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 2026-11-13.

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	11% 9% 3 6% 4 4 4 3 5% 6% 44%	157689
	Night	13% 10% 3 7% 4 4 4 3 5% 6% 40%	152085
Transparency	Day	39% 6% 14% 23% 14% 4	157412
	Night	44% 7% 13% 21% 11% 4	151944
Seeing	Day	17% 12% 25% 27% 16% 4	17609
	Night	22% 6% 17% 34% 19% 2	26661

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	18% 29% 8% 11% 4 4 4 3 4 4 12%	4587
	11th to 20th	Day	13% 13% 4 7% 5% 5% 4 4 5% 6% 35%	4716
	21st to end	Day	21% 14% 3 7% 4 4 4 3 4 5% 31%	5186
February	1st to 10th	Day	23% 21% 5% 9% 4 3 4 3 5% 4 18%	1680
	11th to 20th	Day	17% 20% 5% 11% 5% 4 4 3 4 4 22%	1937
	21st to end	Day	18% 18% 4 11% 6% 4 4 4 3 6% 22%	1730
March	1st to 10th	Day	11% 14% 4 8% 5% 4 5% 4 6% 7% 32%	4618
	11th to 20th	Day	13% 13% 3 8% 4 4 4 3 5% 5% 36%	4856
	21st to end	Day	18% 15% 5% 11% 6% 5% 5% 4 5% 6% 20%	5955
April	1st to 10th	Day	19% 13% 3 8% 6% 5% 6% 4 6% 7% 24%	2520
	11th to 20th	Day	14% 12% 4 8% 6% 5% 5% 5% 5% 7% 30%	2611
	21st to end	Day	13% 10% 4 8% 6% 6% 6% 4 5% 6% 33%	2730
May	1st to 10th	Day	7% 6% 2 6% 4 4 4 3 6% 8% 48%	7966
	11th to 20th	Day	9% 7% 3 8% 5% 6% 6% 5% 7% 11% 33%	8160
	21st to end	Day	9% 7% 3 8% 5% 5% 5% 5% 7% 8% 39%	9429
June	1st to 10th	Day	18% 8% 2 6% 5% 5% 5% 4 5% 7% 35%	3150
	11th to 20th	Day	15% 6% 2 6% 5% 6% 5% 5% 6% 8% 34%	3150
	21st to end	Day	8% 4 2 5% 5% 4 5% 4 5% 7% 51%	3150
July	1st to 10th	Day	3 2 1 3 3 3 3 3 4 6% 69%	8724
	11th to 20th	Day	3 2 1 3 2 2 2 2 4 5% 73%	8220
	21st to end	Day	3 2 1 2 2 2 2 2 3 5% 76%	8916
August	1st to 10th	Day	3 2 1 2 2 3 3 2 4 6% 73%	6441
	11th to 20th	Day	3 2 1 3 3 3 4 4 5% 7% 66%	6056
	21st to end	Day	3 2 1 4 3 4 4 3 6% 7% 61%	6331
September	1st to 10th	Day	6% 3 1 4 3 3 3 3 5% 7% 61%	2520
	11th to 20th	Day	8% 6% 2 5% 3 4 4 4 6% 8% 51%	2373
	21st to end	Day	10% 6% 2 7% 4 4 5% 3 5% 8% 46%	2310
October	1st to 10th	Day	7% 3 1 3 3 3 4 3 6% 10% 57%	5007
	11th to 20th	Day	13% 5% 2 6% 5% 4 4 3 5% 6% 50%	4264
	21st to end	Day	17% 8% 4 10% 7% 6% 6% 4 6% 6% 27%	4564
November	1st to 10th	Day	27% 16% 4 8% 5% 4 3 3 4 6% 21%	1944
	11th to 20th	Day	28% 17% 4 8% 4 4 4 2 4 5% 19%	1771
	21st to end	Day	22% 22% 5% 10% 6% 3 3 2 4 4 19%	1470
December	1st to 10th	Day	17% 12% 5% 12% 6% 4 3 3 4 6% 29%	2360
	11th to 20th	Day	28% 21% 5% 9% 6% 4 4 3 4 5% 12%	2712
	21st to end	Day	21% 24% 6% 12% 5% 4 4 3 3 4 13%	3575
January	1st to 10th	Night	23% 24% 5% 10% 5% 4 4 3 4 4 13%	8349
	11th to 20th	Night	13% 10% 4 9% 4 4 4 4 6% 6% 34%	8182
	21st to end	Night	21% 14% 3 6% 4 3 4 3 4 6% 32%	8994
February	1st to 10th	Night	23% 20% 4 7% 4 4 3 3 4 4 23%	2940
	11th to 20th	Night	18% 17% 4 8% 4 4 4 3 4 6% 27%	2568
	21st to end	Night	15% 18% 4 8% 5% 4 4 4 4 7% 27%	2076
March	1st to 10th	Night	10% 13% 4 8% 5% 4 4 4 7% 6% 35%	5496
