Missoula
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Missoula clear sky chart from 2005-11-06 to 2024-04-10.

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	9% 11% 4 8% 6% 4 5% 5% 6% 7% 36%	82705
	Night	9% 13% 5% 8% 6% 4 5% 5% 5% 7% 33%	86149
Transparency	Day	45% 6% 15% 21% 11% 3	82398
	Night	47% 6% 16% 20% 9% 2	85976
Seeing	Day	16% 13% 25% 28% 15% 3	14321
	Night	15% 7% 21% 39% 17% 1	23834

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	6% 21% 11% 13% 9% 6% 6% 5% 5% 6% 13%	2326
	11th to 20th	Day	8% 17% 7% 15% 8% 4 4 4 6% 5% 22%	2540
	21st to end	Day	10% 17% 6% 11% 9% 4 5% 5% 5% 6% 21%	2794
February	1st to 10th	Day	9% 22% 8% 12% 8% 4 5% 4 4 6% 18%	1638
	11th to 20th	Day	7% 18% 7% 11% 9% 4 6% 6% 5% 6% 22%	1711
	21st to end	Day	8% 17% 6% 11% 10% 4 6% 5% 5% 7% 21%	1570
March	1st to 10th	Day	6% 12% 6% 9% 8% 4 6% 6% 7% 9% 28%	3138
	11th to 20th	Day	7% 10% 5% 8% 5% 4 5% 4 5% 7% 39%	3484
	21st to end	Day	8% 17% 6% 12% 10% 5% 6% 7% 7% 7% 16%	3825
April	1st to 10th	Day	10% 15% 6% 11% 7% 4 6% 6% 6% 7% 23%	2267
	11th to 20th	Day	12% 15% 6% 9% 6% 4 5% 5% 6% 7% 27%	2307
	21st to end	Day	12% 16% 5% 9% 7% 3 5% 5% 5% 6% 27%	2340
May	1st to 10th	Day	8% 10% 4 9% 6% 5% 6% 6% 6% 7% 33%	2340
	11th to 20th	Day	12% 8% 4 6% 6% 4 6% 6% 7% 10% 32%	2407
	21st to end	Day	18% 10% 3 7% 6% 4 6% 5% 6% 7% 26%	2917
June	1st to 10th	Day	16% 9% 4 7% 6% 4 5% 5% 6% 8% 31%	2700
	11th to 20th	Day	17% 9% 4 7% 6% 4 6% 5% 5% 6% 32%	2700
	21st to end	Day	6% 4 2 4 5% 3 5% 6% 6% 7% 52%	2700
July	1st to 10th	Day	3 2 1 4 4 2 5% 6% 6% 7% 60%	2700
	11th to 20th	Day	4 3 1 3 3 2 4 4 5% 6% 67%	2585
	21st to end	Day	3 1 1 2 3 2 3 4 5% 6% 69%	2741
August	1st to 10th	Day	4 3 1 3 4 3 3 4 5% 8% 61%	2405
	11th to 20th	Day	4 3 2 3 4 2 3 4 5% 7% 64%	2299
	21st to end	Day	6% 4 1 4 4 2 4 4 5% 8% 57%	2574
September	1st to 10th	Day	6% 4 2 4 4 2 3 4 4 7% 60%	2134
	11th to 20th	Day	7% 7% 3 5% 5% 3 5% 4 5% 8% 48%	1980
	21st to end	Day	10% 7% 3 4 5% 3 4 4 6% 8% 48%	1980
October	1st to 10th	Day	13% 9% 4 7% 5% 3 4 5% 4 8% 38%	1936
	11th to 20th	Day	11% 11% 3 7% 6% 3 4 4 5% 7% 39%	1732
	21st to end	Day	14% 12% 5% 9% 7% 3 4 4 5% 7% 30%	1782
November	1st to 10th	Day	15% 17% 6% 9% 5% 4 5% 4 5% 7% 24%	1674
	11th to 20th	Day	12% 16% 6% 9% 7% 4 5% 5% 5% 6% 25%	1564
	21st to end	Day	8% 16% 6% 8% 7% 4 5% 5% 5% 8% 29%	1458
December	1st to 10th	Day	10% 16% 6% 11% 7% 4 6% 6% 4 7% 23%	1330
	11th to 20th	Day	9% 21% 6% 11% 7% 4 6% 5% 6% 7% 19%	1685
	21st to end	Day	7% 14% 7% 11% 9% 6% 7% 5% 7% 7% 21%	2442
January	1st to 10th	Night	8% 22% 8% 12% 9% 6% 7% 5% 5% 6% 13%	4648
	11th to 20th	Night	9% 16% 6% 13% 8% 4 5% 4 5% 7% 23%	4420
	21st to end	Night	11% 20% 7% 10% 10% 4 5% 5% 5% 7% 17%	4862
February	1st to 10th	Night	11% 23% 8% 10% 6% 4 4 4 4 6% 20%	2542
	11th to 20th	Night	7% 19% 6% 11% 8% 4 4 5% 5% 6% 24%	2355
