High Prairie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the High Prairie clear sky chart from 2005-11-06 to 2025-05-26.

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% 8% 3 7% 5% 4 4 4 5% 6% 45%	118080
	Night	12% 9% 3 7% 5% 4 4 4 5% 6% 41%	120010
Transparency	Day	38% 5% 13% 23% 15% 7%	117823
	Night	43% 5% 14% 22% 12% 4	119856
Seeing	Day	16% 15% 27% 23% 14% 4	15149
	Night	15% 10% 24% 32% 17% 2	24252

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	23% 19% 8% 16% 7% 6% 6% 3 4 3 6%	3639
	11th to 20th	Day	16% 13% 4 8% 4 5% 5% 3 5% 5% 30%	3640
	21st to end	Day	23% 13% 4 11% 5% 4 3 3 4 4 26%	4159
February	1st to 10th	Day	16% 15% 5% 9% 6% 6% 6% 6% 6% 6% 21%	1800
	11th to 20th	Day	15% 11% 4 7% 6% 6% 7% 4 7% 7% 26%	1755
	21st to end	Day	11% 11% 3 10% 8% 6% 6% 5% 7% 7% 26%	1634
March	1st to 10th	Day	8% 10% 3 8% 7% 6% 8% 6% 8% 9% 28%	4518
	11th to 20th	Day	11% 12% 3 9% 5% 5% 5% 4 5% 6% 36%	4999
	21st to end	Day	10% 10% 4 9% 8% 7% 7% 6% 7% 9% 23%	5748
April	1st to 10th	Day	10% 9% 3 8% 6% 6% 6% 6% 8% 8% 31%	2400
	11th to 20th	Day	8% 8% 3 7% 6% 5% 6% 5% 6% 7% 39%	2369
	21st to end	Day	5% 5% 2 7% 4 5% 6% 5% 8% 9% 43%	2555
May	1st to 10th	Day	9% 5% 2 6% 4 4 5% 4 6% 6% 49%	4560
	11th to 20th	Day	5% 4 1 3 3 3 3 3 5% 7% 63%	4517
	21st to end	Day	7% 6% 2 7% 5% 5% 6% 5% 7% 8% 42%	4886
June	1st to 10th	Day	7% 7% 3 6% 4 5% 4 4 7% 8% 46%	2660
	11th to 20th	Day	4 4 2 5% 5% 5% 4 4 6% 9% 52%	2660
	21st to end	Day	3 3 1 3 3 3 3 3 5% 6% 66%	2660
July	1st to 10th	Day	1 1 1 1 1 1 2 3 3 84%	4420
	11th to 20th	Day	1 1 1 1 1 1 2 2 3 84%	4420
	21st to end	Day	2 1 1 2 1 2 2 1 3 4 82%	4790
August	1st to 10th	Day	2 3 1 3 2 2 2 2 4 4 75%	4318
	11th to 20th	Day	1 2 1 3 2 3 4 3 5% 7% 71%	4026
	21st to end	Day	4 4 2 4 3 3 3 2 4 5% 67%	4194
September	1st to 10th	Day	2 1 1 2 2 2 3 2 4 6% 74%	2280
	11th to 20th	Day	4 3 2 5% 4 4 5% 4 5% 7% 59%	2280
	21st to end	Day	7% 4 2 6% 4 4 4 3 4 6% 57%	2034
October	1st to 10th	Day	6% 4 1 4 4 3 4 4 6% 7% 57%	3180
	11th to 20th	Day	7% 6% 3 8% 5% 5% 6% 5% 8% 8% 40%	3161
	21st to end	Day	11% 8% 3 9% 6% 6% 6% 5% 7% 9% 31%	3232
November	1st to 10th	Day	15% 12% 4 9% 6% 6% 6% 4 7% 7% 25%	1734
	11th to 20th	Day	16% 16% 4 11% 7% 7% 5% 4 6% 7% 17%	1600
	21st to end	Day	17% 13% 3 11% 8% 6% 6% 5% 6% 6% 21%	1600
December	1st to 10th	Day	12% 11% 4 16% 7% 5% 4 3 5% 6% 26%	2620
	11th to 20th	Day	23% 20% 7% 16% 7% 4 4 3 4 4 8%	3028
	21st to end	Day	21% 20% 7% 14% 8% 6% 5% 3 4 3 9%	4004
January	1st to 10th	Night	25% 20% 6% 16% 6% 5% 4 3 4 3 8%	6306
	11th to 20th	Night	18% 12% 4 7% 4 3 4 3 4 6% 35%	6320
	21st to end	Night	22% 13% 5% 10% 5% 3 3 2 3 3 31%	6803
February	1st to 10th	Night	15% 15% 4 8% 6% 5% 5% 4 6% 7% 25%	2600
	11th to 20th	Night	14% 11% 3 8% 6% 5% 5% 3 6% 7% 32%	2532
	21st to end	Night	11% 13% 3 8% 6% 5% 5% 4 6% 8% 29%	1995
