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 2024-11-03.

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% 8% 3 6% 4 4 4 3 5% 7% 50%	101368
	Night	8% 10% 3 7% 4 4 4 3 5% 7% 45%	97820
Transparency	Day	34% 6% 10% 20% 18% 12%	101117
	Night	38% 6% 12% 19% 16% 9%	97659
Seeing	Day	12% 11% 25% 28% 18% 5%	15283
	Night	13% 6% 23% 37% 18% 2	24875

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% 21% 7% 12% 5% 4 4 3 5% 7% 22%	2475
	11th to 20th	Day	11% 16% 7% 13% 6% 4 4 3 4 5% 28%	2614
	21st to end	Day	15% 19% 5% 12% 5% 3 3 3 5% 5% 24%	3146
February	1st to 10th	Day	9% 16% 5% 13% 7% 5% 5% 4 5% 5% 26%	1710
	11th to 20th	Day	11% 14% 5% 10% 5% 5% 5% 4 6% 7% 28%	1681
	21st to end	Day	7% 14% 5% 10% 6% 4 4 4 6% 7% 32%	1570
March	1st to 10th	Day	8% 13% 5% 11% 6% 5% 4 3 4 6% 33%	3308
	11th to 20th	Day	6% 10% 3 5% 4 4 4 3 4 6% 51%	3490
	21st to end	Day	9% 16% 5% 12% 6% 6% 6% 4 6% 7% 24%	3825
April	1st to 10th	Day	9% 12% 4 7% 5% 4 5% 4 7% 7% 36%	2157
	11th to 20th	Day	6% 10% 3 7% 5% 4 4 4 5% 7% 44%	2437
	21st to end	Day	9% 9% 3 7% 5% 4 4 4 5% 8% 41%	2470
May	1st to 10th	Day	9% 10% 3 7% 4 4 4 4 5% 8% 42%	4110
	11th to 20th	Day	4 4 2 4 4 4 4 3 5% 8% 57%	4071
	21st to end	Day	8% 7% 3 6% 4 4 4 4 5% 7% 48%	4763
June	1st to 10th	Day	7% 5% 2 5% 4 4 5% 5% 7% 9% 49%	2782
	11th to 20th	Day	7% 5% 2 6% 4 3 4 4 6% 7% 54%	2850
	21st to end	Day	2 2 1 3 2 2 3 2 4 6% 72%	2850
July	1st to 10th	Day	1 1 1 2 2 2 2 2 4 5% 77%	4682
	11th to 20th	Day	1 2 1 3 2 3 3 3 5% 6% 72%	4394
	21st to end	Day	2 3 1 4 3 3 3 3 4 6% 67%	4454
August	1st to 10th	Day	4 3 1 4 3 4 4 4 6% 7% 61%	4092
	11th to 20th	Day	2 2 1 2 3 3 3 3 4 7% 70%	4028
	21st to end	Day	2 2 1 2 2 2 3 3 4 6% 72%	4521
September	1st to 10th	Day	4 3 1 3 2 2 2 2 4 6% 71%	2203
	11th to 20th	Day	6% 4 1 3 3 3 3 3 5% 7% 63%	2090
	21st to end	Day	6% 3 1 3 3 2 3 2 5% 6% 65%	2090
October	1st to 10th	Day	10% 6% 2 5% 3 3 5% 3 5% 5% 53%	1988
	11th to 20th	Day	7% 6% 1 5% 4 5% 3 3 4 6% 56%	1900
	21st to end	Day	8% 6% 2 5% 5% 5% 4 4 5% 6% 49%	1995
November	1st to 10th	Day	13% 11% 3 6% 3 4 3 3 5% 6% 43%	1692
	11th to 20th	Day	11% 11% 3 6% 4 4 4 4 7% 7% 40%	1595
	21st to end	Day	9% 13% 4 8% 4 4 4 3 4 5% 41%	1520
December	1st to 10th	Day	12% 14% 5% 12% 6% 3 3 3 5% 5% 32%	1520
	11th to 20th	Day	12% 14% 5% 11% 8% 6% 5% 4 5% 7% 24%	1853
	21st to end	Day	9% 14% 5% 8% 5% 4 5% 4 6% 8% 33%	2442
January	1st to 10th	Night	10% 18% 7% 13% 4 4 4 3 5% 9% 25%	4498
	11th to 20th	Night	16% 20% 6% 11% 5% 3 3 2 4 6% 23%	4344
	21st to end	Night	16% 21% 5% 10% 5% 4 3 3 4 8% 21%	4521
February	1st to 10th	Night	11% 15% 4 9% 5% 4 5% 5% 6% 7% 29%	2470
	11th to 20th	Night	12% 15% 4 8% 4 4 4 2 5% 8% 34%	2383
	21st to end	Night	7% 14% 5% 12% 6% 5% 5% 5% 6% 7% 28%	1884
March	1st to 10th	Night	8% 12% 4 9% 6% 5% 5% 4 6% 7% 34%	3565
	11th to 20th	Night	4 7% 3 6% 4 4 4 3 5% 9% 51%	3490
	21st to end	Night	8% 10% 3 8% 5% 6% 5% 4 7% 9% 34%	3828
April	1st to 10th	Night	9% 10% 3 7% 5% 4 4 4 7% 7% 39%	2019
	11th to 20th	Night	7% 11% 3 8% 5% 5% 4 4 5% 6% 42%	1691
