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 2024-03-28.

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	16% 10% 3 6% 5% 3 4 4 5% 6% 37%	78363
	Night	18% 12% 4 6% 5% 3 4 4 5% 6% 34%	81577
Transparency	Day	48% 6% 13% 19% 11% 2	78087
	Night	51% 7% 13% 17% 10% 3	81433
Seeing	Day	18% 12% 25% 26% 15% 3	14087
	Night	23% 6% 18% 33% 19% 2	23435

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	23% 32% 7% 7% 5% 2 3 4 4 4 10%	2457
	11th to 20th	Day	23% 19% 4 6% 6% 4 5% 4 4 5% 21%	2516
	21st to end	Day	32% 19% 4 7% 5% 3 4 3 3 4 14%	2794
February	1st to 10th	Day	25% 20% 6% 8% 5% 2 3 4 5% 4 18%	1520
	11th to 20th	Day	19% 19% 5% 10% 6% 3 4 4 4 5% 22%	1746
	21st to end	Day	19% 17% 5% 10% 7% 3 4 5% 4 6% 21%	1570
March	1st to 10th	Day	21% 16% 5% 7% 6% 3 4 4 4 6% 24%	1900
	11th to 20th	Day	21% 13% 3 7% 5% 3 5% 5% 5% 6% 28%	1980
	21st to end	Day	25% 15% 4 7% 7% 4 5% 4 4 5% 18%	2394
April	1st to 10th	Day	20% 13% 4 7% 7% 4 6% 5% 6% 6% 23%	2160
	11th to 20th	Day	16% 11% 4 7% 7% 4 6% 6% 5% 6% 28%	2233
	21st to end	Day	14% 10% 4 7% 7% 4 6% 5% 5% 6% 31%	2340
May	1st to 10th	Day	11% 8% 3 6% 5% 3 5% 4 6% 8% 40%	2447
	11th to 20th	Day	12% 6% 3 6% 5% 4 6% 6% 7% 8% 37%	2477
	21st to end	Day	16% 7% 3 6% 6% 3 6% 6% 6% 8% 33%	2851
June	1st to 10th	Day	20% 8% 3 6% 5% 4 5% 5% 5% 7% 33%	2700
	11th to 20th	Day	17% 7% 3 6% 6% 5% 5% 6% 6% 8% 30%	2700
	21st to end	Day	7% 4 2 4 5% 3 5% 5% 5% 8% 53%	2700
July	1st to 10th	Day	4 2 1 3 5% 3 4 4 4 7% 63%	2674
	11th to 20th	Day	3 2 1 2 3 2 3 4 6% 6% 67%	2520
	21st to end	Day	2 1 2 2 2 3 3 3 5% 78%	2741
August	1st to 10th	Day	4 3 1 2 2 2 3 3 5% 8% 67%	2507
	11th to 20th	Day	4 2 1 3 3 1 2 4 5% 7% 68%	2352
	21st to end	Day	5% 4 2 5% 4 2 5% 4 6% 6% 57%	2483
September	1st to 10th	Day	6% 3 1 3 4 2 4 4 4 7% 62%	2160
	11th to 20th	Day	9% 5% 2 4 3 3 4 5% 6% 8% 51%	2034
	21st to end	Day	11% 6% 2 6% 5% 3 4 5% 5% 8% 45%	1980
October	1st to 10th	Day	15% 6% 3 5% 5% 3 5% 5% 4 7% 43%	1944
	11th to 20th	Day	21% 7% 3 5% 4 2 4 3 5% 5% 41%	1656
	21st to end	Day	24% 7% 4 6% 6% 3 4 3 4 5% 34%	1782
November	1st to 10th	Day	29% 15% 5% 6% 5% 2 4 4 4 5% 20%	1674
	11th to 20th	Day	29% 16% 4 7% 5% 3 4 3 4 4 21%	1587
	21st to end	Day	23% 20% 5% 8% 7% 3 3 4 4 4 19%	1330
December	1st to 10th	Day	22% 15% 6% 9% 6% 4 4 3 3 5% 22%	1330
	11th to 20th	Day	31% 21% 6% 8% 5% 3 4 2 3 4 12%	1682
	21st to end	Day	23% 20% 4 9% 6% 3 4 4 4 6% 18%	2442
January	1st to 10th	Night	28% 27% 5% 7% 5% 2 3 4 4 3 12%	4503
	11th to 20th	Night	21% 15% 4 8% 6% 3 3 3 3 5% 28%	4382
	21st to end	Night	34% 20% 5% 6% 4 2 3 3 3 5% 15%	4862
February	1st to 10th	Night	24% 19% 5% 6% 4 2 4 3 4 5% 24%	2660
	11th to 20th	Night	19% 16% 4 7% 5% 3 4 4 4 7% 27%	2319
	21st to end	Night	16% 17% 4 8% 5% 3 4 4 4 7% 27%	1884
March	1st to 10th	Night	18% 13% 4 7% 7% 3 4 5% 6% 7% 28%	2280
