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 2024-01-15.

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	14% 10% 3 6% 5% 3 4 4 5% 6% 39%	74568
	Night	16% 10% 3 6% 6% 3 4 4 5% 6% 37%	75213
Transparency	Day	46% 6% 13% 20% 13% 3	74271
	Night	48% 6% 12% 18% 11% 4	75027
Seeing	Day	19% 11% 24% 25% 16% 5%	13759
	Night	22% 6% 16% 32% 21% 3	23067

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	27% 19% 5% 7% 6% 4 4 5% 4 5% 13%	1519
	11th to 20th	Day	25% 18% 5% 7% 6% 4 5% 4 4 5% 18%	1472
	21st to end	Day	20% 20% 7% 9% 6% 3 4 5% 5% 4 18%	1584
February	1st to 10th	Day	22% 18% 5% 8% 6% 3 5% 5% 5% 5% 21%	1440
	11th to 20th	Day	18% 17% 5% 8% 6% 3 4 5% 4 6% 25%	1675
	21st to end	Day	18% 20% 6% 8% 6% 3 4 5% 4 4 23%	1480
March	1st to 10th	Day	20% 16% 5% 7% 5% 4 5% 4 4 6% 25%	1800
	11th to 20th	Day	19% 12% 4 7% 6% 4 6% 5% 5% 7% 25%	1865
	21st to end	Day	22% 16% 4 8% 7% 4 5% 5% 4 6% 20%	2329
April	1st to 10th	Day	18% 11% 4 7% 7% 3 6% 5% 6% 8% 24%	2160
	11th to 20th	Day	16% 10% 4 7% 7% 3 6% 4 5% 7% 31%	2211
	21st to end	Day	15% 8% 4 6% 6% 4 7% 5% 5% 7% 33%	2340
May	1st to 10th	Day	9% 7% 3 7% 5% 3 5% 6% 6% 8% 41%	2448
	11th to 20th	Day	12% 6% 3 6% 6% 4 5% 5% 7% 9% 37%	2477
	21st to end	Day	14% 7% 3 7% 6% 3 6% 5% 7% 8% 35%	2785
June	1st to 10th	Day	18% 6% 3 5% 6% 4 4 4 5% 7% 37%	2700
	11th to 20th	Day	17% 6% 2 6% 6% 4 5% 4 6% 8% 36%	2700
	21st to end	Day	7% 4 1 4 4 3 5% 5% 5% 7% 55%	2700
July	1st to 10th	Day	5% 3 1 3 3 3 3 4 4 6% 65%	2599
	11th to 20th	Day	4 2 1 2 3 2 3 4 4 7% 69%	2520
	21st to end	Day	1 1 1 1 2 1 3 3 3 5% 79%	2741
August	1st to 10th	Day	3 3 1 2 3 2 3 3 4 6% 69%	2507
	11th to 20th	Day	4 2 1 2 2 2 3 4 4 6% 68%	2355
	21st to end	Day	5% 4 2 4 4 3 4 4 5% 7% 58%	2454
September	1st to 10th	Day	6% 3 1 3 3 2 3 4 4 7% 64%	2160
	11th to 20th	Day	9% 4 2 4 4 3 5% 5% 5% 7% 52%	2044
	21st to end	Day	10% 6% 2 5% 5% 3 4 6% 6% 7% 46%	1980
October	1st to 10th	Day	14% 8% 2 6% 5% 2 4 4 5% 5% 45%	1931
	11th to 20th	Day	17% 8% 3 5% 5% 2 4 4 4 6% 43%	1674
	21st to end	Day	22% 9% 4 6% 5% 2 4 4 5% 5% 35%	1782
November	1st to 10th	Day	27% 15% 4 6% 5% 2 4 4 4 6% 24%	1674
	11th to 20th	Day	24% 15% 5% 8% 6% 3 4 3 4 4 24%	1634
	21st to end	Day	21% 19% 5% 11% 7% 2 4 3 4 5% 20%	1340
December	1st to 10th	Day	20% 15% 7% 9% 6% 3 5% 4 5% 7% 20%	1330
	11th to 20th	Day	25% 23% 8% 10% 7% 3 4 3 3 4 10%	1682
	21st to end	Day	20% 21% 5% 10% 7% 4 4 4 4 5% 16%	2476
January	1st to 10th	Night	29% 18% 6% 8% 6% 3 3 4 4 4 16%	2646
	11th to 20th	Night	25% 15% 5% 8% 6% 3 4 3 3 5% 23%	2576
	21st to end	Night	19% 17% 5% 9% 7% 3 4 5% 4 6% 22%	2772
February	1st to 10th	Night	21% 17% 5% 7% 5% 2 3 4 5% 5% 25%	2520