	21st to end	Night	9% 8% 2 6% 5% 4 4 3 6% 6% 47%	1710
May	1st to 10th	Night	10% 12% 3 7% 5% 3 4 4 5% 7% 42%	2860
	11th to 20th	Night	5% 4 1 5% 4 5% 4 3 6% 9% 54%	2834
	21st to end	Night	8% 6% 2 5% 4 4 5% 4 5% 9% 47%	2824
June	1st to 10th	Night	6% 4 2 5% 5% 5% 4 5% 6% 9% 49%	1394
	11th to 20th	Night	7% 5% 1 5% 3 5% 3 4 6% 7% 54%	1330
	21st to end	Night	2 3 1 4 2 2 3 3 4 7% 69%	1330
July	1st to 10th	Night	3 2 1 2 2 3 3 3 4 6% 73%	2274
	11th to 20th	Night	1 1 1 2 3 4 3 3 5% 8% 70%	2565
	21st to end	Night	1 2 1 3 3 3 4 4 6% 8% 65%	3109
August	1st to 10th	Night	3 3 1 3 3 3 4 3 7% 8% 62%	2847
	11th to 20th	Night	2 2 1 3 4 3 4 4 5% 7% 65%	2811
	21st to end	Night	3 3 1 3 3 2 3 2 3 5% 73%	3146
September	1st to 10th	Night	4 3 1 3 2 3 3 3 4 5% 69%	1973
	11th to 20th	Night	6% 4 1 4 3 4 4 3 5% 7% 60%	2090
	21st to end	Night	7% 4 1 3 2 3 3 2 5% 5% 65%	2090
October	1st to 10th	Night	9% 5% 2 5% 3 3 4 3 5% 6% 57%	2191
	11th to 20th	Night	9% 6% 2 5% 3 3 3 3 4 5% 58%	2280
	21st to end	Night	8% 7% 3 5% 4 4 4 3 6% 7% 50%	2602
November	1st to 10th	Night	11% 9% 3 6% 3 3 5% 3 5% 7% 45%	2431
	11th to 20th	Night	10% 12% 3 6% 5% 4 4 4 5% 6% 40%	2565
	21st to end	Night	9% 11% 4 8% 5% 4 4 4 5% 7% 41%	2660
December	1st to 10th	Night	11% 16% 4 9% 6% 4 4 3 4 7% 32%	2660
	11th to 20th	Night	12% 14% 5% 11% 6% 5% 4 4 5% 7% 28%	3337
	21st to end	Night	10% 13% 5% 11% 6% 5% 5% 3 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	50% 7% 12% 21% 8% 1	3308
	11th to 20th	Day	35% 7% 11% 32% 14% 1	3490
	21st to end	Day	57% 11% 14% 14% 4	3825
April	1st to 10th	Day	45% 8% 15% 17% 12% 2	2157
	11th to 20th	Day	39% 6% 12% 26% 14% 3	2440
	21st to end	Day	41% 7% 11% 26% 14% 1	2470
May	1st to 10th	Day	38% 6% 11% 23% 19% 4	4110
	11th to 20th	Day	24% 6% 9% 33% 21% 7%	4074
	21st to end	Day	34% 8% 10% 32% 15% 1	4763
June	1st to 10th	Day	31% 7% 13% 30% 19% 1	2782
	11th to 20th	Day	29% 6% 10% 21% 23% 12%	2850
	21st to end	Day	14% 4 6% 22% 36% 18%	2850
July	1st to 10th	Day	11% 2 4 9% 28% 46%	4609
	11th to 20th	Day	15% 2 4 9% 25% 46%	4319
	21st to end	Day	18% 3 4 12% 32% 31%	4314
August	1st to 10th	Day	22% 3 5% 14% 29% 26%	4078
	11th to 20th	Day	15% 3 5% 19% 38% 20%	4067
	21st to end	Day	14% 3 4 20% 30% 28%	4520
September	1st to 10th	Day	17% 3 7% 17% 33% 23%	2203
	11th to 20th	Day	23% 5% 8% 24% 28% 13%	2090
	21st to end	Day	22% 4 7% 27% 30% 9%	2090
October	1st to 10th	Day	34% 5% 10% 27% 18% 6%	1988
	11th to 20th	Day	31% 5% 14% 32% 14% 3	1900
	21st to end	Day	35% 6% 15% 24% 18% 1	1995
November	1st to 10th	Day	44% 6% 16% 22% 11% 1	1692
	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	45% 8% 15% 20% 11% 1	3565
	11th to 20th	Night	30% 7% 16% 28% 19% 1	3490
	21st to end	Night	44% 9% 16% 26% 4 1	3828
April	1st to 10th	Night	43% 7% 14% 20% 14% 3	2019
	11th to 20th	Night	40% 6% 14% 23% 15% 2	1691
	21st to end	Night	36% 6% 12% 26% 18% 1	1710
May	1st to 10th	Night	40% 6% 12% 21% 18% 3	2860
	11th to 20th	Night	24% 6% 12% 28% 23% 7%	2835
	21st to end	Night	31% 6% 13% 27% 21% 3	2824
June	1st to 10th	Night	30% 8% 13% 23% 24% 2	1394
