 7% 34%	101089
	Night	15% 11% 4 8% 5% 4 4 3 5% 6% 35%	97712
Transparency	Day	48% 7% 12% 20% 12% 1	100886
	Night	49% 6% 12% 20% 12% 1	97587
Seeing	Day	17% 12% 29% 23% 14% 6%	15678
	Night	19% 9% 30% 29% 12% 1	25492

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	16% 18% 7% 10% 6% 6% 5% 3 5% 5% 20%	2527
	11th to 20th	Day	16% 17% 6% 13% 8% 6% 7% 6% 5% 4 12%	2530
	21st to end	Day	27% 20% 7% 13% 4 4 3 1 3 4 14%	2943
February	1st to 10th	Day	13% 15% 5% 11% 8% 6% 6% 4 4 7% 20%	1719
	11th to 20th	Day	15% 11% 6% 13% 7% 7% 5% 4 5% 5% 24%	1848
	21st to end	Day	16% 15% 5% 11% 5% 5% 4 4 5% 5% 24%	1570
March	1st to 10th	Day	16% 16% 5% 8% 6% 5% 4 4 4 6% 26%	3120
	11th to 20th	Day	13% 11% 4 9% 6% 5% 4 4 5% 7% 32%	3479
	21st to end	Day	18% 13% 4 10% 6% 5% 4 4 5% 6% 26%	3815
April	1st to 10th	Day	17% 14% 3 8% 4 5% 4 3 4 7% 30%	2273
	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	20% 11% 3 8% 5% 4 4 3 5% 7% 29%	1809
November	1st to 10th	Day	11% 9% 4 8% 5% 4 4 3 5% 7% 40%	1672
	11th to 20th	Day	15% 15% 4 9% 6% 5% 4 3 4 6% 29%	1710
	21st to end	Day	20% 14% 5% 8% 5% 5% 4 3 4 6% 27%	1710
December	1st to 10th	Day	14% 17% 9% 10% 5% 6% 3 4 5% 4 23%	1710
	11th to 20th	Day	14% 17% 5% 12% 5% 5% 5% 4 6% 6% 20%	1925
	21st to end	Day	21% 23% 7% 12% 7% 6% 4 3 3 4 11%	2783
January	1st to 10th	Night	16% 16% 8% 11% 6% 5% 4 3 4 5% 22%	4428
	11th to 20th	Night	15% 17% 7% 15% 6% 5% 6% 5% 6% 5% 13%	4440
	21st to end	Night	24% 17% 8% 11% 6% 4 4 3 4 4 14%	4715
February	1st to 10th	Night	16% 16% 5% 12% 7% 5% 5% 4 4 4 23%	2457
	11th to 20th	Night	13% 14% 5% 10% 6% 6% 5% 4 6% 5% 28%	2218
	21st to end	Night	18% 12% 5% 11% 5% 5% 4 3 4 6% 28%	1884
March	1st to 10th	Night	16% 13% 5% 8% 4 4 3 2 5% 6% 35%	3733
	11th to 20th	Night	10% 9% 2 6% 4 4 4 4 6% 7% 45%	3481
	21st to end	Night	18% 9% 3 9% 5% 4 4 4 5% 6% 33%	3817
April	1st to 10th	Night	15% 11% 3 6% 5% 5% 4 4 6% 6% 36%	1923
	11th to 20th	Night	19% 9% 3 6% 3 4 4 3 5% 5% 37%	1772
	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	21% 10% 3 6% 5% 4 4 3 4 6% 33%	2614
November	1st to 10th	Night	13% 11% 2 7% 5% 4 4 3 4 5% 42%	2406
	11th to 20th	Night	16% 12% 4 9% 4 5% 4 4 6% 7% 30%	2470
	21st to end	Night	17% 15% 5% 8% 5% 4 4 3 5% 6% 28%	2470
December	1st to 10th	Night	17% 16% 6% 12% 6% 5% 5% 4 6% 5% 20%	2470
	11th to 20th	Night	15% 14% 6% 13% 6% 5% 5% 3 5% 5% 22%	3269
	21st to end	Night	27% 21% 5% 11% 5% 4 4 3 4 5% 12%	4884

