Coldfoot
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coldfoot clear sky chart from 2005-11-06 to 2024-11-28.

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
Transparency	Day	58% 9% 15% 13% 4	108708
	Night	54% 7% 12% 15% 11% 2	101671
Seeing	Day	18% 5% 16% 25% 25% 11%	19590
	Night	13% 4 16% 29% 28% 10%	22383

By Month

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	42% 3 10% 16% 14% 15%	203
	11th to 20th	Day	45% 6% 10% 20% 15% 4	750
	21st to end	Day	36% 5% 8% 13% 36% 1	1383
February	1st to 10th	Day	37% 8% 12% 20% 17% 6%	1049
	11th to 20th	Day	53% 8% 12% 14% 12% 1	1256
	21st to end	Day	57% 10% 10% 15% 8%	1256
March	1st to 10th	Day	49% 6% 8% 16% 21% 1	2924
	11th to 20th	Day	51% 5% 10% 16% 17%	3270
	21st to end	Day	60% 9% 13% 9% 7% 2	4150
April	1st to 10th	Day	63% 6% 12% 12% 6% 2	2513
	11th to 20th	Day	51% 8% 15% 18% 8% 1	2645
	21st to end	Day	48% 10% 18% 18% 6%	3040
May	1st to 10th	Day	62% 9% 11% 13% 4	5434
	11th to 20th	Day	40% 14% 23% 21% 3	5787
	21st to end	Day	52% 13% 19% 15% 2	6998
June	1st to 10th	Day	50% 12% 19% 17% 2	4412
	11th to 20th	Day	49% 11% 18% 18% 3	4560
	21st to end	Day	52% 11% 16% 17% 3	4560
July	1st to 10th	Day	64% 9% 16% 10% 2	7298
	11th to 20th	Day	62% 11% 15% 11% 1	6359
	21st to end	Day	61% 9% 20% 10%	6217
August	1st to 10th	Day	70% 9% 14% 6%	5447
	11th to 20th	Day	80% 7% 8% 4	5016
	21st to end	Day	69% 8% 11% 12%	4979
September	1st to 10th	Day	64% 8% 14% 12% 2	2533
	11th to 20th	Day	70% 8% 12% 10% 1	2280
	21st to end	Day	63% 9% 12% 14% 1 1	2013
October	1st to 10th	Day	58% 8% 12% 18% 4	3040
	11th to 20th	Day	63% 7% 12% 17% 1	2565
	21st to end	Day	58% 7% 13% 18% 4	2328
November	1st to 10th	Day	57% 8% 14% 16% 4 1	1069
	11th to 20th	Day	46% 8% 19% 20% 5% 2	783
	21st to end	Day	62% 7% 7% 14% 9% 1	471
December	1st to 10th	Day	63% 9% 10% 13% 3 2	120
	January	1st to 10th	Night	43% 6% 13% 17% 15% 6%	6745
11th to 20th		Night	45% 7% 10% 19% 16% 4	6237
21st to end		Night	36% 5% 7% 11% 40% 1	6285
February	1st to 10th	Night	40% 6% 11% 20% 17% 5%	3131
	11th to 20th	Night	53% 6% 12% 14% 12% 2	2821
	21st to end	Night	52% 9% 10% 19% 9% 1	2198
March	1st to 10th	Night	46% 6% 10% 15% 23% 1	3928
	11th to 20th	Night	48% 6% 11% 19% 14% 1	3687
	21st to end	Night	65% 9% 9% 8% 8% 1	3481
April	1st to 10th	Night	60% 8% 14% 11% 6% 2	1664
	11th to 20th	Night	51% 9% 17% 15% 6% 2	1484
	21st to end	Night	44% 8% 20% 19% 8%	1140
May	1st to 10th	Night	57% 7% 14% 17% 4 1	1532
	11th to 20th	Night	40% 12% 26% 19% 3	1121
	21st to end	Night	58% 8% 20% 12% 1	587
July	11th to 20th	Night	57% 8% 20% 14%	484
	21st to end	Night	63% 8% 18% 11%	1105
August	1st to 10th	Night	66% 11% 16% 7%	1468
	11th to 20th	Night	78% 6% 11% 4	1888
	21st to end	Night	63% 10% 13% 13% 1	2687
September	1st to 10th	Night	63% 8% 15% 12% 2	1645
	11th to 20th	Night	71% 8% 14% 7% 1	1900
	21st to end	Night	64% 9% 10% 14% 3	2164
October	1st to 10th	Night	57% 7% 13% 18% 5%	3924
	11th to 20th	Night	64% 6% 11% 18% 1	4348
	21st to end	Night	57% 9% 12% 16% 6%	5228
November	1st to 10th	Night	58% 9% 10% 18% 5% 1	3230
	11th to 20th	Night	46% 11% 17% 19% 7% 1	3595
	21st to end	Night	60% 6% 10% 17% 7% 1	3861
December	1st to 10th	Night	60% 6% 9% 16% 7% 1	4068
	11th to 20th	Night	61% 6% 9% 15% 7% 1	5675
	21st to end	Night	55% 6% 10% 10% 14% 5%	8360

