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 2024-03-18.

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% 4 2 4 4 3 4 4 5% 7% 55%	79215
	Night	7% 4 2 3 3 2 3 4 5% 7% 59%	80642
Transparency	Day	29% 6% 10% 21% 23% 13%	78942
	Night	25% 5% 10% 21% 23% 15%	80436
Seeing	Day	9% 8% 25% 32% 20% 5%	13947
	Night	9% 7% 33% 37% 13% 1	24096

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 4 3 1 3 2 3 6% 62%	2847
	11th to 20th	Day	7% 5% 2 3 2 1 2 3 5% 6% 63%	2950
	21st to end	Day	9% 5% 2 5% 5% 2 4 4 4 6% 54%	3487
February	1st to 10th	Day	9% 6% 2 4 3 2 4 4 4 6% 55%	1900
	11th to 20th	Day	11% 6% 2 4 3 2 3 4 5% 6% 54%	1849
	21st to end	Day	9% 5% 2 3 4 1 3 5% 4 6% 57%	1570
March	1st to 10th	Day	11% 6% 2 5% 5% 2 4 4 6% 7% 48%	1926
	11th to 20th	Day	12% 5% 3 5% 3 2 5% 4 3 6% 53%	2057
	21st to end	Day	8% 5% 2 4 4 2 4 4 3 6% 60%	2178
April	1st to 10th	Day	8% 4 3 4 4 2 4 4 5% 8% 56%	2040
	11th to 20th	Day	10% 4 3 5% 5% 3 4 3 5% 6% 53%	2134
	21st to end	Day	8% 4 3 5% 3 2 3 3 3 5% 60%	2168
May	1st to 10th	Day	9% 4 2 5% 5% 3 4 4 6% 8% 50%	2340
	11th to 20th	Day	11% 6% 3 6% 5% 3 4 4 6% 6% 47%	2302
	21st to end	Day	8% 5% 3 6% 5% 3 6% 5% 6% 7% 47%	2531
June	1st to 10th	Day	4 3 1 3 4 2 4 5% 6% 8% 60%	2340
	11th to 20th	Day	4 2 1 3 4 3 4 4 6% 10% 58%	2340
	21st to end	Day	6% 3 2 4 5% 4 5% 5% 6% 9% 51%	2340
July	1st to 10th	Day	7% 5% 2 6% 6% 4 6% 7% 7% 9% 41%	2340
	11th to 20th	Day	4 2 1 2 4 3 5% 5% 5% 9% 59%	2340
	21st to end	Day	3 2 1 4 4 3 5% 5% 5% 11% 56%	2528
August	1st to 10th	Day	2 1 1 2 3 3 4 4 5% 8% 66%	2149
	11th to 20th	Day	8% 3 2 4 4 4 4 5% 6% 10% 50%	2123
	21st to end	Day	5% 4 2 5% 6% 4 6% 5% 7% 10% 47%	2376
September	1st to 10th	Day	9% 4 2 5% 6% 4 5% 5% 6% 7% 47%	2015
	11th to 20th	Day	11% 5% 2 5% 5% 3 5% 5% 6% 9% 45%	1980
	21st to end	Day	9% 4 1 4 4 2 4 4 5% 7% 55%	1980
October	1st to 10th	Day	5% 3 2 5% 4 3 3 4 5% 7% 59%	1980
	11th to 20th	Day	9% 4 2 4 4 2 3 3 3 5% 61%	1980
	21st to end	Day	11% 5% 2 3 3 2 3 2 3 4 63%	1980
November	1st to 10th	Day	10% 5% 2 4 3 2 3 3 4 6% 59%	1719
	11th to 20th	Day	7% 4 2 4 4 2 3 4 5% 7% 59%	1710
	21st to end	Day	10% 7% 2 5% 4 2 3 3 4 6% 55%	1710
December	1st to 10th	Day	11% 6% 2 4 3 2 3 3 5% 6% 55%	1710
	11th to 20th	Day	9% 5% 2 5% 4 3 4 4 4 5% 54%	2161
	21st to end	Day	10% 5% 2 3 3 2 2 3 4 5% 63%	3135
January	1st to 10th	Night	9% 5% 2 4 3 2 3 3 4 5% 61%	4108
	11th to 20th	Night	7% 5% 1 2 2 1 2 2 3 5% 69%	4047
	21st to end	Night	11% 6% 2 4 4 2 3 3 4 7% 53%	4180
February	1st to 10th	Night	8% 6% 2 4 4 2 3 2 4 6% 57%	2280
	11th to 20th	Night	11% 5% 2 5% 3 2 3 3 4 6% 55%	2218
	21st to end	Night	9% 4 2 4 4 2 4 4 5% 5% 57%	1884
March	1st to 10th	Night	10% 5% 2 4 4 2 4 5% 6% 7% 52%	2253
	11th to 20th	Night	11% 5% 2 4 4 2 4 4 5% 6% 53%	2068
	21st to end	Night	5% 4 2 3 4 3 3 3 4 9% 60%	2178
April	1st to 10th	Night	5% 3 1 3 4 2 3 5% 5% 8% 59%	1915
	11th to 20th	Night	8% 5% 2 4 3 2 4 4 4 7% 58%	1777
	21st to end	Night	7% 4 2 3 4 2 2 2 4 6% 64%	1789
