Nakusp
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Nakusp clear sky chart from 2005-11-06 to 2025-07-21.

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	10% 11% 4 9% 6% 6% 6% 4 6% 7% 31%	124169
	Night	11% 15% 5% 11% 6% 5% 5% 4 5% 6% 27%	123628
Transparency	Day	52% 9% 15% 17% 7% 1	123929
	Night	57% 9% 14% 14% 5% 1	123511
Seeing	Day	19% 16% 29% 25% 9% 1	16161
	Night	22% 11% 30% 28% 9%	24884

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	10% 26% 9% 18% 9% 7% 5% 3 3 3 7%	3386
	11th to 20th	Day	8% 19% 5% 10% 5% 6% 7% 6% 7% 8% 18%	3616
	21st to end	Day	9% 17% 7% 14% 8% 6% 6% 4 5% 5% 19%	4004
February	1st to 10th	Day	12% 21% 5% 13% 9% 7% 5% 3 6% 5% 15%	1600
	11th to 20th	Day	8% 19% 7% 15% 8% 5% 5% 4 5% 5% 20%	1750
	21st to end	Day	6% 20% 6% 13% 9% 5% 6% 5% 6% 7% 17%	1650
March	1st to 10th	Day	5% 15% 5% 12% 8% 7% 7% 6% 8% 6% 20%	4518
	11th to 20th	Day	5% 11% 5% 10% 6% 7% 7% 5% 6% 8% 30%	4643
	21st to end	Day	8% 17% 6% 12% 7% 7% 7% 4 7% 7% 19%	5969
April	1st to 10th	Day	9% 16% 5% 13% 7% 6% 6% 4 6% 8% 20%	2400
	11th to 20th	Day	10% 12% 6% 10% 7% 6% 7% 5% 7% 7% 24%	2468
	21st to end	Day	12% 13% 5% 10% 8% 6% 6% 5% 6% 6% 24%	2659
May	1st to 10th	Day	8% 8% 3 8% 5% 5% 6% 4 6% 7% 40%	6320
	11th to 20th	Day	11% 11% 4 10% 6% 6% 6% 5% 8% 10% 23%	6277
	21st to end	Day	11% 10% 3 9% 6% 5% 6% 4 6% 7% 32%	7359
June	1st to 10th	Day	18% 10% 4 8% 6% 6% 5% 4 5% 7% 28%	3000
	11th to 20th	Day	18% 11% 4 9% 7% 6% 7% 5% 6% 7% 21%	3017
	21st to end	Day	11% 6% 3 8% 7% 6% 6% 5% 6% 7% 36%	3200
July	1st to 10th	Day	6% 3 2 4 4 4 4 4 6% 7% 57%	4932
	11th to 20th	Day	3 2 1 3 3 3 3 3 4 6% 67%	4631
	21st to end	Day	5% 3 1 4 3 4 4 4 6% 9% 58%	4791
August	1st to 10th	Day	3 3 1 4 3 4 4 4 7% 7% 58%	4401
	11th to 20th	Day	6% 4 1 4 3 4 5% 5% 7% 9% 51%	4277
	21st to end	Day	9% 5% 2 6% 4 5% 5% 5% 6% 9% 45%	4320
September	1st to 10th	Day	8% 6% 2 7% 4 5% 6% 4 4 8% 46%	2280
	11th to 20th	Day	11% 8% 3 7% 6% 5% 4 4 5% 8% 38%	2199
	21st to end	Day	14% 9% 3 9% 5% 5% 5% 4 6% 7% 33%	2090
October	1st to 10th	Day	11% 7% 3 9% 5% 6% 7% 4 6% 8% 34%	3283
	11th to 20th	Day	16% 10% 3 9% 7% 6% 5% 4 6% 7% 27%	2943
	21st to end	Day	16% 12% 5% 10% 6% 5% 6% 3 5% 6% 26%	3101
November	1st to 10th	Day	20% 17% 6% 13% 8% 7% 5% 4 4 6% 10%	1740
	11th to 20th	Day	15% 19% 5% 11% 8% 7% 5% 5% 5% 6% 14%	1515
	21st to end	Day	13% 22% 6% 15% 9% 7% 5% 3 5% 5% 10%	1400
December	1st to 10th	Day	14% 14% 4 10% 9% 6% 6% 4 6% 7% 21%	2290
	11th to 20th	Day	12% 21% 8% 16% 7% 7% 5% 4 5% 5% 9%	2642
	21st to end	Day	9% 19% 7% 16% 10% 9% 7% 4 4 5% 10%	3498
January	1st to 10th	Night	13% 33% 9% 15% 7% 5% 4 3 3 3 5%	6600
	11th to 20th	Night	9% 16% 7% 14% 8% 7% 7% 4 6% 7% 14%	6282
	21st to end	Night	12% 22% 7% 14% 7% 5% 4 2 4 4 19%	6952
February	1st to 10th	Night	12% 26% 7% 15% 7% 5% 6% 4 4 5% 9%	2800
