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 2024-11-03.

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% 4 4 4 3 5% 7% 56%	100918
	Night	7% 4 1 4 3 3 3 3 5% 7% 59%	98184
Transparency	Day	28% 6% 10% 22% 23% 12%	100731
	Night	25% 6% 11% 22% 23% 14%	98043
Seeing	Day	9% 8% 25% 33% 20% 5%	14876
	Night	9% 7% 33% 38% 13% 1	24796

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	9% 4 2 5% 3 2 2 2 4 6% 62%	2847
	11th to 20th	Day	7% 6% 2 3 2 2 2 2 5% 6% 63%	2950
	21st to end	Day	9% 6% 2 6% 4 3 3 3 5% 6% 54%	3487
February	1st to 10th	Day	9% 7% 2 5% 3 3 4 3 4 5% 55%	1900
	11th to 20th	Day	11% 6% 2 5% 2 3 4 3 5% 6% 53%	1849
	21st to end	Day	9% 6% 2 3 3 2 3 4 4 6% 57%	1570
March	1st to 10th	Day	10% 7% 2 7% 4 3 4 3 5% 6% 49%	3180
	11th to 20th	Day	15% 8% 3 7% 5% 4 4 3 4 6% 42%	3480
	21st to end	Day	6% 5% 2 6% 4 4 4 4 5% 7% 54%	3814
April	1st to 10th	Day	7% 5% 2 4 4 3 3 3 5% 8% 56%	2154
	11th to 20th	Day	10% 5% 2 5% 5% 4 4 3 5% 6% 52%	2254
	21st to end	Day	8% 5% 2 5% 4 3 3 2 4 6% 59%	2289
May	1st to 10th	Day	11% 6% 2 6% 4 3 4 3 5% 6% 49%	4082
	11th to 20th	Day	12% 6% 2 6% 3 4 3 3 4 5% 51%	4082
	21st to end	Day	7% 5% 2 5% 4 5% 5% 4 6% 7% 50%	4477
June	1st to 10th	Day	4 3 1 4 4 3 4 4 6% 8% 59%	2470
	11th to 20th	Day	4 3 1 4 4 4 4 3 6% 10% 58%	2470
	21st to end	Day	5% 4 2 5% 5% 5% 4 4 6% 9% 51%	2470
July	1st to 10th	Day	4 4 1 4 4 5% 6% 4 7% 7% 53%	4120
	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 3 2 2 3 4 63%	2090
November	1st to 10th	Day	10% 5% 1 5% 3 3 3 2 4 6% 58%	1739
	11th to 20th	Day	7% 4 2 4 3 3 4 3 6% 7% 59%	1710
	21st to end	Day	10% 7% 2 5% 4 2 3 2 4 6% 55%	1710
December	1st to 10th	Day	11% 6% 2 4 3 3 3 2 5% 6% 54%	1710
	11th to 20th	Day	9% 5% 2 5% 4 4 4 3 5% 5% 54%	2161
	21st to end	Day	10% 5% 2 3 2 2 2 2 4 4 63%	3135
January	1st to 10th	Night	9% 5% 2 5% 2 3 2 2 4 5% 61%	4108
	11th to 20th	Night	7% 6% 1 3 2 2 2 2 3 5% 69%	4047
	21st to end	Night	11% 7% 2 5% 3 3 3 3 4 7% 53%	4180
February	1st to 10th	Night	8% 6% 2 5% 3 3 3 2 5% 6% 57%	2280
	11th to 20th	Night	11% 6% 2 5% 3 3 3 3 4 6% 55%	2218
	21st to end	Night	9% 5% 1 4 3 3 3 3 6% 5% 57%	1884
March	1st to 10th	Night	7% 5% 1 4 3 3 4 4 5% 7% 57%	3681
	11th to 20th	Night	14% 7% 2 6% 3 3 4 4 5% 6% 46%	3480
	21st to end	Night	6% 6% 2 6% 3 3 4 3 5% 7% 55%	3817
April	1st to 10th	Night	5% 3 2 4 4 3 4 4 6% 7% 59%	2021
	11th to 20th	Night	8% 6% 1 5% 3 4 4 3 4 7% 56%	1877
	21st to end	Night	7% 5% 2 3 3 2 2 2 4 6% 63%	1888
May	1st to 10th	Night	12% 7% 2 4 3 3 3 3 4 7% 53%	2823
	11th to 20th	Night	7% 5% 2 5% 3 3 3 3 5% 7% 56%	2823
	21st to end	Night	6% 4 2 5% 4 4 3 4 6% 8% 55%	3090
June	1st to 10th	Night	2 3 1 3 3 4 3 4 6% 10% 63%	1710
	11th to 20th	Night	2 2 2 1 3 3 4 7% 9% 66%	1710
	21st to end	Night	3 3 1 3 4 3 3 4 5% 8% 62%	1710
July	1st to 10th	Night	4 2 1 3 3 4 3 4 6% 8% 61%	2850
	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 3 3 2 2 2 4 5% 62%	2380
	11th to 20th	Night	5% 4 1 3 3 3 3 3 4 6% 64%	2470
	21st to end	Night	11% 5% 2 4 3 3 3 4 5% 6% 54%	2470
December	1st to 10th	Night	9% 5% 1 4 2 2 3 3 5% 6% 58%	2470
	11th to 20th	Night	8% 5% 2 6% 4 4 4 4 5% 6% 52%	3036
	21st to end	Night	10% 6% 2 4 3 2 3 2 3 6% 59%	4532

