Kah-Nee-Ta Resort
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kah-Nee-Ta Resort clear sky chart from 2005-11-06 to 2025-10-04.

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	7% 7% 2 6% 4 4 4 4 5% 6% 49%	135647
	Night	9% 8% 3 7% 5% 4 5% 4 6% 7% 43%	131047
Transparency	Day	33% 7% 12% 22% 18% 9%	130419
	Night	37% 8% 15% 22% 14% 5%	127285
Seeing	Day	11% 12% 23% 27% 20% 7%	15748
	Night	12% 6% 20% 39% 21% 2	24723

By Month

Percentage Cloud Cover SW (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	16% 16% 6% 16% 8% 7% 6% 5% 7% 6% 8%	3639
	11th to 20th	Day	15% 12% 3 8% 5% 6% 7% 5% 5% 6% 28%	3640
	21st to end	Day	11% 11% 3 8% 6% 5% 6% 6% 8% 9% 28%	4232
February	1st to 10th	Day	13% 13% 4 7% 6% 6% 6% 6% 7% 7% 26%	1800
	11th to 20th	Day	10% 11% 4 8% 6% 7% 5% 5% 9% 5% 30%	1755
	21st to end	Day	8% 13% 4 10% 7% 6% 6% 4 7% 7% 28%	1650
March	1st to 10th	Day	8% 9% 3 9% 5% 5% 6% 6% 8% 9% 31%	4535
	11th to 20th	Day	10% 13% 4 8% 6% 5% 5% 3 5% 6% 35%	5000
	21st to end	Day	9% 11% 4 10% 7% 6% 7% 5% 7% 9% 24%	5744
April	1st to 10th	Day	10% 11% 3 8% 7% 5% 6% 5% 6% 8% 31%	2400
	11th to 20th	Day	9% 10% 3 7% 6% 5% 5% 4 6% 6% 40%	2369
	21st to end	Day	7% 7% 2 7% 5% 5% 5% 4 6% 8% 44%	2500
May	1st to 10th	Day	10% 6% 2 5% 4 3 4 3 5% 6% 53%	6320
	11th to 20th	Day	6% 5% 2 5% 4 4 5% 4 6% 7% 52%	6277
	21st to end	Day	6% 5% 2 5% 4 4 4 4 6% 8% 53%	6902
June	1st to 10th	Day	9% 6% 2 5% 5% 4 4 4 6% 8% 47%	2800
	11th to 20th	Day	7% 4 2 5% 4 4 4 3 6% 7% 54%	2800
	21st to end	Day	3 3 1 3 2 3 3 3 4 6% 68%	2800
July	1st to 10th	Day	1 1 1 2 1 1 2 2 3 3 83%	6319
	11th to 20th	Day	1 1 1 1 1 2 1 2 3 86%	6320
	21st to end	Day	2 1 1 2 1 1 2 2 3 5% 80%	6880
August	1st to 10th	Day	2 2 1 3 2 2 2 2 5% 5% 72%	6005
	11th to 20th	Day	2 1 1 3 3 3 3 3 4 6% 72%	5779
	21st to end	Day	4 3 1 3 3 3 3 3 4 7% 66%	5984
September	1st to 10th	Day	2 2 1 3 2 3 3 2 4 5% 74%	2400
	11th to 20th	Day	4 3 2 5% 4 4 4 4 5% 6% 59%	2400
	21st to end	Day	8% 5% 2 5% 3 3 3 3 5% 7% 58%	2143
October	1st to 10th	Day	6% 4 2 4 3 3 4 3 5% 7% 60%	3211
	11th to 20th	Day	6% 5% 2 6% 5% 5% 5% 4 7% 10% 45%	3161
	21st to end	Day	11% 9% 3 8% 6% 6% 6% 4 6% 6% 34%	3264
November	1st to 10th	Day	13% 12% 4 9% 6% 6% 6% 3 6% 8% 27%	1764
	11th to 20th	Day	13% 13% 4 11% 8% 6% 6% 5% 7% 7% 20%	1602
	21st to end	Day	11% 12% 2 10% 7% 5% 5% 5% 7% 8% 29%	1600
December	1st to 10th	Day	9% 8% 4 7% 6% 6% 7% 5% 6% 6% 37%	2620
	11th to 20th	Day	14% 15% 6% 13% 8% 6% 6% 5% 7% 7% 13%	3028
	21st to end	Day	13% 16% 5% 12% 8% 8% 7% 5% 6% 6% 13%	4004
January	1st to 10th	Night	16% 16% 7% 17% 8% 6% 6% 4 5% 6% 10%	6306
	11th to 20th	Night	15% 12% 4 8% 5% 5% 7% 5% 7% 6% 26%	6320
	21st to end	Night	12% 11% 4 9% 5% 5% 5% 5% 8% 7% 28%	6732
February	1st to 10th	Night	11% 13% 4 9% 7% 5% 5% 4 6% 8% 27%	2600
	11th to 20th	Night	10% 12% 3 8% 6% 5% 5% 4 6% 7% 33%	2532
