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 2026-09-29.

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% 11% 4 11% 7% 7% 6% 5% 7% 8% 26%	155694
	Night	6% 13% 5% 14% 8% 7% 7% 5% 7% 7% 20%	144362
Transparency	Day	53% 10% 17% 15% 5%	155346
	Night	58% 9% 15% 13% 5%	144294
Seeing	Day	15% 14% 28% 25% 14% 4	19764
	Night	13% 9% 26% 31% 18% 3	25793

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	2 12% 6% 17% 12% 10% 9% 7% 6% 7% 11%	2728
	11th to 20th	Day	4 15% 6% 14% 9% 8% 7% 7% 7% 9% 15%	3497
	21st to end	Day	4 17% 5% 16% 6% 7% 6% 5% 8% 11% 15%	3932
February	1st to 10th	Day	3 13% 5% 15% 9% 10% 8% 5% 7% 6% 19%	1513
	11th to 20th	Day	3 12% 7% 14% 9% 9% 7% 5% 7% 8% 20%	1640
	21st to end	Day	2 11% 6% 16% 10% 8% 8% 5% 6% 8% 19%	1528
March	1st to 10th	Day	2 9% 4 15% 12% 12% 9% 5% 6% 7% 20%	4551
	11th to 20th	Day	2 12% 6% 17% 13% 9% 6% 6% 7% 7% 15%	4792
	21st to end	Day	1 9% 5% 16% 10% 7% 8% 6% 8% 8% 23%	6070
April	1st to 10th	Day	3 12% 6% 14% 8% 7% 7% 5% 7% 8% 23%	2525
	11th to 20th	Day	3 13% 7% 12% 8% 7% 6% 4 7% 8% 25%	2902
	21st to end	Day	4 16% 5% 10% 7% 6% 7% 5% 6% 7% 27%	2940
May	1st to 10th	Day	7% 14% 4 9% 6% 6% 6% 5% 8% 8% 27%	9087
	11th to 20th	Day	7% 14% 5% 10% 7% 7% 7% 5% 7% 7% 25%	9352
	21st to end	Day	4 8% 3 9% 7% 8% 7% 5% 7% 8% 33%	10540
June	1st to 10th	Day	10% 11% 3 8% 6% 6% 6% 6% 6% 7% 30%	3762
	11th to 20th	Day	11% 10% 3 10% 7% 6% 6% 5% 7% 9% 25%	3780
	21st to end	Day	8% 7% 3 9% 7% 7% 7% 5% 8% 9% 31%	3780
July	1st to 10th	Day	10% 8% 3 10% 6% 6% 6% 5% 7% 9% 30%	10587
	11th to 20th	Day	9% 7% 3 9% 6% 6% 6% 5% 8% 9% 33%	9726
	21st to end	Day	12% 8% 3 8% 6% 6% 6% 5% 7% 10% 30%	10218
August	1st to 10th	Day	7% 5% 2 5% 5% 4 5% 5% 7% 9% 46%	7226
	11th to 20th	Day	11% 7% 2 7% 5% 5% 5% 4 6% 8% 40%	6410
	21st to end	Day	18% 12% 3 9% 6% 6% 6% 4 6% 7% 24%	7082
September	1st to 10th	Day	17% 12% 5% 9% 6% 6% 5% 5% 5% 7% 24%	2552
	11th to 20th	Day	14% 11% 4 9% 5% 5% 6% 4 7% 7% 28%	2520
	21st to end	Day	16% 17% 5% 12% 6% 5% 6% 4 6% 5% 18%	2220
October	1st to 10th	Day	10% 21% 6% 14% 7% 7% 5% 4 5% 6% 16%	3270
	11th to 20th	Day	9% 19% 6% 11% 7% 6% 6% 5% 8% 7% 17%	2933
	21st to end	Day	11% 18% 6% 13% 9% 7% 6% 4 6% 6% 14%	2857
November	1st to 10th	Day	8% 19% 6% 16% 11% 8% 7% 3 5% 6% 11%	1442
	11th to 20th	Day	5% 22% 9% 22% 10% 6% 5% 3 4 5% 9%	1316
	21st to end	Day	6% 16% 7% 16% 9% 8% 7% 6% 7% 7% 12%	1165
December	1st to 10th	Day	9% 19% 7% 14% 9% 6% 8% 5% 7% 6% 10%	1680
	11th to 20th	Day	2 11% 6% 18% 11% 10% 8% 5% 7% 8% 13%	1547
	21st to end	Day	4 15% 8% 23% 11% 9% 6% 4 5% 6% 9%	2024
January	1st to 10th	Night	3 13% 7% 21% 12% 9% 9% 5% 5% 6% 10%	10221
	11th to 20th	Night	3 14% 6% 13% 9% 8% 7% 7% 9% 10% 14%	9399
	21st to end	Night	6% 14% 5% 15% 8% 8% 8% 6% 8% 9% 13%	10251
February	1st to 10th	Night	3 14% 5% 15% 10% 8% 7% 5% 7% 7% 18%	3107
	11th to 20th	Night	3 13% 5% 13% 9% 7% 8% 5% 8% 8% 20%	2867
