Rathdrum
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rathdrum clear sky chart from 2005-11-06 to 2026-02-16.

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% 10% 3 7% 4 4 4 3 5% 6% 42%	134350
	Night	13% 11% 3 7% 5% 4 4 3 5% 6% 38%	135208
Transparency	Day	42% 6% 13% 22% 13% 4	134077
	Night	45% 7% 13% 19% 12% 4	135058
Seeing	Day	18% 11% 24% 26% 17% 5%	16410
	Night	22% 6% 16% 33% 21% 3	25732

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% 27% 7% 13% 5% 5% 4 3 4 4 8%	4723
	11th to 20th	Day	12% 10% 3 8% 7% 7% 6% 4 5% 7% 32%	4716
	21st to end	Day	18% 15% 4 7% 6% 5% 4 4 5% 6% 27%	5186
February	1st to 10th	Day	20% 20% 5% 9% 4 4 5% 3 5% 4 20%	1680
	11th to 20th	Day	17% 19% 5% 9% 5% 4 4 4 4 6% 24%	1914
	21st to end	Day	18% 21% 4 10% 5% 4 5% 3 4 4 23%	1650
March	1st to 10th	Day	10% 13% 3 7% 4 6% 6% 5% 7% 7% 31%	4518
	11th to 20th	Day	12% 12% 3 8% 5% 4 4 3 4 6% 38%	4729
	21st to end	Day	17% 17% 4 10% 6% 6% 5% 4 5% 7% 20%	5870
April	1st to 10th	Day	17% 13% 4 7% 7% 6% 5% 5% 5% 8% 25%	2400
	11th to 20th	Day	13% 10% 3 8% 6% 5% 5% 4 5% 6% 34%	2461
	21st to end	Day	13% 9% 3 8% 5% 6% 6% 4 6% 6% 34%	2600
May	1st to 10th	Day	8% 6% 2 7% 5% 5% 5% 4 7% 8% 45%	6144
	11th to 20th	Day	9% 8% 3 8% 5% 5% 5% 4 7% 11% 35%	6277
	21st to end	Day	9% 6% 2 7% 5% 5% 6% 4 6% 8% 42%	7077
June	1st to 10th	Day	17% 7% 2 6% 5% 5% 4 3 6% 7% 38%	3000
	11th to 20th	Day	15% 6% 2 6% 6% 5% 5% 4 7% 8% 37%	3000
	21st to end	Day	7% 4 1 5% 4 4 4 4 5% 7% 55%	3000
July	1st to 10th	Day	4 2 1 3 2 2 3 2 4 5% 71%	6511
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 5% 78%	6320
	21st to end	Day	3 2 1 3 2 2 3 2 4 5% 74%	6874
August	1st to 10th	Day	3 3 1 3 2 3 3 2 4 6% 68%	4541
	11th to 20th	Day	3 3 1 4 2 3 3 3 5% 7% 64%	4253
	21st to end	Day	3 3 2 4 3 3 4 3 5% 7% 62%	4446
September	1st to 10th	Day	5% 3 1 3 3 3 3 3 4 7% 65%	2400
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 4 5% 7% 51%	2270
	21st to end	Day	9% 6% 2 5% 4 4 5% 4 6% 7% 48%	2200
October	1st to 10th	Day	8% 5% 1 5% 3 3 3 3 4 7% 56%	3509
	11th to 20th	Day	12% 7% 3 6% 4 5% 4 3 5% 7% 43%	3031
	21st to end	Day	19% 10% 5% 9% 5% 4 5% 4 5% 6% 29%	3200
November	1st to 10th	Day	26% 15% 4 7% 4 3 3 3 4 6% 24%	1854
	11th to 20th	Day	24% 17% 5% 9% 5% 4 4 3 4 4 22%	1806
	21st to end	Day	20% 20% 5% 12% 6% 4 3 3 4 4 19%	1480
December	1st to 10th	Day	16% 14% 6% 13% 5% 5% 4 4 5% 7% 21%	2360
	11th to 20th	Day	23% 25% 7% 11% 5% 5% 4 3 4 4 10%	2712
	21st to end	Day	21% 27% 6% 11% 5% 5% 3 2 4 4 11%	3638
January	1st to 10th	Night	22% 20% 5% 11% 5% 5% 5% 3 5% 5% 12%	8172
	11th to 20th	Night	11% 10% 3 10% 6% 7% 6% 4 6% 9% 28%	8182
	21st to end	Night	18% 14% 3 7% 4 5% 4 3 5% 7% 30%	8994
February	1st to 10th	Night	20% 19% 5% 8% 5% 3 4 3 5% 6% 23%	2940
	11th to 20th	Night	16% 16% 4 8% 5% 5% 3 2 4 5% 30%	2481