	11th to 20th	Night	15% 13% 3 7% 5% 4 4 2 3 4 40%	5350
	21st to end	Night	18% 10% 4 11% 7% 6% 7% 5% 7% 6% 19%	5257
April	1st to 10th	Night	12% 11% 3 7% 6% 6% 5% 4 7% 8% 33%	2100
	11th to 20th	Night	15% 9% 3 7% 5% 5% 4 3 4 7% 37%	1960
	21st to end	Night	12% 7% 3 7% 5% 4 4 5% 6% 8% 39%	1890
May	1st to 10th	Night	8% 5% 2 5% 4 4 5% 4 7% 9% 47%	4950
	11th to 20th	Night	11% 7% 3 7% 5% 5% 5% 4 6% 9% 38%	4700
	21st to end	Night	12% 7% 3 7% 4 4 5% 4 6% 8% 41%	4742
June	1st to 10th	Night	13% 7% 3 7% 4 4 5% 4 5% 9% 39%	1470
	11th to 20th	Night	11% 6% 2 6% 5% 5% 6% 4 7% 8% 40%	1470
	21st to end	Night	7% 5% 2 5% 3 3 4 4 5% 8% 53%	1470
July	1st to 10th	Night	3 2 1 3 2 2 3 2 4 7% 71%	4232
	11th to 20th	Night	3 1 1 2 2 2 3 3 4 6% 73%	4740
	21st to end	Night	3 3 1 2 2 2 2 2 3 5% 74%	5152
August	1st to 10th	Night	2 2 1 2 1 2 2 2 3 6% 77%	3709
	11th to 20th	Night	2 3 1 3 2 3 3 4 5% 8% 65%	4001
	21st to end	Night	3 2 1 4 4 4 5% 4 6% 7% 62%	4812
September	1st to 10th	Night	5% 3 1 3 3 2 5% 4 5% 7% 63%	2100
	11th to 20th	Night	7% 4 2 5% 5% 4 5% 4 5% 7% 51%	2247
	21st to end	Night	11% 5% 2 5% 3 4 4 3 5% 7% 51%	2310
October	1st to 10th	Night	6% 3 1 3 2 3 3 3 6% 9% 62%	5199
	11th to 20th	Night	11% 5% 2 5% 3 3 5% 3 5% 7% 52%	5895
	21st to end	Night	14% 8% 3 7% 5% 5% 6% 5% 5% 6% 36%	6547
November	1st to 10th	Night	26% 11% 3 9% 5% 4 4 3 5% 6% 24%	2795
	11th to 20th	Night	24% 17% 3 7% 5% 4 4 4 5% 6% 22%	2869
	21st to end	Night	25% 18% 4 7% 4 4 4 2 5% 5% 23%	3150
December	1st to 10th	Night	15% 13% 5% 7% 5% 4 4 3 5% 6% 33%	5040
	11th to 20th	Night	24% 22% 5% 9% 5% 4 4 3 4 4 15%	5700
	21st to end	Night	21% 23% 6% 11% 6% 5% 4 3 3 4 13%	7623

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	75% 6% 11% 6% 1	4587
	11th to 20th	Day	51% 8% 23% 14% 5% 1	4740
	21st to end	Day	55% 7% 18% 15% 5%	5187
February	1st to 10th	Day	68% 7% 11% 9% 4 1	1680
	11th to 20th	Day	65% 7% 11% 11% 5%	1947
	21st to end	Day	66% 6% 8% 14% 6%	1730
March	1st to 10th	Day	48% 7% 15% 18% 12%	4618
	11th to 20th	Day	48% 6% 20% 23% 3	4857
	21st to end	Day	63% 8% 13% 12% 3	5955
April	1st to 10th	Day	57% 8% 16% 16% 3	2520
	11th to 20th	Day	51% 6% 15% 19% 8% 1	2611
	21st to end	Day	50% 8% 14% 21% 7% 1	2730
May	1st to 10th	Day	33% 5% 14% 33% 15%	7966
	11th to 20th	Day	39% 8% 20% 25% 8%	8163
	21st to end	Day	39% 8% 19% 29% 6%	9430
June	1st to 10th	Day	47% 6% 13% 21% 12% 1	3150
	11th to 20th	Day	44% 6% 14% 22% 12% 2	3150
	21st to end	Day	31% 6% 16% 29% 17% 2	3150
July	1st to 10th	Day	16% 4 8% 26% 31% 15%	8651
	11th to 20th	Day	16% 2 6% 23% 29% 24%	8145
	21st to end	Day	13% 2 5% 30% 34% 15%	8723
August	1st to 10th	Day	13% 3 5% 30% 32% 17%	6424
	11th to 20th	Day	16% 5% 13% 47% 18% 2	6097
	21st to end	Day	20% 4 13% 37% 24% 2	6330
September	1st to 10th	Day	23% 4 13% 32% 21% 8%	2520
