Fort McKavett
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort McKavett clear sky chart from 2005-11-06 to 2025-07-06.

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	8% 5% 2 5% 3 3 4 3 5% 7% 56%	120158
	Night	7% 4 2 4 3 3 3 3 5% 7% 59%	118918
Transparency	Day	27% 5% 9% 21% 23% 15%	124070
	Night	24% 5% 9% 21% 23% 17%	123137
Seeing	Day	9% 8% 26% 32% 20% 5%	15769
	Night	9% 7% 34% 37% 12% 1	25732

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	10% 4 2 5% 3 2 2 2 3 6% 60%	4077
	11th to 20th	Day	8% 5% 2 3 2 2 2 2 4 6% 64%	4236
	21st to end	Day	15% 5% 2 5% 3 3 3 3 4 5% 53%	4994
February	1st to 10th	Day	10% 7% 2 4 3 3 4 3 4 5% 56%	2000
	11th to 20th	Day	11% 6% 2 5% 2 3 4 3 5% 6% 54%	1949
	21st to end	Day	9% 6% 2 3 3 2 3 4 4 5% 57%	1650
March	1st to 10th	Day	7% 5% 2 6% 3 3 4 3 4 5% 58%	4576
	11th to 20th	Day	11% 5% 2 5% 4 3 3 2 3 5% 56%	4980
	21st to end	Day	6% 5% 2 6% 4 4 4 3 4 6% 56%	5462
April	1st to 10th	Day	7% 5% 2 4 3 3 3 3 5% 7% 56%	2268
	11th to 20th	Day	9% 5% 2 5% 5% 4 3 3 5% 6% 52%	2374
	21st to end	Day	8% 5% 2 5% 4 3 3 3 4 6% 59%	2410
May	1st to 10th	Day	10% 6% 2 6% 4 4 4 3 5% 6% 49%	5862
	11th to 20th	Day	10% 6% 2 6% 4 4 3 3 5% 6% 52%	5862
	21st to end	Day	9% 5% 2 6% 4 4 5% 4 6% 8% 46%	6434
June	1st to 10th	Day	4 3 1 4 4 4 4 4 6% 8% 59%	2600
	11th to 20th	Day	4 3 1 4 4 4 4 3 6% 9% 59%	2600
	21st to end	Day	5% 3 2 5% 4 5% 5% 4 6% 9% 52%	2600
July	1st to 10th	Day	5% 4 1 5% 4 5% 6% 4 7% 7% 52%	4186
	11th to 20th	Day	2 2 1 3 3 3 5% 4 6% 10% 61%	4120
	21st to end	Day	5% 3 1 5% 4 5% 5% 4 5% 9% 53%	4421
August	1st to 10th	Day	1 1 1 2 2 3 3 3 5% 6% 72%	3785
	11th to 20th	Day	4 2 1 3 2 3 3 3 5% 7% 67%	3726
	21st to end	Day	4 3 2 5% 4 5% 5% 4 7% 10% 51%	4180
September	1st to 10th	Day	10% 5% 2 6% 5% 5% 5% 4 6% 7% 47%	2126
	11th to 20th	Day	10% 5% 2 5% 4 4 4 4 6% 8% 46%	2090
	21st to end	Day	9% 4 1 4 3 4 3 3 5% 7% 55%	2090
October	1st to 10th	Day	5% 3 2 5% 3 3 3 3 5% 7% 61%	2090
	11th to 20th	Day	9% 4 2 5% 3 3 3 3 4 5% 61%	2090
	21st to end	Day	10% 5% 1 3 2 2 2 2 3 4 64%	2090
November	1st to 10th	Day	10% 5% 1 5% 3 3 3 2 4 6% 58%	1811
	11th to 20th	Day	7% 4 2 4 3 2 4 3 6% 7% 60%	1800
	21st to end	Day	10% 7% 2 5% 4 2 3 2 4 6% 56%	1800
December	1st to 10th	Day	17% 8% 3 5% 3 2 3 2 4 5% 48%	2940
	11th to 20th	Day	8% 6% 2 6% 4 4 5% 4 4 5% 51%	3391
	21st to end	Day	8% 4 2 3 2 2 2 2 3 4 67%	4488
January	1st to 10th	Night	9% 4 2 6% 3 3 2 2 3 5% 61%	5888
	11th to 20th	Night	6% 4 1 2 1 2 2 2 3 5% 72%	5785
	21st to end	Night	19% 7% 2 5% 3 2 3 2 4 6% 49%	5984
February	1st to 10th	Night	8% 6% 2 5% 3 3 3 2 5% 6% 58%	2400
	11th to 20th	Night	11% 6% 2 5% 3 3 3 2 5% 6% 54%	2338
	21st to end	Night	9% 5% 1 4 3 3 3 3 6% 5% 57%	1980
March	1st to 10th	Night	5% 4 1 4 3 3 4 4 6% 7% 60%	5293