	21st to end	Night	14% 16% 4 8% 5% 5% 5% 3 5% 6% 28%	1980
March	1st to 10th	Night	9% 11% 3 8% 4 4 4 4 6% 7% 39%	5376
	11th to 20th	Night	14% 13% 3 7% 4 3 4 3 4 5% 41%	5270
	21st to end	Night	15% 13% 3 9% 6% 6% 7% 5% 7% 7% 21%	5104
April	1st to 10th	Night	11% 11% 3 6% 5% 5% 6% 6% 7% 7% 33%	2000
	11th to 20th	Night	12% 10% 2 7% 5% 5% 4 3 5% 6% 40%	1889
	21st to end	Night	10% 9% 3 7% 6% 5% 5% 4 6% 7% 39%	1800
May	1st to 10th	Night	9% 5% 2 6% 5% 5% 5% 4 6% 7% 46%	3808
	11th to 20th	Night	10% 8% 3 8% 5% 5% 5% 4 6% 9% 38%	3616
	21st to end	Night	10% 5% 2 6% 4 4 5% 4 6% 7% 45%	3795
June	1st to 10th	Night	14% 5% 2 6% 4 5% 5% 4 5% 6% 44%	1400
	11th to 20th	Night	11% 4 3 6% 5% 5% 5% 4 7% 9% 41%	1400
	21st to end	Night	6% 5% 2 5% 5% 4 4 4 6% 8% 54%	1400
July	1st to 10th	Night	4 1 1 2 2 2 2 2 4 5% 76%	3445
	11th to 20th	Night	2 2 1 2 2 2 2 2 2 4 80%	3640
	21st to end	Night	3 2 1 3 2 2 2 2 4 5% 73%	3969
August	1st to 10th	Night	3 3 1 2 2 1 3 2 5% 7% 71%	2609
	11th to 20th	Night	3 3 2 5% 4 3 4 4 5% 7% 61%	2802
	21st to end	Night	3 3 1 4 3 4 4 4 5% 6% 62%	3466
September	1st to 10th	Night	4 2 1 4 3 3 3 2 5% 7% 65%	2000
	11th to 20th	Night	7% 5% 2 6% 4 4 5% 3 6% 8% 51%	2130
	21st to end	Night	11% 5% 2 5% 4 3 4 3 6% 7% 53%	2200
October	1st to 10th	Night	7% 3 2 4 3 3 3 3 5% 8% 59%	3687
	11th to 20th	Night	12% 5% 2 5% 4 4 4 4 6% 7% 47%	4120
	21st to end	Night	14% 7% 3 6% 4 5% 4 4 6% 7% 41%	4600
November	1st to 10th	Night	23% 12% 3 7% 4 4 4 3 6% 7% 26%	2665
	11th to 20th	Night	21% 16% 3 8% 5% 5% 5% 4 4 5% 25%	2809
	21st to end	Night	23% 14% 3 8% 6% 4 3 3 4 6% 25%	3116
December	1st to 10th	Night	12% 11% 4 10% 6% 5% 5% 4 6% 10% 26%	5040
	11th to 20th	Night	21% 22% 6% 11% 6% 5% 4 3 4 5% 13%	5700
	21st to end	Night	21% 21% 7% 12% 6% 5% 5% 4 4 4 12%	7603

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% 5% 1	4723
	11th to 20th	Day	48% 9% 21% 16% 5% 1	4740
	21st to end	Day	56% 6% 17% 14% 5%	5187
February	1st to 10th	Day	67% 6% 11% 9% 5% 1	1680
	11th to 20th	Day	63% 7% 12% 11% 7%	1924
	21st to end	Day	66% 6% 8% 15% 4	1650
March	1st to 10th	Day	49% 5% 14% 18% 13%	4518
	11th to 20th	Day	48% 6% 17% 26% 3	4729
	21st to end	Day	64% 7% 13% 12% 3	5870
April	1st to 10th	Day	58% 6% 17% 16% 4	2400
	11th to 20th	Day	50% 6% 14% 19% 10% 1	2461
	21st to end	Day	50% 8% 14% 19% 8% 1	2600
May	1st to 10th	Day	36% 6% 12% 28% 18%	6144
	11th to 20th	Day	39% 7% 18% 28% 7%	6280
	21st to end	Day	37% 8% 19% 27% 8%	7078
June	1st to 10th	Day	45% 6% 13% 23% 12% 1	3000
	11th to 20th	Day	43% 7% 14% 22% 11% 2	3000
	21st to end	Day	28% 6% 15% 30% 18% 3	3000
July	1st to 10th	Day	16% 3 9% 23% 30% 18%	6442
	11th to 20th	Day	11% 3 6% 24% 30% 27%	6245
	21st to end	Day	14% 3 6% 32% 30% 15%	6681
August	1st to 10th	Day	18% 3 6% 25% 36% 12%	4524
	11th to 20th	Day	18% 4 10% 40% 24% 4	4294
	21st to end	Day	20% 4 12% 35% 25% 3	4445