	11th to 20th	Night	11% 21% 7% 14% 7% 5% 5% 4 4 4 17%	2536
	21st to end	Night	8% 24% 7% 15% 8% 6% 5% 4 5% 6% 13%	1980
March	1st to 10th	Night	6% 15% 6% 14% 7% 6% 5% 4 6% 7% 24%	5376
	11th to 20th	Night	6% 16% 5% 10% 6% 6% 6% 4 5% 6% 30%	5341
	21st to end	Night	9% 18% 5% 12% 6% 6% 6% 5% 8% 7% 18%	5006
April	1st to 10th	Night	9% 14% 4 11% 6% 5% 6% 5% 7% 7% 26%	2000
	11th to 20th	Night	11% 14% 5% 8% 6% 6% 5% 4 6% 7% 28%	1882
	21st to end	Night	12% 12% 4 8% 5% 5% 4 5% 6% 7% 34%	1739
May	1st to 10th	Night	8% 8% 2 7% 4 5% 5% 4 6% 7% 44%	3640
	11th to 20th	Night	13% 11% 5% 11% 6% 6% 6% 4 5% 7% 26%	3616
	21st to end	Night	12% 9% 3 7% 5% 5% 5% 4 6% 8% 36%	3515
June	1st to 10th	Night	18% 10% 3 7% 4 4 4 5% 6% 6% 33%	1400
	11th to 20th	Night	17% 10% 3 7% 5% 6% 6% 5% 6% 9% 27%	1372
	21st to end	Night	8% 6% 2 7% 6% 5% 5% 4 6% 9% 44%	1200
July	1st to 10th	Night	6% 4 1 4 4 4 4 3 5% 6% 58%	2242
	11th to 20th	Night	4 2 1 4 3 3 4 3 5% 6% 64%	2545
	21st to end	Night	6% 2 1 4 4 3 4 3 7% 7% 58%	2762
August	1st to 10th	Night	3 2 1 4 2 3 4 4 7% 8% 61%	2529
	11th to 20th	Night	4 3 2 6% 4 4 4 3 8% 9% 52%	2551
	21st to end	Night	11% 5% 3 6% 4 3 4 4 6% 7% 48%	3338
September	1st to 10th	Night	8% 5% 2 5% 5% 4 4 4 4 7% 52%	1900
	11th to 20th	Night	10% 8% 3 6% 4 4 3 3 5% 7% 46%	1981
	21st to end	Night	12% 9% 2 8% 4 4 4 4 5% 7% 40%	2090
October	1st to 10th	Night	10% 8% 3 8% 4 5% 5% 4 6% 7% 40%	3694
	11th to 20th	Night	17% 10% 3 8% 5% 5% 4 4 5% 6% 32%	3987
	21st to end	Night	17% 14% 4 9% 6% 5% 5% 4 5% 6% 25%	4457
November	1st to 10th	Night	20% 19% 5% 12% 7% 6% 6% 3 5% 5% 12%	2555
	11th to 20th	Night	16% 22% 5% 13% 8% 6% 6% 4 4 5% 11%	2862
	21st to end	Night	14% 23% 6% 15% 9% 6% 5% 3 4 4 10%	3000
December	1st to 10th	Night	10% 17% 5% 11% 7% 5% 4 4 5% 8% 23%	4890
	11th to 20th	Night	12% 22% 8% 17% 10% 8% 5% 3 3 3 8%	5550
	21st to end	Night	10% 24% 7% 15% 9% 7% 6% 4 5% 5% 9%	7458

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	78% 9% 8% 4 1	3386
	11th to 20th	Day	54% 10% 21% 8% 6% 1	3640
	21st to end	Day	69% 8% 12% 9% 2	4004
February	1st to 10th	Day	71% 8% 8% 6% 6% 1	1600
	11th to 20th	Day	67% 9% 12% 8% 4 1	1759
	21st to end	Day	69% 8% 11% 8% 3	1650
March	1st to 10th	Day	61% 9% 10% 13% 6%	4518
	11th to 20th	Day	51% 13% 16% 17% 3	4643
	21st to end	Day	65% 12% 11% 10% 3	5969
April	1st to 10th	Day	64% 10% 14% 10% 2	2400
	11th to 20th	Day	60% 9% 13% 14% 3	2468
	21st to end	Day	61% 8% 14% 14% 2	2659
May	1st to 10th	Day	43% 9% 12% 27% 9%	6320
	11th to 20th	Day	57% 10% 15% 15% 2	6280
	21st to end	Day	51% 10% 18% 20% 2	7360
June	1st to 10th	Day	59% 8% 11% 15% 6% 1	3000
	11th to 20th	Day	62% 10% 10% 15% 4	3017
	21st to end	Day	48% 9% 14% 20% 8% 1	3200
July	1st to 10th	Day	29% 6% 11% 24% 22% 8%	4858
	11th to 20th	Day	20% 5% 10% 28% 29% 8%	4553
	21st to end	Day	24% 5% 15% 29% 21% 5%	4640