	11th to 20th	Day	32% 6% 13% 28% 19% 2	2373
	21st to end	Day	37% 7% 20% 23% 10% 3	2310
October	1st to 10th	Day	24% 4 19% 42% 11%	5006
	11th to 20th	Day	36% 4 19% 23% 16% 1	4266
	21st to end	Day	54% 8% 20% 14% 4	4562
November	1st to 10th	Day	65% 7% 14% 10% 3	1944
	11th to 20th	Day	68% 7% 11% 9% 3 1	1771
	21st to end	Day	71% 6% 11% 9% 4	1470
December	1st to 10th	Day	58% 10% 17% 14% 2	2360
	11th to 20th	Day	76% 5% 13% 4 2	2714
	21st to end	Day	75% 6% 10% 6% 3	3575
January	1st to 10th	Night	74% 8% 10% 7% 1	8350
	11th to 20th	Night	50% 9% 18% 16% 5% 2	8220
	21st to end	Night	55% 8% 18% 16% 3	8994
February	1st to 10th	Night	64% 7% 12% 12% 5% 1	2940
	11th to 20th	Night	59% 7% 13% 14% 6%	2569
	21st to end	Night	58% 7% 13% 15% 7% 1	2076
March	1st to 10th	Night	44% 8% 17% 20% 10%	5496
	11th to 20th	Night	48% 5% 16% 25% 6%	5350
	21st to end	Night	60% 12% 14% 12% 2	5257
April	1st to 10th	Night	48% 8% 18% 21% 6%	2100
	11th to 20th	Night	47% 5% 13% 22% 12% 1	1960
	21st to end	Night	42% 8% 14% 25% 10% 1	1890
May	1st to 10th	Night	31% 7% 11% 34% 16% 1	4947
	11th to 20th	Night	39% 8% 15% 26% 11%	4700
	21st to end	Night	39% 7% 14% 31% 8% 1	4746
June	1st to 10th	Night	41% 6% 11% 25% 15% 2	1470
	11th to 20th	Night	39% 7% 13% 24% 15% 3	1470
	21st to end	Night	28% 6% 15% 26% 21% 5%	1470
July	1st to 10th	Night	14% 3 7% 25% 34% 18%	4196
	11th to 20th	Night	13% 3 5% 24% 27% 29%	4692
	21st to end	Night	14% 2 3 25% 34% 22%	5040
August	1st to 10th	Night	12% 2 4 23% 36% 23%	3701
	11th to 20th	Night	18% 4 10% 44% 21% 4	4026
	21st to end	Night	21% 5% 11% 32% 28% 4	4812
September	1st to 10th	Night	20% 6% 11% 29% 25% 9%	2100
	11th to 20th	Night	31% 7% 11% 26% 20% 5%	2247
	21st to end	Night	32% 5% 20% 26% 13% 4	2310
October	1st to 10th	Night	20% 3 18% 48% 11%	5199
	11th to 20th	Night	33% 5% 14% 27% 21% 1	5895
	21st to end	Night	46% 7% 19% 21% 5%	6547
November	1st to 10th	Night	61% 9% 16% 11% 4	2795
	11th to 20th	Night	63% 9% 14% 9% 4 1	2869
	21st to end	Night	65% 6% 14% 12% 3	3150
December	1st to 10th	Night	54% 11% 17% 16% 2	5040
	11th to 20th	Night	73% 7% 14% 5% 1	5697
	21st to end	Night	73% 8% 11% 6% 2	7623

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% 20% 19% 20% 8% 1	220
	11th to 20th	Day	27% 19% 21% 18% 12% 4	220
	21st to end	Day	29% 8% 28% 24% 10% 1	242
February	1st to 10th	Day	28% 18% 28% 18% 7% 1	220
	11th to 20th	Day	28% 15% 24% 26% 6% 1	450
	21st to end	Day	26% 18% 24% 23% 9%	446
March	1st to 10th	Day	25% 17% 26% 20% 10% 2	540
	11th to 20th	Day	25% 16% 20% 24% 14% 1	540
	21st to end	Day	29% 16% 25% 22% 7% 1	594
April	1st to 10th	Day	24% 17% 25% 21% 10% 3	540
	11th to 20th	Day	20% 18% 27% 20% 11% 3	532
	21st to end	Day	18% 14% 26% 25% 14% 4	540
May	1st to 10th	Day	12% 13% 27% 29% 15% 4	543