March	1st to 10th	Night	7% 9% 3 9% 6% 6% 7% 5% 8% 9% 31%	5376
	11th to 20th	Night	10% 9% 3 8% 6% 5% 5% 4 5% 6% 40%	5000
	21st to end	Night	11% 10% 3 8% 7% 7% 8% 6% 7% 8% 24%	5226
April	1st to 10th	Night	11% 8% 3 7% 5% 5% 5% 6% 6% 9% 36%	2000
	11th to 20th	Night	8% 6% 2 6% 5% 5% 5% 4 6% 7% 46%	1979
	21st to end	Night	6% 5% 2 5% 4 4 5% 5% 9% 9% 46%	1843
May	1st to 10th	Night	10% 8% 2 5% 4 3 3 3 4 6% 52%	2620
	11th to 20th	Night	4 3 1 3 3 3 3 3 5% 7% 64%	2596
	21st to end	Night	3 4 1 5% 4 5% 5% 5% 7% 10% 50%	2805
June	1st to 10th	Night	8% 6% 2 6% 4 5% 5% 5% 6% 7% 46%	1520
	11th to 20th	Night	5% 4 1 4 4 3 4 3 5% 9% 58%	1520
	21st to end	Night	2 3 1 3 3 4 4 3 5% 5% 68%	1520
July	1st to 10th	Night	1 1 1 1 1 1 2 2 3 86%	2540
	11th to 20th	Night	1 1 1 2 2 1 2 3 4 83%	2540
	21st to end	Night	1 1 1 1 1 2 1 2 4 86%	2761
August	1st to 10th	Night	3 2 1 2 2 2 2 2 3 5% 75%	2612
	11th to 20th	Night	2 2 1 3 2 3 3 3 5% 5% 73%	2812
	21st to end	Night	2 3 1 2 3 2 3 2 4 5% 72%	3484
September	1st to 10th	Night	1 2 1 3 2 2 2 3 3 5% 76%	1900
	11th to 20th	Night	4 3 2 4 3 4 5% 3 4 5% 63%	1900
	21st to end	Night	6% 3 1 4 3 4 4 3 5% 6% 60%	2142
October	1st to 10th	Night	5% 4 1 4 3 3 3 3 5% 8% 61%	3800
	11th to 20th	Night	7% 5% 2 6% 5% 5% 5% 5% 7% 8% 46%	3777
	21st to end	Night	11% 7% 3 8% 5% 5% 6% 5% 6% 7% 37%	4330
November	1st to 10th	Night	17% 8% 4 8% 4 5% 5% 5% 7% 6% 31%	2563
	11th to 20th	Night	18% 12% 4 8% 6% 5% 6% 5% 5% 6% 25%	2800
	21st to end	Night	14% 11% 3 10% 6% 6% 6% 5% 5% 7% 28%	2800
December	1st to 10th	Night	11% 10% 3 12% 5% 5% 5% 3 5% 6% 34%	4560
	11th to 20th	Night	26% 17% 5% 14% 7% 6% 5% 3 4 4 9%	5176
	21st to end	Night	24% 17% 5% 10% 6% 5% 4 3 4 5% 15%	6952

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	79% 5% 7% 8% 1	3639
	11th to 20th	Day	55% 4 19% 17% 5%	3640
	21st to end	Day	62% 4 7% 17% 9%	4159
February	1st to 10th	Day	61% 9% 16% 12% 3	1800
	11th to 20th	Day	52% 9% 18% 17% 4	1764
	21st to end	Day	51% 9% 17% 15% 8%	1634
March	1st to 10th	Day	48% 8% 12% 19% 12%	4518
	11th to 20th	Day	47% 5% 13% 28% 6%	4999
	21st to end	Day	54% 6% 16% 20% 4	5748
April	1st to 10th	Day	44% 8% 19% 21% 8%	2400
	11th to 20th	Day	39% 7% 18% 21% 12% 2	2372
	21st to end	Day	32% 7% 21% 26% 12% 2	2555
May	1st to 10th	Day	32% 5% 12% 28% 20% 2	4560
	11th to 20th	Day	21% 3 13% 38% 21% 4	4520
	21st to end	Day	35% 7% 24% 27% 7%	4887
June	1st to 10th	Day	34% 6% 15% 30% 13% 3	2660
	11th to 20th	Day	26% 4 16% 37% 13% 3	2660
	21st to end	Day	18% 3 15% 35% 21% 8%	2660
July	1st to 10th	Day	6% 2 7% 18% 29% 38%	4351
	11th to 20th	Day	8% 2 5% 13% 27% 45%	4345
	21st to end	Day	9% 2 7% 23% 38% 22%	4639
August	1st to 10th	Day	15% 2 6% 20% 34% 23%	4302
	11th to 20th	Day	15% 2 11% 39% 24% 8%	4065
	21st to end	Day	22% 2 11% 26% 31% 7%	4193
September	1st to 10th	Day	12% 2 9% 34% 28% 14%	2280