August	1st to 10th	Day	23% 7% 18% 35% 15% 2	4384
	11th to 20th	Day	29% 6% 26% 28% 9% 1	4319
	21st to end	Day	38% 8% 22% 26% 6% 1	4319
September	1st to 10th	Day	38% 7% 16% 27% 10% 2	2280
	11th to 20th	Day	43% 9% 14% 24% 10% 1	2199
	21st to end	Day	50% 9% 17% 15% 7% 1	2090
October	1st to 10th	Day	48% 8% 26% 16% 2	3283
	11th to 20th	Day	53% 7% 18% 20% 2	2943
	21st to end	Day	58% 9% 18% 14% 2	3101
November	1st to 10th	Day	74% 10% 9% 7% 1	1740
	11th to 20th	Day	71% 10% 10% 7% 3	1515
	21st to end	Day	71% 11% 11% 5% 2	1400
December	1st to 10th	Day	58% 12% 22% 7% 1	2290
	11th to 20th	Day	76% 9% 11% 3 1	2644
	21st to end	Day	71% 10% 11% 6% 2	3498
January	1st to 10th	Night	82% 7% 8% 3 1	6600
	11th to 20th	Night	65% 10% 11% 8% 5% 1	6320
	21st to end	Night	70% 7% 13% 9% 1	6952
February	1st to 10th	Night	75% 7% 7% 6% 5%	2800
	11th to 20th	Night	65% 10% 11% 9% 4 1	2538
	21st to end	Night	69% 7% 11% 8% 4	1980
March	1st to 10th	Night	56% 10% 14% 14% 5%	5376
	11th to 20th	Night	54% 9% 18% 15% 3	5342
	21st to end	Night	62% 13% 10% 13% 2	5006
April	1st to 10th	Night	54% 13% 17% 13% 4	2000
	11th to 20th	Night	54% 9% 16% 15% 5% 1	1882
	21st to end	Night	49% 10% 15% 21% 5%	1739
May	1st to 10th	Night	41% 8% 14% 29% 8%	3637
	11th to 20th	Night	54% 12% 14% 17% 3	3616
	21st to end	Night	42% 12% 17% 25% 3	3515
June	1st to 10th	Night	51% 9% 12% 19% 8% 1	1400
	11th to 20th	Night	55% 11% 12% 17% 5%	1372
	21st to end	Night	39% 9% 15% 27% 9% 1	1200
July	1st to 10th	Night	28% 6% 9% 24% 25% 8%	2207
	11th to 20th	Night	21% 5% 11% 24% 29% 9%	2500
	21st to end	Night	26% 5% 12% 28% 21% 9%	2674
August	1st to 10th	Night	20% 6% 16% 43% 13% 3	2521
	11th to 20th	Night	28% 6% 23% 30% 12% 1	2575
	21st to end	Night	36% 7% 23% 25% 8% 1	3338
September	1st to 10th	Night	32% 6% 16% 29% 14% 2	1900
	11th to 20th	Night	39% 7% 13% 26% 12% 2	1981
	21st to end	Night	43% 9% 20% 18% 9% 1	2090
October	1st to 10th	Night	44% 9% 22% 21% 4	3694
	11th to 20th	Night	50% 7% 20% 20% 4	3987
	21st to end	Night	59% 9% 16% 14% 1	4457
November	1st to 10th	Night	71% 9% 9% 8% 2	2555
	11th to 20th	Night	73% 9% 9% 6% 3	2862
	21st to end	Night	75% 9% 10% 6% 1	3000
December	1st to 10th	Night	58% 11% 23% 7% 1	4890
	11th to 20th	Night	81% 8% 9% 2	5547
	21st to end	Night	76% 10% 8% 4 2	7458

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	22% 21% 30% 16% 11% 2	200
	11th to 20th	Day	25% 22% 29% 18% 6% 1	200
	21st to end	Day	22% 19% 34% 17% 8%	220
February	1st to 10th	Day	25% 26% 30% 16% 4 1	200
	11th to 20th	Day	19% 21% 37% 16% 7%	368
	21st to end	Day	21% 20% 31% 21% 7%	414
March	1st to 10th	Day	21% 27% 29% 18% 6%	500
	11th to 20th	Day	19% 27% 25% 21% 8%	500
	21st to end	Day	23% 21% 28% 21% 7% 1	550
April	1st to 10th	Day	22% 21% 31% 20% 5% 1	500
	11th to 20th	Day	23% 20% 28% 20% 8% 1	492