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	25% 4 5% 16% 26% 24%	2848
	11th to 20th	Day	23% 4 7% 16% 32% 18%	2950
	21st to end	Day	31% 6% 7% 15% 29% 13%	3487
February	1st to 10th	Day	30% 4 7% 15% 22% 22%	1900
	11th to 20th	Day	32% 4 7% 20% 20% 17%	1859
	21st to end	Day	28% 5% 6% 13% 27% 21%	1570
March	1st to 10th	Day	35% 5% 6% 11% 20% 23%	3180
	11th to 20th	Day	43% 7% 7% 12% 18% 13%	3480
	21st to end	Day	26% 7% 10% 15% 22% 20%	3814
April	1st to 10th	Day	28% 5% 9% 19% 20% 19%	2154
	11th to 20th	Day	32% 6% 7% 16% 22% 17%	2254
	21st to end	Day	29% 5% 7% 20% 24% 15%	2289
May	1st to 10th	Day	35% 7% 10% 13% 22% 14%	4120
	11th to 20th	Day	34% 6% 8% 17% 24% 11%	4086
	21st to end	Day	29% 10% 13% 22% 16% 10%	4489
June	1st to 10th	Day	22% 7% 14% 30% 23% 5%	2470
	11th to 20th	Day	22% 6% 13% 27% 24% 8%	2470
	21st to end	Day	27% 9% 14% 23% 21% 7%	2470
July	1st to 10th	Day	27% 8% 15% 36% 13% 1	4056
	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	23% 7% 10% 22% 25% 14%	2090
	11th to 20th	Day	28% 4 7% 17% 25% 20%	2090
	21st to end	Day	26% 4 5% 16% 31% 19%	2090
November	1st to 10th	Day	29% 4 10% 23% 21% 14%	1739
	11th to 20th	Day	25% 5% 9% 19% 23% 19%	1710
	21st to end	Day	32% 5% 5% 17% 26% 16%	1710
December	1st to 10th	Day	32% 3 8% 19% 27% 12%	1710
	11th to 20th	Day	31% 6% 8% 12% 25% 17%	2159
	21st to end	Day	26% 3 4 17% 29% 21%	3135
January	1st to 10th	Night	27% 3 5% 14% 29% 22%	4108
	11th to 20th	Night	21% 3 5% 19% 27% 26%	4047
	21st to end	Night	31% 5% 6% 14% 28% 16%	4180
February	1st to 10th	Night	29% 5% 7% 14% 24% 20%	2280
	11th to 20th	Night	31% 4 7% 17% 21% 20%	2218
	21st to end	Night	27% 5% 7% 14% 24% 23%	1884
March	1st to 10th	Night	24% 6% 8% 16% 28% 18%	3681
	11th to 20th	Night	38% 7% 7% 15% 17% 14%	3480
	21st to end	Night	27% 7% 10% 18% 19% 19%	3817
April	1st to 10th	Night	23% 6% 12% 20% 18% 22%	2021
	11th to 20th	Night	29% 5% 11% 17% 19% 19%	1877
	21st to end	Night	25% 4 11% 23% 24% 13%	1888
May	1st to 10th	Night	31% 7% 10% 17% 21% 13%	2850
	11th to 20th	Night	25% 8% 12% 22% 19% 13%	2824
	21st to end	Night	25% 9% 13% 26% 15% 12%	3099
June	1st to 10th	Night	17% 7% 17% 35% 21% 3	1710
	11th to 20th	Night	14% 7% 16% 31% 25% 7%	1710
	21st to end	Night	19% 8% 15% 28% 23% 7%	1710
July	1st to 10th	Night	20% 7% 20% 37% 15% 1	2805
	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	18% 5% 13% 24% 23% 17%	2090
	11th to 20th	Night	26% 4 8% 17% 25% 20%	2090
	21st to end	Night	25% 4 6% 16% 27% 22%	2488
November	1st to 10th	Night	25% 4 9% 20% 25% 17%	2380
	11th to 20th	Night	23% 5% 9% 21% 23% 19%	2470
	21st to end	Night	31% 4 8% 16% 25% 16%	2470
December	1st to 10th	Night	27% 5% 8% 20% 25% 15%	2470
	11th to 20th	Night	33% 5% 6% 15% 20% 21%	3037
	21st to end	Night	28% 4 5% 15% 28% 21%	4532

