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 2024-11-30.

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	12% 9% 3 6% 4 4 4 3 5% 6% 42%	105418
	Night	14% 10% 3 7% 5% 4 4 3 5% 6% 39%	102759
Transparency	Day	42% 6% 12% 21% 14% 5%	105186
	Night	45% 6% 12% 20% 12% 5%	102636
Seeing	Day	19% 11% 24% 26% 17% 5%	14959
	Night	22% 6% 16% 32% 21% 3	24127

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% 27% 6% 9% 4 5% 4 4 4 4 9%	2539
	11th to 20th	Day	23% 16% 3 7% 6% 5% 5% 4 4 5% 22%	2516
	21st to end	Day	28% 21% 5% 9% 5% 4 4 3 4 3 14%	2794
February	1st to 10th	Day	22% 19% 5% 9% 4 4 5% 3 5% 4 20%	1520
	11th to 20th	Day	18% 18% 5% 9% 5% 4 4 4 4 6% 25%	1770
	21st to end	Day	18% 21% 4 10% 5% 4 5% 3 4 4 23%	1570
March	1st to 10th	Day	14% 16% 4 8% 5% 5% 5% 4 6% 6% 28%	3138
	11th to 20th	Day	11% 10% 2 6% 4 4 4 3 4 5% 45%	3297
	21st to end	Day	18% 17% 4 10% 7% 6% 5% 4 5% 5% 20%	4092
April	1st to 10th	Day	17% 13% 4 7% 6% 6% 5% 5% 5% 8% 24%	2280
	11th to 20th	Day	14% 10% 4 8% 6% 5% 5% 4 5% 6% 32%	2336
	21st to end	Day	14% 9% 3 8% 5% 6% 6% 4 5% 6% 33%	2470
May	1st to 10th	Day	11% 8% 2 8% 5% 6% 5% 5% 6% 7% 37%	4296
	11th to 20th	Day	8% 6% 2 6% 5% 5% 4 4 7% 11% 43%	4377
	21st to end	Day	11% 7% 3 8% 6% 6% 6% 4 7% 8% 32%	4931
June	1st to 10th	Day	18% 7% 2 6% 5% 5% 4 3 6% 7% 37%	2850
	11th to 20th	Day	16% 6% 2 6% 6% 5% 5% 4 6% 8% 36%	2850
	21st to end	Day	7% 4 1 5% 4 4 4 4 5% 7% 55%	2850
July	1st to 10th	Day	3 2 1 3 2 2 2 2 3 5% 75%	4555
	11th to 20th	Day	2 1 1 2 2 2 2 2 3 5% 79%	4420
	21st to end	Day	1 1 1 2 2 2 3 2 4 5% 75%	4790
August	1st to 10th	Day	3 3 1 3 2 3 3 2 4 6% 69%	4401
	11th to 20th	Day	3 3 1 4 3 3 3 3 6% 7% 64%	4120
	21st to end	Day	3 3 1 4 3 3 4 3 5% 7% 63%	4310
September	1st to 10th	Day	6% 3 1 3 3 3 3 3 4 7% 64%	2280
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 4 5% 7% 50%	2157
	21st to end	Day	10% 6% 2 5% 4 4 5% 4 7% 6% 47%	2090
October	1st to 10th	Day	9% 5% 1 5% 3 3 3 3 4 7% 56%	3402
	11th to 20th	Day	12% 7% 3 6% 4 5% 4 3 5% 7% 43%	2938
	21st to end	Day	19% 10% 5% 9% 5% 4 5% 4 5% 6% 29%	3101
November	1st to 10th	Day	26% 16% 4 7% 4 3 3 3 4 6% 24%	1764
	11th to 20th	Day	24% 17% 5% 9% 4 4 4 3 4 4 23%	1720
	21st to end	Day	20% 21% 5% 12% 5% 3 3 3 4 4 19%	1406
December	1st to 10th	Day	20% 16% 6% 9% 5% 5% 4 3 5% 7% 20%	1330
	11th to 20th	Day	25% 24% 7% 11% 6% 4 4 3 3 4 10%	1682
	21st to end	Day	20% 22% 5% 12% 5% 5% 3 3 4 5% 16%	2476
January	1st to 10th	Night	25% 22% 5% 9% 5% 5% 4 3 4 3 13%	4406
	11th to 20th	Night	20% 16% 4 10% 5% 4 4 2 3 6% 27%	4382
	21st to end	Night	29% 21% 4 8% 4 4 3 3 3 5% 17%	4862
February	1st to 10th	Night	21% 18% 5% 7% 5% 3 4 3 4 5% 25%	2660
	11th to 20th	Night	16% 15% 4 8% 5% 5% 4 3 5% 5% 29%	2294
	21st to end	Night	14% 16% 4 8% 6% 5% 5% 4 5% 6% 28%	1884