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	66% 6% 12% 14% 3	2528
	11th to 20th	Day	70% 9% 10% 8% 3	2530
	21st to end	Day	77% 4 8% 7% 3	2943
February	1st to 10th	Day	63% 7% 10% 13% 6% 1	1719
	11th to 20th	Day	61% 6% 9% 15% 9% 1	1858
	21st to end	Day	61% 6% 12% 14% 6% 1	1570
March	1st to 10th	Day	58% 7% 10% 18% 6%	3120
	11th to 20th	Day	48% 8% 14% 21% 8% 1	3479
	21st to end	Day	58% 7% 11% 14% 8% 1	3815
April	1st to 10th	Day	54% 6% 10% 19% 11%	2273
	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	40% 6% 11% 26% 14% 2	2085
	11th to 20th	Day	50% 6% 11% 21% 12%	1898
	21st to end	Day	54% 6% 13% 18% 9% 1	1809
November	1st to 10th	Day	43% 7% 11% 24% 15% 1	1672
	11th to 20th	Day	56% 6% 11% 18% 8% 2	1710
	21st to end	Day	59% 5% 14% 15% 6% 1	1710
December	1st to 10th	Day	64% 7% 11% 13% 4	1710
	11th to 20th	Day	61% 8% 13% 14% 3	1922
	21st to end	Day	76% 6% 9% 6% 3	2783
January	1st to 10th	Night	63% 7% 10% 14% 5% 1	4428
	11th to 20th	Night	70% 6% 12% 8% 4	4440
	21st to end	Night	73% 5% 9% 9% 3	4715
February	1st to 10th	Night	63% 7% 10% 13% 6% 2	2457
	11th to 20th	Night	57% 6% 10% 19% 8% 1	2219
	21st to end	Night	58% 4 13% 16% 7% 2	1884
March	1st to 10th	Night	49% 6% 13% 24% 7% 1	3733
	11th to 20th	Night	35% 8% 14% 22% 19% 1	3481
	21st to end	Night	50% 6% 13% 21% 9% 1	3817
April	1st to 10th	Night	47% 7% 11% 21% 13% 1	1923
	11th to 20th	Night	46% 6% 12% 17% 17% 2	1772
	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	38% 5% 11% 25% 19% 1	2095
	11th to 20th	Night	48% 6% 11% 20% 15% 1	2280
	21st to end	Night	52% 6% 11% 21% 10% 1	2614
November	1st to 10th	Night	44% 6% 11% 23% 15% 1	2406
	11th to 20th	Night	52% 6% 15% 18% 8% 1	2470
	21st to end	Night	56% 6% 13% 18% 7%	2470
December	1st to 10th	Night	64% 8% 10% 12% 6%	2470
	11th to 20th	Night	61% 7% 13% 13% 5%	3271
	21st to end	Night	74% 6% 11% 7% 3	4884

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% 37% 17% 6% 1	270
	11th to 20th	Day	22% 18% 42% 15% 2 1	270
	21st to end	Day	29% 16% 33% 18% 4	297
February	1st to 10th	Day	24% 19% 36% 16% 3 1	270
	11th to 20th	Day	26% 17% 39% 16% 2	270
	21st to end	Day	26% 25% 35% 12% 1	225
March	1st to 10th	Day	21% 23% 39% 13% 3	270
	11th to 20th	Day	23% 13% 37% 21% 6% 1	459
	21st to end	Day	25% 18% 33% 18% 5% 1	506
April	1st to 10th	Day	20% 14% 37% 20% 8% 1	460
	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	29% 15% 36% 14% 4 1	306
November	1st to 10th	Day	13% 17% 34% 26% 8% 2	270
	11th to 20th	Day	19% 25% 31% 19% 6% 1	270
	21st to end	Day	27% 14% 41% 15% 3	270
December	1st to 10th	Day	23% 27% 31% 11% 7%	270
	11th to 20th	Day	22% 23% 39% 13% 3	270
	21st to end	Day	25% 26% 32% 16% 1	297
January	1st to 10th	Night	22% 15% 37% 20% 5% 1	950
	11th to 20th	Night	23% 15% 36% 21% 5% 1	950
	21st to end	Night	20% 11% 38% 26% 5%	941
February	1st to 10th	Night	24% 14% 38% 21% 4	760
	11th to 20th	Night	21% 15% 37% 24% 3	743
	21st to end	Night	24% 14% 41% 18% 3	628
March	1st to 10th	Night	21% 12% 35% 25% 7%	760
	11th to 20th	Night	17% 15% 38% 23% 6% 1	760
	21st to end	Night	25% 11% 33% 24% 7%	836
April	1st to 10th	Night	19% 13% 37% 26% 5% 1	593
	11th to 20th	Night	21% 11% 34% 24% 9% 1	563
	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	26% 12% 33% 23% 6%	805
November	1st to 10th	Night	19% 11% 31% 28% 11% 1	740
	11th to 20th	Night	22% 15% 34% 23% 6%	760
	21st to end	Night	24% 12% 34% 25% 4	760
December	1st to 10th	Night	23% 14% 38% 20% 5%	760
	11th to 20th	Night	23% 14% 38% 21% 4	940
	21st to end	Night	31% 13% 35% 19% 2	1045

Page generated at 2024-10-21 02:20:05. Version ac07

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