Carcross
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carcross clear sky chart from 2005-11-06 to 2024-11-02.

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% 12% 4 11% 7% 7% 6% 5% 7% 8% 25%	102876
	Night	6% 14% 5% 14% 8% 7% 7% 5% 6% 7% 20%	96134
Transparency	Day	54% 10% 17% 14% 4	102575
	Night	59% 10% 15% 12% 4 1	96082
Seeing	Day	15% 13% 28% 26% 14% 4	17166
	Night	13% 9% 26% 32% 18% 3	23339

By Month

Percentage Cloud Cover NW (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	3 11% 5% 13% 15% 12% 13% 8% 5% 7% 8%	1460
	11th to 20th	Day	5% 15% 7% 18% 7% 5% 5% 6% 6% 11% 16%	1857
	21st to end	Day	6% 25% 7% 19% 6% 5% 6% 4 5% 5% 11%	2122
February	1st to 10th	Day	3 13% 6% 15% 9% 9% 8% 5% 7% 6% 20%	1368
	11th to 20th	Day	4 12% 7% 14% 9% 9% 7% 5% 7% 8% 20%	1480
	21st to end	Day	2 11% 6% 16% 11% 8% 7% 5% 6% 9% 19%	1386
March	1st to 10th	Day	1 8% 4 14% 13% 14% 10% 6% 5% 7% 18%	3096
	11th to 20th	Day	3 16% 7% 16% 9% 7% 6% 5% 8% 7% 16%	3280
	21st to end	Day	2 9% 6% 18% 11% 8% 8% 6% 6% 6% 21%	4149
April	1st to 10th	Day	3 12% 5% 14% 8% 7% 7% 5% 7% 8% 23%	2285
	11th to 20th	Day	3 13% 7% 12% 8% 6% 6% 4 7% 8% 26%	2622
	21st to end	Day	5% 16% 5% 11% 7% 6% 7% 5% 6% 7% 26%	2660
May	1st to 10th	Day	7% 14% 5% 9% 7% 6% 6% 5% 8% 7% 27%	4908
	11th to 20th	Day	5% 15% 5% 11% 8% 7% 6% 5% 7% 7% 23%	5013
	21st to end	Day	7% 9% 3 10% 7% 6% 6% 4 6% 8% 35%	5632
June	1st to 10th	Day	11% 11% 3 9% 7% 6% 6% 6% 6% 8% 28%	3404
	11th to 20th	Day	12% 10% 3 10% 6% 6% 6% 5% 7% 9% 25%	3420
	21st to end	Day	8% 7% 3 9% 7% 7% 7% 5% 7% 9% 30%	3420
July	1st to 10th	Day	8% 6% 2 7% 6% 6% 6% 6% 8% 9% 36%	5681
	11th to 20th	Day	14% 9% 4 11% 7% 6% 6% 5% 8% 8% 23%	5226
	21st to end	Day	12% 8% 2 8% 5% 6% 5% 4 6% 9% 34%	5486
August	1st to 10th	Day	7% 5% 2 5% 4 3 5% 4 6% 8% 50%	4928
	11th to 20th	Day	14% 9% 3 7% 5% 5% 5% 4 6% 8% 35%	4349
	21st to end	Day	18% 12% 3 8% 6% 6% 6% 5% 6% 7% 24%	4873
September	1st to 10th	Day	17% 13% 5% 9% 7% 7% 5% 5% 5% 6% 21%	2309
	11th to 20th	Day	13% 12% 4 9% 5% 6% 6% 4 7% 7% 28%	2280
	21st to end	Day	16% 17% 5% 13% 6% 5% 6% 4 6% 5% 18%	2027
October	1st to 10th	Day	13% 16% 5% 11% 6% 6% 5% 5% 5% 7% 21%	1900
	11th to 20th	Day	10% 17% 6% 12% 8% 6% 6% 5% 7% 6% 17%	1710
	21st to end	Day	8% 18% 6% 12% 9% 8% 6% 4 6% 6% 16%	1686