	11th to 20th	Night	17% 15% 4 7% 6% 4 4 3 5% 5% 30%	2169
	21st to end	Night	15% 14% 4 6% 6% 4 5% 5% 5% 7% 29%	1776
March	1st to 10th	Night	17% 12% 4 8% 6% 4 5% 6% 5% 6% 28%	2160
	11th to 20th	Night	18% 10% 3 6% 6% 3 5% 4 5% 6% 32%	2094
	21st to end	Night	18% 11% 3 7% 7% 4 7% 6% 5% 7% 25%	2026
April	1st to 10th	Night	11% 10% 3 5% 5% 4 7% 7% 7% 7% 34%	1800
	11th to 20th	Night	14% 9% 3 7% 6% 4 4 4 4 5% 39%	1699
	21st to end	Night	11% 9% 2 6% 6% 4 6% 5% 6% 7% 38%	1620
May	1st to 10th	Night	8% 6% 2 5% 5% 4 5% 6% 7% 8% 44%	1510
	11th to 20th	Night	9% 6% 2 6% 6% 2 6% 4 7% 9% 43%	1416
	21st to end	Night	12% 6% 3 6% 6% 2 6% 5% 6% 9% 38%	1487
June	1st to 10th	Night	14% 5% 2 6% 5% 3 6% 5% 5% 7% 42%	1260
	11th to 20th	Night	12% 4 3 6% 6% 3 5% 5% 6% 9% 41%	1260
	21st to end	Night	6% 4 2 4 5% 2 4 5% 5% 8% 55%	1260
July	1st to 10th	Night	3 1 1 2 3 2 3 3 4 6% 72%	1357
	11th to 20th	Night	3 1 1 3 3 1 3 3 3 7% 72%	1440
	21st to end	Night	1 1 1 2 2 1 3 3 3 5% 78%	1576
August	1st to 10th	Night	3 2 1 2 3 1 2 3 4 7% 73%	1432
	11th to 20th	Night	3 2 1 3 3 2 2 3 4 6% 70%	1545
	21st to end	Night	4 3 1 3 3 2 4 4 5% 7% 64%	1898
September	1st to 10th	Night	5% 2 1 4 3 2 3 3 5% 7% 66%	1800
	11th to 20th	Night	7% 4 2 5% 6% 3 5% 4 5% 8% 51%	1916
	21st to end	Night	12% 5% 2 4 5% 2 3 3 6% 7% 52%	1980
October	1st to 10th	Night	13% 5% 3 5% 4 3 3 4 5% 7% 48%	2025
	11th to 20th	Night	16% 6% 2 5% 5% 3 4 4 4 6% 45%	2286
	21st to end	Night	19% 7% 3 5% 5% 3 3 4 5% 6% 41%	2574
November	1st to 10th	Night	24% 12% 3 6% 5% 3 4 4 5% 7% 26%	2405
	11th to 20th	Night	21% 14% 4 6% 6% 3 5% 5% 4 5% 26%	2541
	21st to end	Night	23% 12% 4 7% 6% 3 4 4 5% 6% 26%	2818
December	1st to 10th	Night	18% 15% 5% 9% 6% 3 5% 4 5% 6% 25%	2850
	11th to 20th	Night	25% 20% 5% 8% 7% 3 5% 4 4 4 15%	3510
	21st to end	Night	20% 16% 6% 10% 8% 4 5% 6% 4 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	73% 6% 11% 7% 3	1519
	11th to 20th	Day	67% 6% 14% 8% 3 1	1472
	21st to end	Day	68% 7% 12% 10% 3 1	1584
February	1st to 10th	Day	67% 6% 12% 10% 4 1	1440
	11th to 20th	Day	63% 7% 13% 11% 6%	1685
	21st to end	Day	67% 5% 7% 15% 5%	1480
March	1st to 10th	Day	62% 5% 14% 12% 5% 1	1800
	11th to 20th	Day	59% 7% 12% 18% 3	1865
	21st to end	Day	67% 6% 15% 10% 2	2329
April	1st to 10th	Day	59% 6% 16% 16% 4	2160
	11th to 20th	Day	53% 6% 14% 18% 9% 1	2211
	21st to end	Day	51% 8% 13% 19% 7% 1	2340
May	1st to 10th	Day	39% 7% 17% 27% 10%	2448
	11th to 20th	Day	43% 6% 17% 24% 9%	2480
	21st to end	Day	46% 7% 17% 24% 6% 1	2786
June	1st to 10th	Day	47% 6% 13% 23% 10% 1	2700
	11th to 20th	Day	45% 7% 15% 22% 8% 2	2700
	21st to end	Day	28% 7% 15% 30% 18% 3	2700
July	1st to 10th	Day	20% 5% 9% 31% 24% 11%	2530