March	1st to 10th	Night	11% 13% 3 8% 5% 5% 4 4 6% 6% 35%	3736
	11th to 20th	Night	13% 9% 2 5% 4 3 3 3 4 4 50%	3682
	21st to end	Night	15% 12% 3 9% 7% 6% 7% 5% 6% 7% 24%	3560
April	1st to 10th	Night	11% 11% 3 5% 5% 5% 6% 6% 7% 7% 34%	1900
	11th to 20th	Night	13% 10% 2 8% 6% 5% 4 3 5% 6% 39%	1794
	21st to end	Night	11% 9% 2 7% 6% 5% 5% 4 6% 7% 38%	1710
May	1st to 10th	Night	11% 7% 2 7% 6% 6% 6% 5% 7% 7% 36%	2652
	11th to 20th	Night	6% 5% 2 6% 4 4 5% 4 7% 10% 48%	2516
	21st to end	Night	14% 7% 3 7% 5% 5% 5% 4 7% 8% 34%	2641
June	1st to 10th	Night	14% 6% 2 6% 4 4 6% 4 5% 6% 42%	1330
	11th to 20th	Night	12% 4 3 7% 5% 5% 5% 4 7% 9% 41%	1330
	21st to end	Night	6% 4 2 5% 4 3 4 3 6% 7% 55%	1330
July	1st to 10th	Night	2 1 1 3 2 2 2 2 4 5% 75%	2401
	11th to 20th	Night	2 1 1 2 2 1 2 2 3 4 82%	2540
	21st to end	Night	2 2 1 2 2 1 2 2 4 5% 77%	2762
August	1st to 10th	Night	3 3 1 2 2 1 3 2 5% 6% 72%	2529
	11th to 20th	Night	3 3 2 4 4 3 4 3 5% 7% 62%	2715
	21st to end	Night	3 3 1 4 3 4 4 4 5% 6% 63%	3360
September	1st to 10th	Night	4 2 1 4 2 3 3 2 5% 7% 66%	1900
	11th to 20th	Night	7% 5% 2 6% 4 4 5% 3 6% 8% 50%	2023
	21st to end	Night	11% 5% 2 5% 4 3 4 3 6% 7% 52%	2090
October	1st to 10th	Night	7% 3 2 4 3 3 3 3 5% 8% 59%	3574
	11th to 20th	Night	12% 5% 1 5% 4 4 4 4 5% 7% 47%	3993
	21st to end	Night	14% 7% 3 6% 4 4 4 4 6% 7% 41%	4457
November	1st to 10th	Night	24% 12% 3 7% 4 4 4 3 6% 7% 26%	2535
	11th to 20th	Night	21% 16% 3 7% 5% 5% 5% 4 4 5% 25%	2675
	21st to end	Night	23% 13% 3 8% 6% 4 4 4 4 6% 25%	2967
December	1st to 10th	Night	18% 16% 5% 9% 5% 5% 4 3 5% 5% 25%	2850
	11th to 20th	Night	24% 21% 5% 10% 6% 5% 4 3 4 4 15%	3510
	21st to end	Night	20% 17% 6% 11% 7% 5% 6% 4 5% 5% 15%	5209

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	77% 7% 9% 5% 2	2539
	11th to 20th	Day	64% 5% 13% 13% 3 2	2540
	21st to end	Day	73% 6% 12% 6% 2 1	2794
February	1st to 10th	Day	68% 6% 12% 9% 4 1	1520
	11th to 20th	Day	63% 7% 13% 11% 7%	1780
	21st to end	Day	67% 6% 8% 15% 5%	1570
March	1st to 10th	Day	55% 6% 13% 16% 10%	3138
	11th to 20th	Day	43% 6% 19% 30% 3	3297
	21st to end	Day	66% 7% 12% 10% 4	4092
April	1st to 10th	Day	59% 6% 16% 15% 3	2280
	11th to 20th	Day	52% 6% 14% 18% 10% 1	2336
	21st to end	Day	52% 8% 13% 19% 7% 1	2470
May	1st to 10th	Day	44% 8% 13% 27% 8%	4296
	11th to 20th	Day	33% 7% 18% 33% 8% 1	4380
	21st to end	Day	46% 10% 18% 22% 4	4932
June	1st to 10th	Day	47% 6% 13% 23% 11% 1	2850
	11th to 20th	Day	44% 7% 15% 22% 10% 2	2850
	21st to end	Day	28% 6% 15% 30% 18% 3	2850
July	1st to 10th	Day	13% 3 6% 22% 34% 21%	4486
	11th to 20th	Day	11% 3 6% 14% 29% 38%	4345
	21st to end	Day	12% 3 6% 22% 37% 20%	4639
August	1st to 10th	Day	17% 3 6% 25% 37% 13%	4384
	11th to 20th	Day	18% 4 10% 40% 24% 3	4161
	21st to end	Day	20% 4 12% 36% 25% 3	4309
September	1st to 10th	Day	21% 5% 11% 32% 23% 10%	2280
