Idaho City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Idaho City clear sky chart from 2005-11-06 to 2025-05-26.

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	7% 10% 3 7% 4 4 4 3 4 6% 49%	117760
	Night	8% 10% 3 6% 4 4 4 3 5% 6% 47%	120323
Transparency	Day	35% 5% 8% 20% 19% 12%	117504
	Night	36% 5% 9% 22% 17% 9%	120169
Seeing	Day	15% 11% 29% 28% 14% 3	15083
	Night	15% 4 15% 40% 23% 3	24510

By Month

Percentage Cloud Cover SW (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	7% 23% 8% 11% 5% 5% 4 3 4 5% 25%	3639
	11th to 20th	Day	7% 14% 7% 7% 4 4 3 2 4 6% 41%	3640
	21st to end	Day	10% 14% 4 6% 4 4 3 2 3 5% 44%	4004
February	1st to 10th	Day	11% 19% 6% 10% 6% 3 3 3 4 5% 29%	1755
	11th to 20th	Day	10% 22% 5% 8% 5% 5% 4 3 4 5% 28%	1950
	21st to end	Day	8% 21% 8% 10% 7% 4 4 4 5% 5% 25%	1650
March	1st to 10th	Day	5% 13% 6% 12% 5% 5% 4 4 6% 8% 31%	4518
	11th to 20th	Day	6% 14% 4 10% 5% 4 4 3 4 5% 41%	4855
	21st to end	Day	9% 18% 5% 11% 6% 6% 6% 4 5% 7% 23%	5692
April	1st to 10th	Day	11% 15% 5% 8% 5% 4 3 4 5% 7% 32%	2400
	11th to 20th	Day	9% 13% 3 7% 5% 5% 5% 3 5% 6% 39%	2437
	21st to end	Day	9% 12% 3 7% 5% 4 5% 3 5% 6% 40%	2600
May	1st to 10th	Day	7% 13% 4 8% 6% 5% 5% 4 5% 5% 40%	4240
	11th to 20th	Day	6% 5% 2 5% 4 3 4 3 4 6% 58%	4312
	21st to end	Day	7% 7% 3 6% 5% 4 5% 4 5% 6% 47%	4886
June	1st to 10th	Day	12% 7% 3 7% 5% 4 5% 4 6% 7% 40%	2660
	11th to 20th	Day	9% 6% 2 4 4 4 4 3 5% 7% 51%	2660
	21st to end	Day	3 3 1 3 3 2 3 3 4 5% 68%	2660
July	1st to 10th	Day	2 1 1 1 1 1 2 2 3 4 81%	4420
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 5% 77%	4420
	21st to end	Day	2 2 1 3 2 3 2 2 4 5% 72%	4790
August	1st to 10th	Day	3 3 2 5% 4 4 4 4 5% 7% 60%	4198
	11th to 20th	Day	1 2 1 3 2 2 2 2 4 5% 76%	4028
	21st to end	Day	2 3 1 4 3 2 2 2 3 4 73%	4249
September	1st to 10th	Day	4 2 1 3 2 2 2 2 4 6% 72%	2280
	11th to 20th	Day	7% 5% 2 5% 3 3 3 3 4 6% 59%	2090
	21st to end	Day	7% 5% 2 4 2 2 3 2 5% 6% 62%	2090
October	1st to 10th	Day	6% 5% 2 5% 3 3 3 2 3 5% 64%	3490
	11th to 20th	Day	8% 6% 2 6% 4 4 4 3 4 6% 54%	3045
	21st to end	Day	7% 10% 3 9% 5% 4 3 3 5% 7% 44%	3101
November	1st to 10th	Day	14% 13% 3 7% 4 4 4 3 6% 7% 36%	1764
	11th to 20th	Day	15% 13% 4 7% 5% 4 5% 4 5% 6% 34%	1800