	21st to end	Day	20% 19% 28% 24% 8% 3	500
May	1st to 10th	Day	16% 19% 28% 26% 9% 1	503
	11th to 20th	Day	19% 13% 27% 25% 15% 1	528
	21st to end	Day	18% 14% 25% 30% 13% 1	769
June	1st to 10th	Day	22% 16% 32% 24% 6%	730
	11th to 20th	Day	22% 16% 29% 26% 7% 1	747
	21st to end	Day	14% 12% 29% 32% 12% 1	930
July	1st to 10th	Day	14% 9% 28% 37% 12% 1	750
	11th to 20th	Day	10% 13% 32% 30% 12% 2	566
	21st to end	Day	8% 10% 34% 35% 11% 3	532
August	1st to 10th	Day	8% 11% 30% 33% 14% 3	487
	11th to 20th	Day	9% 12% 29% 33% 13% 3	477
	21st to end	Day	12% 16% 28% 29% 13% 1	539
September	1st to 10th	Day	15% 14% 31% 27% 11% 2	490
	11th to 20th	Day	17% 15% 30% 28% 10% 1	490
	21st to end	Day	20% 22% 30% 19% 9%	490
October	1st to 10th	Day	22% 16% 29% 23% 11%	490
	11th to 20th	Day	27% 14% 28% 19% 12%	362
	21st to end	Day	29% 20% 29% 18% 3 1	330
November	1st to 10th	Day	31% 17% 28% 20% 5%	287
	11th to 20th	Day	30% 16% 32% 16% 8%	200
	21st to end	Day	20% 16% 33% 22% 6% 4	200
December	1st to 10th	Day	25% 16% 22% 24% 13% 2	200
	11th to 20th	Day	28% 16% 34% 17% 5% 1	200
	21st to end	Day	24% 14% 37% 20% 5%	220
January	1st to 10th	Night	33% 17% 28% 18% 4	925
	11th to 20th	Night	28% 12% 34% 23% 4	800
	21st to end	Night	23% 15% 34% 25% 4	880
February	1st to 10th	Night	26% 14% 33% 21% 6%	800
	11th to 20th	Night	22% 13% 34% 26% 5%	784
	21st to end	Night	21% 13% 32% 24% 10%	660
March	1st to 10th	Night	21% 15% 32% 24% 9%	800
	11th to 20th	Night	21% 15% 30% 29% 5%	800
	21st to end	Night	21% 12% 33% 24% 10%	880
April	1st to 10th	Night	17% 12% 31% 29% 10%	800
	11th to 20th	Night	22% 11% 33% 28% 6%	694
	21st to end	Night	19% 9% 29% 35% 8%	539
May	1st to 10th	Night	12% 9% 32% 35% 12%	400
	11th to 20th	Night	16% 7% 27% 37% 13%	394
	21st to end	Night	18% 8% 28% 37% 9%	433
June	1st to 10th	Night	23% 11% 29% 30% 8%	400
	11th to 20th	Night	21% 11% 25% 32% 11%	400
	21st to end	Night	11% 6% 32% 37% 14%	400
July	1st to 10th	Night	9% 5% 25% 50% 10% 1	390
	11th to 20th	Night	7% 4 27% 49% 14%	388
	21st to end	Night	5% 2 27% 47% 18%	416
August	1st to 10th	Night	6% 3 16% 47% 28%	378
	11th to 20th	Night	8% 3 19% 44% 25%	404
	21st to end	Night	9% 5% 23% 46% 16%	741
September	1st to 10th	Night	11% 6% 27% 39% 17%	760
	11th to 20th	Night	17% 7% 19% 36% 20% 1	760
	21st to end	Night	20% 8% 31% 30% 11%	760
October	1st to 10th	Night	19% 8% 29% 34% 9%	760
	11th to 20th	Night	27% 8% 28% 30% 7%	760
	21st to end	Night	31% 11% 33% 21% 6%	836
November	1st to 10th	Night	35% 13% 31% 17% 4	780
	11th to 20th	Night	31% 18% 27% 19% 4	862
	21st to end	Night	29% 13% 31% 21% 6%	1000
December	1st to 10th	Night	26% 11% 34% 23% 6%	1000
	11th to 20th	Night	29% 14% 36% 18% 3 1	1000
	21st to end	Night	29% 14% 37% 16% 4 1	1100

Page generated at 2025-07-17 22:10:02. Version ac07

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