Sandpoint
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sandpoint 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	13% 10% 3 7% 4 4 4 3 5% 6% 40%	123742
	Night	15% 12% 3 7% 4 4 4 3 5% 6% 37%	124050
Transparency	Day	43% 6% 14% 21% 12% 4	123507
	Night	47% 7% 13% 19% 10% 3	123928
Seeing	Day	18% 12% 25% 27% 16% 3	15887
	Night	22% 6% 17% 34% 19% 2	24991

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	20% 31% 7% 10% 4 3 3 2 4 3 14%	3529
	11th to 20th	Day	15% 15% 4 7% 5% 5% 5% 3 5% 5% 30%	3616
	21st to end	Day	24% 15% 3 6% 4 4 3 2 4 5% 30%	4004
February	1st to 10th	Day	24% 21% 5% 9% 4 3 4 3 5% 4 18%	1600
	11th to 20th	Day	18% 20% 5% 11% 5% 4 4 3 4 5% 22%	1842
	21st to end	Day	19% 18% 4 11% 6% 4 3 3 4 6% 22%	1650
March	1st to 10th	Day	11% 14% 4 8% 5% 4 5% 4 6% 7% 32%	4518
	11th to 20th	Day	12% 13% 3 8% 4 4 4 3 5% 5% 37%	4752
	21st to end	Day	18% 15% 5% 11% 6% 5% 5% 4 5% 6% 19%	5827
April	1st to 10th	Day	19% 13% 4 8% 7% 5% 6% 4 6% 7% 23%	2400
	11th to 20th	Day	14% 12% 3 8% 6% 5% 5% 5% 5% 6% 30%	2485
	21st to end	Day	13% 10% 4 8% 6% 6% 5% 4 5% 6% 32%	2600
May	1st to 10th	Day	9% 7% 3 7% 5% 5% 5% 4 6% 7% 43%	6143
	11th to 20th	Day	11% 8% 3 8% 5% 6% 6% 5% 7% 10% 31%	6277
	21st to end	Day	9% 7% 3 9% 5% 5% 5% 5% 6% 8% 38%	7241
June	1st to 10th	Day	18% 8% 2 6% 5% 5% 5% 4 5% 7% 35%	3000
	11th to 20th	Day	16% 7% 2 7% 6% 6% 5% 5% 6% 8% 32%	3000
	21st to end	Day	7% 4 2 5% 5% 4 5% 4 5% 7% 52%	3000
July	1st to 10th	Day	2 2 1 3 3 3 3 3 4 5% 71%	4834
	11th to 20th	Day	2 1 2 2 2 2 2 4 5% 78%	4560
	21st to end	Day	2 1 1 2 2 3 3 3 4 5% 75%	4791
August	1st to 10th	Day	4 2 1 3 2 3 3 3 5% 7% 67%	4401
	11th to 20th	Day	3 2 1 3 2 2 2 3 5% 7% 68%	4117
	21st to end	Day	4 3 1 4 3 4 4 3 6% 7% 60%	4352
September	1st to 10th	Day	6% 3 1 4 3 3 3 3 4 7% 63%	2280
	11th to 20th	Day	9% 5% 2 5% 3 4 4 4 6% 8% 51%	2147
	21st to end	Day	11% 6% 2 7% 4 4 5% 3 5% 8% 46%	2090
October	1st to 10th	Day	10% 4 1 4 4 3 4 3 5% 8% 54%	3415
	11th to 20th	Day	16% 5% 2 6% 4 4 4 3 5% 6% 44%	2906
	21st to end	Day	21% 8% 4 9% 6% 5% 5% 3 5% 5% 29%	3101
November	1st to 10th	Day	28% 16% 4 8% 4 3 3 3 4 5% 21%	1764
	11th to 20th	Day	29% 17% 4 8% 4 4 4 2 4 5% 20%	1670
	21st to end	Day	23% 22% 5% 10% 7% 3 3 2 4 4 18%	1400
December	1st to 10th	Day	16% 11% 5% 12% 6% 4 3 3 4 6% 30%	2290
	11th to 20th	Day	28% 21% 5% 9% 6% 4 3 3 3 5% 12%	2642
	21st to end	Day	21% 24% 6% 12% 5% 4 4 3 3 4 13%	3498
January	1st to 10th	Night	24% 26% 5% 9% 4 4 4 3 4 4 13%	6445
	11th to 20th	Night	15% 12% 5% 10% 5% 4 4 3 4 5% 32%	6282
	21st to end	Night	24% 16% 3 6% 4 3 3 3 3 6% 30%	6952
February	1st to 10th	Night	23% 20% 4 7% 4 3 3 2 4 4 24%	2800
	11th to 20th	Night	19% 17% 5% 8% 4 4 4 3 4 7% 27%	2443
	21st to end	Night	16% 18% 4 8% 5% 4 4 4 4 7% 27%	1980
