Idaho Falls
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Idaho Falls clear sky chart from 2005-11-06 to 2024-03-23.

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	8% 8% 3 6% 5% 3 4 4 5% 7% 47%	78689
	Night	9% 10% 4 6% 5% 3 4 4 5% 7% 42%	81221
Transparency	Day	37% 6% 11% 20% 17% 8%	78398
	Night	41% 6% 13% 19% 14% 7%	81032
Seeing	Day	12% 11% 25% 28% 18% 5%	14366
	Night	13% 6% 23% 37% 18% 2	24171

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	10% 20% 7% 11% 6% 3 4 4 4 8% 22%	2475
	11th to 20th	Day	12% 15% 7% 12% 7% 3 5% 3 3 5% 28%	2614
	21st to end	Day	15% 18% 6% 10% 6% 3 4 3 5% 5% 24%	3146
February	1st to 10th	Day	10% 15% 5% 11% 8% 4 5% 5% 5% 6% 26%	1710
	11th to 20th	Day	11% 13% 6% 9% 6% 4 5% 5% 6% 7% 28%	1681
	21st to end	Day	7% 13% 6% 9% 7% 4 4 4 5% 8% 32%	1570
March	1st to 10th	Day	8% 10% 5% 9% 7% 4 5% 4 5% 7% 35%	1998
	11th to 20th	Day	7% 10% 3 5% 5% 3 6% 6% 6% 9% 39%	2090
	21st to end	Day	10% 14% 5% 9% 6% 3 5% 5% 5% 7% 31%	2201
April	1st to 10th	Day	10% 11% 4 7% 5% 3 5% 5% 6% 8% 36%	2042
	11th to 20th	Day	7% 9% 4 7% 6% 3 5% 5% 5% 8% 43%	2307
	21st to end	Day	8% 9% 3 6% 5% 3 5% 5% 5% 8% 42%	2340
May	1st to 10th	Day	6% 7% 2 6% 5% 3 5% 5% 6% 9% 46%	2340
	11th to 20th	Day	6% 7% 2 5% 6% 4 5% 6% 6% 8% 44%	2301
	21st to end	Day	10% 7% 3 5% 6% 4 5% 6% 6% 8% 39%	2690
June	1st to 10th	Day	7% 4 2 4 5% 3 5% 6% 7% 9% 49%	2635
	11th to 20th	Day	7% 5% 2 5% 4 3 3 5% 5% 8% 53%	2700
	21st to end	Day	2 2 1 3 3 2 3 3 4 6% 71%	2700
July	1st to 10th	Day	2 2 1 3 3 2 3 4 5% 8% 68%	2670
	11th to 20th	Day	2 2 1 2 2 2 3 4 4 6% 72%	2507
	21st to end	Day	3 3 1 3 3 2 4 5% 5% 7% 64%	2545
August	1st to 10th	Day	4 3 2 3 4 3 4 4 5% 6% 63%	2328
	11th to 20th	Day	3 2 1 2 3 2 3 3 4 6% 73%	2299
	21st to end	Day	3 3 1 2 3 2 3 5% 4 7% 67%	2574
September	1st to 10th	Day	4 3 1 3 2 2 3 3 3 6% 71%	2088
	11th to 20th	Day	6% 3 2 2 3 2 3 3 4 7% 64%	1980
	21st to end	Day	7% 3 2 3 3 2 3 3 5% 6% 64%	1980
October	1st to 10th	Day	11% 5% 2 4 4 2 5% 4 5% 5% 51%	1884
	11th to 20th	Day	7% 6% 2 4 4 4 3 4 4 7% 55%	1800
	21st to end	Day	8% 6% 2 4 5% 4 4 5% 5% 6% 50%	1890
November	1st to 10th	Day	13% 10% 4 5% 4 3 4 3 5% 6% 43%	1674
	11th to 20th	Day	11% 9% 4 5% 5% 3 4 5% 6% 7% 40%	1595
	21st to end	Day	10% 11% 5% 7% 5% 3 3 4 5% 5% 41%	1520
December	1st to 10th	Day	12% 13% 5% 11% 6% 3 4 4 5% 5% 32%	1520
	11th to 20th	Day	12% 13% 5% 10% 9% 4 5% 5% 5% 7% 25%	1853
	21st to end	Day	10% 13% 5% 7% 5% 3 4 5% 6% 8% 33%	2442
January	1st to 10th	Night	10% 17% 7% 12% 5% 3 4 4 4 9% 25%	4498
	11th to 20th	Night	16% 20% 6% 10% 6% 3 3 3 4 6% 23%	4344
	21st to end	Night	17% 20% 6% 8% 7% 3 4 3 4 8% 21%	4521
February	1st to 10th	Night	11% 15% 5% 8% 6% 3 5% 5% 5% 7% 29%	2470
	11th to 20th	Night	13% 14% 5% 8% 5% 3 4 3 5% 8% 34%	2383
	21st to end	Night	8% 12% 6% 10% 7% 4 5% 7% 5% 7% 28%	1884