	11th to 20th	Night	28% 5% 11% 17% 28% 11%	1330
	21st to end	Night	17% 3 6% 17% 31% 27%	1330
July	1st to 10th	Night	14% 2 5% 10% 23% 47%	2238
	11th to 20th	Night	14% 1 4 10% 22% 49%	2517
	21st to end	Night	16% 3 5% 12% 29% 34%	3011
August	1st to 10th	Night	19% 3 5% 11% 29% 32%	2838
	11th to 20th	Night	18% 3 5% 18% 32% 24%	2838
	21st to end	Night	16% 3 5% 16% 28% 32%	3146
September	1st to 10th	Night	18% 4 5% 11% 31% 30%	1973
	11th to 20th	Night	24% 5% 8% 21% 25% 17%	2090
	21st to end	Night	23% 3 7% 23% 32% 11%	2090
October	1st to 10th	Night	30% 3 11% 25% 23% 8%	2191
	11th to 20th	Night	31% 3 10% 34% 18% 4	2280
	21st to end	Night	33% 7% 13% 26% 19% 2	2602
November	1st to 10th	Night	39% 7% 14% 25% 13% 2	2431
	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% 20% 31% 24% 7%	506
April	1st to 10th	Day	18% 20% 27% 23% 10% 2	460
	11th to 20th	Day	15% 20% 34% 19% 10% 2	452
	21st to end	Day	15% 14% 28% 26% 14% 3	460
May	1st to 10th	Day	10% 16% 29% 26% 14% 4	463
	11th to 20th	Day	10% 14% 27% 27% 18% 4	488
	21st to end	Day	14% 8% 22% 28% 21% 7%	698
June	1st to 10th	Day	8% 11% 25% 26% 22% 8%	680
	11th to 20th	Day	14% 13% 28% 29% 15% 2	680
	21st to end	Day	4 5% 26% 35% 24% 6%	680
July	1st to 10th	Day	3 6% 21% 35% 28% 6%	640
	11th to 20th	Day	2 6% 24% 40% 23% 5%	484
	21st to end	Day	3 3 20% 34% 30% 10%	531
August	1st to 10th	Day	5% 4 26% 31% 26% 8%	487
	11th to 20th	Day	4 4 22% 32% 27% 10%	477
	21st to end	Day	5% 9% 23% 30% 23% 10%	539
September	1st to 10th	Day	4 7% 23% 26% 29% 10%	490
	11th to 20th	Day	9% 10% 24% 29% 21% 7%	490
	21st to end	Day	9% 10% 22% 28% 24% 8%	490
October	1st to 10th	Day	12% 8% 18% 26% 27% 9%	388
	11th to 20th	Day	10% 14% 19% 21% 22% 13%	300
	21st to end	Day	16% 13% 23% 30% 16% 3	330
November	1st to 10th	Day	21% 12% 24% 25% 12% 7%	276
	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	836
April	1st to 10th	Night	15% 9% 25% 36% 14% 1	717
	11th to 20th	Night	13% 11% 31% 35% 9% 1	563
	21st to end	Night	12% 6% 25% 38% 17% 2	570
May	1st to 10th	Night	11% 8% 26% 35% 19% 1	570
	11th to 20th	Night	11% 6% 22% 35% 24% 3	561
	21st to end	Night	12% 6% 21% 41% 18% 3	617
June	1st to 10th	Night	8% 6% 23% 35% 25% 4	444
	11th to 20th	Night	9% 6% 27% 39% 17%	380
	21st to end	Night	3 3 18% 46% 25% 5%	380
July	1st to 10th	Night	3 1 17% 46% 29% 4	370
	11th to 20th	Night	2 1 17% 52% 26% 2	380
	21st to end	Night	3 1 17% 45% 30% 4	624
August	1st to 10th	Night	5% 3 16% 45% 28% 2	567
	11th to 20th	Night	3 2 17% 45% 31% 3	564
	21st to end	Night	4 3 21% 42% 28% 3	627
September	1st to 10th	Night	6% 2 21% 41% 26% 5%	670
	11th to 20th	Night	8% 3 17% 39% 27% 5%	760
	21st to end	Night	9% 3 18% 38% 24% 7%	760
October	1st to 10th	Night	12% 4 19% 39% 25% 2	760
	11th to 20th	Night	11% 7% 20% 36% 23% 3	760
	21st to end	Night	11% 8% 22% 41% 15% 4	836
November	1st to 10th	Night	15% 8% 24% 35% 16% 2	748
	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 2024-10-31 01:39:21. Version ac07

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