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% 6% 1	270
	11th to 20th	Day	16% 12% 35% 28% 8% 1	270
	21st to end	Day	10% 15% 40% 25% 9%	297
February	1st to 10th	Day	15% 17% 40% 20% 8% 1	270
	11th to 20th	Day	18% 17% 40% 21% 4	270
	21st to end	Day	14% 14% 50% 20% 1	225
March	1st to 10th	Day	11% 17% 45% 23% 4	270
	11th to 20th	Day	14% 16% 43% 18% 8% 1	270
	21st to end	Day	12% 16% 50% 16% 4 1	297
April	1st to 10th	Day	9% 19% 44% 25% 3	334
	11th to 20th	Day	11% 20% 44% 21% 4	452
	21st to end	Day	10% 17% 39% 27% 6%	469
May	1st to 10th	Day	10% 12% 43% 30% 5%	653
	11th to 20th	Day	12% 10% 34% 31% 11% 1	675
	21st to end	Day	9% 7% 35% 38% 10% 1	734
June	1st to 10th	Day	6% 3 18% 49% 21% 3	680
	11th to 20th	Day	3 1 24% 50% 18% 4	680
	21st to end	Day	4 2 15% 44% 29% 7%	680
July	1st to 10th	Day	7% 1 9% 40% 32% 11%	671
	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% 11% 24% 27% 18% 3	330
November	1st to 10th	Day	14% 5% 31% 33% 15% 1	276
	11th to 20th	Day	15% 10% 30% 24% 15% 5%	270
	21st to end	Day	17% 17% 37% 18% 9% 2	270
December	1st to 10th	Day	17% 8% 30% 33% 10% 2	270
	11th to 20th	Day	9% 17% 38% 27% 8% 1	270
	21st to end	Day	13% 14% 38% 28% 7%	297
January	1st to 10th	Night	12% 8% 40% 31% 8%	950
	11th to 20th	Night	12% 9% 40% 31% 7%	903
	21st to end	Night	13% 10% 41% 28% 7%	836
February	1st to 10th	Night	12% 11% 44% 27% 5%	760
	11th to 20th	Night	14% 11% 46% 26% 3	744
	21st to end	Night	12% 15% 50% 22% 1	628
March	1st to 10th	Night	13% 11% 48% 24% 3	733
	11th to 20th	Night	13% 10% 46% 27% 5%	570
	21st to end	Night	6% 15% 54% 23% 2	627
April	1st to 10th	Night	6% 10% 56% 25% 3	570
	11th to 20th	Night	8% 14% 55% 21% 2	563
	21st to end	Night	8% 11% 55% 20% 6%	570
May	1st to 10th	Night	8% 11% 52% 25% 3	570
	11th to 20th	Night	10% 7% 43% 32% 8%	561
	21st to end	Night	5% 7% 45% 35% 8%	617
June	1st to 10th	Night	1 2 27% 56% 12% 1	570
	11th to 20th	Night	2 1 36% 53% 7%	570
	21st to end	Night	2 1 24% 53% 19% 1	570
July	1st to 10th	Night	7% 1 9% 55% 26% 2	555
	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	12% 4 29% 41% 13% 1	884
	11th to 20th	Night	7% 7% 35% 37% 13% 2	950
	21st to end	Night	14% 9% 35% 30% 11% 1	950
December	1st to 10th	Night	12% 6% 34% 39% 8% 1	950
	11th to 20th	Night	12% 11% 36% 35% 6%	950
	21st to end	Night	10% 10% 39% 34% 7%	1045

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