September	1st to 10th	Day	20% 5% 11% 31% 23% 10%	2400
	11th to 20th	Day	32% 6% 13% 25% 21% 3	2270
	21st to end	Day	35% 6% 19% 25% 12% 3	2200
October	1st to 10th	Day	29% 4 13% 38% 16%	3509
	11th to 20th	Day	41% 5% 19% 23% 12% 1	3031
	21st to end	Day	55% 7% 15% 18% 6%	3200
November	1st to 10th	Day	63% 7% 14% 13% 3	1854
	11th to 20th	Day	67% 7% 13% 9% 4 1	1806
	21st to end	Day	67% 6% 11% 12% 4	1480
December	1st to 10th	Day	59% 11% 17% 11% 2	2360
	11th to 20th	Day	78% 6% 9% 6% 1	2714
	21st to end	Day	76% 6% 9% 6% 3	3638
January	1st to 10th	Night	72% 9% 11% 8% 1	8172
	11th to 20th	Night	48% 12% 19% 15% 5% 1	8220
	21st to end	Night	54% 7% 17% 17% 5%	8994
February	1st to 10th	Night	63% 6% 13% 12% 4 1	2940
	11th to 20th	Night	57% 6% 15% 14% 7% 1	2482
	21st to end	Night	56% 7% 12% 18% 7% 1	1980
March	1st to 10th	Night	42% 6% 14% 23% 14% 1	5376
	11th to 20th	Night	46% 5% 15% 26% 7%	5270
	21st to end	Night	56% 11% 14% 16% 3	5104
April	1st to 10th	Night	46% 7% 16% 23% 7% 1	2000
	11th to 20th	Night	46% 4 11% 23% 14% 1	1889
	21st to end	Night	44% 7% 12% 24% 12% 1	1800
May	1st to 10th	Night	35% 7% 11% 25% 22% 1	3805
	11th to 20th	Night	40% 7% 13% 27% 12% 1	3616
	21st to end	Night	34% 9% 15% 30% 11% 1	3795
June	1st to 10th	Night	39% 7% 10% 24% 18% 2	1400
	11th to 20th	Night	38% 5% 12% 23% 17% 4	1400
	21st to end	Night	28% 6% 10% 29% 21% 6%	1400
July	1st to 10th	Night	12% 2 7% 19% 35% 24%	3405
	11th to 20th	Night	11% 2 3 20% 29% 36%	3592
	21st to end	Night	14% 3 5% 25% 31% 23%	3857
August	1st to 10th	Night	15% 3 5% 20% 38% 19%	2601
	11th to 20th	Night	21% 4 8% 33% 27% 7%	2827
	21st to end	Night	22% 5% 10% 26% 29% 8%	3466
September	1st to 10th	Night	19% 4 9% 28% 28% 13%	2000
	11th to 20th	Night	31% 5% 11% 24% 22% 7%	2130
	21st to end	Night	31% 5% 16% 28% 16% 5%	2200
October	1st to 10th	Night	25% 4 12% 42% 17% 1	3687
	11th to 20th	Night	37% 5% 15% 24% 19% 1	4120
	21st to end	Night	40% 7% 17% 26% 8% 2	4600
November	1st to 10th	Night	57% 7% 16% 15% 4 1	2665
	11th to 20th	Night	63% 7% 14% 11% 5% 1	2809
	21st to end	Night	61% 6% 16% 13% 4	3116
December	1st to 10th	Night	52% 14% 18% 15% 2	5040
	11th to 20th	Night	73% 7% 12% 7% 1	5697
	21st to end	Night	72% 9% 10% 7% 2	7603

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% 16% 20% 11% 3	220
	11th to 20th	Day	32% 10% 18% 22% 13% 6%	220
	21st to end	Day	31% 7% 24% 22% 13% 3	242
February	1st to 10th	Day	30% 15% 28% 15% 9% 3	220
	11th to 20th	Day	31% 14% 21% 23% 11% 1	458
	21st to end	Day	31% 14% 23% 21% 10% 1	414
March	1st to 10th	Day	26% 18% 23% 20% 10% 2	500
	11th to 20th	Day	24% 12% 23% 21% 18% 2	500
	21st to end	Day	30% 16% 23% 21% 9% 1	550
April	1st to 10th	Day	25% 14% 27% 21% 10% 4	500
	11th to 20th	Day	19% 19% 26% 20% 12% 4	492
	21st to end	Day	18% 14% 26% 25% 13% 4	500
May	1st to 10th	Day	14% 12% 26% 30% 14% 5%	503