	11th to 20th	Day	32% 6% 14% 24% 21% 3	2157
	21st to end	Day	35% 7% 19% 24% 11% 3	2090
October	1st to 10th	Day	29% 4 13% 38% 16%	3402
	11th to 20th	Day	41% 4 20% 23% 11% 1	2938
	21st to end	Day	55% 7% 14% 18% 6%	3101
November	1st to 10th	Day	63% 7% 14% 13% 3	1764
	11th to 20th	Day	66% 7% 13% 9% 4 1	1720
	21st to end	Day	67% 5% 11% 12% 4	1406
December	1st to 10th	Day	66% 7% 11% 13% 3	1330
	11th to 20th	Day	78% 6% 9% 6% 1	1684
	21st to end	Day	69% 6% 12% 9% 4	2476
January	1st to 10th	Night	74% 7% 9% 8% 1	4406
	11th to 20th	Night	59% 5% 14% 16% 4 2	4420
	21st to end	Night	71% 6% 13% 8% 2 1	4862
February	1st to 10th	Night	63% 6% 13% 13% 4 1	2660
	11th to 20th	Night	58% 6% 16% 13% 7%	2295
	21st to end	Night	56% 7% 12% 17% 7% 1	1884
March	1st to 10th	Night	45% 7% 13% 24% 9% 1	3736
	11th to 20th	Night	39% 5% 19% 31% 6%	3682
	21st to end	Night	56% 12% 13% 16% 4	3560
April	1st to 10th	Night	46% 7% 15% 23% 7% 1	1900
	11th to 20th	Night	48% 5% 11% 22% 13% 1	1794
	21st to end	Night	45% 7% 12% 24% 11% 1	1710
May	1st to 10th	Night	43% 8% 14% 23% 12% 1	2652
	11th to 20th	Night	28% 6% 14% 35% 16% 1	2516
	21st to end	Night	44% 11% 15% 21% 9%	2641
June	1st to 10th	Night	41% 7% 11% 24% 17% 2	1330
	11th to 20th	Night	39% 6% 13% 24% 15% 4	1330
	21st to end	Night	27% 6% 10% 29% 22% 6%	1330
July	1st to 10th	Night	12% 3 5% 17% 35% 28%	2361
	11th to 20th	Night	9% 2 4 13% 21% 51%	2492
	21st to end	Night	11% 2 4 17% 33% 33%	2674
August	1st to 10th	Night	14% 3 5% 20% 39% 19%	2521
	11th to 20th	Night	21% 4 7% 33% 27% 7%	2740
	21st to end	Night	21% 5% 11% 26% 29% 8%	3360
September	1st to 10th	Night	19% 4 9% 28% 28% 13%	1900
	11th to 20th	Night	32% 5% 11% 23% 22% 7%	2023
	21st to end	Night	31% 5% 16% 28% 15% 5%	2090
October	1st to 10th	Night	25% 4 12% 42% 17% 1	3574
	11th to 20th	Night	37% 5% 15% 24% 19% 1	3993
	21st to end	Night	40% 7% 16% 26% 8% 2	4457
November	1st to 10th	Night	57% 8% 16% 15% 4 1	2535
	11th to 20th	Night	62% 6% 14% 11% 5% 2	2675
	21st to end	Night	60% 6% 16% 13% 4	2967
December	1st to 10th	Night	62% 7% 12% 15% 3	2850
	11th to 20th	Night	72% 6% 12% 9% 1	3507
	21st to end	Night	66% 10% 12% 9% 3	5209

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% 16% 16% 21% 12% 4	180
	11th to 20th	Day	38% 10% 16% 20% 9% 7%	180
	21st to end	Day	36% 8% 25% 19% 12% 1	198
February	1st to 10th	Day	33% 16% 29% 12% 9% 1	180
	11th to 20th	Day	33% 14% 21% 23% 9% 1	404
	21st to end	Day	31% 15% 23% 21% 9% 2	382
March	1st to 10th	Day	28% 18% 22% 19% 10% 2	460
	11th to 20th	Day	23% 12% 23% 22% 18% 2	460
	21st to end	Day	29% 16% 23% 22% 9% 1	506
April	1st to 10th	Day	26% 13% 28% 20% 9% 3	460
	11th to 20th	Day	20% 19% 25% 21% 12% 4	452
	21st to end	Day	19% 15% 27% 25% 11% 3	460
May	1st to 10th	Day	15% 12% 25% 31% 13% 4	463