	21st to end	Night	2 13% 5% 13% 11% 8% 7% 5% 6% 8% 22%	2275
March	1st to 10th	Night	2 10% 4 17% 9% 9% 10% 8% 7% 7% 18%	5543
	11th to 20th	Night	2 14% 7% 17% 11% 9% 7% 5% 6% 7% 16%	5383
	21st to end	Night	2 11% 6% 16% 8% 7% 8% 6% 9% 8% 20%	5124
April	1st to 10th	Night	3 11% 5% 13% 7% 7% 7% 4 7% 9% 27%	2095
	11th to 20th	Night	4 13% 4 10% 8% 6% 6% 5% 7% 8% 28%	1664
	21st to end	Night	5% 13% 4 9% 6% 6% 6% 5% 6% 8% 32%	1680
May	1st to 10th	Night	3 12% 4 8% 5% 5% 6% 6% 8% 9% 33%	3819
	11th to 20th	Night	4 12% 5% 12% 7% 6% 6% 5% 7% 7% 28%	3510
	21st to end	Night	3 6% 3 8% 7% 7% 7% 6% 8% 8% 36%	3630
June	1st to 10th	Night	13% 6% 4 10% 7% 5% 5% 4 7% 8% 31%	856
	11th to 20th	Night	11% 10% 2 10% 8% 5% 7% 5% 8% 8% 25%	840
	21st to end	Night	7% 6% 3 9% 7% 6% 8% 6% 10% 10% 28%	840
July	1st to 10th	Night	9% 6% 3 8% 7% 6% 6% 7% 8% 9% 33%	2358
	11th to 20th	Night	9% 6% 3 7% 5% 6% 5% 4 6% 9% 39%	3233
	21st to end	Night	15% 8% 3 9% 6% 6% 6% 5% 8% 7% 29%	3850
August	1st to 10th	Night	8% 4 1 6% 4 4 5% 3 6% 8% 50%	2928
	11th to 20th	Night	9% 5% 2 6% 5% 5% 6% 4 7% 10% 42%	3655
	21st to end	Night	17% 12% 4 8% 5% 5% 5% 4 6% 6% 28%	4066
September	1st to 10th	Night	12% 11% 4 10% 6% 6% 6% 5% 8% 7% 26%	2067
	11th to 20th	Night	12% 9% 4 8% 7% 5% 6% 4 6% 8% 32%	2100
	21st to end	Night	14% 15% 5% 10% 6% 7% 6% 5% 5% 6% 20%	2354
October	1st to 10th	Night	10% 16% 5% 11% 8% 8% 7% 5% 6% 7% 18%	3920
	11th to 20th	Night	9% 21% 7% 12% 7% 6% 6% 4 5% 5% 17%	4215
	21st to end	Night	9% 15% 6% 13% 7% 6% 7% 5% 7% 6% 17%	4943
November	1st to 10th	Night	6% 18% 7% 16% 11% 7% 6% 4 6% 6% 12%	3076
	11th to 20th	Night	4 20% 8% 21% 11% 8% 5% 4 6% 6% 8%	3302
	21st to end	Night	4 17% 7% 18% 11% 8% 7% 5% 7% 7% 11%	3432
December	1st to 10th	Night	9% 17% 7% 16% 8% 7% 7% 5% 7% 7% 11%	5720
	11th to 20th	Night	3 12% 7% 20% 14% 8% 7% 4 6% 7% 11%	6865
	21st to end	Night	3 18% 8% 22% 10% 7% 6% 4 5% 5% 11%	9174

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	65% 11% 8% 5% 10% 1	2728
	11th to 20th	Day	59% 9% 14% 7% 10% 1	3515
	21st to end	Day	58% 9% 13% 12% 7%	3933
February	1st to 10th	Day	62% 8% 9% 9% 10% 2	1513
	11th to 20th	Day	61% 9% 12% 9% 8% 1	1648
	21st to end	Day	61% 9% 12% 13% 5% 1	1528
March	1st to 10th	Day	59% 8% 14% 9% 9% 1	4551
	11th to 20th	Day	63% 8% 16% 8% 5%	4792
	21st to end	Day	53% 12% 16% 14% 5%	6070
April	1st to 10th	Day	56% 11% 17% 12% 4	2525
	11th to 20th	Day	56% 8% 16% 14% 5% 1	2902
	21st to end	Day	53% 10% 17% 15% 4	2940
May	1st to 10th	Day	49% 11% 18% 19% 3	9087
	11th to 20th	Day	54% 8% 14% 21% 3	9355
	21st to end	Day	44% 8% 17% 20% 10%	10541
June	1st to 10th	Day	49% 9% 21% 16% 4	3762
	11th to 20th	Day	52% 10% 22% 14% 2	3780
	21st to end	Day	46% 13% 23% 16% 3	3780
July	1st to 10th	Day	49% 9% 21% 17% 5%	10498
	11th to 20th	Day	44% 11% 24% 20% 1	9633
	21st to end	Day	47% 12% 23% 16% 2	9997
