Martin State Airport
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Martin State Airport clear sky chart from 2005-11-06 to 2025-07-21.

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	15% 6% 2 5% 4 4 4 4 6% 8% 43%	120169
	Night	16% 6% 2 5% 4 4 4 3 5% 7% 44%	118963
Transparency	Day	37% 7% 13% 24% 16% 3	123801
	Night	39% 6% 11% 23% 17% 4	123469
Seeing	Day	16% 10% 25% 27% 17% 5%	15880
	Night	17% 9% 29% 30% 13% 1	25283

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% 4 2 4 3 3 3 3 5% 6% 52%	3597
	11th to 20th	Day	14% 8% 3 7% 4 4 4 3 4 4 46%	3986
	21st to end	Day	16% 7% 2 5% 3 4 4 3 4 7% 44%	4466
February	1st to 10th	Day	15% 7% 2 6% 5% 5% 4 4 6% 7% 40%	1800
	11th to 20th	Day	18% 8% 2 5% 3 3 4 4 5% 7% 41%	1849
	21st to end	Day	18% 8% 3 7% 3 2 4 3 5% 5% 42%	1650
March	1st to 10th	Day	19% 4 1 4 3 3 4 3 5% 6% 47%	4704
	11th to 20th	Day	12% 7% 2 5% 3 3 3 3 5% 6% 49%	4980
	21st to end	Day	17% 6% 2 6% 4 4 4 4 5% 6% 42%	5647
April	1st to 10th	Day	16% 6% 2 5% 4 4 5% 4 6% 7% 42%	2400
	11th to 20th	Day	12% 6% 2 5% 4 5% 4 4 6% 7% 46%	2374
	21st to end	Day	17% 5% 2 5% 4 4 4 4 5% 8% 43%	2400
May	1st to 10th	Day	23% 7% 2 5% 4 4 4 4 6% 8% 33%	5684
	11th to 20th	Day	23% 6% 2 6% 4 4 4 4 6% 8% 33%	6318
	21st to end	Day	17% 5% 2 5% 4 4 4 4 6% 9% 41%	6934
June	1st to 10th	Day	11% 4 2 5% 5% 4 5% 4 7% 10% 42%	2800
	11th to 20th	Day	12% 5% 2 5% 4 4 5% 5% 6% 9% 43%	2800
	21st to end	Day	9% 4 1 4 3 4 5% 5% 8% 10% 46%	2800
July	1st to 10th	Day	5% 4 1 6% 4 5% 6% 6% 8% 11% 44%	4580
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 5% 8% 11% 41%	4580
	21st to end	Day	10% 6% 2 6% 5% 6% 6% 5% 8% 10% 37%	4498
August	1st to 10th	Day	16% 5% 2 6% 4 5% 5% 5% 7% 10% 35%	4104
	11th to 20th	Day	11% 4 2 6% 3 4 5% 4 6% 9% 44%	3804
	21st to end	Day	10% 4 2 5% 3 4 4 4 7% 8% 49%	4180
September	1st to 10th	Day	13% 5% 2 6% 4 4 4 4 4 7% 48%	2280
	11th to 20th	Day	11% 5% 1 5% 4 4 4 3 6% 8% 51%	2280
	21st to end	Day	19% 8% 3 6% 4 3 4 4 5% 8% 37%	2027
October	1st to 10th	Day	18% 5% 2 5% 3 2 3 2 5% 7% 47%	1900
	11th to 20th	Day	16% 5% 1 4 3 3 3 3 5% 6% 50%	1900
	21st to end	Day	14% 6% 2 5% 4 3 4 3 4 6% 49%	2090
November	1st to 10th	Day	12% 6% 2 4 3 2 3 4 4 7% 52%	1787
	11th to 20th	Day	14% 6% 2 3 4 3 4 4 5% 6% 49%	1800
	21st to end	Day	15% 6% 2 4 4 4 3 4 4 6% 47%	1620
December	1st to 10th	Day	13% 7% 2 5% 4 3 4 3 6% 7% 48%	2600
	11th to 20th	Day	20% 8% 2 5% 3 3 4 2 4 6% 42%	2990
	21st to end	Day	15% 6% 2 5% 4 5% 4 3 5% 7% 42%	3960
January	1st to 10th	Night	14% 6% 2 5% 4 4 4 3 4 5% 49%	6349
	11th to 20th	Night	14% 7% 2 5% 3 3 3 2 4 5% 51%	5969
	21st to end	Night	17% 7% 2 6% 3 3 3 3 4 5% 46%	6490
February	1st to 10th	Night	17% 8% 3 6% 5% 4 4 3 6% 6% 41%	2600
	11th to 20th	Night	19% 7% 2 6% 3 3 3 3 4 6% 43%	2435
	21st to end	Night	17% 7% 2 6% 4 4 4 3 5% 6% 43%	1980