	21st to end	Night	11% 14% 3 8% 6% 6% 6% 4 6% 7% 29%	1980
March	1st to 10th	Night	6% 9% 4 9% 6% 6% 6% 5% 7% 9% 34%	5344
	11th to 20th	Night	9% 10% 3 8% 5% 5% 5% 4 5% 7% 39%	5000
	21st to end	Night	10% 11% 4 10% 7% 6% 7% 5% 8% 10% 23%	5231
April	1st to 10th	Night	10% 9% 3 9% 5% 4 5% 4 7% 8% 37%	2000
	11th to 20th	Night	8% 8% 3 8% 5% 4 5% 4 6% 7% 42%	1979
	21st to end	Night	8% 7% 3 6% 5% 4 5% 4 6% 8% 45%	1896
May	1st to 10th	Night	10% 5% 1 4 2 3 3 2 5% 6% 59%	3640
	11th to 20th	Night	5% 5% 2 5% 4 4 4 4 5% 6% 57%	3616
	21st to end	Night	8% 5% 1 4 3 3 3 3 5% 7% 58%	3972
June	1st to 10th	Night	10% 5% 2 6% 4 4 4 4 5% 6% 50%	1600
	11th to 20th	Night	5% 4 2 6% 3 3 3 3 5% 7% 58%	1600
	21st to end	Night	4 4 1 3 2 3 3 3 4 5% 69%	1600
July	1st to 10th	Night	1 1 1 2 2 2 2 2 3 4 81%	3640
	11th to 20th	Night	1 1 1 2 1 1 2 2 3 86%	3640
	21st to end	Night	2 2 1 2 1 2 2 2 4 6% 79%	3970
August	1st to 10th	Night	2 3 1 3 2 3 3 3 5% 7% 68%	3780
	11th to 20th	Night	2 2 1 3 3 3 3 2 4 6% 72%	4070
	21st to end	Night	3 3 1 3 2 3 3 2 4 6% 69%	5015
September	1st to 10th	Night	2 1 1 3 2 2 2 3 3 5% 76%	2000
	11th to 20th	Night	5% 2 1 4 3 3 4 3 5% 6% 64%	2000
	21st to end	Night	6% 4 1 4 3 3 4 3 5% 7% 61%	2254
October	1st to 10th	Night	5% 4 2 4 2 3 3 3 3 5% 67%	3836
	11th to 20th	Night	7% 6% 2 6% 4 5% 5% 3 6% 8% 48%	3777
	21st to end	Night	9% 7% 2 8% 5% 6% 6% 5% 7% 8% 38%	4299
November	1st to 10th	Night	13% 10% 4 8% 6% 6% 5% 4 5% 8% 31%	2535
	11th to 20th	Night	13% 12% 4 9% 5% 6% 6% 4 7% 7% 26%	2795
	21st to end	Night	10% 10% 3 8% 6% 5% 6% 5% 6% 8% 34%	2800
December	1st to 10th	Night	8% 7% 2 7% 6% 6% 8% 7% 9% 8% 32%	4560
	11th to 20th	Night	16% 16% 5% 13% 9% 7% 7% 4 7% 6% 11%	5176
	21st to end	Night	16% 13% 4 14% 9% 7% 7% 5% 4 5% 15%	6952

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% 12% 13% 8% 2	3639
	11th to 20th	Day	52% 8% 15% 18% 8% 1	3640
	21st to end	Day	45% 10% 12% 19% 10% 3	4232
February	1st to 10th	Day	53% 9% 16% 17% 5% 1	1800
	11th to 20th	Day	47% 12% 15% 18% 7% 1	1764
	21st to end	Day	47% 11% 17% 16% 8%	1650
March	1st to 10th	Day	40% 8% 13% 24% 13% 1	4535
	11th to 20th	Day	46% 6% 13% 24% 11%	5000
	21st to end	Day	50% 12% 15% 17% 5%	5744
April	1st to 10th	Day	46% 10% 16% 18% 9% 1	2400
	11th to 20th	Day	41% 8% 16% 20% 13% 3	2372
	21st to end	Day	34% 8% 17% 26% 12% 2	2500
May	1st to 10th	Day	28% 7% 10% 27% 25% 3	6320
	11th to 20th	Day	29% 7% 14% 27% 20% 3	6280
	21st to end	Day	26% 8% 19% 32% 13% 1	6904
June	1st to 10th	Day	34% 7% 13% 27% 16% 3	2800
	11th to 20th	Day	28% 6% 14% 32% 17% 4	2800
	21st to end	Day	17% 4 13% 32% 24% 9%	2800
July	1st to 10th	Day	9% 2 5% 17% 31% 36%	6251
	11th to 20th	Day	7% 1 5% 10% 29% 48%	6245
	21st to end	Day	10% 2 6% 28% 32% 21%	6681
August	1st to 10th	Day	14% 3 5% 17% 36% 25%	4376
	11th to 20th	Day	15% 3 9% 33% 29% 11%	4178