	21st to end	Day	11% 12% 4 8% 4 5% 4 4 4 7% 37%	1785
December	1st to 10th	Day	9% 10% 3 5% 3 3 3 2 3 5% 54%	2620
	11th to 20th	Day	12% 19% 6% 11% 5% 5% 4 4 6% 6% 22%	3028
	21st to end	Day	12% 17% 6% 10% 5% 4 4 3 5% 6% 29%	4004
January	1st to 10th	Night	10% 19% 6% 9% 5% 5% 4 3 5% 6% 29%	6306
	11th to 20th	Night	9% 15% 6% 8% 4 4 3 2 3 5% 40%	6320
	21st to end	Night	9% 13% 4 8% 4 4 4 3 5% 6% 41%	6952
February	1st to 10th	Night	12% 18% 4 8% 5% 4 3 3 4 6% 31%	2640
	11th to 20th	Night	10% 17% 4 8% 4 3 3 4 5% 7% 36%	2338
	21st to end	Night	10% 17% 6% 11% 6% 4 5% 3 4 5% 30%	1980
March	1st to 10th	Night	6% 14% 5% 8% 5% 4 3 3 4 8% 40%	5376
	11th to 20th	Night	8% 16% 4 7% 4 3 3 3 4 5% 42%	5144
	21st to end	Night	6% 12% 4 8% 5% 6% 6% 5% 8% 9% 33%	5280
April	1st to 10th	Night	10% 11% 3 7% 5% 4 4 4 6% 7% 41%	2000
	11th to 20th	Night	9% 8% 3 6% 4 5% 5% 3 5% 5% 46%	1911
	21st to end	Night	7% 6% 3 6% 4 5% 4 3 5% 7% 49%	1800
May	1st to 10th	Night	8% 10% 2 4 3 4 4 4 6% 8% 48%	2950
	11th to 20th	Night	5% 4 1 4 4 3 4 4 4 6% 61%	2803
	21st to end	Night	6% 6% 2 6% 4 4 4 3 5% 7% 53%	2805
June	1st to 10th	Night	11% 4 2 5% 5% 4 5% 3 7% 9% 45%	1520
	11th to 20th	Night	8% 6% 2 4 3 2 4 3 5% 6% 58%	1520
	21st to end	Night	3 3 1 3 3 4 4 4 5% 5% 66%	1520
July	1st to 10th	Night	1 1 2 2 2 3 2 3 4 81%	2540
	11th to 20th	Night	1 1 1 2 2 3 2 3 4 4 77%	2540
	21st to end	Night	2 2 1 4 3 3 3 3 5% 6% 68%	2761
August	1st to 10th	Night	3 4 1 5% 4 4 4 3 5% 7% 60%	2738
	11th to 20th	Night	1 2 2 2 2 3 2 4 5% 76%	2811
	21st to end	Night	2 3 1 3 2 2 2 2 3 4 75%	3424
September	1st to 10th	Night	2 2 1 3 2 2 2 2 3 5% 74%	1900
	11th to 20th	Night	7% 3 2 4 3 3 4 3 5% 5% 62%	2089
	21st to end	Night	7% 3 2 3 2 2 2 3 4 5% 67%	2090
October	1st to 10th	Night	5% 3 1 3 3 2 3 2 4 6% 68%	3490
	11th to 20th	Night	7% 5% 2 5% 3 4 3 3 4 5% 59%	3883
	21st to end	Night	8% 9% 2 6% 4 4 5% 4 6% 8% 44%	4457
November	1st to 10th	Night	13% 10% 2 6% 4 4 4 2 6% 7% 41%	2535
	11th to 20th	Night	16% 11% 3 6% 5% 5% 4 4 5% 6% 37%	2600
	21st to end	Night	11% 13% 3 6% 4 4 4 3 4 7% 40%	2612
December	1st to 10th	Night	8% 9% 3 4 3 4 3 3 4 6% 53%	4560
	11th to 20th	Night	10% 19% 5% 11% 6% 4 5% 4 6% 7% 22%	5176
	21st to end	Night	12% 15% 5% 10% 5% 5% 5% 4 6% 6% 27%	6952