	11th to 20th	Day	18% 10% 28% 23% 15% 5%	528
	21st to end	Day	14% 9% 21% 28% 20% 9%	643
June	1st to 10th	Day	18% 8% 23% 25% 21% 5%	730
	11th to 20th	Day	17% 14% 29% 23% 15% 3	730
	21st to end	Day	7% 9% 23% 30% 24% 7%	730
July	1st to 10th	Day	7% 5% 25% 32% 26% 4	613
	11th to 20th	Day	5% 8% 27% 32% 22% 6%	524
	21st to end	Day	3 7% 23% 36% 22% 9%	575
August	1st to 10th	Day	7% 4 23% 34% 24% 8%	527
	11th to 20th	Day	5% 3 21% 37% 24% 10%	517
	21st to end	Day	7% 9% 26% 27% 22% 10%	583
September	1st to 10th	Day	7% 8% 25% 26% 23% 11%	530
	11th to 20th	Day	12% 9% 23% 25% 22% 8%	530
	21st to end	Day	12% 12% 27% 22% 21% 5%	530
October	1st to 10th	Day	12% 9% 25% 27% 19% 7%	530
	11th to 20th	Day	23% 11% 19% 26% 13% 8%	390
	21st to end	Day	31% 8% 21% 25% 12% 3	363
November	1st to 10th	Day	36% 9% 18% 24% 12%	330
	11th to 20th	Day	37% 11% 18% 19% 14% 1	286
	21st to end	Day	29% 11% 22% 24% 13% 1	220
December	1st to 10th	Day	34% 8% 21% 16% 15% 6%	220
	11th to 20th	Day	38% 14% 19% 19% 8% 2	220
	21st to end	Day	38% 11% 18% 21% 11% 2	242
January	1st to 10th	Night	40% 8% 15% 25% 10% 2	840
	11th to 20th	Night	30% 7% 15% 31% 15% 2	840
	21st to end	Night	27% 6% 15% 34% 16% 2	924
February	1st to 10th	Night	33% 8% 19% 27% 11% 2	840
	11th to 20th	Night	28% 7% 15% 34% 15% 1	804
	21st to end	Night	23% 10% 20% 26% 18% 2	660
March	1st to 10th	Night	22% 9% 17% 34% 17% 2	800
	11th to 20th	Night	24% 7% 17% 32% 19% 1	800
	21st to end	Night	23% 8% 21% 33% 13% 2	880
April	1st to 10th	Night	19% 7% 18% 37% 18% 2	800
	11th to 20th	Night	18% 6% 25% 34% 16% 2	701
	21st to end	Night	16% 8% 19% 35% 21% 2	600
May	1st to 10th	Night	12% 5% 18% 34% 27% 4	477
	11th to 20th	Night	13% 4 16% 30% 28% 8%	394
	21st to end	Night	15% 4 14% 32% 30% 5%	433
June	1st to 10th	Night	15% 6% 15% 35% 26% 4	400
	11th to 20th	Night	14% 4 24% 33% 22% 3	400
	21st to end	Night	7% 2 14% 38% 34% 5%	400
July	1st to 10th	Night	4 2 11% 39% 42% 2	390
	11th to 20th	Night	3 2 14% 44% 34% 2	388
	21st to end	Night	2 1 9% 40% 44% 4	438
August	1st to 10th	Night	3 2 11% 37% 40% 6%	398
	11th to 20th	Night	3 2 6% 39% 39% 10%	531
	21st to end	Night	5% 4 12% 36% 39% 4	790
September	1st to 10th	Night	6% 2 12% 38% 36% 6%	800
	11th to 20th	Night	10% 4 13% 33% 34% 8%	800
	21st to end	Night	15% 3 16% 35% 27% 5%	800
October	1st to 10th	Night	16% 4 13% 39% 27% 2	800
	11th to 20th	Night	20% 6% 14% 32% 25% 3	800
	21st to end	Night	23% 5% 21% 32% 18% 3	880
November	1st to 10th	Night	31% 7% 14% 34% 13%	820
	11th to 20th	Night	33% 8% 17% 28% 13% 1	840
	21st to end	Night	32% 8% 14% 28% 16% 2	1016
December	1st to 10th	Night	27% 8% 15% 31% 17% 1	1050
	11th to 20th	Night	36% 8% 17% 30% 9%	1050
	21st to end	Night	37% 9% 18% 27% 9% 1	1148

Page generated at 2026-02-12 22:42:14. Version ac07

Copyright © 2026 Attilla Danko.