	11th to 20th	Night	20% 10% 3 6% 7% 4 5% 5% 4 6% 32%	2199
	21st to end	Night	20% 10% 3 7% 7% 4 6% 5% 6% 6% 25%	2113
April	1st to 10th	Night	12% 10% 3 7% 7% 4 6% 6% 6% 9% 32%	1800
	11th to 20th	Night	17% 8% 3 6% 6% 3 5% 5% 4 6% 35%	1678
	21st to end	Night	12% 7% 3 7% 6% 4 4 5% 5% 8% 39%	1620
May	1st to 10th	Night	10% 6% 3 5% 7% 3 5% 6% 7% 10% 38%	1512
	11th to 20th	Night	11% 5% 2 5% 5% 4 5% 5% 6% 10% 43%	1416
	21st to end	Night	13% 7% 4 6% 5% 4 4 6% 6% 9% 37%	1424
June	1st to 10th	Night	15% 7% 3 6% 5% 4 4 5% 5% 9% 37%	1260
	11th to 20th	Night	13% 6% 2 6% 6% 3 6% 6% 7% 8% 36%	1260
	21st to end	Night	7% 3 2 4 4 2 3 5% 5% 9% 56%	1260
July	1st to 10th	Night	2 2 1 2 3 2 3 4 4 6% 71%	1282
	11th to 20th	Night	2 1 1 2 3 2 3 4 4 8% 71%	1440
	21st to end	Night	1 1 1 1 2 1 3 3 4 5% 78%	1576
August	1st to 10th	Night	3 2 1 2 2 1 2 3 4 7% 73%	1432
	11th to 20th	Night	3 3 1 3 2 2 3 3 4 6% 69%	1546
	21st to end	Night	4 3 1 3 3 2 4 4 5% 6% 66%	1871
September	1st to 10th	Night	5% 3 1 3 3 1 4 5% 5% 6% 65%	1800
	11th to 20th	Night	7% 4 2 4 6% 4 4 6% 5% 7% 51%	1926
	21st to end	Night	12% 5% 2 4 4 3 4 4 5% 7% 50%	1980
October	1st to 10th	Night	13% 5% 2 5% 6% 3 4 5% 5% 6% 46%	2015
	11th to 20th	Night	18% 6% 3 5% 5% 3 4 4 4 6% 43%	2303
	21st to end	Night	20% 7% 3 5% 5% 2 4 5% 5% 6% 38%	2574
November	1st to 10th	Night	28% 11% 3 7% 6% 3 3 4 5% 6% 23%	2405
	11th to 20th	Night	24% 16% 4 6% 5% 3 4 4 5% 5% 24%	2571
	21st to end	Night	26% 16% 4 6% 4 3 4 3 4 5% 24%	2850
December	1st to 10th	Night	24% 17% 5% 5% 5% 3 4 3 5% 6% 23%	2850
	11th to 20th	Night	28% 21% 5% 7% 5% 2 3 3 4 5% 16%	3510
	21st to end	Night	21% 19% 5% 8% 7% 4 5% 5% 4 5% 17%	5214

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% 7% 9% 4 1	2457
	11th to 20th	Day	67% 6% 13% 10% 3 1	2540
	21st to end	Day	74% 8% 10% 6% 2	2794
February	1st to 10th	Day	69% 7% 11% 9% 3 1	1520
	11th to 20th	Day	65% 8% 11% 10% 5%	1756
	21st to end	Day	66% 5% 8% 14% 6%	1570
March	1st to 10th	Day	62% 7% 13% 13% 5% 1	1900
	11th to 20th	Day	56% 8% 15% 18% 3 1	1981
	21st to end	Day	69% 6% 14% 10% 2	2394
April	1st to 10th	Day	59% 8% 15% 15% 3	2160
	11th to 20th	Day	54% 6% 14% 18% 7% 1	2233
	21st to end	Day	51% 8% 15% 19% 6% 1	2340
May	1st to 10th	Day	41% 5% 19% 26% 9%	2447
	11th to 20th	Day	41% 9% 19% 23% 8%	2480
	21st to end	Day	46% 7% 19% 22% 6%	2852
June	1st to 10th	Day	50% 6% 14% 20% 9% 1	2700
	11th to 20th	Day	49% 7% 15% 21% 7% 2	2700
	21st to end	Day	29% 6% 16% 30% 17% 2	2700
July	1st to 10th	Day	22% 4 10% 31% 24% 9%	2601
	11th to 20th	Day	16% 4 12% 25% 32% 10%	2445
	21st to end	Day	11% 3 6% 27% 41% 12%	2589
August	1st to 10th	Day	17% 4 10% 30% 29% 10%	2490
	11th to 20th	Day	16% 5% 13% 31% 30% 4	2352
	21st to end	Day	25% 5% 12% 29% 25% 3	2483