	11th to 20th	Day	24% 4 16% 26% 22% 7%	2280
	21st to end	Day	29% 4 15% 29% 18% 5%	2034
October	1st to 10th	Day	26% 5% 12% 32% 23% 3	3180
	11th to 20th	Day	39% 5% 18% 23% 13% 1	3161
	21st to end	Day	47% 6% 11% 26% 8% 1	3232
November	1st to 10th	Day	56% 8% 14% 18% 4	1734
	11th to 20th	Day	63% 9% 13% 12% 3	1600
	21st to end	Day	61% 7% 16% 11% 5% 1	1600
December	1st to 10th	Day	59% 5% 14% 19% 4	2620
	11th to 20th	Day	80% 4 8% 6% 1	3028
	21st to end	Day	79% 4 8% 8% 1	4004
January	1st to 10th	Night	79% 6% 7% 7% 1	6306
	11th to 20th	Night	49% 5% 19% 22% 4	6320
	21st to end	Night	59% 4 8% 19% 10%	6803
February	1st to 10th	Night	56% 10% 18% 14% 3	2600
	11th to 20th	Night	49% 8% 18% 19% 5% 1	2534
	21st to end	Night	48% 9% 16% 19% 6% 1	1995
March	1st to 10th	Night	45% 7% 15% 23% 10%	5376
	11th to 20th	Night	44% 5% 16% 29% 7%	5000
	21st to end	Night	53% 7% 19% 19% 2	5226
April	1st to 10th	Night	40% 8% 21% 23% 7% 1	2000
	11th to 20th	Night	35% 6% 20% 25% 12% 2	1979
	21st to end	Night	31% 9% 19% 28% 12% 2	1843
May	1st to 10th	Night	32% 4 12% 32% 19% 1	2620
	11th to 20th	Night	18% 4 15% 40% 19% 3	2596
	21st to end	Night	25% 6% 36% 28% 5%	2805
June	1st to 10th	Night	35% 6% 14% 33% 9% 2	1520
	11th to 20th	Night	23% 4 21% 38% 14% 1	1520
	21st to end	Night	18% 3 13% 38% 22% 6%	1520
July	1st to 10th	Night	6% 2 8% 17% 32% 35%	2500
	11th to 20th	Night	9% 2 6% 16% 28% 39%	2492
	21st to end	Night	6% 1 8% 22% 40% 23%	2674
August	1st to 10th	Night	14% 2 5% 22% 35% 22%	2604
	11th to 20th	Night	15% 2 13% 41% 23% 6%	2839
	21st to end	Night	16% 3 14% 29% 31% 8%	3484
September	1st to 10th	Night	11% 3 13% 31% 28% 14%	1900
	11th to 20th	Night	22% 5% 14% 30% 18% 11%	1900
	21st to end	Night	23% 4 15% 30% 22% 6%	2142
October	1st to 10th	Night	22% 3 12% 37% 25% 1	3800
	11th to 20th	Night	35% 5% 20% 26% 13% 1	3777
	21st to end	Night	44% 7% 12% 26% 11% 1	4330
November	1st to 10th	Night	50% 8% 15% 20% 7%	2563
	11th to 20th	Night	58% 9% 14% 16% 4	2800
	21st to end	Night	53% 9% 16% 16% 5% 1	2800
December	1st to 10th	Night	50% 6% 14% 27% 3	4560
	11th to 20th	Night	79% 6% 9% 6% 1	5176
	21st to end	Night	72% 6% 10% 11% 2	6952

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	34% 17% 17% 19% 12% 3	200
	11th to 20th	Day	33% 10% 18% 27% 11% 2	200
	21st to end	Day	23% 9% 24% 25% 18% 2	284
February	1st to 10th	Day	25% 15% 24% 22% 11% 2	400
	11th to 20th	Day	27% 15% 24% 24% 9% 1	395
	21st to end	Day	22% 18% 25% 25% 8% 2	407
March	1st to 10th	Day	22% 17% 27% 23% 9% 2	500
	11th to 20th	Day	21% 17% 23% 23% 12% 3	500
	21st to end	Day	22% 20% 28% 20% 9% 1	550
April	1st to 10th	Day	23% 21% 27% 17% 10% 2	500
	11th to 20th	Day	17% 27% 27% 17% 9% 4	492
	21st to end	Day	16% 22% 31% 21% 8% 2	500
May	1st to 10th	Day	16% 20% 30% 20% 11% 3	503
	11th to 20th	Day	19% 17% 30% 17% 13% 4	528