	11th to 20th	Night	10% 5% 2 4 3 3 3 3 4 6% 58%	4980
	21st to end	Night	6% 5% 2 5% 3 3 3 3 5% 7% 58%	5467
April	1st to 10th	Night	5% 4 2 4 4 3 4 4 6% 7% 59%	2127
	11th to 20th	Night	8% 6% 1 5% 3 3 4 3 4 7% 56%	1977
	21st to end	Night	7% 5% 2 4 3 2 2 2 4 6% 62%	1987
May	1st to 10th	Night	12% 7% 2 5% 3 3 3 3 5% 6% 52%	4053
	11th to 20th	Night	5% 4 1 5% 3 4 4 4 6% 8% 56%	4053
	21st to end	Night	7% 5% 2 5% 4 4 4 4 6% 10% 48%	4443
June	1st to 10th	Night	2 3 1 3 3 4 3 3 6% 10% 62%	1800
	11th to 20th	Night	2 2 2 2 3 3 3 7% 9% 66%	1800
	21st to end	Night	3 3 1 3 4 3 3 4 5% 9% 62%	1800
July	1st to 10th	Night	5% 3 1 3 4 4 3 4 6% 8% 60%	2895
	11th to 20th	Night	1 1 2 2 2 2 2 4 9% 74%	2850
	21st to end	Night	2 3 1 4 4 3 3 3 5% 9% 62%	3124
August	1st to 10th	Night	1 1 1 3 2 3 3 2 4 6% 74%	3155
	11th to 20th	Night	2 2 1 3 3 3 4 4 5% 9% 65%	3113
	21st to end	Night	3 2 1 4 3 3 5% 4 7% 11% 56%	3487
September	1st to 10th	Night	6% 4 1 5% 4 3 4 4 5% 8% 54%	2052
	11th to 20th	Night	8% 4 1 3 3 3 4 4 6% 10% 53%	2090
	21st to end	Night	7% 4 2 4 3 3 3 3 5% 8% 58%	2090
October	1st to 10th	Night	4 3 1 3 3 3 2 2 4 6% 68%	2090
	11th to 20th	Night	9% 4 2 3 3 3 3 3 3 5% 62%	2090
	21st to end	Night	9% 4 1 4 3 2 2 2 3 5% 64%	2488
November	1st to 10th	Night	9% 5% 2 4 3 2 3 2 4 5% 62%	2483
	11th to 20th	Night	5% 4 1 3 3 3 3 3 4 6% 64%	2600
	21st to end	Night	11% 5% 2 4 3 3 3 4 5% 6% 55%	2600
December	1st to 10th	Night	16% 7% 2 5% 2 3 3 3 4 6% 48%	4250
	11th to 20th	Night	6% 5% 2 6% 4 4 4 3 5% 6% 54%	4816
	21st to end	Night	8% 5% 2 4 3 2 2 2 3 5% 63%	6490

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	27% 3 4 22% 26% 18%	4078
	11th to 20th	Day	23% 3 5% 19% 28% 21%	4236
	21st to end	Day	34% 4 5% 12% 26% 17%	4994
February	1st to 10th	Day	30% 4 6% 14% 22% 24%	2000
	11th to 20th	Day	31% 4 7% 22% 20% 17%	1959
	21st to end	Day	28% 5% 6% 12% 27% 22%	1650
March	1st to 10th	Day	28% 4 5% 13% 18% 32%	4576
	11th to 20th	Day	31% 5% 5% 9% 17% 34%	4980
	21st to end	Day	27% 5% 8% 16% 24% 20%	5464
April	1st to 10th	Day	28% 5% 9% 19% 20% 20%	2268
	11th to 20th	Day	32% 6% 7% 16% 22% 17%	2374
	21st to end	Day	29% 5% 7% 21% 24% 15%	2410
May	1st to 10th	Day	35% 6% 9% 13% 23% 15%	5900
	11th to 20th	Day	33% 5% 7% 13% 26% 16%	5866
	21st to end	Day	32% 8% 11% 24% 17% 8%	6447
June	1st to 10th	Day	22% 7% 14% 30% 23% 5%	2600
	11th to 20th	Day	21% 6% 13% 26% 26% 8%	2600
	21st to end	Day	26% 9% 15% 24% 20% 7%	2600
July	1st to 10th	Day	28% 8% 15% 36% 13% 1	4122
	11th to 20th	Day	18% 6% 14% 36% 22% 3	4051
	21st to end	Day	25% 6% 14% 32% 21% 3	4282
August	1st to 10th	Day	13% 5% 10% 37% 33% 2	3772
	11th to 20th	Day	17% 6% 15% 42% 17% 2	3762
	21st to end	Day	26% 10% 16% 24% 21% 3	4179
September	1st to 10th	Day	36% 6% 10% 20% 18% 9%	2126
