Boise
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Boise clear sky chart from 2005-11-06 to 2024-11-04.

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% 7% 2 5% 4 4 4 3 5% 7% 52%	105126
	Night	10% 8% 2 6% 4 4 4 3 5% 6% 48%	102561
Transparency	Day	32% 4 10% 20% 20% 14%	104870
	Night	36% 4 11% 20% 17% 12%	102406
Seeing	Day	10% 8% 23% 29% 22% 7%	14467
	Night	14% 4 18% 38% 23% 3	23767

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	14% 17% 4 10% 6% 6% 5% 4 7% 7% 20%	2539
	11th to 20th	Day	14% 17% 6% 12% 7% 5% 6% 4 5% 6% 18%	2540
	21st to end	Day	18% 12% 5% 12% 7% 6% 6% 3 5% 7% 18%	2794
February	1st to 10th	Day	13% 12% 4 7% 6% 5% 5% 4 6% 7% 31%	1679
	11th to 20th	Day	11% 13% 3 8% 5% 4 5% 4 5% 7% 34%	1850
	21st to end	Day	11% 12% 4 7% 6% 5% 5% 4 5% 7% 34%	1570
March	1st to 10th	Day	10% 13% 4 9% 7% 6% 5% 4 6% 9% 27%	3138
	11th to 20th	Day	8% 7% 2 5% 3 3 4 3 4 5% 56%	3356
	21st to end	Day	10% 10% 3 8% 6% 7% 6% 5% 6% 9% 29%	4000
April	1st to 10th	Day	11% 9% 3 6% 5% 4 6% 5% 5% 8% 39%	2280
	11th to 20th	Day	7% 9% 3 5% 5% 5% 5% 4 6% 8% 44%	2292
	21st to end	Day	9% 6% 3 6% 4 4 4 4 6% 8% 47%	2470
May	1st to 10th	Day	8% 9% 2 5% 4 4 5% 4 6% 7% 48%	4110
	11th to 20th	Day	5% 4 1 3 3 2 2 2 4 6% 66%	4192
	21st to end	Day	6% 6% 1 4 4 4 4 4 6% 8% 53%	4813
June	1st to 10th	Day	9% 5% 2 7% 4 5% 5% 5% 6% 9% 43%	2660
	11th to 20th	Day	7% 4 1 4 3 3 4 3 5% 8% 57%	2660
	21st to end	Day	3 3 1 3 2 2 3 3 4 5% 72%	2660
July	1st to 10th	Day	1 2 2 1 1 2 2 3 3 82%	4420
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 4 78%	4420
	21st to end	Day	3 2 1 3 2 2 2 2 4 5% 74%	4790
August	1st to 10th	Day	4 4 1 4 3 3 3 3 5% 7% 63%	4225
	11th to 20th	Day	2 1 3 2 2 2 2 3 5% 79%	4028
	21st to end	Day	2 3 1 3 2 2 2 2 3 4 76%	4194
September	1st to 10th	Day	3 2 1 2 2 2 2 2 3 6% 74%	2280
	11th to 20th	Day	4 5% 2 3 3 3 3 2 5% 6% 64%	2104
	21st to end	Day	7% 4 2 3 2 2 2 3 3 6% 66%	2090
October	1st to 10th	Day	5% 4 2 4 3 2 2 2 3 5% 68%	3490
	11th to 20th	Day	8% 5% 2 4 3 3 4 4 5% 8% 55%	3046
	21st to end	Day	7% 7% 3 6% 3 4 3 4 5% 8% 49%	3101
November	1st to 10th	Day	14% 10% 2 5% 5% 4 4 4 5% 7% 41%	1701
	11th to 20th	Day	16% 9% 2 6% 5% 5% 6% 4 6% 7% 35%	1710
	21st to end	Day	13% 7% 3 8% 5% 7% 6% 5% 6% 10% 32%	1682
December	1st to 10th	Day	17% 10% 3 9% 5% 4 4 4 5% 6% 33%	1520
	11th to 20th	Day	16% 12% 4 11% 7% 6% 5% 4 7% 8% 20%	1928
	21st to end	Day	13% 11% 4 11% 6% 6% 5% 4 7% 9% 27%	2794
January	1st to 10th	Night	15% 15% 4 10% 5% 5% 4 3 5% 7% 25%	4406
	11th to 20th	Night	21% 18% 4 10% 5% 6% 4 3 4 5% 21%	4420
	21st to end	Night	17% 13% 3 9% 5% 4 5% 3 4 7% 28%	4862
February	1st to 10th	Night	16% 10% 3 8% 5% 5% 4 4 5% 7% 34%	2498
	11th to 20th	Night	12% 12% 2 5% 4 4 5% 4 6% 7% 38%	2218
	21st to end	Night	13% 13% 4 6% 5% 5% 6% 4 5% 7% 32%	1884