March	1st to 10th	Night	9% 12% 4 7% 6% 4 5% 5% 6% 7% 34%	2181
	11th to 20th	Night	6% 8% 4 6% 6% 3 5% 5% 6% 9% 42%	2090
	21st to end	Night	9% 10% 4 8% 7% 4 5% 5% 6% 7% 35%	2200
April	1st to 10th	Night	10% 10% 4 7% 6% 3 4 5% 6% 7% 39%	1914
	11th to 20th	Night	7% 10% 3 7% 5% 4 5% 5% 5% 7% 42%	1601
	21st to end	Night	9% 8% 2 5% 5% 3 4 4 6% 6% 49%	1620
May	1st to 10th	Night	8% 7% 3 5% 5% 3 4 6% 5% 9% 46%	1620
	11th to 20th	Night	8% 5% 2 4 5% 4 5% 5% 7% 10% 45%	1594
	21st to end	Night	12% 6% 2 5% 5% 3 6% 5% 6% 9% 41%	1586
June	1st to 10th	Night	6% 4 2 4 5% 3 5% 6% 6% 8% 50%	1321
	11th to 20th	Night	8% 5% 1 4 4 3 5% 4 5% 7% 54%	1260
	21st to end	Night	2 3 1 4 2 2 2 3 4 7% 70%	1260
July	1st to 10th	Night	2 1 1 2 3 2 4 4 6% 9% 66%	1286
	11th to 20th	Night	1 1 1 2 2 1 4 3 5% 7% 73%	1451
	21st to end	Night	2 2 1 3 4 2 3 5% 5% 7% 65%	1773
August	1st to 10th	Night	4 3 2 3 4 3 4 4 6% 8% 59%	1611
	11th to 20th	Night	2 2 1 2 4 2 3 4 5% 8% 67%	1602
	21st to end	Night	3 3 1 3 4 2 3 4 3 7% 67%	1782
September	1st to 10th	Night	4 3 1 3 3 2 3 3 4 5% 69%	1868
	11th to 20th	Night	6% 3 1 3 3 3 4 4 4 7% 62%	1980
	21st to end	Night	8% 4 2 3 3 2 3 3 5% 5% 63%	1980
October	1st to 10th	Night	9% 5% 2 5% 3 2 4 3 5% 6% 55%	2075
	11th to 20th	Night	9% 6% 2 4 4 2 4 4 4 5% 58%	2160
	21st to end	Night	8% 6% 3 5% 5% 2 4 5% 5% 7% 50%	2465
November	1st to 10th	Night	12% 8% 3 5% 4 2 4 5% 5% 7% 45%	2405
	11th to 20th	Night	10% 11% 4 6% 6% 3 5% 4 5% 7% 40%	2565
	21st to end	Night	9% 10% 4 7% 5% 3 4 5% 5% 7% 41%	2660
December	1st to 10th	Night	11% 15% 5% 8% 7% 3 4 4 4 7% 32%	2660
	11th to 20th	Night	12% 14% 6% 9% 8% 3 4 5% 5% 7% 28%	3337
	21st to end	Night	11% 13% 5% 9% 7% 4 5% 5% 5% 7% 31%	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	61% 9% 13% 13% 3 1	2475
	11th to 20th	Day	59% 7% 13% 14% 6% 1	2614
	21st to end	Day	61% 9% 12% 12% 6% 1	3146
February	1st to 10th	Day	58% 9% 12% 16% 4 1	1710
	11th to 20th	Day	53% 9% 15% 16% 6% 1	1690
	21st to end	Day	52% 8% 14% 16% 8% 1	1570
March	1st to 10th	Day	49% 9% 13% 20% 7% 2	1998
	11th to 20th	Day	43% 9% 13% 24% 10% 2	2090
	21st to end	Day	55% 7% 14% 17% 7%	2201
April	1st to 10th	Day	46% 8% 14% 17% 13% 2	2042
	11th to 20th	Day	41% 6% 12% 25% 13% 3	2310
	21st to end	Day	41% 7% 12% 26% 14% 1	2340
May	1st to 10th	Day	35% 8% 12% 24% 20% 2	2340
	11th to 20th	Day	36% 9% 9% 29% 14% 3	2304
	21st to end	Day	42% 11% 11% 24% 11% 1	2690
June	1st to 10th	Day	31% 7% 13% 29% 19% 1	2635
	11th to 20th	Day	30% 6% 10% 22% 22% 11%	2700
	21st to end	Day	14% 4 6% 22% 36% 17%	2700
July	1st to 10th	Day	15% 3 6% 16% 35% 24%	2597
	11th to 20th	Day	15% 3 5% 13% 29% 36%	2432
	21st to end	Day	20% 4 6% 14% 26% 31%	2404
August	1st to 10th	Day	21% 5% 7% 15% 28% 23%	2313
	11th to 20th	Day	14% 3 5% 17% 37% 24%	2299
	21st to end	Day	19% 4 6% 17% 34% 21%	2574
September	1st to 10th	Day	17% 4 7% 17% 32% 24%	2088
