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 2024-11-04.

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	13% 10% 3 6% 4 4 4 3 5% 6% 41%	105284
	Night	16% 11% 3 6% 4 4 4 3 5% 6% 38%	102277
Transparency	Day	43% 6% 13% 21% 13% 4	105049
	Night	47% 7% 13% 19% 11% 4	102158
Seeing	Day	18% 12% 25% 27% 15% 3	14994
	Night	22% 6% 18% 34% 19% 2	24085

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	22% 33% 7% 8% 4 3 3 3 4 4 10%	2457
	11th to 20th	Day	22% 20% 4 7% 5% 5% 5% 3 4 5% 21%	2516
	21st to end	Day	32% 20% 4 9% 4 4 4 2 3 4 14%	2794
February	1st to 10th	Day	25% 21% 5% 9% 4 3 4 3 5% 4 18%	1520
	11th to 20th	Day	19% 19% 4 11% 5% 4 4 3 4 5% 22%	1746
	21st to end	Day	19% 19% 4 11% 6% 4 3 3 4 6% 21%	1570
March	1st to 10th	Day	15% 16% 4 8% 5% 5% 5% 4 5% 7% 27%	3138
	11th to 20th	Day	13% 11% 2 6% 3 3 4 3 4 5% 45%	3320
	21st to end	Day	20% 16% 5% 10% 6% 6% 5% 4 5% 5% 18%	4062
April	1st to 10th	Day	20% 13% 4 8% 7% 5% 5% 4 6% 6% 23%	2280
	11th to 20th	Day	15% 12% 3 8% 6% 5% 5% 5% 5% 6% 29%	2359
	21st to end	Day	13% 10% 4 8% 6% 6% 5% 4 5% 6% 31%	2470
May	1st to 10th	Day	12% 10% 3 8% 6% 5% 5% 4 5% 7% 34%	4295
	11th to 20th	Day	8% 6% 2 7% 4 5% 5% 5% 7% 11% 39%	4377
	21st to end	Day	13% 9% 4 10% 6% 5% 6% 5% 7% 8% 27%	5053
June	1st to 10th	Day	19% 9% 3 7% 5% 5% 5% 4 5% 7% 33%	2850
	11th to 20th	Day	16% 7% 2 7% 6% 6% 5% 5% 6% 8% 31%	2850
	21st to end	Day	7% 4 2 5% 5% 4 5% 4 5% 7% 53%	2850
July	1st to 10th	Day	2 2 1 3 3 3 3 3 4 5% 71%	4686
	11th to 20th	Day	2 1 2 2 2 2 2 4 5% 78%	4420
	21st to end	Day	2 1 1 2 2 3 3 3 4 5% 75%	4790
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	29% 16% 4 8% 4 3 3 3 4 5% 20%	1701
	11th to 20th	Day	29% 17% 4 8% 4 3 4 2 4 5% 20%	1587
	21st to end	Day	22% 22% 5% 9% 6% 3 3 2 4 4 19%	1330
December	1st to 10th	Day	22% 16% 6% 9% 6% 5% 3 3 4 5% 21%	1330
	11th to 20th	Day	31% 22% 6% 8% 5% 4 3 2 3 4 12%	1682
	21st to end	Day	23% 20% 4 10% 5% 4 3 3 4 6% 18%	2442
January	1st to 10th	Night	28% 28% 5% 8% 4 3 3 3 4 3 12%	4503
	11th to 20th	Night	21% 16% 4 9% 5% 4 3 3 3 5% 28%	4382
	21st to end	Night	33% 22% 4 6% 4 3 3 2 3 4 15%	4862
February	1st to 10th	Night	24% 20% 4 7% 4 3 3 2 4 4 24%	2660
	11th to 20th	Night	19% 17% 4 8% 4 4 4 3 4 7% 26%	2319
	21st to end	Night	15% 19% 4 8% 4 4 4 4 5% 7% 27%	1884
March	1st to 10th	Night	12% 14% 4 8% 5% 4 4 4 6% 7% 32%	3736
	11th to 20th	Night	15% 10% 2 6% 4 3 3 2 3 4 47%	3659
	21st to end	Night	20% 11% 3 10% 7% 6% 6% 4 6% 5% 22%	3587
April	1st to 10th	Night	12% 11% 3 7% 7% 5% 5% 4 7% 8% 31%	1900
	11th to 20th	Night	16% 9% 3 7% 5% 5% 5% 3 4 7% 36%	1772
	21st to end	Night	13% 8% 3 7% 5% 4 4 5% 5% 8% 38%	1710
May	1st to 10th	Night	13% 8% 3 8% 6% 5% 5% 5% 7% 8% 31%	2654
	11th to 20th	Night	9% 4 2 5% 4 4 4 4 6% 11% 46%	2516
	21st to end	Night	16% 8% 3 8% 6% 6% 5% 4 7% 9% 29%	2522
June	1st to 10th	Night	15% 7% 3 7% 4 4 4 4 5% 9% 38%	1330
	11th to 20th	Night	12% 7% 2 6% 5% 5% 6% 5% 7% 8% 36%	1330
	21st to end	Night	7% 4 2 4 3 2 4 4 5% 9% 56%	1330
July	1st to 10th	Night	1 2 1 3 2 2 3 3 4 6% 73%	2270
	11th to 20th	Night	2 1 1 2 2 2 2 2 3 4 81%	2540
	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	28% 12% 3 8% 5% 4 3 4 5% 6% 22%	2450
	11th to 20th	Night	23% 17% 3 6% 5% 4 4 4 5% 6% 23%	2571