	21st to end	Day	17% 3 8% 28% 30% 14%	4311
September	1st to 10th	Day	14% 3 8% 26% 31% 17%	2400
	11th to 20th	Day	23% 6% 12% 27% 23% 9%	2400
	21st to end	Day	27% 6% 13% 25% 22% 7%	2143
October	1st to 10th	Day	25% 6% 9% 25% 28% 8%	3211
	11th to 20th	Day	33% 8% 18% 24% 16% 1	3161
	21st to end	Day	45% 7% 12% 23% 11% 2	3264
November	1st to 10th	Day	52% 9% 14% 18% 7% 1	1764
	11th to 20th	Day	57% 11% 15% 13% 4	1602
	21st to end	Day	49% 9% 17% 17% 7%	1600
December	1st to 10th	Day	43% 7% 15% 24% 11%	2620
	11th to 20th	Day	63% 9% 15% 11% 1	3028
	21st to end	Day	63% 9% 15% 10% 2	4004
January	1st to 10th	Night	69% 11% 12% 7% 1	6306
	11th to 20th	Night	49% 10% 17% 17% 7% 1	6320
	21st to end	Night	47% 11% 12% 17% 10% 3	6732
February	1st to 10th	Night	51% 10% 18% 15% 5%	2600
	11th to 20th	Night	45% 10% 19% 20% 6% 1	2534
	21st to end	Night	48% 11% 15% 17% 8% 1	1980
March	1st to 10th	Night	39% 10% 14% 25% 11% 1	5344
	11th to 20th	Night	40% 7% 18% 27% 8%	5000
	21st to end	Night	47% 15% 21% 14% 3	5231
April	1st to 10th	Night	41% 9% 21% 21% 7% 1	2000
	11th to 20th	Night	38% 9% 18% 22% 11% 2	1979
	21st to end	Night	35% 10% 17% 24% 11% 3	1896
May	1st to 10th	Night	25% 7% 10% 27% 30%	3637
	11th to 20th	Night	25% 6% 19% 33% 16% 1	3616
	21st to end	Night	24% 9% 29% 29% 10%	3972
June	1st to 10th	Night	34% 9% 13% 28% 14% 1	1600
	11th to 20th	Night	25% 7% 16% 36% 13% 3	1600
	21st to end	Night	19% 4 13% 33% 23% 8%	1600
July	1st to 10th	Night	10% 2 7% 23% 26% 33%	3600
	11th to 20th	Night	7% 2 6% 13% 27% 45%	3592
	21st to end	Night	9% 2 5% 33% 32% 19%	3857
August	1st to 10th	Night	13% 2 7% 18% 36% 23%	2750
	11th to 20th	Night	12% 3 11% 38% 26% 9%	2947
	21st to end	Night	13% 3 12% 30% 30% 12%	3608
September	1st to 10th	Night	12% 4 10% 29% 31% 15%	2000
	11th to 20th	Night	20% 7% 13% 28% 23% 10%	2000
	21st to end	Night	22% 5% 12% 28% 25% 8%	2254
October	1st to 10th	Night	21% 4 11% 30% 30% 3	3836
	11th to 20th	Night	30% 8% 20% 24% 15% 1	3777
	21st to end	Night	40% 8% 14% 27% 11% 1	4299
November	1st to 10th	Night	47% 10% 13% 20% 9% 1	2535
	11th to 20th	Night	53% 10% 16% 17% 4	2795
	21st to end	Night	44% 10% 18% 21% 7% 1	2800
December	1st to 10th	Night	41% 7% 21% 24% 7%	4560
	11th to 20th	Night	67% 10% 12% 11% 2	5176
	21st to end	Night	60% 14% 13% 9% 4	6952

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	26% 14% 24% 22% 12% 4	200
	11th to 20th	Day	22% 9% 20% 31% 16% 3	200
	21st to end	Day	17% 8% 19% 31% 20% 4	318
February	1st to 10th	Day	21% 15% 21% 28% 13% 3	400
	11th to 20th	Day	17% 16% 25% 26% 14% 2	395
	21st to end	Day	18% 16% 26% 26% 13% 1	414
March	1st to 10th	Day	19% 15% 26% 28% 11% 2	500
	11th to 20th	Day	17% 16% 21% 29% 14% 4	500
	21st to end	Day	17% 16% 27% 27% 11% 1	550
April	1st to 10th	Day	20% 17% 23% 22% 13% 5%	500
	11th to 20th	Day	15% 16% 29% 21% 12% 6%	492