March	1st to 10th	Night	17% 6% 2 5% 3 3 3 3 4 5% 49%	5144
	11th to 20th	Night	10% 7% 2 4 3 3 4 3 5% 7% 52%	4980
	21st to end	Night	14% 7% 2 6% 4 4 4 3 5% 5% 45%	5284
April	1st to 10th	Night	17% 7% 2 6% 4 4 5% 3 5% 7% 40%	2000
	11th to 20th	Night	14% 6% 3 6% 4 3 4 4 5% 6% 45%	1975
	21st to end	Night	18% 6% 2 4 3 3 3 3 5% 8% 45%	2000
May	1st to 10th	Night	24% 8% 2 6% 5% 4 5% 4 5% 8% 30%	4238
	11th to 20th	Night	25% 8% 3 6% 3 3 4 4 5% 7% 31%	3575
	21st to end	Night	21% 6% 2 6% 4 4 4 3 6% 8% 37%	3920
June	1st to 10th	Night	12% 5% 2 6% 4 3 4 4 6% 9% 46%	1600
	11th to 20th	Night	13% 5% 2 6% 5% 5% 5% 4 6% 8% 41%	1600
	21st to end	Night	11% 5% 2 5% 6% 4 5% 3 7% 10% 42%	1600
July	1st to 10th	Night	8% 4 3 7% 6% 6% 6% 5% 8% 9% 39%	2600
	11th to 20th	Night	10% 6% 2 6% 5% 5% 5% 5% 8% 11% 37%	2600
	21st to end	Night	13% 7% 3 7% 5% 4 6% 4 6% 8% 37%	3050
August	1st to 10th	Night	19% 5% 2 6% 5% 5% 4 5% 6% 9% 33%	2825
	11th to 20th	Night	12% 7% 3 8% 5% 6% 6% 4 7% 7% 36%	2992
	21st to end	Night	13% 5% 2 5% 3 4 4 3 5% 8% 48%	3476
September	1st to 10th	Night	13% 7% 2 6% 3 4 3 3 5% 7% 46%	1900
	11th to 20th	Night	11% 6% 2 5% 3 3 4 3 4 7% 52%	1900
	21st to end	Night	20% 7% 3 7% 4 4 3 3 5% 6% 39%	2149
October	1st to 10th	Night	20% 6% 2 6% 4 3 4 2 4 5% 43%	2280
	11th to 20th	Night	16% 5% 1 4 4 2 3 3 4 6% 52%	2280
	21st to end	Night	17% 4 1 4 3 3 4 4 4 7% 50%	2508
November	1st to 10th	Night	11% 5% 2 5% 3 3 4 3 5% 5% 53%	2508
	11th to 20th	Night	16% 6% 2 5% 3 3 2 3 5% 5% 49%	2600
	21st to end	Night	14% 5% 2 5% 4 3 4 3 5% 6% 48%	2775
December	1st to 10th	Night	12% 5% 2 6% 4 3 4 3 4 7% 50%	4580
	11th to 20th	Night	22% 6% 2 4 3 3 4 3 5% 7% 40%	5205
	21st to end	Night	17% 6% 3 6% 4 4 4 4 6% 7% 38%	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	32% 4 8% 29% 24% 5%	3598
	11th to 20th	Day	40% 4 8% 22% 18% 7%	3986
	21st to end	Day	40% 5% 12% 26% 14% 2	4466
February	1st to 10th	Day	42% 6% 14% 25% 12% 2	1800
	11th to 20th	Day	42% 5% 10% 26% 15% 3	1858
	21st to end	Day	45% 4 12% 21% 14% 4	1650
March	1st to 10th	Day	35% 5% 10% 24% 18% 7%	4704
	11th to 20th	Day	34% 5% 10% 26% 19% 6%	4980
	21st to end	Day	42% 5% 10% 19% 18% 6%	5647
April	1st to 10th	Day	39% 8% 12% 19% 17% 5%	2400
	11th to 20th	Day	36% 6% 12% 22% 18% 6%	2374
	21st to end	Day	38% 7% 12% 20% 19% 4	2400
May	1st to 10th	Day	46% 8% 15% 18% 10% 2	5716
	11th to 20th	Day	46% 9% 13% 22% 10% 1	6322
	21st to end	Day	38% 7% 14% 23% 16% 1	6949
June	1st to 10th	Day	34% 9% 16% 24% 16% 2	2800
	11th to 20th	Day	35% 11% 13% 23% 15% 2	2800
	21st to end	Day	29% 11% 17% 25% 18% 2	2800
July	1st to 10th	Day	31% 11% 21% 19% 13% 5%	4510
	11th to 20th	Day	35% 9% 18% 27% 10% 2	4505
	21st to end	Day	39% 10% 16% 19% 15% 1	4355
August	1st to 10th	Day	42% 9% 16% 25% 8% 1	4091
	11th to 20th	Day	34% 8% 14% 29% 13% 1	3842
	21st to end	Day	30% 8% 15% 28% 16% 2	4180