	21st to end	Day	13% 17% 31% 24% 12% 4	550
June	1st to 10th	Day	14% 20% 29% 19% 14% 4	490
	11th to 20th	Day	15% 24% 33% 16% 10% 2	490
	21st to end	Day	7% 17% 33% 26% 14% 4	490
July	1st to 10th	Day	5% 12% 42% 24% 14% 3	486
	11th to 20th	Day	5% 13% 36% 27% 16% 3	484
	21st to end	Day	3 11% 35% 24% 18% 8%	531
August	1st to 10th	Day	5% 9% 29% 24% 23% 10%	487
	11th to 20th	Day	2 9% 28% 29% 21% 11%	477
	21st to end	Day	8% 13% 27% 23% 20% 9%	539
September	1st to 10th	Day	4 12% 25% 27% 22% 9%	490
	11th to 20th	Day	10% 12% 26% 25% 23% 5%	490
	21st to end	Day	12% 14% 23% 28% 19% 6%	490
October	1st to 10th	Day	13% 13% 24% 24% 16% 10%	490
	11th to 20th	Day	15% 14% 22% 23% 19% 7%	490
	21st to end	Day	19% 16% 23% 22% 15% 5%	411
November	1st to 10th	Day	26% 12% 19% 26% 13% 3	285
	11th to 20th	Day	32% 10% 23% 24% 9% 3	200
	21st to end	Day	25% 9% 18% 29% 18% 3	200
December	1st to 10th	Day	23% 9% 23% 25% 14% 6%	200
	11th to 20th	Day	36% 11% 21% 26% 7% 1	200
	21st to end	Day	29% 11% 21% 26% 11% 1	220
January	1st to 10th	Night	29% 9% 21% 28% 11% 1	800
	11th to 20th	Night	27% 9% 18% 30% 14% 2	800
	21st to end	Night	23% 8% 18% 31% 18% 2	880
February	1st to 10th	Night	24% 12% 17% 33% 14% 1	800
	11th to 20th	Night	19% 12% 22% 29% 16% 1	784
	21st to end	Night	21% 14% 20% 33% 11% 1	660
March	1st to 10th	Night	18% 11% 21% 35% 14% 1	800
	11th to 20th	Night	15% 12% 24% 35% 13% 2	800
	21st to end	Night	16% 16% 27% 30% 10% 1	880
April	1st to 10th	Night	14% 16% 26% 29% 14% 1	800
	11th to 20th	Night	13% 17% 28% 26% 14% 2	791
	21st to end	Night	9% 17% 33% 28% 13% 1	643
May	1st to 10th	Night	10% 15% 30% 31% 15% 1	400
	11th to 20th	Night	10% 11% 28% 32% 16% 2	394
	21st to end	Night	7% 8% 35% 36% 13% 2	422
June	1st to 10th	Night	12% 12% 33% 28% 14% 1	380
	11th to 20th	Night	9% 17% 38% 27% 9%	380
	21st to end	Night	5% 13% 34% 31% 16% 1	380
July	1st to 10th	Night	3 8% 34% 36% 18% 1	370
	11th to 20th	Night	1 8% 41% 35% 13% 1	368
	21st to end	Night	2 9% 30% 38% 20% 1	416
August	1st to 10th	Night	2 6% 27% 41% 22% 3	422
	11th to 20th	Night	3 5% 19% 33% 32% 8%	564
	21st to end	Night	3 11% 28% 31% 23% 4	822
September	1st to 10th	Night	2 7% 27% 31% 30% 3	760
	11th to 20th	Night	6% 6% 26% 26% 31% 5%	760
	21st to end	Night	7% 7% 21% 34% 28% 4	760
October	1st to 10th	Night	11% 8% 19% 38% 21% 4	760
	11th to 20th	Night	13% 7% 20% 31% 26% 3	760
	21st to end	Night	17% 8% 23% 31% 18% 2	836
November	1st to 10th	Night	19% 9% 21% 36% 14% 1	780
	11th to 20th	Night	25% 9% 22% 30% 13% 1	800
	21st to end	Night	17% 8% 22% 34% 16% 3	800
December	1st to 10th	Night	23% 7% 20% 32% 17% 2	800
	11th to 20th	Night	26% 9% 18% 32% 14% 1	800
	21st to end	Night	28% 11% 21% 30% 9% 1	880

Page generated at 2025-05-23 06:20:57. Version ac07

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