Kalispell
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kalispell clear sky chart from 2005-11-06 to 2025-10-19.

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% 9% 3 8% 5% 5% 5% 4 6% 7% 39%	130538
	Night	7% 10% 4 9% 6% 5% 5% 4 6% 8% 37%	127904
Transparency	Day	42% 10% 14% 20% 11% 4	130252
	Night	45% 11% 14% 18% 9% 3	127767
Seeing	Day	14% 15% 24% 26% 17% 4	16490
	Night	15% 11% 19% 34% 18% 2	25609

By Month

Percentage Cloud Cover NW (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	8% 21% 9% 20% 10% 7% 5% 4 4 5% 8%	3200
	11th to 20th	Day	7% 14% 5% 13% 8% 7% 6% 4 6% 7% 23%	3616
	21st to end	Day	7% 14% 6% 18% 7% 5% 5% 4 4 6% 24%	4004
February	1st to 10th	Day	11% 19% 6% 13% 8% 6% 5% 5% 6% 6% 16%	1661
	11th to 20th	Day	7% 16% 6% 14% 7% 5% 6% 5% 8% 7% 19%	1790
	21st to end	Day	8% 18% 6% 13% 8% 6% 6% 4 6% 5% 20%	1650
March	1st to 10th	Day	5% 11% 4 8% 6% 5% 5% 5% 7% 12% 32%	4518
	11th to 20th	Day	4 14% 4 11% 7% 6% 6% 4 5% 8% 31%	4949
	21st to end	Day	7% 16% 5% 12% 7% 7% 7% 5% 7% 9% 18%	5561
April	1st to 10th	Day	9% 14% 4 10% 7% 7% 6% 5% 8% 7% 24%	2405
	11th to 20th	Day	12% 12% 4 10% 6% 6% 6% 4 6% 6% 28%	2570
	21st to end	Day	13% 10% 3 10% 7% 5% 5% 5% 7% 6% 28%	2600
May	1st to 10th	Day	11% 10% 3 8% 5% 4 4 3 4 6% 42%	5880
	11th to 20th	Day	9% 9% 3 9% 6% 7% 7% 5% 8% 9% 28%	6450
	21st to end	Day	10% 7% 2 7% 5% 5% 6% 5% 6% 8% 39%	7405
June	1st to 10th	Day	16% 7% 3 7% 6% 6% 4 4 6% 7% 33%	3000
	11th to 20th	Day	16% 7% 2 7% 6% 5% 6% 5% 7% 8% 30%	3000
	21st to end	Day	8% 4 2 5% 4 4 5% 5% 7% 9% 46%	3000
July	1st to 10th	Day	4 2 1 4 3 3 4 3 5% 7% 63%	6780
	11th to 20th	Day	5% 2 1 2 2 2 2 2 4 5% 74%	6648
	21st to end	Day	3 2 1 3 2 2 3 2 5% 8% 69%	6874
August	1st to 10th	Day	5% 3 1 4 3 3 5% 4 6% 9% 58%	4457
	11th to 20th	Day	5% 3 1 4 3 3 4 4 6% 8% 60%	4158
	21st to end	Day	5% 3 2 5% 3 4 4 4 5% 8% 58%	4664
September	1st to 10th	Day	6% 4 2 4 4 4 4 3 6% 7% 57%	2400
	11th to 20th	Day	8% 4 2 5% 5% 5% 6% 4 6% 8% 47%	2200
	21st to end	Day	8% 5% 2 5% 6% 5% 5% 5% 7% 8% 46%	2200
October	1st to 10th	Day	7% 5% 2 4 4 3 4 3 5% 7% 57%	3512
	11th to 20th	Day	8% 6% 2 7% 4 4 5% 4 6% 8% 45%	3042
	21st to end	Day	10% 12% 4 10% 6% 6% 6% 4 7% 8% 27%	3101
November	1st to 10th	Day	14% 17% 4 10% 6% 6% 5% 5% 6% 6% 20%	1764
	11th to 20th	Day	9% 14% 5% 13% 7% 6% 6% 5% 7% 6% 21%	1604
	21st to end	Day	9% 15% 5% 13% 9% 8% 4 4 7% 8% 19%	1445
December	1st to 10th	Day	5% 13% 5% 9% 6% 8% 5% 3 5% 11% 30%	2290
	11th to 20th	Day	6% 15% 6% 17% 10% 8% 7% 5% 6% 7% 14%	2642
	21st to end	Day	8% 17% 7% 18% 11% 8% 6% 4 6% 5% 11%	3498
January	1st to 10th	Night	8% 21% 7% 17% 10% 7% 6% 4 5% 5% 10%	6766
	11th to 20th	Night	6% 11% 5% 13% 8% 6% 6% 4 5% 8% 28%	6305
	21st to end	Night	9% 15% 7% 11% 6% 6% 6% 4 5% 8% 22%	6952
February	1st to 10th	Night	12% 15% 6% 11% 7% 6% 5% 4 5% 6% 23%	2738