	11th to 20th	Day	22% 5% 8% 23% 28% 13%	1980
	21st to end	Day	23% 4 8% 28% 30% 8%	1980
October	1st to 10th	Day	36% 5% 11% 27% 17% 5%	1884
	11th to 20th	Day	32% 5% 15% 31% 14% 3	1800
	21st to end	Day	35% 7% 16% 24% 18% 1	1890
November	1st to 10th	Day	44% 6% 16% 22% 11% 1	1674
	11th to 20th	Day	43% 7% 19% 22% 7% 2	1595
	21st to end	Day	45% 5% 18% 20% 10% 2	1520
December	1st to 10th	Day	55% 8% 14% 15% 6% 2	1520
	11th to 20th	Day	60% 8% 13% 16% 3	1851
	21st to end	Day	48% 8% 17% 17% 10% 1	2442
January	1st to 10th	Night	57% 7% 15% 15% 5%	4498
	11th to 20th	Night	63% 6% 12% 13% 4 1	4344
	21st to end	Night	61% 10% 15% 9% 4 1	4521
February	1st to 10th	Night	54% 9% 14% 16% 6% 1	2470
	11th to 20th	Night	51% 7% 15% 18% 9% 1	2384
	21st to end	Night	54% 7% 14% 16% 7% 1	1884
March	1st to 10th	Night	48% 7% 14% 21% 8% 1	2181
	11th to 20th	Night	38% 7% 14% 25% 13% 2	2090
	21st to end	Night	48% 8% 14% 22% 7% 1	2200
April	1st to 10th	Night	44% 7% 14% 18% 14% 3	1914
	11th to 20th	Night	41% 6% 14% 23% 14% 2	1601
	21st to end	Night	36% 6% 12% 27% 19% 1	1620
May	1st to 10th	Night	34% 7% 11% 26% 20% 2	1620
	11th to 20th	Night	33% 8% 12% 24% 21% 3	1595
	21st to end	Night	38% 9% 14% 24% 13% 2	1586
June	1st to 10th	Night	30% 8% 13% 23% 24% 2	1321
	11th to 20th	Night	28% 5% 12% 18% 27% 10%	1260
	21st to end	Night	16% 3 6% 18% 31% 25%	1260
July	1st to 10th	Night	15% 3 7% 16% 29% 28%	1250
	11th to 20th	Night	12% 2 6% 13% 25% 42%	1403
	21st to end	Night	18% 3 7% 11% 24% 37%	1674
August	1st to 10th	Night	23% 5% 8% 15% 22% 27%	1602
	11th to 20th	Night	15% 3 5% 15% 33% 27%	1602
	21st to end	Night	19% 3 7% 15% 27% 29%	1782
September	1st to 10th	Night	19% 4 5% 12% 30% 30%	1868
	11th to 20th	Night	23% 5% 8% 21% 26% 18%	1980
	21st to end	Night	24% 4 7% 23% 32% 10%	1980
October	1st to 10th	Night	31% 3 11% 26% 21% 7%	2075
	11th to 20th	Night	31% 3 10% 34% 18% 3	2160
	21st to end	Night	33% 7% 13% 26% 19% 2	2465
November	1st to 10th	Night	39% 7% 14% 25% 13% 2	2405
	11th to 20th	Night	45% 6% 15% 23% 9% 2	2565
	21st to end	Night	44% 5% 18% 22% 11% 2	2660
December	1st to 10th	Night	53% 7% 18% 14% 7% 2	2660
	11th to 20th	Night	56% 7% 17% 16% 5%	3338
	21st to end	Night	53% 6% 14% 15% 10% 1	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	23% 14% 18% 24% 14% 6%	180
	11th to 20th	Day	19% 8% 25% 28% 18% 2	203
	21st to end	Day	22% 7% 26% 30% 13% 2	297
February	1st to 10th	Day	19% 20% 29% 23% 8% 1	270
	11th to 20th	Day	20% 14% 29% 27% 9% 1	286
	21st to end	Day	16% 19% 31% 26% 8% 1	382
March	1st to 10th	Day	15% 22% 30% 26% 7% 1	460
	11th to 20th	Day	12% 15% 30% 29% 12% 1	460
	21st to end	Day	19% 18% 32% 23% 7%	471
April	1st to 10th	Day	19% 19% 26% 23% 10% 2	420
	11th to 20th	Day	15% 21% 34% 18% 10% 2	412
	21st to end	Day	14% 14% 28% 26% 14% 4	420
May	1st to 10th	Day	9% 15% 30% 27% 16% 4	423