November	1st to 10th	Day	8% 18% 6% 16% 12% 8% 6% 3 5% 6% 11%	1309
	11th to 20th	Day	5% 22% 8% 21% 11% 5% 5% 4 4 5% 10%	1192
	21st to end	Day	6% 17% 7% 15% 8% 8% 6% 6% 7% 7% 12%	1055
December	1st to 10th	Day	5% 15% 7% 14% 10% 7% 9% 5% 9% 8% 11%	950
	11th to 20th	Day	3 12% 5% 13% 9% 8% 9% 6% 10% 10% 15%	967
	21st to end	Day	5% 17% 5% 17% 10% 9% 7% 4 6% 7% 12%	1386
January	1st to 10th	Night	4 13% 5% 17% 12% 12% 11% 6% 5% 5% 10%	5513
	11th to 20th	Night	3 13% 7% 15% 9% 7% 5% 5% 9% 12% 14%	5039
	21st to end	Night	8% 21% 7% 18% 8% 7% 7% 4 5% 5% 11%	5535
February	1st to 10th	Night	3 14% 5% 15% 10% 7% 7% 5% 7% 8% 19%	2812
	11th to 20th	Night	3 14% 5% 13% 9% 7% 8% 5% 8% 8% 20%	2587
	21st to end	Night	2 12% 5% 13% 10% 7% 6% 5% 6% 9% 24%	2065
March	1st to 10th	Night	1 11% 5% 13% 8% 10% 9% 7% 6% 8% 22%	3768
	11th to 20th	Night	3 19% 8% 16% 7% 7% 7% 5% 5% 6% 18%	3682
	21st to end	Night	2 11% 6% 17% 9% 7% 7% 5% 7% 7% 22%	3493
April	1st to 10th	Night	3 12% 5% 13% 7% 6% 7% 4 7% 8% 27%	1895
	11th to 20th	Night	4 13% 4 10% 9% 6% 6% 5% 7% 8% 29%	1504
	21st to end	Night	5% 13% 4 10% 6% 6% 6% 5% 6% 8% 31%	1520
May	1st to 10th	Night	3 12% 3 9% 5% 5% 6% 6% 8% 9% 34%	2051
	11th to 20th	Night	5% 12% 5% 13% 8% 7% 7% 5% 7% 7% 25%	1882
	21st to end	Night	6% 8% 4 9% 8% 6% 6% 5% 6% 9% 33%	1942
June	1st to 10th	Night	14% 6% 4 10% 7% 6% 5% 4 6% 7% 31%	774
	11th to 20th	Night	12% 11% 3 10% 8% 5% 6% 5% 8% 9% 24%	760
	21st to end	Night	7% 7% 3 9% 7% 7% 8% 6% 11% 10% 27%	760
July	1st to 10th	Night	7% 4 2 6% 6% 5% 6% 8% 9% 11% 38%	1278
	11th to 20th	Night	14% 8% 4 10% 6% 7% 6% 5% 6% 8% 25%	1733
	21st to end	Night	13% 8% 3 10% 7% 7% 6% 5% 8% 6% 27%	2066
August	1st to 10th	Night	6% 5% 2 6% 4 4 5% 3 7% 8% 50%	2003
	11th to 20th	Night	10% 5% 2 7% 5% 5% 6% 4 8% 10% 38%	2489
	21st to end	Night	18% 14% 4 7% 5% 5% 5% 4 6% 6% 26%	2794
September	1st to 10th	Night	12% 12% 4 10% 6% 6% 6% 5% 8% 6% 25%	1870
	11th to 20th	Night	11% 9% 4 8% 7% 5% 6% 4 6% 8% 32%	1900
	21st to end	Night	15% 15% 5% 10% 6% 7% 6% 5% 5% 6% 20%	2151
October	1st to 10th	Night	12% 16% 5% 10% 6% 7% 6% 4 6% 7% 21%	2280
	11th to 20th	Night	11% 20% 7% 11% 7% 6% 5% 4 5% 5% 18%	2470
	21st to end	Night	8% 16% 7% 14% 9% 7% 6% 5% 6% 5% 17%	2911
November	1st to 10th	Night	6% 18% 7% 17% 11% 7% 6% 4 6% 7% 12%	2791
	11th to 20th	Night	4 19% 8% 20% 11% 8% 5% 4 6% 6% 8%	2987