	11th to 20th	Day	35% 6% 13% 20% 19% 6%	2090
	21st to end	Day	28% 6% 11% 22% 21% 13%	2090
October	1st to 10th	Day	14% 4 6% 13% 25% 37%	3480
	11th to 20th	Day	23% 4 6% 19% 22% 26%	3458
	21st to end	Day	20% 3 4 19% 41% 13%	3428
November	1st to 10th	Day	29% 4 9% 22% 21% 15%	1811
	11th to 20th	Day	24% 5% 8% 19% 22% 21%	1800
	21st to end	Day	31% 4 5% 19% 26% 16%	1800
December	1st to 10th	Day	41% 2 5% 17% 24% 11%	2940
	11th to 20th	Day	33% 5% 8% 13% 26% 15%	3389
	21st to end	Day	22% 2 4 20% 28% 23%	4488
January	1st to 10th	Night	27% 3 6% 19% 29% 16%	5888
	11th to 20th	Night	18% 2 4 19% 29% 27%	5785
	21st to end	Night	38% 4 4 12% 23% 19%	5984
February	1st to 10th	Night	28% 4 7% 14% 24% 22%	2400
	11th to 20th	Night	32% 4 7% 18% 20% 20%	2338
	21st to end	Night	27% 5% 7% 13% 24% 24%	1980
March	1st to 10th	Night	21% 5% 6% 18% 26% 23%	5293
	11th to 20th	Night	28% 5% 5% 11% 16% 34%	4980
	21st to end	Night	26% 5% 8% 16% 24% 21%	5467
April	1st to 10th	Night	23% 6% 12% 19% 17% 22%	2127
	11th to 20th	Night	29% 5% 10% 17% 19% 19%	1977
	21st to end	Night	25% 4 12% 23% 23% 13%	1987
May	1st to 10th	Night	32% 6% 9% 19% 18% 15%	4080
	11th to 20th	Night	25% 7% 12% 18% 22% 17%	4054
	21st to end	Night	30% 8% 13% 26% 14% 9%	4452
June	1st to 10th	Night	17% 7% 17% 35% 21% 3	1800
	11th to 20th	Night	14% 6% 16% 31% 25% 8%	1800
	21st to end	Night	19% 8% 16% 29% 23% 6%	1800
July	1st to 10th	Night	21% 7% 19% 36% 15% 1	2850
	11th to 20th	Night	9% 4 15% 43% 24% 4	2796
	21st to end	Night	18% 5% 17% 37% 22% 1	3025
August	1st to 10th	Night	13% 4 12% 31% 38% 2	3144
	11th to 20th	Night	15% 6% 18% 44% 16% 2	3143
	21st to end	Night	20% 10% 22% 25% 21% 2	3487
September	1st to 10th	Night	27% 8% 13% 22% 20% 10%	2052
	11th to 20th	Night	28% 8% 15% 23% 19% 7%	2090
	21st to end	Night	25% 5% 13% 24% 18% 15%	2090
October	1st to 10th	Night	12% 3 8% 15% 23% 39%	3480
	11th to 20th	Night	19% 3 10% 16% 27% 25%	3460
	21st to end	Night	17% 3 5% 24% 34% 17%	4088
November	1st to 10th	Night	25% 4 8% 20% 25% 18%	2483
	11th to 20th	Night	23% 4 8% 21% 23% 21%	2600
	21st to end	Night	30% 4 8% 17% 25% 16%	2600
December	1st to 10th	Night	40% 3 5% 19% 19% 14%	4250
	11th to 20th	Night	30% 4 7% 16% 24% 18%	4817
	21st to end	Night	24% 3 5% 20% 28% 20%	6490

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	10% 13% 46% 24% 5% 1	300
	11th to 20th	Day	15% 13% 36% 27% 8% 1	300
	21st to end	Day	12% 15% 42% 23% 8%	330
February	1st to 10th	Day	16% 15% 38% 22% 9% 1	300
	11th to 20th	Day	17% 17% 40% 21% 4	300
	21st to end	Day	14% 12% 50% 22% 2	249
March	1st to 10th	Day	12% 17% 43% 23% 4	300
	11th to 20th	Day	15% 17% 42% 17% 7% 1	300
	21st to end	Day	11% 15% 51% 16% 5% 1	330
April	1st to 10th	Day	10% 19% 43% 24% 4	368
	11th to 20th	Day	10% 20% 45% 21% 4	492