	11th to 20th	Night	8% 17% 6% 11% 6% 4 5% 4 6% 7% 27%	2496
	21st to end	Night	5% 15% 5% 11% 7% 6% 6% 5% 6% 6% 27%	1980
March	1st to 10th	Night	4 9% 3 7% 5% 5% 6% 5% 9% 11% 37%	5376
	11th to 20th	Night	4 9% 4 9% 6% 6% 6% 4 6% 8% 37%	5050
	21st to end	Night	8% 13% 5% 12% 8% 7% 7% 6% 8% 8% 19%	5412
April	1st to 10th	Night	7% 13% 3 8% 5% 5% 5% 4 6% 8% 37%	1995
	11th to 20th	Night	9% 9% 3 9% 6% 6% 5% 4 6% 6% 36%	1781
	21st to end	Night	11% 7% 3 7% 5% 5% 5% 4 6% 8% 38%	1800
May	1st to 10th	Night	11% 9% 3 6% 5% 4 4 4 6% 8% 41%	4100
	11th to 20th	Night	10% 7% 3 7% 5% 5% 5% 6% 7% 10% 35%	3428
	21st to end	Night	12% 7% 2 7% 4 4 4 4 5% 7% 44%	3470
June	1st to 10th	Night	13% 7% 3 6% 4 4 5% 4 6% 6% 43%	1400
	11th to 20th	Night	14% 5% 2 5% 5% 5% 5% 6% 6% 7% 39%	1400
	21st to end	Night	4 5% 2 4 4 5% 4 4 6% 7% 56%	1400
July	1st to 10th	Night	4 1 1 2 2 2 2 2 4 6% 74%	3180
	11th to 20th	Night	3 2 1 2 1 2 2 2 3 4 78%	3308
	21st to end	Night	2 2 1 3 2 3 2 3 4 7% 70%	3969
August	1st to 10th	Night	4 3 1 3 2 2 3 2 5% 8% 67%	2695
	11th to 20th	Night	3 2 1 4 4 4 5% 4 7% 8% 58%	2901
	21st to end	Night	4 2 1 3 2 3 3 3 6% 7% 67%	3245
September	1st to 10th	Night	5% 2 1 5% 3 4 4 3 7% 8% 60%	1997
	11th to 20th	Night	7% 4 2 6% 4 4 3 4 6% 7% 54%	2200
	21st to end	Night	7% 4 2 5% 4 4 4 4 6% 8% 53%	2200
October	1st to 10th	Night	5% 4 2 4 4 4 4 3 6% 9% 55%	3684
	11th to 20th	Night	5% 4 2 4 4 5% 5% 4 7% 9% 51%	4057
	21st to end	Night	7% 7% 3 6% 5% 4 5% 5% 6% 9% 44%	4457
November	1st to 10th	Night	12% 13% 4 9% 6% 6% 5% 4 6% 8% 26%	2535
	11th to 20th	Night	9% 14% 4 10% 7% 6% 6% 4 6% 7% 26%	2775
	21st to end	Night	9% 15% 5% 10% 7% 5% 6% 5% 6% 7% 25%	2954
December	1st to 10th	Night	6% 11% 4 7% 6% 6% 4 5% 7% 14% 31%	4890
	11th to 20th	Night	6% 15% 7% 15% 11% 8% 6% 4 5% 6% 17%	5550
	21st to end	Night	7% 17% 7% 17% 9% 7% 6% 4 5% 6% 14%	7458

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	81% 10% 6% 3	3200
	11th to 20th	Day	61% 11% 14% 10% 3	3640
	21st to end	Day	61% 10% 15% 13% 1	4004
February	1st to 10th	Day	70% 10% 10% 6% 4 1	1661
	11th to 20th	Day	60% 17% 12% 8% 4	1799
	21st to end	Day	65% 11% 10% 10% 4	1650
March	1st to 10th	Day	40% 12% 18% 19% 11%	4518
	11th to 20th	Day	47% 13% 22% 15% 4	4950
	21st to end	Day	58% 14% 14% 11% 3	5561
April	1st to 10th	Day	56% 12% 14% 15% 3	2405
	11th to 20th	Day	54% 10% 13% 17% 5%	2570
	21st to end	Day	51% 12% 14% 16% 6% 1	2600
May	1st to 10th	Day	42% 7% 12% 25% 13% 2	5880
	11th to 20th	Day	41% 17% 19% 17% 7%	6454
	21st to end	Day	36% 14% 18% 22% 9% 1	7406
June	1st to 10th	Day	48% 10% 16% 19% 8%	3000
	11th to 20th	Day	48% 11% 14% 17% 8% 2	3000
	21st to end	Day	31% 10% 18% 26% 15% 1	3000
July	1st to 10th	Day	19% 6% 11% 26% 24% 13%	6706
	11th to 20th	Day	14% 3 9% 27% 22% 26%	6567
	21st to end	Day	15% 3 9% 30% 28% 15%	6681
August	1st to 10th	Day	21% 6% 12% 30% 24% 7%	4440