	21st to end	Night	4 18% 7% 17% 10% 8% 7% 5% 6% 7% 11%	3104
December	1st to 10th	Night	6% 14% 6% 17% 11% 8% 7% 5% 7% 7% 11%	3230
	11th to 20th	Night	4 14% 7% 18% 10% 8% 7% 5% 6% 8% 14%	4225
	21st to end	Night	4 21% 6% 15% 8% 7% 7% 5% 6% 7% 15%	6270

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	69% 13% 7% 6% 3 1	1460
	11th to 20th	Day	62% 8% 11% 8% 10% 2	1875
	21st to end	Day	73% 7% 9% 9% 2	2122
February	1st to 10th	Day	62% 8% 9% 10% 9% 2	1368
	11th to 20th	Day	61% 10% 12% 9% 8% 1	1488
	21st to end	Day	60% 9% 12% 13% 5% 1	1386
March	1st to 10th	Day	62% 7% 12% 10% 7% 1	3096
	11th to 20th	Day	61% 10% 16% 10% 3	3280
	21st to end	Day	59% 12% 14% 10% 4	4149
April	1st to 10th	Day	57% 11% 17% 12% 4	2285
	11th to 20th	Day	56% 8% 16% 13% 5% 1	2622
	21st to end	Day	54% 10% 16% 14% 5%	2660
May	1st to 10th	Day	50% 10% 18% 20% 2	4908
	11th to 20th	Day	54% 10% 17% 16% 4	5016
	21st to end	Day	44% 8% 23% 19% 6%	5633
June	1st to 10th	Day	51% 10% 22% 14% 3	3404
	11th to 20th	Day	52% 11% 23% 13% 2	3420
	21st to end	Day	47% 13% 23% 15% 2	3420
July	1st to 10th	Day	39% 10% 30% 18% 3	5592
	11th to 20th	Day	57% 12% 17% 14% 1	5133
	21st to end	Day	45% 10% 24% 19% 3	5313
August	1st to 10th	Day	31% 10% 20% 25% 14% 1	4909
	11th to 20th	Day	46% 8% 19% 19% 7%	4391
	21st to end	Day	58% 10% 14% 16% 2	4872
September	1st to 10th	Day	62% 10% 14% 13% 2	2309
	11th to 20th	Day	53% 11% 17% 16% 3	2280
	21st to end	Day	67% 9% 14% 9% 2	2027
October	1st to 10th	Day	63% 11% 14% 10% 2	1900
	11th to 20th	Day	64% 11% 16% 7% 2	1710
	21st to end	Day	65% 10% 14% 9% 2	1686
November	1st to 10th	Day	69% 11% 12% 6% 1	1309
	11th to 20th	Day	75% 7% 9% 6% 2	1192
	21st to end	Day	67% 10% 12% 8% 3	1055
December	1st to 10th	Day	66% 13% 13% 7% 1	950
	11th to 20th	Day	56% 11% 10% 18% 5%	969
	21st to end	Day	65% 8% 13% 9% 4	1386
January	1st to 10th	Night	70% 14% 8% 5% 3	5513
	11th to 20th	Night	58% 7% 9% 11% 9% 5%	5083
	21st to end	Night	72% 8% 10% 7% 2	5535
February	1st to 10th	Night	60% 10% 9% 10% 9% 1	2812
	11th to 20th	Night	58% 10% 12% 11% 7% 1	2590
	21st to end	Night	54% 9% 14% 16% 6% 1	2065
March	1st to 10th	Night	56% 5% 13% 17% 8% 1	3768
	11th to 20th	Night	61% 10% 12% 13% 5%	3684
	21st to end	Night	54% 11% 21% 11% 3	3493
April	1st to 10th	Night	52% 9% 17% 17% 5%	1895