March	1st to 10th	Night	11% 14% 2 7% 5% 4 4 4 6% 8% 35%	3736
	11th to 20th	Night	10% 9% 2 5% 4 3 3 2 4 5% 52%	3623
	21st to end	Night	10% 10% 3 8% 6% 6% 6% 4 7% 8% 32%	3649
April	1st to 10th	Night	11% 8% 3 5% 4 4 5% 4 6% 6% 44%	1900
	11th to 20th	Night	10% 7% 2 7% 5% 4 4 4 5% 5% 47%	1834
	21st to end	Night	7% 6% 2 5% 3 4 3 3 7% 7% 52%	1710
May	1st to 10th	Night	11% 6% 2 4 3 4 4 4 6% 8% 48%	2860
	11th to 20th	Night	5% 3 1 4 3 3 3 3 5% 7% 64%	2689
	21st to end	Night	5% 6% 2 6% 5% 3 4 3 5% 6% 55%	2762
June	1st to 10th	Night	11% 5% 2 6% 5% 4 4 3 6% 9% 45%	1520
	11th to 20th	Night	7% 5% 1 4 3 3 4 3 4 7% 60%	1520
	21st to end	Night	3 2 1 4 3 3 4 3 5% 5% 67%	1520
July	1st to 10th	Night	1 1 1 2 2 2 2 2 4 5% 80%	2540
	11th to 20th	Night	1 1 1 2 2 2 3 2 4 5% 78%	2540
	21st to end	Night	2 2 1 4 4 3 3 3 5% 5% 67%	2761
August	1st to 10th	Night	3 4 2 5% 4 3 4 3 5% 7% 60%	2710
	11th to 20th	Night	2 1 1 2 2 2 3 2 3 5% 77%	2811
	21st to end	Night	3 3 1 3 2 2 2 2 3 3 77%	3481
September	1st to 10th	Night	3 3 1 3 2 2 2 2 3 5% 75%	1900
	11th to 20th	Night	5% 3 2 4 3 3 3 3 5% 6% 64%	2076
	21st to end	Night	7% 3 1 4 3 3 3 2 3 5% 67%	2090
October	1st to 10th	Night	4 3 1 4 3 2 3 2 3 5% 70%	3490
	11th to 20th	Night	7% 4 2 5% 3 3 4 2 4 6% 61%	3883
	21st to end	Night	10% 7% 2 5% 3 4 4 4 6% 7% 48%	4457
November	1st to 10th	Night	14% 8% 3 7% 4 4 4 3 5% 7% 43%	2450
	11th to 20th	Night	18% 7% 2 7% 4 4 4 4 5% 6% 39%	2470
	21st to end	Night	14% 9% 2 6% 4 4 3 3 4 7% 43%	2493
December	1st to 10th	Night	16% 11% 3 7% 6% 4 4 3 5% 7% 34%	2660
	11th to 20th	Night	17% 12% 3 10% 6% 5% 5% 4 6% 7% 26%	3276
	21st to end	Night	15% 10% 3 8% 5% 4 5% 3 6% 9% 33%	4862

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% 8% 18% 12% 1	2539
	11th to 20th	Day	65% 8% 14% 12% 2	2540
	21st to end	Day	62% 8% 18% 10% 1	2794
February	1st to 10th	Day	51% 8% 20% 17% 3 1	1679
	11th to 20th	Day	48% 8% 17% 21% 6%	1860
	21st to end	Day	49% 6% 16% 20% 8% 1	1570
March	1st to 10th	Day	49% 9% 12% 22% 7% 1	3138
	11th to 20th	Day	31% 4 12% 40% 13% 1	3356
	21st to end	Day	48% 5% 16% 22% 8% 1	4000
April	1st to 10th	Day	41% 5% 15% 23% 13% 2	2280
	11th to 20th	Day	37% 5% 11% 27% 16% 4	2295
	21st to end	Day	34% 4 14% 28% 18% 2	2470
May	1st to 10th	Day	35% 3 8% 28% 21% 5%	4110
	11th to 20th	Day	21% 3 5% 26% 32% 12%	4195
	21st to end	Day	28% 4 11% 33% 21% 3	4814
June	1st to 10th	Day	36% 5% 11% 27% 19% 2	2660
	11th to 20th	Day	25% 3 7% 25% 28% 11%	2660
	21st to end	Day	15% 2 6% 19% 34% 24%	2660
July	1st to 10th	Day	9% 2 2 9% 19% 59%	4351
	11th to 20th	Day	12% 1 2 6% 20% 59%	4345
	21st to end	Day	14% 2 2 7% 31% 44%	4639
August	1st to 10th	Day	23% 2 4 12% 26% 34%	4209
	11th to 20th	Day	11% 2 2 14% 38% 34%	4067
	21st to end	Day	15% 1 3 17% 35% 30%	4193
September	1st to 10th	Day	13% 2 4 17% 33% 32%	2280