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	61% 6% 9% 18% 5%	3639
	11th to 20th	Day	45% 5% 14% 27% 9% 1	3640
	21st to end	Day	44% 4 13% 21% 15% 3	4004
February	1st to 10th	Day	57% 5% 13% 18% 6% 1	1755
	11th to 20th	Day	57% 6% 12% 16% 8% 1	1960
	21st to end	Day	58% 7% 9% 16% 9% 2	1650
March	1st to 10th	Day	48% 7% 8% 20% 13% 4	4518
	11th to 20th	Day	42% 6% 8% 30% 13% 1	4855
	21st to end	Day	55% 9% 12% 17% 6%	5692
April	1st to 10th	Day	50% 6% 13% 19% 11% 2	2400
	11th to 20th	Day	45% 4 10% 23% 16% 2	2440
	21st to end	Day	43% 6% 10% 25% 16%	2600
May	1st to 10th	Day	43% 6% 7% 23% 19% 3	4240
	11th to 20th	Day	26% 5% 5% 29% 26% 10%	4315
	21st to end	Day	33% 7% 8% 34% 15% 3	4887
June	1st to 10th	Day	40% 7% 10% 27% 16% 1	2660
	11th to 20th	Day	32% 4 5% 23% 27% 9%	2660
	21st to end	Day	18% 4 4 19% 37% 18%	2660
July	1st to 10th	Day	9% 2 2 11% 20% 57%	4351
	11th to 20th	Day	11% 2 2 6% 22% 57%	4345
	21st to end	Day	13% 3 2 9% 34% 39%	4639
August	1st to 10th	Day	22% 5% 4 10% 29% 30%	4182
	11th to 20th	Day	11% 3 2 13% 44% 28%	4067
	21st to end	Day	16% 2 2 18% 34% 28%	4248
September	1st to 10th	Day	15% 3 4 17% 33% 29%	2280
	11th to 20th	Day	26% 4 6% 23% 27% 14%	2090
	21st to end	Day	23% 3 4 27% 31% 11%	2090
October	1st to 10th	Day	24% 3 5% 17% 40% 12%	3490
	11th to 20th	Day	31% 4 10% 25% 26% 4	3045
	21st to end	Day	38% 6% 8% 25% 22% 1	3101
November	1st to 10th	Day	46% 6% 12% 20% 16% 1	1764
	11th to 20th	Day	49% 6% 15% 21% 8%	1800
	21st to end	Day	46% 5% 12% 24% 10% 2	1785
December	1st to 10th	Day	33% 3 15% 40% 8% 1	2620
	11th to 20th	Day	59% 6% 17% 14% 3	3028
	21st to end	Day	55% 5% 13% 19% 8%	4004
January	1st to 10th	Night	55% 6% 13% 20% 5% 1	6306
	11th to 20th	Night	47% 5% 11% 25% 10% 2	6320
	21st to end	Night	42% 7% 9% 25% 12% 5%	6952
February	1st to 10th	Night	54% 6% 14% 20% 5% 1	2640
	11th to 20th	Night	47% 6% 14% 20% 11% 1	2339
	21st to end	Night	54% 6% 9% 18% 12% 2	1980
March	1st to 10th	Night	41% 5% 7% 25% 15% 6%	5376
	11th to 20th	Night	43% 4 6% 27% 17% 1	5144
	21st to end	Night	42% 10% 17% 23% 8%	5280
April	1st to 10th	Night	41% 6% 11% 26% 15% 2	2000
	11th to 20th	Night	38% 5% 10% 26% 19% 2	1911
	21st to end	Night	33% 4 13% 30% 19% 1	1800
May	1st to 10th	Night	32% 5% 8% 30% 21% 4	2950
	11th to 20th	Night	22% 5% 6% 32% 30% 4	2804
	21st to end	Night	29% 5% 11% 35% 19% 1	2805
June	1st to 10th	Night	35% 5% 13% 30% 16% 1	1520
	11th to 20th	Night	26% 5% 7% 25% 30% 8%	1520
	21st to end	Night	18% 4 5% 19% 35% 18%	1520
July	1st to 10th	Night	9% 2 2 9% 22% 56%	2500
	11th to 20th	Night	10% 3 2 8% 19% 57%	2492
	21st to end	Night	17% 4 2 8% 31% 38%	2674
August	1st to 10th	Night	22% 4 4 9% 27% 34%	2730
	11th to 20th	Night	11% 3 2 11% 38% 36%	2838
	21st to end	Night	15% 3 2 17% 31% 32%	3424
September	1st to 10th	Night	15% 2 4 15% 34% 31%	1900
	11th to 20th	Night	24% 3 6% 19% 28% 19%	2089
	21st to end	Night	22% 2 3 26% 31% 16%	2090
October	1st to 10th	Night	19% 3 5% 21% 32% 20%	3490
	11th to 20th	Night	27% 4 10% 24% 28% 7%	3883
	21st to end	Night	36% 6% 11% 25% 19% 3	4457
November	1st to 10th	Night	42% 4 12% 21% 19% 2	2535
	11th to 20th	Night	47% 6% 12% 25% 10%	2600
	21st to end	Night	44% 4 12% 25% 12% 2	2612
December	1st to 10th	Night	31% 5% 18% 36% 10% 1	4560
	11th to 20th	Night	58% 6% 13% 18% 4	5176
	21st to end	Night	53% 6% 13% 19% 7% 1	6952