	11th to 20th	Night	50% 9% 17% 17% 7% 1	1504
	21st to end	Night	50% 9% 16% 18% 6%	1520
May	1st to 10th	Night	39% 10% 24% 24% 3	2051
	11th to 20th	Night	48% 10% 19% 16% 6% 1	1882
	21st to end	Night	40% 8% 22% 22% 7%	1942
June	1st to 10th	Night	48% 9% 22% 17% 3	774
	11th to 20th	Night	50% 10% 28% 10% 2	760
	21st to end	Night	44% 14% 26% 15% 1	760
July	1st to 10th	Night	34% 12% 33% 18% 3	1258
	11th to 20th	Night	54% 12% 17% 15% 2	1703
	21st to end	Night	52% 13% 22% 12% 1	2000
August	1st to 10th	Night	30% 11% 23% 22% 13%	1997
	11th to 20th	Night	39% 10% 28% 17% 6%	2513
	21st to end	Night	57% 9% 16% 16% 1	2794
September	1st to 10th	Night	56% 12% 19% 12% 1	1870
	11th to 20th	Night	48% 11% 20% 18% 3	1900
	21st to end	Night	61% 8% 15% 13% 3	2151
October	1st to 10th	Night	61% 9% 15% 13% 2	2280
	11th to 20th	Night	66% 9% 15% 8% 2	2470
	21st to end	Night	62% 11% 17% 9% 1	2911
November	1st to 10th	Night	70% 9% 13% 6% 2	2791
	11th to 20th	Night	74% 10% 9% 6% 2	2987
	21st to end	Night	70% 9% 11% 8% 1	3104
December	1st to 10th	Night	68% 12% 10% 8% 2	3230
	11th to 20th	Night	65% 8% 11% 11% 4	4222
	21st to end	Night	63% 8% 11% 10% 7% 2	6270

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	4 7% 32% 28% 19% 10%	90
	11th to 20th	Day	17% 7% 21% 27% 22% 7%	175
	21st to end	Day	16% 15% 27% 23% 16% 4	217
February	1st to 10th	Day	11% 8% 31% 31% 14% 5%	370
	11th to 20th	Day	8% 13% 32% 28% 12% 6%	365
	21st to end	Day	7% 12% 37% 26% 13% 5%	307
March	1st to 10th	Day	7% 12% 31% 31% 13% 5%	370
	11th to 20th	Day	10% 15% 35% 25% 12% 2	370
	21st to end	Day	8% 18% 29% 24% 19% 3	500
April	1st to 10th	Day	9% 15% 34% 28% 12% 2	460
	11th to 20th	Day	8% 17% 24% 30% 19% 3	636
	21st to end	Day	10% 14% 30% 28% 15% 3	650
May	1st to 10th	Day	15% 14% 28% 28% 11% 3	653
	11th to 20th	Day	12% 12% 29% 25% 15% 7%	675
	21st to end	Day	12% 11% 29% 26% 18% 4	806
June	1st to 10th	Day	16% 10% 26% 29% 16% 4	870
	11th to 20th	Day	16% 10% 27% 27% 16% 3	870
	21st to end	Day	11% 10% 25% 28% 22% 4	870
July	1st to 10th	Day	13% 9% 24% 30% 19% 5%	850
	11th to 20th	Day	19% 13% 24% 27% 14% 3	668
	21st to end	Day	16% 12% 25% 27% 17% 4	739
August	1st to 10th	Day	15% 12% 28% 27% 14% 5%	676
	11th to 20th	Day	26% 20% 24% 20% 8% 2	665
	21st to end	Day	27% 14% 26% 23% 9% 1	748
September	1st to 10th	Day	28% 18% 22% 18% 11% 3	500