	21st to end	Day	9% 17% 40% 26% 6%	510
May	1st to 10th	Day	10% 12% 43% 30% 5%	703
	11th to 20th	Day	12% 11% 35% 31% 10% 1	725
	21st to end	Day	9% 7% 36% 38% 9% 1	789
June	1st to 10th	Day	6% 3 21% 48% 20% 3	730
	11th to 20th	Day	4 2 24% 49% 18% 3	730
	21st to end	Day	4 2 15% 43% 30% 6%	730
July	1st to 10th	Day	7% 2 9% 40% 31% 11%	697
	11th to 20th	Day	2 1 6% 43% 40% 7%	668
	21st to end	Day	3 1 4 38% 39% 14%	719
August	1st to 10th	Day	1 6% 32% 43% 17%	487
	11th to 20th	Day	9% 1 4 32% 41% 13%	477
	21st to end	Day	5% 1 6% 28% 44% 16%	539
September	1st to 10th	Day	7% 1 5% 29% 40% 17%	336
	11th to 20th	Day	4 2 6% 25% 45% 17%	300
	21st to end	Day	11% 2 8% 32% 33% 14%	300
October	1st to 10th	Day	2 3 13% 38% 37% 7%	300
	11th to 20th	Day	10% 3 25% 42% 17% 2	300
	21st to end	Day	16% 10% 24% 27% 18% 3	330
November	1st to 10th	Day	15% 7% 31% 32% 14% 1	300
	11th to 20th	Day	14% 11% 32% 23% 16% 5%	300
	21st to end	Day	16% 16% 39% 18% 9% 2	300
December	1st to 10th	Day	18% 9% 30% 31% 10% 2	300
	11th to 20th	Day	8% 16% 37% 28% 9% 1	300
	21st to end	Day	13% 15% 37% 28% 7%	330
January	1st to 10th	Night	12% 9% 40% 31% 8%	1000
	11th to 20th	Night	12% 10% 41% 31% 6%	950
	21st to end	Night	15% 11% 41% 27% 7%	880
February	1st to 10th	Night	12% 11% 44% 28% 5%	800
	11th to 20th	Night	15% 13% 45% 26% 3	784
	21st to end	Night	12% 15% 50% 22% 2	660
March	1st to 10th	Night	13% 12% 48% 24% 3	771
	11th to 20th	Night	13% 11% 46% 26% 5%	600
	21st to end	Night	6% 15% 53% 24% 2	660
April	1st to 10th	Night	7% 11% 55% 25% 3	600
	11th to 20th	Night	8% 14% 56% 21% 2	593
	21st to end	Night	8% 12% 55% 20% 6%	600
May	1st to 10th	Night	8% 11% 51% 26% 4	600
	11th to 20th	Night	9% 7% 44% 31% 7%	591
	21st to end	Night	5% 7% 45% 34% 8%	650
June	1st to 10th	Night	1 2 29% 55% 12% 1	600
	11th to 20th	Night	2 1 38% 52% 7%	600
	21st to end	Night	2 1 24% 54% 18% 1	600
July	1st to 10th	Night	7% 2 9% 55% 26% 2	570
	11th to 20th	Night	2 10% 63% 24% 1	552
	21st to end	Night	1 7% 62% 28% 2	624
August	1st to 10th	Night	1 7% 59% 31% 2	567
	11th to 20th	Night	4 1 7% 53% 33% 3	564
	21st to end	Night	4 1 6% 48% 36% 4	627
September	1st to 10th	Night	5% 1 9% 47% 34% 4	570
	11th to 20th	Night	9% 1 7% 48% 34% 2	570
	21st to end	Night	9% 1 15% 50% 24% 2	570
October	1st to 10th	Night	5% 2 21% 48% 24% 1	570
	11th to 20th	Night	12% 4 28% 43% 13% 1	570
	21st to end	Night	12% 7% 31% 34% 15% 1	816
November	1st to 10th	Night	11% 5% 30% 40% 13% 1	923
	11th to 20th	Night	7% 7% 36% 36% 13% 2	1000
	21st to end	Night	13% 9% 36% 30% 11% 1	1000
December	1st to 10th	Night	13% 7% 34% 39% 8% 1	1000
	11th to 20th	Night	12% 11% 36% 35% 6%	1000
	21st to end	Night	10% 10% 40% 34% 7%	1100

Page generated at 2025-07-03 00:30:18. Version ac07

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