March	1st to 10th	Night	10% 13% 4 8% 5% 4 4 4 7% 7% 35%	5376
	11th to 20th	Night	14% 13% 3 7% 5% 4 4 2 3 4 40%	5234
	21st to end	Night	19% 10% 4 11% 7% 6% 7% 6% 7% 6% 19%	5144
April	1st to 10th	Night	12% 11% 3 7% 6% 6% 5% 4 7% 8% 31%	2000
	11th to 20th	Night	15% 9% 3 7% 5% 5% 4 3 4 7% 38%	1866
	21st to end	Night	12% 7% 3 7% 5% 4 4 5% 6% 8% 39%	1800
May	1st to 10th	Night	10% 6% 2 6% 5% 4 5% 4 6% 8% 44%	3810
	11th to 20th	Night	13% 8% 4 7% 5% 5% 5% 4 6% 9% 37%	3616
	21st to end	Night	11% 6% 2 6% 4 4 4 4 6% 8% 43%	3634
June	1st to 10th	Night	14% 7% 2 7% 4 4 4 4 5% 9% 40%	1400
	11th to 20th	Night	12% 6% 2 6% 5% 5% 6% 4 7% 8% 38%	1400
	21st to end	Night	7% 5% 2 5% 3 3 4 4 5% 8% 55%	1400
July	1st to 10th	Night	2 2 1 3 2 2 3 3 4 6% 73%	2342
	11th to 20th	Night	2 1 1 2 2 2 2 2 3 5% 80%	2620
	21st to end	Night	3 2 1 2 2 2 2 2 4 5% 76%	2762
August	1st to 10th	Night	3 3 1 2 2 2 2 2 4 7% 72%	2529
	11th to 20th	Night	3 3 1 4 2 4 4 4 5% 7% 63%	2716
	21st to end	Night	3 2 1 4 4 4 5% 4 5% 6% 62%	3305
September	1st to 10th	Night	5% 3 1 3 3 2 4 4 5% 6% 65%	1900
	11th to 20th	Night	7% 4 2 5% 5% 5% 4 5% 6% 7% 50%	2033
	21st to end	Night	11% 5% 2 5% 3 4 4 3 5% 7% 51%	2090
October	1st to 10th	Night	8% 3 1 4 3 3 3 3 5% 7% 59%	3551
	11th to 20th	Night	14% 4 2 5% 3 3 4 3 4 7% 49%	4023
	21st to end	Night	15% 7% 3 7% 4 4 5% 4 5% 7% 39%	4457
November	1st to 10th	Night	27% 12% 3 8% 5% 4 3 3 5% 6% 24%	2535
	11th to 20th	Night	23% 17% 3 7% 5% 4 4 4 5% 6% 23%	2707
	21st to end	Night	26% 18% 4 7% 4 4 4 2 5% 5% 23%	3000
December	1st to 10th	Night	15% 12% 5% 7% 5% 4 4 3 5% 6% 34%	4890
	11th to 20th	Night	23% 23% 5% 9% 5% 4 4 3 4 4 15%	5550
	21st to end	Night	21% 23% 6% 11% 7% 5% 4 3 3 4 13%	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	76% 7% 10% 7% 1	3529
	11th to 20th	Day	56% 7% 19% 13% 4 1	3640
	21st to end	Day	57% 7% 15% 17% 4	4004
February	1st to 10th	Day	69% 7% 11% 9% 4 2	1600
	11th to 20th	Day	65% 8% 11% 11% 5%	1852
	21st to end	Day	66% 6% 8% 14% 6%	1650
March	1st to 10th	Day	48% 7% 14% 19% 12%	4518
	11th to 20th	Day	47% 6% 20% 24% 3	4753
	21st to end	Day	64% 8% 13% 12% 3	5827
April	1st to 10th	Day	59% 8% 15% 15% 3	2400
	11th to 20th	Day	52% 6% 14% 19% 8% 1	2485
	21st to end	Day	50% 8% 14% 20% 7% 1	2600
May	1st to 10th	Day	38% 6% 13% 25% 17%	6143
	11th to 20th	Day	42% 9% 19% 24% 7%	6280
	21st to end	Day	40% 8% 18% 27% 7%	7242
June	1st to 10th	Day	47% 6% 13% 21% 12% 1	3000
	11th to 20th	Day	46% 6% 14% 21% 11% 2	3000
	21st to end	Day	30% 6% 16% 29% 17% 3	3000
July	1st to 10th	Day	16% 4 8% 23% 32% 18%	4761
	11th to 20th	Day	10% 3 7% 16% 30% 33%	4485
	21st to end	Day	13% 3 6% 24% 35% 19%	4640
August	1st to 10th	Day	17% 4 7% 32% 31% 10%	4384
	11th to 20th	Day	16% 5% 11% 45% 21% 3	4158
	21st to end	Day	22% 4 14% 35% 22% 2	4351
September	1st to 10th	Day	22% 4 13% 32% 21% 8%	2280