	21st to end	Day	9% 20% 25% 24% 16% 5%	500
May	1st to 10th	Day	12% 16% 24% 26% 15% 7%	503
	11th to 20th	Day	15% 14% 24% 24% 15% 8%	528
	21st to end	Day	12% 11% 20% 27% 21% 8%	573
June	1st to 10th	Day	10% 15% 22% 25% 20% 9%	530
	11th to 20th	Day	9% 18% 26% 28% 14% 4	530
	21st to end	Day	5% 11% 21% 31% 25% 8%	530
July	1st to 10th	Day	2 8% 25% 32% 25% 7%	526
	11th to 20th	Day	1 9% 23% 28% 29% 10%	524
	21st to end	Day	2 5% 24% 29% 26% 15%	575
August	1st to 10th	Day	3 6% 19% 31% 24% 16%	527
	11th to 20th	Day	1 6% 18% 28% 28% 19%	517
	21st to end	Day	5% 7% 21% 27% 27% 14%	583
September	1st to 10th	Day	3 4 21% 29% 28% 15%	530
	11th to 20th	Day	6% 7% 20% 27% 31% 10%	530
	21st to end	Day	10% 9% 19% 30% 25% 9%	530
October	1st to 10th	Day	10% 10% 21% 27% 22% 9%	503
	11th to 20th	Day	13% 10% 18% 26% 25% 8%	490
	21st to end	Day	16% 14% 23% 23% 18% 6%	430
November	1st to 10th	Day	18% 12% 23% 30% 15% 3	300
	11th to 20th	Day	16% 11% 26% 22% 22% 5%	200
	21st to end	Day	16% 10% 23% 32% 17% 3	200
December	1st to 10th	Day	10% 12% 22% 27% 21% 10%	200
	11th to 20th	Day	20% 13% 27% 31% 10% 1	200
	21st to end	Day	18% 16% 24% 26% 15% 2	220
January	1st to 10th	Night	20% 8% 24% 33% 13% 3	800
	11th to 20th	Night	17% 8% 21% 31% 20% 2	800
	21st to end	Night	17% 6% 18% 38% 20% 2	880
February	1st to 10th	Night	17% 7% 26% 34% 15% 1	800
	11th to 20th	Night	15% 7% 27% 35% 16% 1	784
	21st to end	Night	21% 8% 24% 35% 12%	660
March	1st to 10th	Night	15% 9% 25% 36% 14% 1	800
	11th to 20th	Night	12% 10% 20% 41% 17% 1	800
	21st to end	Night	11% 10% 28% 35% 16%	880
April	1st to 10th	Night	15% 8% 24% 32% 20% 1	800
	11th to 20th	Night	11% 8% 26% 35% 16% 3	791
	21st to end	Night	12% 7% 24% 36% 20% 1	696
May	1st to 10th	Night	8% 6% 23% 41% 20% 2	400
	11th to 20th	Night	7% 5% 19% 44% 24% 1	394
	21st to end	Night	5% 6% 18% 43% 26% 2	433
June	1st to 10th	Night	13% 4 15% 46% 21% 1	400
	11th to 20th	Night	7% 6% 25% 46% 16% 1	400
	21st to end	Night	8% 1 19% 46% 26% 1	400
July	1st to 10th	Night	2 1 15% 55% 27% 1	390
	11th to 20th	Night	1 15% 60% 21% 2	388
	21st to end	Night	2 1 11% 49% 35% 2	438
August	1st to 10th	Night	2 1 10% 46% 36% 5%	482
	11th to 20th	Night	2 1 7% 37% 44% 9%	599
	21st to end	Night	3 3 18% 42% 30% 4	880
September	1st to 10th	Night	2 2 16% 43% 34% 4	800
	11th to 20th	Night	5% 2 13% 41% 34% 6%	800
	21st to end	Night	7% 5% 13% 39% 32% 5%	800
October	1st to 10th	Night	9% 3 16% 42% 25% 4	772
	11th to 20th	Night	10% 4 19% 38% 26% 4	760
	21st to end	Night	14% 5% 22% 37% 17% 4	836
November	1st to 10th	Night	13% 8% 22% 41% 16% 1	780
	11th to 20th	Night	18% 11% 21% 34% 15% 1	800
	21st to end	Night	14% 7% 20% 39% 18% 2	800
December	1st to 10th	Night	16% 7% 19% 36% 19% 3	800
	11th to 20th	Night	17% 8% 22% 37% 16% 1	800
	21st to end	Night	19% 9% 28% 33% 10% 1	880

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