September	1st to 10th	Day	23% 4 13% 32% 21% 7%	2160
	11th to 20th	Day	31% 7% 13% 26% 21% 3	2034
	21st to end	Day	39% 7% 21% 20% 10% 3	1980
October	1st to 10th	Day	41% 6% 15% 29% 9%	1944
	11th to 20th	Day	47% 3 18% 24% 8%	1656
	21st to end	Day	53% 7% 16% 18% 6%	1782
November	1st to 10th	Day	66% 7% 12% 10% 3	1674
	11th to 20th	Day	67% 7% 12% 9% 3 1	1587
	21st to end	Day	70% 5% 12% 9% 4	1330
December	1st to 10th	Day	67% 6% 11% 13% 3	1330
	11th to 20th	Day	78% 4 11% 5% 1	1684
	21st to end	Day	68% 7% 13% 8% 4	2442
January	1st to 10th	Night	77% 7% 8% 6% 1	4503
	11th to 20th	Night	61% 5% 13% 15% 3 3	4420
	21st to end	Night	74% 7% 11% 6% 1 1	4862
February	1st to 10th	Night	64% 7% 12% 12% 4 1	2660
	11th to 20th	Night	59% 8% 13% 14% 5%	2320
	21st to end	Night	57% 7% 12% 16% 7% 1	1884
March	1st to 10th	Night	55% 7% 15% 15% 7% 1	2280
	11th to 20th	Night	53% 6% 14% 20% 6%	2199
	21st to end	Night	58% 10% 15% 12% 4	2113
April	1st to 10th	Night	48% 8% 17% 21% 7%	1800
	11th to 20th	Night	49% 5% 13% 21% 11% 1	1678
	21st to end	Night	43% 7% 15% 24% 10% 1	1620
May	1st to 10th	Night	39% 7% 15% 26% 12%	1512
	11th to 20th	Night	35% 8% 18% 27% 13%	1416
	21st to end	Night	43% 6% 18% 23% 10%	1424
June	1st to 10th	Night	44% 6% 11% 24% 13% 2	1260
	11th to 20th	Night	42% 7% 15% 22% 11% 3	1260
	21st to end	Night	25% 6% 16% 27% 21% 5%	1260
July	1st to 10th	Night	14% 4 9% 27% 32% 15%	1246
	11th to 20th	Night	13% 4 8% 26% 30% 18%	1392
	21st to end	Night	10% 2 5% 19% 41% 22%	1488
August	1st to 10th	Night	14% 2 8% 23% 34% 19%	1424
	11th to 20th	Night	17% 4 8% 26% 36% 9%	1546
	21st to end	Night	20% 5% 9% 26% 33% 7%	1871
September	1st to 10th	Night	19% 6% 10% 30% 26% 9%	1800
	11th to 20th	Night	30% 7% 11% 24% 22% 5%	1926
	21st to end	Night	33% 5% 20% 24% 13% 5%	1980
October	1st to 10th	Night	38% 5% 13% 33% 10%	2015
	11th to 20th	Night	44% 6% 14% 23% 11% 1	2303
	21st to end	Night	48% 8% 14% 21% 9% 1	2574
November	1st to 10th	Night	62% 8% 14% 11% 4	2405
	11th to 20th	Night	62% 9% 14% 10% 5% 1	2571
	21st to end	Night	63% 6% 15% 12% 3	2850
December	1st to 10th	Night	65% 7% 11% 14% 3	2850
	11th to 20th	Night	72% 7% 13% 7% 2	3507
	21st to end	Night	67% 9% 13% 7% 3	5214

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	33% 17% 20% 18% 9% 2	180
	11th to 20th	Day	33% 21% 18% 14% 9% 4	180
	21st to end	Day	31% 10% 30% 22% 8%	198
February	1st to 10th	Day	31% 18% 29% 17% 4 1	180
	11th to 20th	Day	29% 17% 25% 23% 6% 1	379
	21st to end	Day	26% 18% 24% 22% 10%	382
March	1st to 10th	Day	26% 18% 26% 19% 8% 2	460
	11th to 20th	Day	22% 15% 21% 26% 15% 1	460
	21st to end	Day	30% 17% 24% 20% 7% 2	491
April	1st to 10th	Day	26% 17% 27% 20% 9% 1	420
	11th to 20th	Day	23% 20% 26% 19% 10% 2	412
	21st to end	Day	20% 16% 26% 26% 11% 2	420
May	1st to 10th	Day	14% 14% 26% 30% 13% 2	423