	11th to 20th	Day	21% 8% 14% 36% 19% 2	4197
	21st to end	Day	23% 7% 14% 34% 20% 3	4663
September	1st to 10th	Day	25% 7% 13% 31% 19% 6%	2400
	11th to 20th	Day	33% 10% 16% 25% 14% 1	2200
	21st to end	Day	35% 10% 20% 24% 10% 1	2200
October	1st to 10th	Day	27% 7% 19% 37% 11%	3512
	11th to 20th	Day	36% 9% 23% 25% 7%	3042
	21st to end	Day	53% 11% 17% 17% 3	3101
November	1st to 10th	Day	65% 11% 13% 8% 2	1764
	11th to 20th	Day	63% 14% 14% 5% 4	1604
	21st to end	Day	64% 15% 12% 7% 2	1445
December	1st to 10th	Day	53% 18% 20% 7% 1	2290
	11th to 20th	Day	70% 9% 16% 4 1	2644
	21st to end	Day	72% 12% 9% 6% 1	3498
January	1st to 10th	Night	77% 12% 6% 4 1	6766
	11th to 20th	Night	56% 14% 11% 9% 7% 2	6343
	21st to end	Night	61% 14% 14% 10% 2	6952
February	1st to 10th	Night	62% 12% 12% 9% 4 1	2738
	11th to 20th	Night	58% 13% 15% 9% 4	2497
	21st to end	Night	58% 13% 12% 13% 4 1	1980
March	1st to 10th	Night	37% 15% 20% 17% 10%	5376
	11th to 20th	Night	42% 10% 20% 21% 6%	5050
	21st to end	Night	58% 15% 15% 10% 2	5412
April	1st to 10th	Night	45% 14% 17% 20% 3	1995
	11th to 20th	Night	47% 11% 15% 19% 7% 1	1781
	21st to end	Night	44% 11% 17% 20% 7% 1	1800
May	1st to 10th	Night	40% 9% 11% 23% 16%	4097
	11th to 20th	Night	40% 13% 16% 23% 9%	3428
	21st to end	Night	38% 10% 15% 25% 11% 1	3470
June	1st to 10th	Night	41% 9% 16% 23% 10% 1	1400
	11th to 20th	Night	43% 11% 13% 21% 10% 2	1400
	21st to end	Night	27% 8% 15% 30% 18% 2	1400
July	1st to 10th	Night	14% 4 11% 29% 26% 16%	3145
	11th to 20th	Night	13% 2 7% 28% 20% 29%	3266
	21st to end	Night	15% 5% 11% 27% 23% 19%	3857
August	1st to 10th	Night	17% 4 10% 32% 26% 10%	2687
	11th to 20th	Night	22% 7% 14% 34% 18% 4	2928
	21st to end	Night	17% 5% 13% 37% 24% 5%	3245
September	1st to 10th	Night	21% 7% 15% 31% 18% 8%	1997
	11th to 20th	Night	29% 8% 14% 30% 17% 2	2200
	21st to end	Night	30% 9% 20% 24% 15% 3	2200
October	1st to 10th	Night	27% 7% 18% 34% 14%	3684
	11th to 20th	Night	28% 10% 23% 27% 12%	4057
	21st to end	Night	38% 11% 22% 22% 7%	4457
November	1st to 10th	Night	58% 13% 15% 10% 4	2535
	11th to 20th	Night	58% 13% 17% 8% 3	2775
	21st to end	Night	59% 14% 16% 9% 2	2954
December	1st to 10th	Night	48% 23% 18% 9% 2	4890
	11th to 20th	Night	70% 13% 11% 6% 1	5547
	21st to end	Night	70% 14% 11% 5% 1	7458

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	20% 18% 20% 26% 12% 6%	200
	11th to 20th	Day	21% 16% 25% 21% 11% 8%	200
	21st to end	Day	16% 16% 25% 28% 12% 3	220
February	1st to 10th	Day	22% 23% 25% 25% 6%	231
	11th to 20th	Day	14% 24% 23% 28% 10% 1	335
	21st to end	Day	21% 19% 28% 21% 9% 2	414
March	1st to 10th	Day	16% 22% 28% 21% 11% 2	500
	11th to 20th	Day	17% 18% 23% 23% 15% 4	500
	21st to end	Day	16% 21% 28% 24% 9% 2	550
April	1st to 10th	Day	18% 25% 26% 22% 7% 2	500
	11th to 20th	Day	18% 22% 29% 18% 12% 1	492
	21st to end	Day	15% 22% 24% 23% 13% 3	500