	11th to 20th	Day	32% 6% 14% 26% 20% 2	2147
	21st to end	Day	38% 7% 21% 22% 10% 3	2090
October	1st to 10th	Day	29% 4 17% 36% 13%	3415
	11th to 20th	Day	41% 4 20% 21% 13%	2906
	21st to end	Day	55% 7% 16% 16% 5%	3101
November	1st to 10th	Day	66% 7% 13% 10% 3	1764
	11th to 20th	Day	68% 7% 11% 9% 3 1	1670
	21st to end	Day	71% 6% 11% 9% 3	1400
December	1st to 10th	Day	57% 10% 17% 14% 2	2290
	11th to 20th	Day	77% 5% 13% 4 1	2644
	21st to end	Day	75% 6% 10% 6% 3	3498
January	1st to 10th	Night	76% 8% 9% 6% 1	6445
	11th to 20th	Night	54% 8% 15% 16% 5% 2	6320
	21st to end	Night	58% 7% 17% 15% 3	6952
February	1st to 10th	Night	64% 7% 12% 12% 5% 1	2800
	11th to 20th	Night	59% 7% 13% 14% 6%	2444
	21st to end	Night	57% 7% 12% 16% 7% 1	1980
March	1st to 10th	Night	44% 8% 18% 20% 11%	5376
	11th to 20th	Night	47% 5% 16% 25% 6%	5234
	21st to end	Night	60% 12% 14% 12% 2	5144
April	1st to 10th	Night	49% 8% 17% 20% 6%	2000
	11th to 20th	Night	46% 5% 13% 22% 12% 1	1866
	21st to end	Night	42% 8% 14% 24% 11% 1	1800
May	1st to 10th	Night	37% 8% 11% 26% 18% 1	3807
	11th to 20th	Night	41% 7% 14% 27% 10%	3616
	21st to end	Night	37% 7% 15% 30% 10% 1	3634
June	1st to 10th	Night	41% 6% 11% 25% 15% 2	1400
	11th to 20th	Night	41% 7% 14% 22% 14% 3	1400
	21st to end	Night	26% 6% 16% 27% 21% 5%	1400
July	1st to 10th	Night	12% 4 7% 22% 35% 20%	2306
	11th to 20th	Night	10% 2 5% 16% 25% 42%	2572
	21st to end	Night	12% 2 4 19% 33% 30%	2674
August	1st to 10th	Night	14% 2 5% 29% 34% 15%	2521
	11th to 20th	Night	21% 4 8% 36% 26% 5%	2741
	21st to end	Night	21% 5% 12% 29% 28% 5%	3305
September	1st to 10th	Night	18% 6% 10% 30% 26% 10%	1900
	11th to 20th	Night	31% 8% 11% 24% 21% 5%	2033
	21st to end	Night	32% 5% 20% 26% 13% 5%	2090
October	1st to 10th	Night	25% 4 16% 41% 14%	3551
	11th to 20th	Night	36% 6% 15% 26% 16% 1	4023
	21st to end	Night	43% 7% 19% 21% 8% 1	4457
November	1st to 10th	Night	62% 9% 15% 11% 4	2535
	11th to 20th	Night	62% 9% 14% 10% 4 1	2707
	21st to end	Night	64% 6% 14% 12% 3	3000
December	1st to 10th	Night	53% 11% 18% 17% 2	4890
	11th to 20th	Night	73% 7% 14% 5% 1	5547
	21st to end	Night	74% 8% 11% 6% 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	32% 18% 20% 21% 9% 2	200
	11th to 20th	Day	30% 20% 20% 16% 12% 4	200
	21st to end	Day	29% 9% 28% 24% 10% 1	220
February	1st to 10th	Day	29% 19% 29% 18% 5% 1	200
	11th to 20th	Day	27% 16% 25% 25% 6% 1	415
	21st to end	Day	27% 17% 23% 23% 10%	414
March	1st to 10th	Day	25% 17% 26% 20% 10% 2	500
	11th to 20th	Day	23% 15% 21% 25% 15% 1	500
	21st to end	Day	29% 16% 25% 21% 8% 1	550
April	1st to 10th	Day	25% 18% 26% 20% 9% 2	500
	11th to 20th	Day	20% 18% 28% 20% 11% 3	492
	21st to end	Day	18% 15% 27% 24% 12% 3	500
May	1st to 10th	Day	13% 14% 27% 28% 14% 4	503