May	1st to 10th	Night	7% 4 2 4 3 2 4 4 5% 9% 58%	1620
	11th to 20th	Night	10% 4 2 3 4 3 4 4 7% 9% 52%	1593
	21st to end	Night	6% 4 2 4 5% 2 4 5% 5% 10% 54%	1745
June	1st to 10th	Night	2 2 1 3 3 2 4 4 6% 10% 63%	1620
	11th to 20th	Night	2 2 1 2 2 2 3 4 6% 10% 66%	1620
	21st to end	Night	4 2 2 3 4 2 4 5% 4 9% 62%	1620
July	1st to 10th	Night	7% 3 2 3 4 3 4 5% 7% 11% 51%	1620
	11th to 20th	Night	2 2 1 2 3 1 3 3 5% 10% 69%	1620
	21st to end	Night	1 1 1 1 3 2 3 5% 5% 11% 67%	1785
August	1st to 10th	Night	2 1 1 2 2 1 3 3 4 8% 73%	1790
	11th to 20th	Night	4 4 2 4 5% 3 5% 5% 6% 9% 54%	1778
	21st to end	Night	4 2 2 3 4 2 4 6% 7% 10% 56%	1980
September	1st to 10th	Night	6% 4 2 4 4 3 5% 5% 5% 9% 54%	1944
	11th to 20th	Night	8% 4 2 3 3 2 4 5% 6% 10% 52%	1980
	21st to end	Night	8% 4 2 3 3 2 3 3 5% 8% 58%	1980
October	1st to 10th	Night	5% 3 1 3 3 2 3 3 4 7% 67%	1980
	11th to 20th	Night	10% 4 2 3 3 2 3 3 3 6% 61%	1980
	21st to end	Night	10% 4 1 4 3 2 3 3 3 5% 63%	2357
November	1st to 10th	Night	9% 4 1 3 3 1 3 2 4 5% 63%	2355
	11th to 20th	Night	5% 4 1 3 3 3 3 4 3 6% 64%	2470
	21st to end	Night	11% 5% 2 4 3 2 3 5% 5% 6% 54%	2470
December	1st to 10th	Night	9% 5% 1 4 3 2 3 3 5% 6% 58%	2470
	11th to 20th	Night	8% 5% 2 5% 5% 3 4 4 5% 6% 52%	3036
	21st to end	Night	10% 5% 2 4 4 2 2 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	36% 5% 8% 15% 20% 17%	1926
	11th to 20th	Day	34% 5% 8% 15% 20% 18%	2057
	21st to end	Day	28% 5% 9% 18% 22% 18%	2178
April	1st to 10th	Day	29% 5% 9% 19% 21% 18%	2040
	11th to 20th	Day	32% 6% 7% 17% 22% 16%	2134
	21st to end	Day	29% 4 7% 20% 24% 16%	2168
May	1st to 10th	Day	33% 5% 11% 16% 23% 13%	2340
	11th to 20th	Day	37% 6% 11% 20% 20% 6%	2306
	21st to end	Day	35% 8% 12% 22% 18% 5%	2531
June	1st to 10th	Day	22% 7% 14% 30% 23% 5%	2340
	11th to 20th	Day	22% 6% 14% 28% 23% 7%	2340
	21st to end	Day	28% 9% 14% 23% 20% 7%	2340
July	1st to 10th	Day	35% 11% 17% 24% 11% 1	2276
	11th to 20th	Day	21% 7% 16% 28% 23% 5%	2271
	21st to end	Day	19% 7% 20% 36% 15% 1	2388
August	1st to 10th	Day	18% 6% 13% 36% 24% 3	2136
	11th to 20th	Day	28% 11% 16% 28% 14% 3	2123
	21st to end	Day	30% 10% 16% 24% 16% 4	2376
September	1st to 10th	Day	36% 7% 11% 21% 18% 7%	2015
	11th to 20th	Day	36% 7% 13% 20% 18% 6%	1980
	21st to end	Day	28% 6% 11% 22% 21% 12%	1980
October	1st to 10th	Day	24% 8% 10% 23% 24% 11%	1980
	11th to 20th	Day	28% 4 7% 17% 25% 19%	1980
	21st to end	Day	27% 4 5% 15% 30% 20%	1980
November	1st to 10th	Day	28% 4 9% 23% 22% 14%	1719
	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	30% 5% 9% 17% 24% 15%	2253
	11th to 20th	Night	33% 5% 8% 15% 20% 19%	2068
	21st to end	Night	24% 6% 11% 20% 21% 18%	2178
April	1st to 10th	Night	23% 6% 12% 21% 18% 20%	1915
	11th to 20th	Night	29% 4 11% 17% 19% 20%	1777
	21st to end	Night	24% 4 11% 23% 25% 13%	1789
May	1st to 10th	Night	24% 7% 11% 22% 23% 13%	1620
	11th to 20th	Night	29% 6% 14% 25% 19% 6%	1594
	21st to end	Night	27% 8% 15% 28% 18% 4	1746
June	1st to 10th	Night	16% 7% 17% 34% 22% 4	1620