May	1st to 10th	Day	14% 15% 25% 28% 15% 3	503
	11th to 20th	Day	19% 11% 24% 24% 18% 4	611
	21st to end	Day	19% 13% 16% 26% 20% 5%	789
June	1st to 10th	Day	15% 14% 25% 25% 19% 4	730
	11th to 20th	Day	16% 17% 28% 23% 14% 2	730
	21st to end	Day	10% 10% 24% 26% 25% 5%	730
July	1st to 10th	Day	4 6% 25% 31% 28% 5%	721
	11th to 20th	Day	5% 10% 25% 33% 24% 3	664
	21st to end	Day	3 8% 23% 35% 25% 6%	575
August	1st to 10th	Day	6% 8% 26% 32% 22% 6%	527
	11th to 20th	Day	5% 7% 23% 35% 23% 8%	517
	21st to end	Day	7% 9% 23% 30% 23% 7%	583
September	1st to 10th	Day	8% 9% 27% 26% 22% 8%	530
	11th to 20th	Day	9% 13% 24% 26% 20% 8%	530
	21st to end	Day	11% 16% 26% 25% 16% 6%	530
October	1st to 10th	Day	14% 10% 26% 26% 17% 6%	481
	11th to 20th	Day	15% 15% 23% 23% 17% 7%	324
	21st to end	Day	25% 20% 18% 23% 12% 2	330
November	1st to 10th	Day	26% 17% 22% 22% 13%	300
	11th to 20th	Day	19% 22% 22% 25% 11% 1	300
	21st to end	Day	17% 20% 23% 22% 16% 2	223
December	1st to 10th	Day	23% 22% 14% 21% 17% 5%	200
	11th to 20th	Day	21% 20% 20% 30% 9% 1	200
	21st to end	Day	17% 18% 30% 24% 9% 3	220
January	1st to 10th	Night	25% 15% 23% 25% 10% 1	1000
	11th to 20th	Night	21% 15% 22% 29% 12% 2	810
	21st to end	Night	20% 14% 22% 33% 10% 1	880
February	1st to 10th	Night	21% 17% 23% 30% 10% 1	800
	11th to 20th	Night	20% 17% 22% 31% 10% 1	784
	21st to end	Night	16% 15% 25% 30% 13% 1	660
March	1st to 10th	Night	15% 14% 23% 34% 13% 1	800
	11th to 20th	Night	13% 15% 22% 32% 16% 1	800
	21st to end	Night	15% 15% 22% 32% 14% 2	880
April	1st to 10th	Night	16% 12% 21% 34% 16% 1	795
	11th to 20th	Night	13% 13% 29% 32% 12%	593
	21st to end	Night	16% 11% 26% 31% 16% 1	600
May	1st to 10th	Night	10% 11% 23% 36% 19% 1	600
	11th to 20th	Night	12% 5% 18% 37% 26% 1	406
	21st to end	Night	18% 7% 16% 28% 28% 3	433
June	1st to 10th	Night	15% 8% 18% 35% 22% 4	400
	11th to 20th	Night	16% 10% 23% 30% 21% 1	400
	21st to end	Night	7% 4 16% 42% 29% 3	400
July	1st to 10th	Night	3 2 11% 45% 37% 2	390
	11th to 20th	Night	5% 3 11% 53% 27% 1	388
	21st to end	Night	3 2 10% 45% 38% 2	438
August	1st to 10th	Night	5% 4 9% 39% 40% 3	445
	11th to 20th	Night	5% 2 11% 41% 35% 6%	594
	21st to end	Night	7% 3 14% 42% 33% 1	660
September	1st to 10th	Night	5% 3 12% 42% 33% 4	770
	11th to 20th	Night	10% 4 11% 35% 36% 5%	800
	21st to end	Night	10% 7% 14% 38% 28% 4	800
October	1st to 10th	Night	11% 8% 16% 43% 21% 2	800
	11th to 20th	Night	12% 9% 18% 37% 21% 3	792
	21st to end	Night	19% 11% 23% 32% 15% 1	836
November	1st to 10th	Night	23% 15% 20% 32% 10% 1	780
	11th to 20th	Night	23% 18% 21% 27% 10%	975
	21st to end	Night	19% 15% 19% 34% 13% 1	1000
December	1st to 10th	Night	20% 14% 19% 31% 16% 2	1000
	11th to 20th	Night	21% 15% 22% 33% 9% 1	1000
	21st to end	Night	23% 15% 24% 28% 10% 1	1100

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