	21st to end	Night	26% 17% 4 7% 4 4 4 2 5% 5% 24%	2850
December	1st to 10th	Night	23% 18% 4 6% 5% 4 4 3 5% 5% 22%	2850
	11th to 20th	Night	27% 22% 5% 8% 4 3 3 2 4 5% 16%	3510
	21st to end	Night	21% 20% 5% 10% 6% 5% 5% 4 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	54% 7% 11% 17% 9%	3138
	11th to 20th	Day	42% 6% 23% 26% 3	3321
	21st to end	Day	67% 7% 11% 11% 3	4062
April	1st to 10th	Day	59% 8% 15% 15% 3	2280
	11th to 20th	Day	53% 6% 14% 18% 8% 1	2359
	21st to end	Day	52% 8% 14% 19% 6% 1	2470
May	1st to 10th	Day	47% 7% 14% 24% 8%	4295
	11th to 20th	Day	34% 8% 21% 28% 8%	4380
	21st to end	Day	49% 9% 17% 20% 4	5054
June	1st to 10th	Day	49% 6% 13% 20% 11% 1	2850
	11th to 20th	Day	47% 6% 15% 21% 9% 2	2850
	21st to end	Day	30% 6% 16% 29% 17% 3	2850
July	1st to 10th	Day	15% 4 8% 22% 33% 18%	4613
	11th to 20th	Day	10% 3 7% 15% 31% 34%	4345
	21st to end	Day	13% 3 6% 24% 35% 19%	4639
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	1701
	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	47% 9% 15% 21% 8%	3736
	11th to 20th	Night	42% 6% 20% 28% 4	3659
	21st to end	Night	61% 10% 14% 12% 3	3587
April	1st to 10th	Night	49% 8% 17% 20% 6%	1900
	11th to 20th	Night	48% 5% 13% 21% 12% 1	1772
	21st to end	Night	43% 7% 15% 23% 10% 1	1710
May	1st to 10th	Night	46% 10% 13% 22% 9%	2654
	11th to 20th	Night	29% 8% 15% 35% 12%	2516
	21st to end	Night	48% 9% 15% 20% 8%	2522
June	1st to 10th	Night	43% 6% 11% 24% 14% 2	1330
	11th to 20th	Night	42% 7% 14% 22% 12% 3	1330
	21st to end	Night	25% 6% 15% 27% 22% 5%	1330
July	1st to 10th	Night	12% 4 7% 22% 35% 21%	2234
	11th to 20th	Night	9% 2 4 15% 25% 44%	2492
	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% 8% 14% 11% 4	2450
	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% 16% 24% 21% 8% 2	506
April	1st to 10th	Day	26% 18% 27% 20% 8% 1	460
	11th to 20th	Day	21% 19% 27% 19% 11% 2	452
	21st to end	Day	19% 16% 27% 25% 11% 2	460
May	1st to 10th	Day	14% 15% 26% 29% 13% 2	463
	11th to 20th	Day	17% 10% 28% 26% 16% 3	488
	21st to end	Day	15% 10% 21% 31% 18% 5%	665
June	1st to 10th	Day	21% 10% 24% 24% 19% 3	680
	11th to 20th	Day	16% 14% 30% 23% 14% 3	680
	21st to end	Day	10% 9% 21% 31% 25% 4	680
July	1st to 10th	Day	5% 5% 25% 35% 25% 4	644
	11th to 20th	Day	4 9% 29% 34% 19% 5%	484
	21st to end	Day	3 8% 25% 37% 22% 4	531
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	36% 14% 21% 23% 6%	279
	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% 20% 33% 14% 1	836
April	1st to 10th	Night	19% 6% 19% 37% 18% 1	760
	11th to 20th	Night	18% 7% 24% 35% 14% 2	644
	21st to end	Night	15% 6% 22% 37% 18% 2	570
May	1st to 10th	Night	13% 4 18% 37% 25% 3	455
	11th to 20th	Night	11% 5% 14% 33% 32% 5%	374
	21st to end	Night	17% 7% 15% 31% 26% 5%	411
June	1st to 10th	Night	19% 5% 15% 34% 25% 3	380
	11th to 20th	Night	14% 5% 17% 40% 22% 2	380
	21st to end	Night	8% 3 13% 40% 33% 3	380
July	1st to 10th	Night	3 2 8% 43% 40% 4	370
	11th to 20th	Night	3 1 12% 48% 35% 1	368
	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	34% 7% 17% 34% 8%	754
	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 2024-11-01 19:47:35. Version ac07

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