	11th to 20th	Day	16% 10% 29% 26% 15% 4	568
	21st to end	Day	15% 9% 21% 30% 19% 6%	767
June	1st to 10th	Day	19% 10% 24% 24% 20% 3	780
	11th to 20th	Day	15% 14% 30% 24% 14% 3	780
	21st to end	Day	11% 8% 22% 31% 25% 4	780
July	1st to 10th	Day	5% 5% 25% 34% 25% 5%	741
	11th to 20th	Day	5% 9% 30% 34% 17% 4	564
	21st to end	Day	3 7% 24% 36% 24% 5%	619
August	1st to 10th	Day	5% 6% 24% 34% 24% 7%	567
	11th to 20th	Day	4 5% 24% 33% 25% 9%	557
	21st to end	Day	7% 10% 23% 28% 24% 7%	627
September	1st to 10th	Day	9% 7% 28% 27% 21% 9%	570
	11th to 20th	Day	12% 9% 22% 31% 20% 6%	570
	21st to end	Day	14% 11% 26% 28% 16% 4	570
October	1st to 10th	Day	13% 7% 27% 30% 20% 3	570
	11th to 20th	Day	22% 13% 23% 24% 14% 4	402
	21st to end	Day	27% 13% 24% 24% 9% 2	396
November	1st to 10th	Day	33% 13% 21% 24% 7% 1	360
	11th to 20th	Day	37% 11% 20% 23% 9%	292
	21st to end	Day	29% 13% 24% 26% 7% 1	220
December	1st to 10th	Day	31% 13% 20% 20% 12% 4	220
	11th to 20th	Day	38% 11% 24% 19% 7%	220
	21st to end	Day	36% 12% 21% 24% 5% 1	242
January	1st to 10th	Night	39% 8% 18% 27% 7% 1	904
	11th to 20th	Night	31% 7% 20% 30% 10% 1	840
	21st to end	Night	29% 7% 20% 36% 8%	924
February	1st to 10th	Night	33% 8% 20% 28% 8% 2	840
	11th to 20th	Night	27% 8% 22% 32% 11%	824
	21st to end	Night	25% 9% 21% 31% 14% 1	692
March	1st to 10th	Night	23% 9% 21% 31% 15% 1	840
	11th to 20th	Night	27% 8% 17% 33% 15%	840
	21st to end	Night	24% 7% 21% 33% 13% 1	924
April	1st to 10th	Night	18% 6% 18% 37% 20% 1	840
	11th to 20th	Night	18% 7% 24% 35% 14% 2	712
	21st to end	Night	14% 6% 20% 37% 20% 2	630
May	1st to 10th	Night	13% 3 18% 39% 25% 3	503
	11th to 20th	Night	11% 7% 14% 33% 30% 5%	414
	21st to end	Night	16% 7% 14% 32% 26% 5%	455
June	1st to 10th	Night	18% 5% 14% 35% 25% 3	420
	11th to 20th	Night	12% 5% 18% 42% 22% 2	420
	21st to end	Night	9% 3 12% 40% 34% 3	420
July	1st to 10th	Night	3 2 9% 43% 40% 3	410
	11th to 20th	Night	3 1 13% 49% 32% 1	408
	21st to end	Night	3 2 7% 42% 43% 2	460
August	1st to 10th	Night	4 3 9% 39% 42% 4	418
	11th to 20th	Night	5% 2 8% 38% 41% 6%	559
	21st to end	Night	4 3 14% 40% 37% 3	797
September	1st to 10th	Night	7% 2 13% 40% 33% 6%	840
	11th to 20th	Night	8% 3 12% 34% 37% 5%	840
	21st to end	Night	13% 5% 14% 38% 27% 4	840
October	1st to 10th	Night	14% 4 14% 42% 24% 1	840
	11th to 20th	Night	19% 5% 17% 35% 23% 1	840
	21st to end	Night	25% 5% 21% 33% 14% 2	924
November	1st to 10th	Night	33% 7% 17% 34% 8%	860
	11th to 20th	Night	34% 9% 19% 29% 8% 1	878
	21st to end	Night	33% 8% 18% 29% 11%	1050
December	1st to 10th	Night	31% 8% 17% 30% 13% 1	1050
	11th to 20th	Night	36% 8% 22% 28% 6%	1050
	21st to end	Night	37% 10% 20% 26% 7%	1155

Page generated at 2026-11-10 00:55:18. Version ac07

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