	11th to 20th	Day	11% 13% 27% 27% 18% 4	448
	21st to end	Day	14% 8% 21% 28% 22% 7%	645
June	1st to 10th	Day	8% 11% 24% 27% 23% 8%	630
	11th to 20th	Day	14% 12% 27% 30% 16% 2	630
	21st to end	Day	4 5% 25% 35% 25% 6%	630
July	1st to 10th	Day	4 5% 21% 35% 29% 6%	592
	11th to 20th	Day	2 6% 25% 41% 22% 3	444
	21st to end	Day	3 3 19% 35% 30% 10%	487
August	1st to 10th	Day	5% 4 26% 32% 25% 8%	447
	11th to 20th	Day	4 3 23% 30% 28% 11%	437
	21st to end	Day	4 9% 22% 31% 24% 10%	495
September	1st to 10th	Day	4 7% 24% 27% 29% 8%	450
	11th to 20th	Day	9% 10% 24% 28% 22% 8%	450
	21st to end	Day	9% 10% 21% 28% 24% 8%	450
October	1st to 10th	Day	13% 8% 19% 26% 26% 9%	354
	11th to 20th	Day	11% 14% 20% 22% 22% 10%	270
	21st to end	Day	16% 13% 23% 30% 15% 3	297
November	1st to 10th	Day	21% 11% 24% 24% 12% 7%	270
	11th to 20th	Day	16% 10% 20% 35% 15% 4	270
	21st to end	Day	15% 11% 24% 30% 18% 1	270
December	1st to 10th	Day	23% 9% 25% 27% 13% 4	270
	11th to 20th	Day	24% 8% 27% 29% 12% 1	248
	21st to end	Day	22% 16% 21% 23% 15% 4	198
January	1st to 10th	Night	21% 8% 20% 32% 18% 1	813
	11th to 20th	Night	22% 7% 20% 32% 16% 3	760
	21st to end	Night	22% 5% 21% 36% 15% 2	836
February	1st to 10th	Night	20% 8% 28% 31% 12% 1	760
	11th to 20th	Night	20% 8% 26% 33% 11% 2	744
	21st to end	Night	13% 11% 30% 34% 10% 2	628
March	1st to 10th	Night	14% 9% 27% 36% 13% 1	760
	11th to 20th	Night	10% 8% 29% 36% 16% 2	760
	21st to end	Night	13% 9% 27% 39% 11% 1	800
April	1st to 10th	Night	16% 8% 24% 37% 14% 1	680
	11th to 20th	Night	13% 11% 31% 34% 9% 1	533
	21st to end	Night	12% 6% 24% 37% 18% 2	540
May	1st to 10th	Night	11% 7% 25% 36% 20% 1	540
	11th to 20th	Night	12% 5% 21% 34% 25% 3	531
	21st to end	Night	13% 6% 20% 41% 18% 3	584
June	1st to 10th	Night	9% 5% 21% 35% 26% 4	421
	11th to 20th	Night	9% 6% 28% 39% 18%	360
	21st to end	Night	3 3 17% 46% 26% 6%	360
July	1st to 10th	Night	3 1 17% 46% 29% 5%	350
	11th to 20th	Night	3 1 17% 53% 25% 1	359
	21st to end	Night	3 1 17% 45% 30% 4	591
August	1st to 10th	Night	5% 4 16% 45% 28% 2	537
	11th to 20th	Night	3 1 15% 45% 33% 3	534
	21st to end	Night	4 3 20% 42% 29% 3	594
September	1st to 10th	Night	6% 2 21% 41% 25% 5%	634
	11th to 20th	Night	7% 3 17% 39% 28% 6%	720
	21st to end	Night	10% 3 19% 37% 24% 7%	720
October	1st to 10th	Night	12% 4 19% 38% 24% 2	720
	11th to 20th	Night	11% 7% 21% 36% 21% 4	720
	21st to end	Night	11% 8% 21% 41% 15% 4	792
November	1st to 10th	Night	15% 8% 24% 35% 16% 2	740
	11th to 20th	Night	15% 8% 27% 35% 14% 1	855
	21st to end	Night	15% 7% 22% 36% 18% 2	950
December	1st to 10th	Night	20% 7% 25% 36% 11% 1	950
	11th to 20th	Night	22% 8% 22% 35% 13% 1	950
	21st to end	Night	25% 8% 27% 29% 10% 1	1045

Page generated at 2024-03-19 21:31:06. Version ac07

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