September	1st to 10th	Day	35% 8% 14% 20% 18% 5%	2280
	11th to 20th	Day	32% 7% 12% 24% 22% 4	2280
	21st to end	Day	45% 6% 9% 20% 17% 2	2027
October	1st to 10th	Day	34% 5% 10% 18% 28% 5%	3160
	11th to 20th	Day	24% 4 10% 28% 26% 9%	3140
	21st to end	Day	22% 3 10% 31% 28% 5%	3428
November	1st to 10th	Day	33% 4 13% 26% 20% 4	1787
	11th to 20th	Day	35% 6% 11% 23% 23% 4	1800
	21st to end	Day	38% 5% 10% 28% 17% 2	1620
December	1st to 10th	Day	35% 4 17% 27% 12% 4	2600
	11th to 20th	Day	43% 4 12% 29% 10% 1	2986
	21st to end	Day	40% 7% 16% 21% 15% 1	3960
January	1st to 10th	Night	36% 5% 7% 24% 23% 4	6349
	11th to 20th	Night	35% 4 9% 25% 20% 7%	5969
	21st to end	Night	39% 4 9% 28% 18% 2	6490
February	1st to 10th	Night	43% 5% 13% 24% 13% 1	2600
	11th to 20th	Night	43% 4 9% 21% 18% 5%	2437
	21st to end	Night	43% 4 10% 20% 18% 5%	1980
March	1st to 10th	Night	38% 4 8% 26% 13% 10%	5144
	11th to 20th	Night	31% 6% 13% 27% 17% 6%	4980
	21st to end	Night	40% 5% 9% 18% 24% 5%	5284
April	1st to 10th	Night	42% 5% 11% 18% 19% 5%	2000
	11th to 20th	Night	38% 6% 11% 20% 19% 5%	1975
	21st to end	Night	38% 6% 11% 21% 19% 5%	2000
May	1st to 10th	Night	52% 7% 11% 16% 10% 3	4268
	11th to 20th	Night	49% 8% 13% 17% 11% 1	3576
	21st to end	Night	43% 8% 13% 20% 13% 2	3927
June	1st to 10th	Night	35% 8% 12% 25% 19% 2	1600
	11th to 20th	Night	39% 8% 14% 24% 13% 2	1600
	21st to end	Night	35% 9% 13% 24% 17% 3	1600
July	1st to 10th	Night	38% 9% 21% 16% 12% 3	2560
	11th to 20th	Night	37% 10% 20% 23% 9% 2	2552
	21st to end	Night	43% 8% 14% 21% 14% 1	2953
August	1st to 10th	Night	45% 8% 18% 20% 9%	2814
	11th to 20th	Night	44% 9% 13% 23% 11% 1	3020
	21st to end	Night	33% 7% 12% 29% 17% 2	3476
September	1st to 10th	Night	37% 8% 11% 21% 17% 5%	1900
	11th to 20th	Night	34% 6% 8% 25% 23% 4	1900
	21st to end	Night	46% 6% 10% 17% 18% 3	2149
October	1st to 10th	Night	43% 5% 9% 19% 20% 4	3800
	11th to 20th	Night	24% 4 11% 24% 30% 7%	3779
	21st to end	Night	23% 4 11% 32% 24% 6%	4120
November	1st to 10th	Night	33% 5% 11% 25% 20% 6%	2508
	11th to 20th	Night	37% 5% 10% 22% 20% 6%	2600
	21st to end	Night	36% 5% 12% 25% 20% 3	2775
December	1st to 10th	Night	34% 5% 13% 30% 17% 2	4580
	11th to 20th	Night	44% 5% 13% 18% 16% 4	5208
	21st to end	Night	41% 7% 13% 21% 16% 1	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% 24% 33% 17% 7% 1	200
	11th to 20th	Day	19% 27% 31% 19% 4	283
	21st to end	Day	16% 18% 41% 19% 5% 1	330
February	1st to 10th	Day	20% 14% 41% 19% 6%	300
	11th to 20th	Day	25% 21% 38% 14% 2	396
	21st to end	Day	23% 19% 32% 21% 5%	414
March	1st to 10th	Day	15% 21% 34% 25% 4 1	500
	11th to 20th	Day	19% 19% 31% 23% 7% 1	500
	21st to end	Day	20% 15% 34% 26% 5% 2	550
April	1st to 10th	Day	19% 18% 35% 22% 5% 2	500
	11th to 20th	Day	13% 18% 30% 24% 11% 3	492
	21st to end	Day	19% 12% 29% 27% 11% 2	500