	21st to end	Night	7% 16% 7% 11% 8% 5% 6% 5% 4 6% 23%	1884
March	1st to 10th	Night	5% 12% 5% 10% 7% 4 5% 6% 6% 8% 31%	3736
	11th to 20th	Night	7% 11% 4 8% 5% 3 4 4 4 7% 45%	3495
	21st to end	Night	11% 19% 6% 9% 8% 4 7% 6% 7% 6% 17%	3828
April	1st to 10th	Night	9% 14% 4 6% 7% 4 6% 6% 6% 8% 30%	1900
	11th to 20th	Night	12% 11% 5% 8% 7% 3 6% 5% 5% 5% 32%	1601
	21st to end	Night	10% 11% 4 7% 5% 3 6% 5% 6% 8% 35%	1620
May	1st to 10th	Night	9% 9% 4 8% 7% 3 5% 5% 6% 8% 36%	1620
	11th to 20th	Night	9% 6% 3 5% 6% 4 6% 6% 8% 10% 39%	1481
	21st to end	Night	16% 8% 4 8% 7% 3 5% 5% 6% 7% 31%	1358
June	1st to 10th	Night	16% 8% 4 5% 7% 2 4 4 5% 8% 37%	1260
	11th to 20th	Night	17% 7% 4 5% 6% 3 5% 5% 6% 7% 37%	1260
	21st to end	Night	5% 4 1 3 4 3 4 4 6% 9% 57%	1260
July	1st to 10th	Night	4 2 1 2 2 1 3 5% 6% 8% 67%	1260
	11th to 20th	Night	3 2 1 2 3 2 2 3 5% 7% 70%	1372
	21st to end	Night	2 1 1 2 3 2 2 3 5% 7% 73%	1576
August	1st to 10th	Night	3 3 2 3 3 2 2 5% 5% 9% 64%	1532
	11th to 20th	Night	3 2 1 3 3 2 4 5% 6% 8% 63%	1602
	21st to end	Night	6% 4 1 3 3 2 4 5% 5% 7% 60%	1782
September	1st to 10th	Night	7% 5% 2 3 4 1 3 4 5% 7% 60%	1821
	11th to 20th	Night	9% 4 2 4 5% 2 5% 4 5% 7% 52%	1980
	21st to end	Night	11% 6% 2 6% 4 2 4 3 5% 7% 52%	1980
October	1st to 10th	Night	9% 8% 4 7% 6% 3 5% 4 5% 5% 43%	2024
	11th to 20th	Night	12% 8% 2 5% 4 3 5% 6% 5% 6% 43%	2226
	21st to end	Night	14% 12% 4 7% 6% 3 4 5% 4 7% 34%	2574
November	1st to 10th	Night	16% 13% 4 7% 6% 3 4 5% 4 7% 29%	2405
	11th to 20th	Night	12% 17% 5% 9% 6% 4 4 4 5% 6% 27%	2594
	21st to end	Night	8% 12% 4 9% 7% 4 5% 5% 6% 8% 31%	2721
December	1st to 10th	Night	9% 17% 7% 8% 7% 4 5% 5% 5% 7% 25%	2850
	11th to 20th	Night	9% 19% 8% 10% 7% 3 5% 4 5% 8% 20%	3506
	21st to end	Night	8% 14% 6% 11% 7% 6% 8% 8% 7% 8% 19%	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	64% 7% 18% 10% 1	2326
	11th to 20th	Day	61% 5% 15% 16% 3 1	2540
	21st to end	Day	59% 6% 20% 12% 3 1	2794
February	1st to 10th	Day	65% 6% 15% 12% 2	1638
	11th to 20th	Day	59% 5% 17% 13% 5%	1720
	21st to end	Day	59% 5% 10% 18% 6% 1	1570
March	1st to 10th	Day	45% 8% 15% 21% 11%	3138
	11th to 20th	Day	41% 6% 21% 29% 3	3484
	21st to end	Day	61% 9% 16% 11% 3	3825
April	1st to 10th	Day	56% 6% 17% 17% 4	2267
	11th to 20th	Day	55% 4 12% 21% 7% 1	2310
	21st to end	Day	56% 6% 13% 20% 5%	2340
May	1st to 10th	Day	46% 5% 15% 24% 8% 1	2340
	11th to 20th	Day	45% 6% 20% 20% 8%	2410
	21st to end	Day	55% 6% 17% 15% 6%	2918
June	1st to 10th	Day	49% 8% 17% 19% 6%	2700
	11th to 20th	Day	49% 5% 12% 21% 10% 3	2700
	21st to end	Day	29% 5% 13% 32% 19% 2	2700
July	1st to 10th	Day	22% 4 9% 26% 29% 9%	2626
	11th to 20th	Day	18% 3 9% 20% 29% 20%	2506
	21st to end	Day	14% 4 6% 22% 36% 19%	2589
August	1st to 10th	Day	20% 5% 9% 28% 27% 11%	2388