August	1st to 10th	Day	32% 10% 20% 26% 11%	7207
	11th to 20th	Day	41% 9% 25% 20% 6%	6452
	21st to end	Day	58% 9% 14% 16% 3	7081
September	1st to 10th	Day	58% 10% 15% 15% 2	2552
	11th to 20th	Day	53% 10% 17% 16% 3	2520
	21st to end	Day	67% 9% 13% 9% 2	2220
October	1st to 10th	Day	68% 9% 11% 10% 1	3270
	11th to 20th	Day	63% 9% 15% 12% 2	2933
	21st to end	Day	65% 11% 14% 8% 2	2857
November	1st to 10th	Day	69% 11% 12% 7% 1	1442
	11th to 20th	Day	76% 7% 9% 6% 2	1316
	21st to end	Day	67% 10% 11% 8% 3	1165
December	1st to 10th	Day	67% 15% 11% 5% 2	1680
	11th to 20th	Day	62% 8% 12% 13% 4	1549
	21st to end	Day	72% 7% 10% 7% 3	2024
January	1st to 10th	Night	71% 10% 7% 4 8%	10222
	11th to 20th	Night	57% 9% 13% 11% 9% 3	9443
	21st to end	Night	60% 8% 13% 13% 5%	10251
February	1st to 10th	Night	60% 10% 9% 10% 9% 1	3107
	11th to 20th	Night	58% 10% 12% 11% 8% 1	2870
	21st to end	Night	56% 8% 14% 15% 6% 1	2275
March	1st to 10th	Night	58% 6% 14% 14% 8% 1	5543
	11th to 20th	Night	62% 8% 11% 11% 7%	5385
	21st to end	Night	52% 10% 18% 13% 7%	5124
April	1st to 10th	Night	52% 9% 17% 17% 5%	2095
	11th to 20th	Night	50% 9% 17% 17% 6% 1	1664
	21st to end	Night	48% 10% 16% 19% 6%	1680
May	1st to 10th	Night	40% 9% 24% 21% 6%	3816
	11th to 20th	Night	48% 9% 17% 20% 6%	3510
	21st to end	Night	38% 7% 16% 29% 9%	3634
June	1st to 10th	Night	47% 9% 22% 19% 3	856
	11th to 20th	Night	51% 10% 26% 12% 1	840
	21st to end	Night	43% 13% 26% 17% 1	840
July	1st to 10th	Night	43% 10% 23% 20% 3	2338
	11th to 20th	Night	39% 11% 29% 19% 1	3203
	21st to end	Night	50% 13% 24% 12% 2	3766
August	1st to 10th	Night	32% 9% 24% 24% 10%	2922
	11th to 20th	Night	36% 9% 32% 18% 4	3679
	21st to end	Night	54% 9% 16% 18% 3	4066
September	1st to 10th	Night	54% 12% 19% 13% 2	2067
	11th to 20th	Night	48% 11% 20% 19% 3	2100
	21st to end	Night	61% 8% 14% 13% 3	2354
October	1st to 10th	Night	60% 8% 15% 14% 3	3920
	11th to 20th	Night	65% 8% 13% 11% 3	4215
	21st to end	Night	59% 11% 19% 10% 2	4943
November	1st to 10th	Night	69% 9% 13% 7% 2	3076
	11th to 20th	Night	75% 9% 9% 6% 2	3302
	21st to end	Night	69% 9% 11% 8% 2	3432
December	1st to 10th	Night	67% 12% 9% 10% 2	5720
	11th to 20th	Night	69% 7% 11% 10% 3	6862
	21st to end	Night	71% 7% 9% 8% 5% 1	9174

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	5% 11% 30% 26% 17% 11%	110
	11th to 20th	Day	20% 9% 20% 27% 18% 6%	215
	21st to end	Day	15% 14% 28% 24% 14% 5%	263
February	1st to 10th	Day	11% 9% 31% 30% 15% 4	430
	11th to 20th	Day	8% 14% 31% 28% 13% 6%	425
	21st to end	Day	7% 13% 37% 26% 12% 4	355
March	1st to 10th	Day	8% 13% 30% 32% 13% 5%	430
	11th to 20th	Day	10% 15% 34% 24% 13% 4	430
	21st to end	Day	7% 16% 27% 24% 20% 5%	586
April	1st to 10th	Day	9% 14% 34% 27% 13% 2	540
	11th to 20th	Day	9% 19% 24% 28% 17% 3	736
	21st to end	Day	11% 17% 29% 27% 14% 3	750
May	1st to 10th	Day	18% 16% 28% 26% 10% 2	753