May	1st to 10th	Day	22% 12% 29% 24% 11% 1	503
	11th to 20th	Day	19% 8% 26% 30% 13% 3	527
	21st to end	Day	18% 6% 18% 27% 23% 8%	573
June	1st to 10th	Day	12% 6% 24% 27% 24% 8%	530
	11th to 20th	Day	14% 6% 18% 32% 24% 7%	530
	21st to end	Day	10% 2 20% 35% 24% 9%	530
July	1st to 10th	Day	10% 2 12% 31% 31% 13%	525
	11th to 20th	Day	4 1 9% 39% 35% 11%	524
	21st to end	Day	11% 2 16% 34% 31% 6%	532
August	1st to 10th	Day	9% 4 11% 34% 32% 9%	486
	11th to 20th	Day	11% 3 10% 33% 32% 10%	479
	21st to end	Day	9% 2 16% 30% 29% 14%	539
September	1st to 10th	Day	16% 3 17% 24% 28% 13%	490
	11th to 20th	Day	12% 2 18% 29% 27% 11%	490
	21st to end	Day	26% 7% 19% 28% 17% 3	490
October	1st to 10th	Day	21% 6% 18% 27% 20% 7%	490
	11th to 20th	Day	15% 9% 28% 27% 17% 4	490
	21st to end	Day	16% 9% 30% 27% 14% 4	539
November	1st to 10th	Day	14% 10% 32% 28% 12% 4	408
	11th to 20th	Day	14% 14% 35% 26% 10% 1	400
	21st to end	Day	16% 19% 26% 27% 10% 1	220
December	1st to 10th	Day	18% 15% 36% 26% 6% 1	200
	11th to 20th	Day	20% 19% 28% 25% 10%	200
	21st to end	Day	20% 13% 31% 27% 8%	220
January	1st to 10th	Night	18% 17% 42% 20% 3	800
	11th to 20th	Night	22% 14% 33% 26% 4	800
	21st to end	Night	17% 15% 41% 25% 2	880
February	1st to 10th	Night	20% 13% 37% 28% 3	800
	11th to 20th	Night	22% 19% 39% 19% 1	783
	21st to end	Night	21% 16% 38% 21% 3	660
March	1st to 10th	Night	16% 16% 38% 25% 5%	800
	11th to 20th	Night	18% 15% 38% 23% 6% 1	800
	21st to end	Night	19% 10% 40% 25% 6% 1	880
April	1st to 10th	Night	19% 14% 40% 21% 6%	800
	11th to 20th	Night	16% 10% 34% 31% 9%	791
	21st to end	Night	19% 10% 30% 31% 9%	800
May	1st to 10th	Night	21% 9% 27% 33% 10% 1	704
	11th to 20th	Night	19% 7% 28% 33% 12%	394
	21st to end	Night	15% 5% 20% 37% 21% 2	433
June	1st to 10th	Night	12% 3 24% 39% 23% 1	400
	11th to 20th	Night	10% 4 24% 39% 23% 1	400
	21st to end	Night	12% 2 17% 48% 20% 2	400
July	1st to 10th	Night	10% 3 15% 37% 33% 2	390
	11th to 20th	Night	7% 1 10% 43% 36% 3	388
	21st to end	Night	9% 3 15% 43% 30% 2	600
August	1st to 10th	Night	12% 2 13% 39% 32% 3	567
	11th to 20th	Night	12% 4 15% 37% 29% 4	681
	21st to end	Night	13% 2 15% 34% 30% 6%	836
September	1st to 10th	Night	15% 3 18% 33% 27% 5%	760
	11th to 20th	Night	13% 3 14% 36% 30% 5%	760
	21st to end	Night	22% 6% 20% 30% 20% 2	760
October	1st to 10th	Night	21% 5% 21% 29% 19% 5%	760
	11th to 20th	Night	17% 8% 28% 31% 15% 1	760
	21st to end	Night	18% 9% 30% 26% 15% 1	836
November	1st to 10th	Night	14% 6% 33% 33% 13% 2	780
	11th to 20th	Night	19% 14% 29% 30% 8% 1	800
	21st to end	Night	15% 15% 33% 29% 8% 1	800
December	1st to 10th	Night	20% 13% 36% 23% 8%	800
	11th to 20th	Night	19% 11% 40% 25% 6%	800
	21st to end	Night	19% 11% 35% 32% 3	880

Page generated at 2025-07-18 01:10:04. Version ac07

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