	11th to 20th	Day	19% 5% 11% 29% 29% 8%	2299
	21st to end	Day	24% 4 11% 31% 23% 6%	2574
September	1st to 10th	Day	25% 4 10% 31% 22% 9%	2134
	11th to 20th	Day	33% 4 14% 29% 15% 4	1980
	21st to end	Day	34% 4 19% 28% 14% 1	1980
October	1st to 10th	Day	45% 6% 15% 26% 7%	1936
	11th to 20th	Day	43% 4 18% 26% 8% 1	1732
	21st to end	Day	52% 5% 15% 22% 6%	1782
November	1st to 10th	Day	57% 6% 16% 16% 4	1674
	11th to 20th	Day	55% 7% 19% 15% 3	1564
	21st to end	Day	47% 6% 24% 18% 4	1458
December	1st to 10th	Day	58% 7% 18% 13% 5%	1330
	11th to 20th	Day	61% 6% 21% 11% 2	1684
	21st to end	Day	55% 8% 16% 14% 7%	2442
January	1st to 10th	Night	65% 10% 14% 10% 1	4648
	11th to 20th	Night	59% 5% 15% 17% 3 1	4420
	21st to end	Night	64% 8% 14% 11% 3	4862
February	1st to 10th	Night	64% 5% 15% 13% 3	2542
	11th to 20th	Night	58% 5% 19% 15% 2	2356
	21st to end	Night	57% 5% 13% 18% 6% 1	1884
March	1st to 10th	Night	42% 7% 16% 23% 12%	3736
	11th to 20th	Night	38% 6% 23% 29% 4	3495
	21st to end	Night	61% 9% 16% 12% 3	3828
April	1st to 10th	Night	47% 7% 20% 21% 4	1900
	11th to 20th	Night	50% 6% 15% 23% 6% 1	1601
	21st to end	Night	45% 6% 18% 24% 7%	1620
May	1st to 10th	Night	44% 5% 16% 27% 8%	1620
	11th to 20th	Night	39% 8% 20% 23% 10%	1481
	21st to end	Night	50% 6% 22% 16% 6%	1358
June	1st to 10th	Night	45% 6% 19% 23% 7%	1260
	11th to 20th	Night	45% 5% 16% 22% 10% 2	1260
	21st to end	Night	23% 6% 15% 34% 20% 2	1260
July	1st to 10th	Night	14% 5% 9% 34% 28% 10%	1225
	11th to 20th	Night	15% 2 11% 27% 30% 16%	1328
	21st to end	Night	12% 3 6% 27% 33% 19%	1488
August	1st to 10th	Night	17% 5% 11% 28% 28% 11%	1524
	11th to 20th	Night	19% 5% 10% 28% 28% 8%	1602
	21st to end	Night	23% 4 12% 26% 29% 6%	1782
September	1st to 10th	Night	25% 3 12% 27% 24% 10%	1821
	11th to 20th	Night	30% 5% 13% 29% 19% 4	1980
	21st to end	Night	32% 5% 17% 28% 16% 2	1980
October	1st to 10th	Night	40% 6% 18% 27% 9%	2024
	11th to 20th	Night	39% 4 20% 28% 9%	2226
	21st to end	Night	48% 6% 17% 20% 8%	2574
November	1st to 10th	Night	52% 5% 18% 20% 4 1	2405
	11th to 20th	Night	54% 6% 20% 16% 4	2594
	21st to end	Night	46% 5% 23% 21% 5%	2721
December	1st to 10th	Night	55% 7% 16% 17% 5%	2850
	11th to 20th	Night	59% 8% 19% 13% 1	3507
	21st to end	Night	55% 10% 15% 13% 7%	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	16% 12% 23% 30% 18% 2	180
	11th to 20th	Day	19% 6% 22% 32% 15% 6%	180
	21st to end	Day	17% 13% 25% 31% 11% 3	198
February	1st to 10th	Day	24% 17% 29% 24% 6%	236
	11th to 20th	Day	15% 21% 24% 28% 12% 1	316
	21st to end	Day	22% 15% 25% 29% 9% 1	382
March	1st to 10th	Day	20% 18% 28% 27% 7% 1	460
	11th to 20th	Day	17% 15% 25% 24% 17% 2	460
	21st to end	Day	20% 18% 30% 24% 7% 1	506
April	1st to 10th	Day	21% 18% 30% 22% 9%	457
	11th to 20th	Day	24% 20% 31% 18% 7% 1	412
	21st to end	Day	24% 20% 25% 20% 9% 2	420