	11th to 20th	Day	18% 10% 26% 25% 16% 6%	488
	21st to end	Day	15% 9% 21% 29% 19% 8%	595
June	1st to 10th	Day	19% 8% 23% 24% 20% 5%	680
	11th to 20th	Day	18% 14% 29% 22% 15% 3	680
	21st to end	Day	7% 9% 23% 30% 24% 7%	680
July	1st to 10th	Day	7% 5% 25% 33% 26% 4	569
	11th to 20th	Day	5% 9% 27% 32% 22% 6%	484
	21st to end	Day	3 7% 24% 35% 22% 8%	531
August	1st to 10th	Day	7% 3 23% 34% 24% 8%	487
	11th to 20th	Day	5% 3 21% 36% 25% 10%	477
	21st to end	Day	6% 9% 28% 26% 20% 10%	539
September	1st to 10th	Day	8% 8% 27% 26% 21% 10%	490
	11th to 20th	Day	12% 10% 25% 26% 21% 8%	490
	21st to end	Day	13% 12% 28% 21% 21% 5%	490
October	1st to 10th	Day	13% 10% 25% 27% 19% 7%	490
	11th to 20th	Day	22% 11% 19% 26% 14% 8%	357
	21st to end	Day	34% 7% 21% 25% 11% 3	330
November	1st to 10th	Day	37% 9% 18% 25% 12%	300
	11th to 20th	Day	37% 11% 17% 18% 15% 1	260
	21st to end	Day	28% 11% 22% 24% 14% 2	199
December	1st to 10th	Day	34% 8% 23% 17% 15% 4	180
	11th to 20th	Day	37% 13% 21% 21% 6% 2	180
	21st to end	Day	39% 8% 18% 22% 11% 2	198
January	1st to 10th	Night	41% 8% 15% 23% 10% 2	760
	11th to 20th	Night	33% 7% 15% 28% 15% 2	760
	21st to end	Night	29% 6% 16% 31% 16% 2	836
February	1st to 10th	Night	34% 8% 19% 27% 10% 2	760
	11th to 20th	Night	28% 7% 16% 32% 15% 2	744
	21st to end	Night	23% 10% 20% 27% 18% 2	628
March	1st to 10th	Night	22% 9% 17% 33% 17% 2	760
	11th to 20th	Night	24% 7% 17% 31% 20% 1	760
	21st to end	Night	23% 8% 21% 33% 14% 2	836
April	1st to 10th	Night	19% 7% 18% 37% 18% 2	760
	11th to 20th	Night	19% 7% 25% 33% 15% 2	666
	21st to end	Night	16% 8% 20% 34% 20% 2	570
May	1st to 10th	Night	11% 6% 19% 34% 27% 4	453
	11th to 20th	Night	12% 4 16% 31% 29% 8%	374
	21st to end	Night	16% 4 15% 31% 29% 5%	411
June	1st to 10th	Night	15% 6% 15% 35% 25% 4	380
	11th to 20th	Night	15% 4 24% 32% 22% 3	380
	21st to end	Night	7% 2 14% 38% 35% 4	380
July	1st to 10th	Night	4 2 11% 39% 42% 2	370
	11th to 20th	Night	3 2 14% 44% 34% 2	368
	21st to end	Night	2 1 9% 41% 43% 4	416
August	1st to 10th	Night	3 2 11% 37% 41% 7%	378
	11th to 20th	Night	4 3 6% 38% 39% 11%	504
	21st to end	Night	5% 4 13% 36% 39% 4	750
September	1st to 10th	Night	6% 2 13% 38% 35% 6%	760
	11th to 20th	Night	10% 3 13% 32% 34% 8%	760
	21st to end	Night	15% 3 15% 35% 27% 5%	760
October	1st to 10th	Night	16% 4 13% 38% 27% 2	760
	11th to 20th	Night	20% 5% 14% 32% 26% 3	760
	21st to end	Night	23% 5% 21% 31% 18% 3	836
November	1st to 10th	Night	32% 7% 13% 33% 14%	780
	11th to 20th	Night	33% 8% 17% 28% 13% 1	800
	21st to end	Night	32% 8% 14% 29% 16% 2	967
December	1st to 10th	Night	27% 8% 16% 31% 17% 1	950
	11th to 20th	Night	36% 7% 16% 31% 10%	950
	21st to end	Night	37% 9% 17% 27% 9% 1	1040

Page generated at 2024-11-27 14:30:49. Version ac07

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