	11th to 20th	Day	17% 4 11% 24% 33% 12%	2445
	21st to end	Day	10% 3 5% 24% 44% 14%	2589
August	1st to 10th	Day	17% 4 8% 26% 33% 13%	2490
	11th to 20th	Day	17% 4 11% 29% 33% 6%	2355
	21st to end	Day	24% 6% 10% 29% 26% 4	2454
September	1st to 10th	Day	22% 5% 11% 32% 23% 8%	2160
	11th to 20th	Day	32% 6% 13% 24% 22% 4	2044
	21st to end	Day	37% 6% 20% 23% 11% 3	1980
October	1st to 10th	Day	41% 5% 12% 31% 11%	1931
	11th to 20th	Day	44% 5% 17% 25% 9% 1	1674
	21st to end	Day	52% 6% 16% 19% 6%	1782
November	1st to 10th	Day	63% 7% 13% 13% 3	1674
	11th to 20th	Day	65% 7% 13% 9% 4 1	1634
	21st to end	Day	66% 5% 12% 13% 4	1340
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	73% 5% 9% 10% 2 1	2646
	11th to 20th	Night	63% 7% 14% 13% 2 1	2576
	21st to end	Night	64% 7% 14% 11% 3 1	2772
February	1st to 10th	Night	62% 6% 13% 13% 5% 1	2520
	11th to 20th	Night	57% 6% 16% 14% 7%	2170
	21st to end	Night	56% 7% 11% 18% 7% 1	1776
March	1st to 10th	Night	56% 6% 13% 16% 7% 1	2160
	11th to 20th	Night	53% 7% 13% 19% 8%	2094
	21st to end	Night	57% 9% 14% 15% 5%	2026
April	1st to 10th	Night	46% 7% 15% 24% 7% 1	1800
	11th to 20th	Night	49% 4 10% 22% 13% 1	1699
	21st to end	Night	45% 7% 12% 24% 11% 1	1620
May	1st to 10th	Night	36% 7% 16% 28% 12% 1	1510
	11th to 20th	Night	36% 6% 14% 29% 15% 1	1416
	21st to end	Night	40% 8% 16% 26% 10%	1487
June	1st to 10th	Night	42% 6% 10% 24% 17% 2	1260
	11th to 20th	Night	40% 6% 13% 25% 13% 4	1260
	21st to end	Night	27% 6% 10% 30% 21% 6%	1260
July	1st to 10th	Night	15% 3 6% 26% 33% 18%	1317
	11th to 20th	Night	14% 3 7% 23% 32% 22%	1392
	21st to end	Night	11% 2 4 17% 40% 27%	1488
August	1st to 10th	Night	14% 3 8% 17% 37% 21%	1424
	11th to 20th	Night	16% 3 8% 24% 35% 13%	1545
	21st to end	Night	20% 5% 8% 24% 32% 10%	1898
September	1st to 10th	Night	19% 4 9% 28% 28% 12%	1800
	11th to 20th	Night	31% 5% 10% 23% 24% 8%	1916
	21st to end	Night	32% 5% 16% 27% 15% 5%	1980
October	1st to 10th	Night	37% 4 11% 34% 13% 1	2025
	11th to 20th	Night	43% 4 14% 24% 14% 1	2286
	21st to end	Night	44% 7% 14% 22% 10% 1	2574
November	1st to 10th	Night	58% 7% 15% 15% 4 1	2405
	11th to 20th	Night	62% 6% 14% 11% 5% 2	2541
	21st to end	Night	59% 6% 17% 14% 5%	2818
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	39% 9% 16% 19% 10% 8%	168
	21st to end	Day	35% 8% 27% 18% 11% 1	176
February	1st to 10th	Day	31% 17% 31% 11% 9% 1	160
	11th to 20th	Day	32% 14% 21% 22% 9% 1	369
	21st to end	Day	29% 14% 23% 22% 10% 2	346
March	1st to 10th	Day	29% 19% 22% 19% 9% 2	420
	11th to 20th	Day	25% 13% 22% 22% 17% 1	420
	21st to end	Day	30% 16% 23% 21% 8% 1	462
April	1st to 10th	Day	25% 13% 29% 20% 9% 3	420