	11th to 20th	Day	22% 15% 25% 23% 12% 3	490
	21st to end	Day	25% 21% 27% 17% 7% 2	453
October	1st to 10th	Day	24% 19% 31% 17% 7% 2	390
	11th to 20th	Day	23% 18% 31% 18% 7% 3	390
	21st to end	Day	15% 14% 28% 27% 13% 3	429
November	1st to 10th	Day	15% 18% 28% 26% 9% 4	182
	11th to 20th	Day	16% 9% 29% 27% 15% 4	180
	21st to end	Day	8% 17% 32% 28% 9% 5%	180
December	1st to 10th	Day	10% 12% 31% 25% 18% 4	180
	11th to 20th	Day	14% 4 24% 28% 19% 11%	93
	21st to end	Day	3 14% 30% 25% 19% 8%	99
January	1st to 10th	Night	10% 5% 28% 34% 20% 3	932
	11th to 20th	Night	13% 11% 32% 29% 13% 3	850
	21st to end	Night	12% 12% 29% 29% 15% 3	935
February	1st to 10th	Night	9% 8% 26% 41% 13% 2	850
	11th to 20th	Night	9% 10% 33% 32% 14% 3	834
	21st to end	Night	6% 7% 34% 35% 15% 3	703
March	1st to 10th	Night	6% 10% 28% 32% 20% 4	769
	11th to 20th	Night	8% 9% 27% 35% 18% 2	696
	21st to end	Night	6% 9% 22% 32% 24% 6%	627
April	1st to 10th	Night	6% 7% 22% 36% 24% 4	570
	11th to 20th	Night	8% 6% 23% 32% 28% 4	563
	21st to end	Night	12% 5% 19% 35% 25% 4	570
May	1st to 10th	Night	8% 6% 21% 32% 28% 4	394
	11th to 20th	Night	11% 6% 22% 34% 25% 2	374
	21st to end	Night	11% 6% 18% 34% 28% 2	411
June	1st to 10th	Night	16% 3 22% 31% 27%	204
	11th to 20th	Night	16% 4 16% 36% 28% 1	190
	21st to end	Night	9% 3 21% 36% 31% 1	190
July	1st to 10th	Night	11% 4 21% 39% 23% 1	185
	11th to 20th	Night	15% 7% 19% 38% 21%	272
	21st to end	Night	12% 6% 25% 34% 22% 2	416
August	1st to 10th	Night	13% 6% 23% 33% 24% 1	436
	11th to 20th	Night	17% 7% 28% 29% 16% 3	564
	21st to end	Night	25% 7% 22% 28% 16% 2	627
September	1st to 10th	Night	19% 9% 26% 29% 16% 1	570
	11th to 20th	Night	16% 10% 23% 28% 19% 4	570
	21st to end	Night	23% 12% 25% 25% 12% 3	755
October	1st to 10th	Night	22% 13% 24% 25% 14% 1	760
	11th to 20th	Night	21% 12% 23% 29% 13% 2	760
	21st to end	Night	15% 8% 31% 30% 14% 2	939
November	1st to 10th	Night	14% 9% 24% 36% 15% 2	835
	11th to 20th	Night	13% 10% 25% 31% 17% 4	850
	21st to end	Night	12% 14% 27% 29% 15% 3	914
December	1st to 10th	Night	12% 10% 28% 32% 17% 3	1040
	11th to 20th	Night	15% 7% 23% 35% 16% 5%	1040
	21st to end	Night	13% 9% 27% 31% 16% 4	1144

Page generated at 2024-10-29 21:22:55. Version ac07

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