	11th to 20th	Day	22% 3 8% 24% 27% 16%	2104
	21st to end	Day	21% 3 6% 26% 33% 12%	2090
October	1st to 10th	Day	22% 2 7% 17% 40% 13%	3490
	11th to 20th	Day	29% 3 11% 27% 26% 4	3046
	21st to end	Day	34% 3 11% 29% 22% 1	3101
November	1st to 10th	Day	42% 6% 15% 24% 13%	1701
	11th to 20th	Day	46% 7% 19% 22% 5%	1710
	21st to end	Day	46% 8% 19% 21% 6%	1682
December	1st to 10th	Day	50% 9% 19% 16% 5%	1520
	11th to 20th	Day	57% 11% 20% 10% 1	1928
	21st to end	Day	52% 9% 17% 18% 4	2794
January	1st to 10th	Night	60% 6% 19% 14% 1	4406
	11th to 20th	Night	65% 6% 13% 13% 2	4420
	21st to end	Night	56% 8% 18% 16% 2	4862
February	1st to 10th	Night	50% 7% 18% 21% 3 1	2498
	11th to 20th	Night	44% 6% 17% 23% 10% 1	2219
	21st to end	Night	50% 5% 13% 20% 10% 1	1884
March	1st to 10th	Night	45% 6% 11% 26% 10% 1	3736
	11th to 20th	Night	35% 3 7% 31% 22% 1	3623
	21st to end	Night	46% 6% 13% 27% 7%	3649
April	1st to 10th	Night	40% 4 11% 26% 15% 3	1900
	11th to 20th	Night	37% 5% 10% 26% 20% 3	1834
	21st to end	Night	31% 4 11% 28% 24% 2	1710
May	1st to 10th	Night	31% 4 7% 28% 23% 6%	2860
	11th to 20th	Night	20% 3 5% 25% 37% 9%	2689
	21st to end	Night	28% 5% 11% 28% 25% 3	2762
June	1st to 10th	Night	36% 4 12% 25% 20% 2	1520
	11th to 20th	Night	25% 3 7% 23% 32% 9%	1520
	21st to end	Night	19% 3 5% 17% 31% 25%	1520
July	1st to 10th	Night	9% 1 2 9% 19% 60%	2500
	11th to 20th	Night	11% 2 2 7% 18% 61%	2492
	21st to end	Night	19% 2 2 6% 27% 43%	2674
August	1st to 10th	Night	24% 2 3 10% 23% 38%	2702
	11th to 20th	Night	11% 2 3 10% 28% 46%	2838
	21st to end	Night	15% 1 2 13% 32% 35%	3481
September	1st to 10th	Night	14% 2 3 12% 31% 37%	1900
	11th to 20th	Night	23% 2 6% 19% 26% 24%	2076
	21st to end	Night	21% 3 4 21% 32% 19%	2090
October	1st to 10th	Night	19% 2 5% 18% 31% 25%	3490
	11th to 20th	Night	27% 2 9% 26% 29% 7%	3883
	21st to end	Night	35% 3 10% 28% 21% 3	4457
November	1st to 10th	Night	42% 3 12% 22% 19% 2	2450
	11th to 20th	Night	45% 5% 13% 27% 10%	2470
	21st to end	Night	42% 4 16% 28% 10% 1	2493
December	1st to 10th	Night	49% 8% 19% 16% 8%	2660
	11th to 20th	Night	56% 7% 17% 17% 3	3276
	21st to end	Night	49% 6% 22% 18% 5%	4862

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	26% 6% 20% 25% 19% 5%	180
	11th to 20th	Day	18% 9% 21% 24% 21% 8%	180
	21st to end	Day	19% 4 21% 32% 15% 10%	198
February	1st to 10th	Day	21% 11% 27% 22% 16% 4	286
	11th to 20th	Day	17% 11% 29% 25% 14% 3	455
	21st to end	Day	17% 12% 30% 26% 13% 2	382
March	1st to 10th	Day	17% 11% 30% 29% 12% 1	460
	11th to 20th	Day	13% 9% 31% 27% 16% 4	460
	21st to end	Day	16% 12% 33% 23% 14% 2	506
April	1st to 10th	Day	14% 18% 25% 22% 16% 5%	460
	11th to 20th	Day	11% 17% 30% 24% 14% 4	452
	21st to end	Day	11% 15% 31% 25% 14% 4	460
May	1st to 10th	Day	6% 15% 30% 29% 16% 4	463