	11th to 20th	Day	17% 10% 29% 25% 15% 4	528
	21st to end	Day	15% 9% 21% 30% 20% 6%	716
June	1st to 10th	Day	20% 10% 23% 24% 20% 2	730
	11th to 20th	Day	15% 14% 30% 23% 14% 3	730
	21st to end	Day	10% 8% 22% 31% 25% 4	730
July	1st to 10th	Day	5% 6% 25% 34% 25% 5%	692
	11th to 20th	Day	4 9% 29% 34% 19% 5%	524
	21st to end	Day	3 8% 25% 37% 23% 4	532
August	1st to 10th	Day	5% 6% 25% 34% 23% 6%	487
	11th to 20th	Day	4 5% 24% 33% 26% 8%	477
	21st to end	Day	7% 11% 24% 29% 22% 6%	539
September	1st to 10th	Day	8% 8% 29% 27% 20% 7%	490
	11th to 20th	Day	12% 11% 23% 32% 18% 4	490
	21st to end	Day	15% 12% 27% 27% 15% 4	490
October	1st to 10th	Day	15% 8% 27% 29% 19% 3	490
	11th to 20th	Day	23% 13% 22% 23% 14% 5%	338
	21st to end	Day	30% 13% 24% 24% 8% 1	330
November	1st to 10th	Day	34% 13% 21% 24% 7% 1	300
	11th to 20th	Day	37% 11% 21% 22% 9%	260
	21st to end	Day	30% 12% 24% 27% 8% 1	200
December	1st to 10th	Day	29% 13% 20% 22% 13% 4	200
	11th to 20th	Day	37% 10% 25% 20% 8% 1	200
	21st to end	Day	37% 11% 22% 24% 5% 1	220
January	1st to 10th	Night	39% 7% 19% 27% 7% 1	861
	11th to 20th	Night	33% 7% 20% 29% 10% 1	800
	21st to end	Night	29% 6% 21% 35% 8%	880
February	1st to 10th	Night	33% 8% 21% 29% 8% 2	800
	11th to 20th	Night	27% 8% 22% 33% 10%	784
	21st to end	Night	25% 8% 21% 31% 14% 1	660
March	1st to 10th	Night	23% 9% 21% 31% 15% 1	800
	11th to 20th	Night	26% 7% 17% 34% 16% 1	800
	21st to end	Night	24% 7% 20% 33% 14% 1	880
April	1st to 10th	Night	19% 6% 18% 37% 19% 1	800
	11th to 20th	Night	17% 7% 24% 36% 14% 2	678
	21st to end	Night	15% 6% 21% 37% 19% 2	600
May	1st to 10th	Night	13% 3 18% 37% 25% 3	479
	11th to 20th	Night	11% 6% 13% 33% 31% 5%	394
	21st to end	Night	16% 7% 14% 32% 27% 5%	433
June	1st to 10th	Night	18% 5% 15% 35% 26% 3	400
	11th to 20th	Night	13% 5% 17% 41% 22% 2	400
	21st to end	Night	8% 3 12% 40% 34% 3	400
July	1st to 10th	Night	4 2 9% 42% 39% 3	390
	11th to 20th	Night	4 1 12% 48% 33% 1	388
	21st to end	Night	3 2 7% 43% 43% 2	416
August	1st to 10th	Night	4 2 10% 38% 42% 4	378
	11th to 20th	Night	5% 2 8% 36% 42% 7%	505
	21st to end	Night	4 3 15% 39% 37% 3	721
September	1st to 10th	Night	6% 1 14% 41% 32% 6%	760
	11th to 20th	Night	8% 3 12% 34% 37% 5%	760
	21st to end	Night	14% 4 15% 37% 27% 4	760
October	1st to 10th	Night	15% 4 15% 40% 24% 1	760
	11th to 20th	Night	19% 4 16% 35% 24% 1	760
	21st to end	Night	25% 5% 22% 32% 14% 2	836
November	1st to 10th	Night	33% 7% 17% 35% 8%	780
	11th to 20th	Night	33% 9% 20% 29% 8% 1	828
	21st to end	Night	34% 8% 18% 30% 11%	1000
December	1st to 10th	Night	31% 7% 17% 30% 13% 1	1000
	11th to 20th	Night	35% 8% 22% 29% 7%	1000
	21st to end	Night	37% 10% 20% 27% 6%	1100

Page generated at 2025-07-17 22:09:59. Version ac07

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