May	1st to 10th	Day	13% 18% 30% 29% 10% 1	423
	11th to 20th	Day	23% 12% 25% 25% 13% 2	469
	21st to end	Day	21% 13% 18% 25% 18% 4	679
June	1st to 10th	Day	17% 13% 21% 26% 18% 5%	630
	11th to 20th	Day	22% 17% 26% 21% 12% 2	630
	21st to end	Day	9% 12% 22% 32% 22% 2	630
July	1st to 10th	Day	5% 9% 27% 30% 26% 3	621
	11th to 20th	Day	7% 14% 28% 32% 17% 2	505
	21st to end	Day	3 10% 31% 34% 19% 2	487
August	1st to 10th	Day	6% 12% 27% 31% 19% 6%	447
	11th to 20th	Day	7% 8% 23% 33% 22% 6%	437
	21st to end	Day	8% 11% 26% 33% 18% 4	495
September	1st to 10th	Day	9% 13% 25% 27% 21% 4	450
	11th to 20th	Day	11% 11% 24% 27% 20% 6%	450
	21st to end	Day	17% 13% 21% 26% 20% 4	450
October	1st to 10th	Day	18% 8% 21% 34% 16% 3	406
	11th to 20th	Day	19% 11% 22% 27% 13% 7%	270
	21st to end	Day	21% 10% 27% 32% 8% 2	297
November	1st to 10th	Day	23% 12% 23% 34% 8%	270
	11th to 20th	Day	21% 8% 25% 33% 12% 1	270
	21st to end	Day	14% 9% 20% 43% 13% 1	240
December	1st to 10th	Day	23% 8% 25% 26% 13% 4	180
	11th to 20th	Day	19% 10% 28% 32% 9% 1	180
	21st to end	Day	15% 10% 28% 33% 11% 3	198
January	1st to 10th	Night	19% 8% 23% 36% 12% 1	898
	11th to 20th	Night	17% 9% 25% 35% 12% 2	760
	21st to end	Night	16% 7% 24% 41% 12% 1	836
February	1st to 10th	Night	21% 9% 29% 31% 8% 1	760
	11th to 20th	Night	17% 9% 28% 35% 9% 1	744
	21st to end	Night	14% 11% 28% 34% 13% 1	628
March	1st to 10th	Night	13% 7% 28% 40% 11% 1	760
	11th to 20th	Night	13% 9% 25% 38% 15%	760
	21st to end	Night	17% 8% 24% 39% 12% 1	836
April	1st to 10th	Night	15% 9% 23% 38% 13% 1	760
	11th to 20th	Night	15% 10% 25% 38% 12%	533
	21st to end	Night	15% 9% 21% 38% 16% 1	540
May	1st to 10th	Night	14% 9% 23% 34% 20%	540
	11th to 20th	Night	11% 6% 17% 37% 26% 2	444
	21st to end	Night	18% 6% 17% 27% 31% 2	389
June	1st to 10th	Night	17% 6% 16% 35% 22% 4	360
	11th to 20th	Night	19% 7% 18% 37% 18% 1	360
	21st to end	Night	7% 3 14% 43% 34% 1	360
July	1st to 10th	Night	5% 1 7% 50% 35% 1	350
	11th to 20th	Night	4 2 10% 57% 27%	348
	21st to end	Night	3 1 8% 55% 32% 1	394
August	1st to 10th	Night	3 2 10% 51% 33% 1	458
	11th to 20th	Night	4 2 10% 48% 34% 3	534
	21st to end	Night	7% 4 12% 47% 29% 1	594
September	1st to 10th	Night	9% 1 15% 44% 28% 3	697
	11th to 20th	Night	12% 2 11% 38% 35% 2	720
	21st to end	Night	14% 6% 14% 39% 24% 3	720
October	1st to 10th	Night	13% 6% 18% 42% 21% 1	720
	11th to 20th	Night	18% 4 15% 42% 19% 3	720
	21st to end	Night	19% 7% 20% 37% 15% 2	792
November	1st to 10th	Night	22% 6% 21% 41% 10%	740
	11th to 20th	Night	22% 9% 23% 36% 9% 1	884
	21st to end	Night	13% 7% 24% 43% 12%	950
December	1st to 10th	Night	17% 8% 24% 37% 12% 2	950
	11th to 20th	Night	16% 7% 28% 39% 9%	950
	21st to end	Night	18% 10% 28% 35% 9% 1	1045

Page generated at 2024-04-07 07:28:16. Version ac07

Copyright © 2024 Attilla Danko.