	11th to 20th	Day	15% 8% 24% 27% 18% 7%	488
	21st to end	Day	8% 8% 19% 32% 19% 13%	529
June	1st to 10th	Day	10% 7% 23% 27% 24% 9%	490
	11th to 20th	Day	8% 12% 27% 33% 15% 5%	490
	21st to end	Day	4 7% 24% 32% 26% 7%	490
July	1st to 10th	Day	3 5% 21% 37% 27% 8%	486
	11th to 20th	Day	2 3 23% 39% 27% 6%	484
	21st to end	Day	4 2 17% 38% 31% 8%	531
August	1st to 10th	Day	5% 4 21% 35% 27% 9%	487
	11th to 20th	Day	3 3 19% 31% 32% 13%	477
	21st to end	Day	4 5% 19% 29% 30% 14%	539
September	1st to 10th	Day	5% 4 15% 28% 36% 13%	490
	11th to 20th	Day	7% 5% 19% 29% 28% 13%	490
	21st to end	Day	6% 5% 19% 32% 30% 7%	490
October	1st to 10th	Day	7% 10% 18% 24% 30% 11%	490
	11th to 20th	Day	11% 7% 21% 26% 26% 10%	380
	21st to end	Day	14% 7% 25% 28% 22% 3	330
November	1st to 10th	Day	18% 9% 21% 33% 17% 3	279
	11th to 20th	Day	14% 8% 18% 35% 19% 6%	270
	21st to end	Day	15% 7% 15% 33% 25% 5%	257
December	1st to 10th	Day	23% 5% 21% 24% 18% 9%	180
	11th to 20th	Day	26% 4 23% 28% 14% 4	180
	21st to end	Day	18% 10% 25% 26% 17% 4	198
January	1st to 10th	Night	22% 6% 18% 30% 20% 3	760
	11th to 20th	Night	21% 5% 17% 31% 22% 4	760
	21st to end	Night	19% 4 16% 32% 25% 4	836
February	1st to 10th	Night	22% 4 21% 34% 16% 3	760
	11th to 20th	Night	18% 3 23% 35% 18% 2	744
	21st to end	Night	16% 7% 24% 37% 14% 3	628
March	1st to 10th	Night	18% 8% 24% 34% 15% 2	760
	11th to 20th	Night	16% 6% 20% 39% 17% 2	760
	21st to end	Night	17% 8% 24% 36% 12% 2	836
April	1st to 10th	Night	15% 7% 19% 39% 18% 2	760
	11th to 20th	Night	12% 8% 26% 36% 16% 3	706
	21st to end	Night	9% 8% 24% 42% 15% 2	570
May	1st to 10th	Night	10% 7% 23% 40% 18% 2	570
	11th to 20th	Night	10% 5% 19% 35% 27% 4	482
	21st to end	Night	9% 5% 17% 35% 29% 5%	411
June	1st to 10th	Night	12% 5% 14% 39% 27% 3	380
	11th to 20th	Night	9% 6% 21% 38% 25% 2	380
	21st to end	Night	3 2 18% 45% 30% 3	380
July	1st to 10th	Night	2 1 12% 51% 32% 2	370
	11th to 20th	Night	2 1 14% 56% 27% 1	368
	21st to end	Night	3 1 10% 49% 34% 3	416
August	1st to 10th	Night	4 2 12% 48% 33% 1	481
	11th to 20th	Night	1 2 11% 47% 37% 2	564
	21st to end	Night	4 2 13% 46% 31% 4	819
September	1st to 10th	Night	3 1 10% 43% 37% 5%	760
	11th to 20th	Night	6% 3 10% 39% 37% 6%	760
	21st to end	Night	9% 2 14% 37% 29% 9%	760
October	1st to 10th	Night	9% 3 15% 42% 27% 5%	760
	11th to 20th	Night	9% 4 15% 39% 28% 6%	760
	21st to end	Night	13% 4 18% 38% 22% 5%	836
November	1st to 10th	Night	16% 5% 17% 36% 23% 3	754
	11th to 20th	Night	21% 4 18% 36% 19% 3	760
	21st to end	Night	19% 2 16% 37% 22% 5%	760
December	1st to 10th	Night	21% 3 17% 37% 19% 3	760
	11th to 20th	Night	24% 4 16% 38% 16% 3	760
	21st to end	Night	28% 5% 21% 32% 13% 2	836

Page generated at 2024-11-01 20:47:50. Version ac07

Copyright © 2024 Attilla Danko.