	11th to 20th	Day	17% 9% 28% 26% 16% 4	448
	21st to end	Day	16% 9% 20% 31% 19% 5%	613
June	1st to 10th	Day	21% 10% 23% 24% 19% 3	630
	11th to 20th	Day	17% 14% 30% 22% 13% 3	630
	21st to end	Day	10% 9% 21% 31% 25% 4	630
July	1st to 10th	Day	6% 5% 26% 35% 25% 3	596
	11th to 20th	Day	5% 10% 32% 33% 17% 4	444
	21st to end	Day	2 8% 26% 37% 22% 4	487
August	1st to 10th	Day	5% 6% 26% 34% 25% 5%	447
	11th to 20th	Day	4 6% 25% 33% 24% 8%	437
	21st to end	Day	7% 11% 25% 30% 21% 6%	495
September	1st to 10th	Day	9% 8% 31% 28% 20% 4	450
	11th to 20th	Day	12% 11% 23% 32% 19% 4	450
	21st to end	Day	16% 13% 26% 27% 15% 4	450
October	1st to 10th	Day	15% 9% 27% 29% 18% 2	450
	11th to 20th	Day	23% 15% 23% 23% 12% 4	306
	21st to end	Day	30% 13% 23% 24% 8% 1	297
November	1st to 10th	Day	35% 14% 21% 24% 6%	270
	11th to 20th	Day	37% 10% 21% 23% 9%	234
	21st to end	Day	28% 9% 25% 28% 8% 1	180
December	1st to 10th	Day	31% 13% 21% 21% 11% 3	180
	11th to 20th	Day	37% 10% 26% 21% 6% 1	180
	21st to end	Day	37% 11% 22% 24% 5% 1	198
January	1st to 10th	Night	40% 8% 19% 25% 7% 1	818
	11th to 20th	Night	34% 7% 21% 27% 10% 1	760
	21st to end	Night	31% 7% 21% 33% 7%	836
February	1st to 10th	Night	33% 8% 22% 29% 8% 1	760
	11th to 20th	Night	28% 7% 23% 31% 11%	744
	21st to end	Night	25% 9% 21% 31% 14% 1	628
March	1st to 10th	Night	23% 9% 22% 31% 14% 1	760
	11th to 20th	Night	26% 7% 16% 34% 16% 1	760
	21st to end	Night	24% 7% 21% 33% 14% 1	820
April	1st to 10th	Night	19% 6% 18% 38% 19% 1	720
	11th to 20th	Night	18% 8% 24% 34% 14% 2	610
	21st to end	Night	15% 6% 21% 37% 18% 2	540
May	1st to 10th	Night	14% 3 18% 37% 25% 3	432
	11th to 20th	Night	11% 5% 14% 32% 32% 5%	354
	21st to end	Night	17% 7% 14% 30% 27% 5%	389
June	1st to 10th	Night	19% 4 15% 33% 26% 3	360
	11th to 20th	Night	14% 5% 18% 39% 22% 2	360
	21st to end	Night	8% 3 12% 39% 35% 3	360
July	1st to 10th	Night	3 2 9% 43% 40% 4	350
	11th to 20th	Night	3 1 13% 49% 33% 1	348
	21st to end	Night	3 2 7% 43% 43% 3	394
August	1st to 10th	Night	4 2 9% 37% 43% 4	358
	11th to 20th	Night	5% 2 7% 36% 43% 7%	478
	21st to end	Night	4 3 14% 40% 36% 3	683
September	1st to 10th	Night	6% 1 15% 42% 31% 5%	720
	11th to 20th	Night	9% 3 12% 33% 38% 5%	720
	21st to end	Night	14% 4 15% 36% 27% 4	720
October	1st to 10th	Night	16% 5% 14% 39% 25% 1	720
	11th to 20th	Night	20% 4 17% 34% 23% 1	720
	21st to end	Night	25% 5% 22% 32% 15% 2	792
November	1st to 10th	Night	33% 7% 17% 34% 8%	740
	11th to 20th	Night	33% 9% 20% 30% 9% 1	786
	21st to end	Night	33% 7% 18% 30% 12%	950
December	1st to 10th	Night	32% 7% 17% 31% 12% 1	950
	11th to 20th	Night	36% 8% 22% 28% 6%	950
	21st to end	Night	37% 9% 20% 27% 6%	1045

Page generated at 2024-03-24 20:36:59. Version ac07

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