	11th to 20th	Day	22% 20% 25% 19% 10% 4	412
	21st to end	Day	19% 15% 27% 25% 12% 3	420
May	1st to 10th	Day	15% 12% 26% 30% 14% 3	423
	11th to 20th	Day	18% 10% 26% 25% 16% 6%	448
	21st to end	Day	15% 8% 19% 30% 20% 8%	547
June	1st to 10th	Day	19% 8% 23% 24% 21% 5%	630
	11th to 20th	Day	19% 13% 29% 22% 14% 3	630
	21st to end	Day	7% 8% 23% 30% 24% 7%	630
July	1st to 10th	Day	7% 6% 25% 33% 26% 3	525
	11th to 20th	Day	5% 9% 29% 32% 20% 5%	444
	21st to end	Day	2 8% 26% 34% 21% 9%	487
August	1st to 10th	Day	8% 3 23% 34% 25% 8%	447
	11th to 20th	Day	5% 3 21% 37% 24% 11%	437
	21st to end	Day	6% 9% 28% 27% 21% 9%	495
September	1st to 10th	Day	8% 9% 28% 27% 20% 8%	450
	11th to 20th	Day	11% 10% 25% 25% 21% 8%	450
	21st to end	Day	13% 12% 28% 22% 21% 4	450
October	1st to 10th	Day	14% 9% 25% 26% 18% 7%	450
	11th to 20th	Day	22% 11% 20% 25% 13% 8%	324
	21st to end	Day	34% 8% 21% 24% 10% 3	297
November	1st to 10th	Day	38% 9% 18% 26% 10%	270
	11th to 20th	Day	37% 10% 17% 19% 16% 1	234
	21st to end	Day	28% 9% 22% 23% 15% 2	180
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	34% 8% 14% 27% 16% 2	736
	21st to end	Night	29% 6% 15% 31% 16% 2	792
February	1st to 10th	Night	35% 7% 19% 27% 10% 2	720
	11th to 20th	Night	28% 7% 17% 32% 15% 2	704
	21st to end	Night	22% 10% 21% 27% 18% 2	592
March	1st to 10th	Night	23% 8% 17% 33% 17% 2	720
	11th to 20th	Night	25% 7% 17% 31% 19% 1	720
	21st to end	Night	24% 7% 21% 32% 14% 2	792
April	1st to 10th	Night	18% 7% 18% 37% 19% 2	720
	11th to 20th	Night	19% 6% 25% 32% 16% 2	631
	21st to end	Night	16% 8% 20% 34% 20% 2	540
May	1st to 10th	Night	11% 5% 19% 34% 27% 4	430
	11th to 20th	Night	12% 4 15% 31% 30% 8%	354
	21st to end	Night	16% 3 14% 31% 30% 6%	389
June	1st to 10th	Night	15% 5% 15% 35% 25% 5%	360
	11th to 20th	Night	16% 4 24% 31% 22% 3	360
	21st to end	Night	7% 2 13% 38% 36% 4	360
July	1st to 10th	Night	4 2 10% 39% 42% 2	350
	11th to 20th	Night	3 2 15% 45% 33% 2	348
	21st to end	Night	2 1 9% 41% 43% 4	394
August	1st to 10th	Night	3 2 11% 35% 42% 7%	358
	11th to 20th	Night	4 3 5% 38% 40% 11%	477
	21st to end	Night	5% 5% 12% 36% 39% 4	710
September	1st to 10th	Night	7% 2 14% 38% 34% 5%	720
	11th to 20th	Night	10% 3 13% 31% 35% 8%	720
	21st to end	Night	16% 3 15% 35% 27% 5%	720
October	1st to 10th	Night	17% 4 13% 37% 27% 2	720
	11th to 20th	Night	20% 5% 14% 31% 26% 3	720
	21st to end	Night	23% 4 20% 30% 18% 3	792
November	1st to 10th	Night	32% 7% 13% 34% 14%	740
	11th to 20th	Night	32% 8% 17% 28% 14% 1	760
	21st to end	Night	32% 8% 14% 28% 16% 2	918
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

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