	11th to 20th	Day	13% 13% 29% 25% 14% 6%	775
	21st to end	Day	12% 13% 30% 25% 16% 4	924
June	1st to 10th	Day	16% 11% 26% 28% 15% 3	990
	11th to 20th	Day	15% 11% 27% 27% 17% 3	990
	21st to end	Day	11% 10% 25% 28% 22% 4	990
July	1st to 10th	Day	13% 11% 25% 30% 17% 4	969
	11th to 20th	Day	17% 14% 24% 26% 15% 4	768
	21st to end	Day	15% 12% 26% 27% 16% 4	849
August	1st to 10th	Day	14% 12% 28% 27% 14% 4	776
	11th to 20th	Day	25% 20% 24% 21% 8% 3	765
	21st to end	Day	25% 15% 27% 23% 9% 1	858
September	1st to 10th	Day	26% 18% 23% 19% 12% 3	581
	11th to 20th	Day	24% 16% 24% 21% 12% 2	570
	21st to end	Day	26% 21% 27% 17% 7% 3	520
October	1st to 10th	Day	25% 19% 30% 16% 7% 2	420
	11th to 20th	Day	24% 18% 31% 17% 7% 3	420
	21st to end	Day	15% 15% 28% 26% 13% 3	462
November	1st to 10th	Day	17% 18% 28% 24% 9% 3	220
	11th to 20th	Day	14% 11% 30% 26% 14% 5%	220
	21st to end	Day	7% 15% 29% 30% 14% 5%	220
December	1st to 10th	Day	12% 15% 30% 23% 16% 5%	220
	11th to 20th	Day	12% 4 25% 30% 19% 11%	113
	21st to end	Day	4 12% 31% 26% 20% 7%	121
January	1st to 10th	Night	10% 6% 28% 33% 21% 3	1040
	11th to 20th	Night	15% 12% 31% 29% 12% 2	950
	21st to end	Night	12% 12% 29% 28% 16% 3	1045
February	1st to 10th	Night	9% 9% 27% 40% 14% 2	950
	11th to 20th	Night	9% 10% 31% 32% 15% 3	934
	21st to end	Night	6% 9% 33% 35% 14% 3	783
March	1st to 10th	Night	6% 10% 28% 32% 20% 4	851
	11th to 20th	Night	8% 9% 27% 34% 19% 4	769
	21st to end	Night	6% 8% 21% 32% 26% 7%	693
April	1st to 10th	Night	6% 7% 23% 36% 24% 3	630
	11th to 20th	Night	9% 7% 24% 30% 26% 3	623
	21st to end	Night	12% 6% 21% 34% 23% 3	630
May	1st to 10th	Night	9% 9% 22% 32% 25% 4	436
	11th to 20th	Night	11% 7% 22% 34% 24% 2	414
	21st to end	Night	11% 7% 21% 33% 26% 2	455
June	1st to 10th	Night	15% 4 24% 31% 26%	226
	11th to 20th	Night	16% 3 16% 36% 28% 1	210
	21st to end	Night	9% 3 20% 38% 30%	210
July	1st to 10th	Night	11% 5% 23% 39% 21% 1	205
	11th to 20th	Night	15% 7% 21% 36% 21%	302
	21st to end	Night	12% 7% 25% 35% 21% 2	460
August	1st to 10th	Night	13% 6% 23% 33% 23% 1	482
	11th to 20th	Night	17% 8% 26% 27% 18% 3	624
	21st to end	Night	24% 7% 22% 29% 16% 2	693
September	1st to 10th	Night	19% 9% 26% 29% 16% 1	630
	11th to 20th	Night	17% 11% 23% 27% 19% 3	630
	21st to end	Night	24% 13% 24% 25% 13% 2	827
October	1st to 10th	Night	21% 14% 24% 25% 14% 1	800
	11th to 20th	Night	22% 13% 22% 28% 12% 2	800
	21st to end	Night	15% 9% 30% 29% 15% 2	993
November	1st to 10th	Night	15% 10% 25% 34% 14% 2	930
	11th to 20th	Night	12% 11% 25% 31% 18% 4	950
	21st to end	Night	11% 13% 27% 30% 16% 3	1022
December	1st to 10th	Night	13% 11% 29% 30% 16% 2	1160
	11th to 20th	Night	13% 7% 23% 34% 18% 5%	1160
	21st to end	Night	12% 9% 27% 31% 16% 4	1276

Page generated at 2026-09-26 00:18:42. Version ac07

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