	11th to 20th	Night	14% 7% 17% 31% 24% 7%	1620
	21st to end	Night	20% 8% 15% 28% 23% 7%	1620
July	1st to 10th	Night	25% 11% 20% 27% 15% 2	1575
	11th to 20th	Night	12% 6% 16% 33% 28% 6%	1566
	21st to end	Night	9% 7% 25% 38% 19% 1	1686
August	1st to 10th	Night	11% 6% 15% 37% 28% 3	1779
	11th to 20th	Night	23% 10% 16% 31% 16% 3	1778
	21st to end	Night	21% 10% 20% 27% 17% 4	1980
September	1st to 10th	Night	27% 8% 13% 23% 21% 9%	1944
	11th to 20th	Night	28% 9% 16% 22% 19% 6%	1980
	21st to end	Night	25% 6% 13% 24% 18% 14%	1980
October	1st to 10th	Night	19% 5% 14% 25% 23% 14%	1980
	11th to 20th	Night	27% 4 8% 17% 25% 20%	1980
	21st to end	Night	26% 4 6% 16% 25% 23%	2357
November	1st to 10th	Night	25% 4 8% 20% 25% 17%	2355
	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	15% 15% 43% 18% 8% 1	261
	21st to end	Day	12% 16% 50% 16% 5% 2	264
April	1st to 10th	Day	10% 18% 44% 26% 3	300
	11th to 20th	Day	10% 20% 44% 21% 4	412
	21st to end	Day	10% 18% 40% 25% 7%	428
May	1st to 10th	Day	10% 11% 43% 30% 6%	603
	11th to 20th	Day	12% 9% 34% 32% 12% 1	625
	21st to end	Day	10% 7% 34% 39% 10% 1	679
June	1st to 10th	Day	6% 3 18% 49% 22% 3	630
	11th to 20th	Day	3 1 23% 50% 19% 4	630
	21st to end	Day	4 2 16% 44% 28% 7%	630
July	1st to 10th	Day	7% 1 10% 39% 33% 11%	621
	11th to 20th	Day	2 5% 43% 42% 8%	618
	21st to end	Day	2 1 3 38% 41% 15%	666
August	1st to 10th	Day	2 6% 33% 44% 15%	447
	11th to 20th	Day	9% 1 4 30% 41% 14%	437
	21st to end	Day	5% 1 6% 28% 43% 17%	495
September	1st to 10th	Day	6% 1 4 28% 42% 19%	305
	11th to 20th	Day	5% 1 5% 25% 45% 19%	270
	21st to end	Day	11% 2 8% 30% 34% 14%	270
October	1st to 10th	Day	3 3 14% 39% 37% 4	270
	11th to 20th	Day	11% 4 26% 39% 18% 2	270
	21st to end	Day	18% 11% 23% 27% 19% 2	297
November	1st to 10th	Day	14% 5% 30% 34% 15% 1	270
	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% 26% 5%	564
	21st to end	Night	6% 15% 54% 24% 2	594
April	1st to 10th	Night	6% 10% 56% 25% 3	540
	11th to 20th	Night	8% 13% 55% 23% 2	533
	21st to end	Night	7% 10% 57% 20% 6%	540
May	1st to 10th	Night	7% 11% 52% 26% 4	540
	11th to 20th	Night	10% 7% 43% 32% 8%	531
	21st to end	Night	5% 6% 45% 36% 8% 1	584
June	1st to 10th	Night	1 2 27% 57% 13% 1	540
	11th to 20th	Night	2 1 36% 53% 8%	540
	21st to end	Night	1 1 24% 53% 19% 1	540
July	1st to 10th	Night	7% 1 9% 54% 27% 2	525
	11th to 20th	Night	2 9% 63% 24% 2	522
	21st to end	Night	1 6% 62% 28% 2	591
August	1st to 10th	Night	1 7% 59% 31% 2	537
	11th to 20th	Night	4 1 7% 51% 35% 3	534
	21st to end	Night	3 2 6% 48% 37% 5%	594
September	1st to 10th	Night	4 1 9% 48% 34% 4	540
	11th to 20th	Night	9% 1 6% 47% 35% 2	540
	21st to end	Night	9% 1 15% 50% 24% 1	540
October	1st to 10th	Night	5% 2 21% 48% 23% 1	540
	11th to 20th	Night	12% 4 27% 42% 13% 1	540
	21st to end	Night	12% 7% 31% 34% 14% 1	773
November	1st to 10th	Night	12% 4 29% 41% 13% 1	875
	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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