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	23% 9% 28% 20% 17% 4	200
	11th to 20th	Day	19% 9% 24% 24% 17% 8%	200
	21st to end	Day	15% 8% 25% 28% 18% 7%	220
February	1st to 10th	Day	27% 11% 25% 22% 11% 3	293
	11th to 20th	Day	21% 14% 32% 24% 8% 1	495
	21st to end	Day	22% 15% 28% 25% 7% 2	414
March	1st to 10th	Day	20% 16% 34% 23% 6% 1	500
	11th to 20th	Day	20% 15% 29% 21% 12% 2	500
	21st to end	Day	24% 17% 28% 22% 8% 1	550
April	1st to 10th	Day	22% 16% 27% 22% 12% 1	500
	11th to 20th	Day	19% 18% 33% 20% 8% 1	492
	21st to end	Day	18% 18% 32% 22% 8% 2	500
May	1st to 10th	Day	18% 12% 33% 24% 11% 1	503
	11th to 20th	Day	22% 15% 27% 24% 9% 3	528
	21st to end	Day	17% 7% 26% 29% 15% 6%	550
June	1st to 10th	Day	13% 12% 30% 25% 17% 3	490
	11th to 20th	Day	17% 14% 31% 26% 10% 2	490
	21st to end	Day	6% 10% 32% 32% 17% 2	490
July	1st to 10th	Day	5% 8% 34% 36% 14% 3	486
	11th to 20th	Day	2 10% 36% 34% 15% 3	484
	21st to end	Day	3 7% 33% 36% 16% 5%	531
August	1st to 10th	Day	5% 7% 33% 33% 17% 4	487
	11th to 20th	Day	3 10% 27% 33% 22% 6%	477
	21st to end	Day	5% 11% 28% 32% 20% 4	539
September	1st to 10th	Day	7% 9% 23% 37% 18% 6%	490
	11th to 20th	Day	9% 8% 29% 32% 19% 2	490
	21st to end	Day	8% 9% 32% 29% 18% 3	490
October	1st to 10th	Day	13% 10% 24% 29% 19% 6%	490
	11th to 20th	Day	12% 9% 28% 26% 17% 7%	361
	21st to end	Day	19% 10% 22% 31% 16% 3	330
November	1st to 10th	Day	23% 6% 21% 33% 14% 3	300
	11th to 20th	Day	18% 10% 22% 32% 14% 5%	300
	21st to end	Day	17% 5% 25% 31% 18% 4	293
December	1st to 10th	Day	26% 6% 19% 20% 19% 11%	200
	11th to 20th	Day	25% 9% 22% 27% 13% 5%	200
	21st to end	Day	20% 8% 24% 32% 13% 3	220
January	1st to 10th	Night	23% 4 18% 33% 20% 3	800
	11th to 20th	Night	23% 4 18% 33% 19% 3	800
	21st to end	Night	19% 3 15% 40% 21% 4	880
February	1st to 10th	Night	23% 4 20% 36% 16% 2	800
	11th to 20th	Night	18% 5% 19% 37% 18% 2	784
	21st to end	Night	19% 6% 17% 39% 16% 3	660
March	1st to 10th	Night	18% 6% 20% 39% 15% 2	800
	11th to 20th	Night	19% 4 17% 38% 20% 2	800
	21st to end	Night	19% 7% 18% 39% 16% 2	880
April	1st to 10th	Night	16% 6% 18% 38% 19% 2	800
	11th to 20th	Night	14% 7% 20% 42% 14% 2	723
	21st to end	Night	10% 5% 24% 42% 18% 2	600
May	1st to 10th	Night	12% 5% 21% 42% 19% 2	600
	11th to 20th	Night	11% 3 18% 35% 29% 4	523
	21st to end	Night	12% 4 12% 37% 31% 4	422
June	1st to 10th	Night	12% 3 11% 40% 31% 3	380
	11th to 20th	Night	11% 4 14% 47% 23% 2	380
	21st to end	Night	3 1 11% 51% 32% 3	380
July	1st to 10th	Night	2 1 9% 51% 35% 2	370
	11th to 20th	Night	2 1 10% 58% 28% 1	368
	21st to end	Night	3 9% 49% 38% 2	416
August	1st to 10th	Night	5% 1 9% 47% 34% 4	496
	11th to 20th	Night	2 2 9% 48% 36% 3	564
	21st to end	Night	3 2 11% 47% 33% 4	788
September	1st to 10th	Night	4 2 7% 49% 34% 4	760
	11th to 20th	Night	8% 2 8% 39% 36% 6%	760
	21st to end	Night	9% 2 12% 38% 32% 8%	760
October	1st to 10th	Night	10% 3 10% 43% 31% 4	760
	11th to 20th	Night	11% 4 13% 40% 27% 4	760
	21st to end	Night	15% 2 16% 41% 22% 4	836
November	1st to 10th	Night	18% 4 14% 41% 22% 2	780
	11th to 20th	Night	21% 3 20% 37% 17% 2	800
	21st to end	Night	17% 4 18% 39% 18% 5%	800
December	1st to 10th	Night	19% 4 15% 41% 20% 2	800
	11th to 20th	Night	23% 5% 17% 37% 16% 3	800
	21st to end	Night	27% 5% 20% 35% 11% 3	880

Page generated at 2025-05-23 07:21:03. Version ac07

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