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	11% 17% 44% 22% 6%	18
	11th to 20th	Day	2 4 23% 38% 26% 7%	90
	21st to end	Day	5% 2 17% 31% 33% 11%	122
February	1st to 10th	Day	4 4 14% 26% 32% 20%	280
	11th to 20th	Day	7% 6% 20% 29% 22% 15%	279
	21st to end	Day	5% 6% 17% 36% 27% 10%	307
March	1st to 10th	Day	5% 5% 16% 29% 29% 16%	370
	11th to 20th	Day	6% 6% 19% 27% 26% 16%	428
	21st to end	Day	7% 6% 23% 31% 23% 11%	616
April	1st to 10th	Day	7% 4 24% 29% 25% 11%	610
	11th to 20th	Day	12% 6% 17% 29% 26% 9%	640
	21st to end	Day	8% 3 14% 27% 29% 19%	650
May	1st to 10th	Day	14% 3 17% 26% 26% 14%	746
	11th to 20th	Day	13% 3 15% 26% 29% 13%	913
	21st to end	Day	14% 3 12% 27% 33% 12%	1145
June	1st to 10th	Day	16% 4 15% 24% 25% 15%	1175
	11th to 20th	Day	14% 4 15% 23% 33% 10%	1250
	21st to end	Day	15% 4 16% 28% 30% 8%	1250
July	1st to 10th	Day	18% 5% 13% 27% 28% 10%	1174
	11th to 20th	Day	28% 5% 14% 20% 22% 11%	1036
	21st to end	Day	29% 7% 13% 20% 23% 8%	992
August	1st to 10th	Day	34% 6% 14% 23% 19% 5%	838
	11th to 20th	Day	39% 6% 14% 17% 17% 7%	665
	21st to end	Day	39% 8% 15% 15% 18% 6%	748
September	1st to 10th	Day	28% 8% 15% 20% 19% 9%	647
	11th to 20th	Day	34% 6% 16% 21% 17% 7%	580
	21st to end	Day	23% 4 16% 19% 26% 12%	416
October	1st to 10th	Day	20% 5% 21% 26% 18% 11%	390
	11th to 20th	Day	14% 4 13% 31% 23% 16%	390
	21st to end	Day	16% 3 18% 23% 23% 17%	396
November	1st to 10th	Day	11% 6% 18% 25% 28% 13%	189
	11th to 20th	Day	3 3 11% 30% 32% 21%	100
	21st to end	Day	13% 4 11% 33% 20% 19%	97
December	1st to 10th	Day	12% 2 21% 28% 30% 7%	43
	January	1st to 10th	Night	7% 3 21% 31% 26% 12%	1130
11th to 20th		Night	7% 3 18% 33% 30% 9%	1076
21st to end		Night	6% 4 15% 34% 31% 9%	1034
February	1st to 10th	Night	4 3 18% 31% 31% 13%	893
	11th to 20th	Night	10% 4 19% 36% 24% 7%	834
	21st to end	Night	8% 4 17% 39% 27% 6%	703
March	1st to 10th	Night	5% 3 15% 40% 28% 10%	660
	11th to 20th	Night	7% 3 15% 36% 29% 10%	660
	21st to end	Night	8% 3 21% 32% 27% 9%	633
April	1st to 10th	Night	7% 3 18% 31% 33% 8%	570
	11th to 20th	Night	9% 2 15% 34% 30% 10%	558
	21st to end	Night	9% 3 11% 27% 34% 16%	380
May	1st to 10th	Night	14% 2 11% 19% 40% 14%	258
	11th to 20th	Night	16% 3 9% 30% 33% 9%	187
	21st to end	Night	15% 2 10% 24% 42% 7%	182
July	11th to 20th	Night	33% 4 9% 15% 31% 8%	119
	21st to end	Night	26% 5% 7% 25% 31% 5%	208
August	1st to 10th	Night	29% 5% 8% 24% 27% 8%	279
	11th to 20th	Night	38% 5% 11% 14% 27% 5%	376
	21st to end	Night	36% 6% 9% 15% 25% 10%	571
September	1st to 10th	Night	28% 4 11% 19% 28% 10%	570
	11th to 20th	Night	29% 5% 12% 23% 26% 5%	570
	21st to end	Night	22% 4 14% 30% 22% 8%	623
October	1st to 10th	Night	19% 7% 18% 27% 20% 9%	742
	11th to 20th	Night	19% 4 15% 26% 27% 10%	860
	21st to end	Night	15% 5% 12% 26% 30% 11%	946
November	1st to 10th	Night	13% 6% 21% 29% 23% 9%	880
	11th to 20th	Night	6% 5% 14% 28% 28% 19%	1007
	21st to end	Night	12% 3 19% 28% 26% 12%	1180
December	1st to 10th	Night	13% 5% 17% 30% 26% 9%	1132
	11th to 20th	Night	8% 7% 18% 26% 29% 11%	1220
	21st to end	Night	6% 5% 17% 31% 31% 9%	1342

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