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 2026-09-29.

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 6% 4 4 4 3 5% 6% 50%	158645
	Night	11% 8% 3 7% 4 4 4 3 5% 6% 45%	150130
Transparency	Day	35% 4 12% 26% 17% 7%	153383
	Night	40% 5% 13% 24% 14% 4	146395
Seeing	Day	16% 15% 28% 23% 14% 4	16912
	Night	15% 10% 24% 32% 16% 2	25833

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	21% 18% 7% 15% 7% 6% 6% 3 4 3 7%	4722
	11th to 20th	Day	12% 10% 3 9% 5% 6% 5% 3 5% 6% 35%	4740
	21st to end	Day	20% 13% 5% 12% 6% 4 4 3 4 4 25%	5384
February	1st to 10th	Day	16% 15% 5% 9% 6% 6% 6% 6% 6% 6% 20%	1890
	11th to 20th	Day	15% 11% 4 7% 6% 6% 7% 4 7% 7% 26%	1845
	21st to end	Day	12% 11% 4 10% 8% 6% 6% 5% 6% 6% 27%	1713
March	1st to 10th	Day	8% 10% 3 8% 7% 6% 8% 6% 8% 9% 28%	4618
	11th to 20th	Day	11% 11% 3 9% 5% 5% 5% 4 6% 6% 35%	5109
	21st to end	Day	10% 10% 4 9% 7% 7% 7% 6% 7% 9% 23%	5875
April	1st to 10th	Day	9% 9% 3 8% 6% 6% 7% 5% 7% 9% 32%	2520
	11th to 20th	Day	8% 8% 3 7% 6% 5% 6% 5% 6% 7% 38%	2489
	21st to end	Day	5% 5% 2 6% 4 5% 6% 5% 8% 9% 44%	2682
May	1st to 10th	Day	7% 4 2 5% 3 4 4 4 5% 6% 56%	8195
	11th to 20th	Day	4 4 2 5% 4 4 5% 4 7% 9% 53%	8160
	21st to end	Day	5% 4 1 5% 4 4 5% 4 6% 8% 52%	8992
June	1st to 10th	Day	7% 6% 2 5% 4 5% 4 4 6% 8% 48%	2940
	11th to 20th	Day	4 4 2 5% 4 4 4 4 6% 9% 54%	2940
	21st to end	Day	3 3 1 4 3 3 3 3 5% 6% 65%	2940
July	1st to 10th	Day	1 1 1 1 1 1 2 2 3 4 83%	8219
	11th to 20th	Day	2 2 1 2 1 1 1 2 2 3 83%	8220
	21st to end	Day	2 2 1 2 1 2 2 2 3 4 81%	8922
August	1st to 10th	Day	2 2 1 2 2 2 2 2 3 4 78%	7952
	11th to 20th	Day	1 1 1 3 2 2 3 3 4 6% 73%	7563
	21st to end	Day	5% 4 2 4 3 3 3 2 4 6% 65%	7789
September	1st to 10th	Day	3 1 1 3 2 3 3 2 5% 7% 70%	2520
	11th to 20th	Day	4 3 2 5% 3 3 4 4 5% 7% 59%	2520
	21st to end	Day	6% 4 2 5% 4 4 4 3 4 6% 57%	2228
October	1st to 10th	Day	6% 4 1 4 4 3 4 4 6% 7% 57%	3280
	11th to 20th	Day	7% 6% 3 8% 5% 5% 6% 5% 8% 8% 40%	3261
	21st to end	Day	11% 8% 3 9% 6% 6% 6% 5% 7% 8% 31%	3335
November	1st to 10th	Day	15% 12% 4 9% 6% 6% 6% 4 7% 7% 24%	1822
	11th to 20th	Day	16% 16% 4 11% 7% 7% 5% 4 6% 6% 18%	1680
	21st to end	Day	17% 13% 3 10% 7% 6% 6% 5% 6% 6% 21%	1680
December	1st to 10th	Day	13% 12% 4 15% 7% 5% 4 3 5% 6% 25%	2700
	11th to 20th	Day	23% 20% 7% 16% 7% 4 4 3 4 4 8%	3108
	21st to end	Day	21% 20% 7% 14% 8% 6% 5% 3 4 3 9%	4092
January	1st to 10th	Night	24% 18% 6% 14% 6% 5% 5% 3 5% 4 10%	8172
	11th to 20th	Night	14% 9% 3 7% 4 4 4 3 4 6% 41%	8220
	21st to end	Night	19% 13% 5% 10% 5% 4 3 2 4 4 31%	8806
February	1st to 10th	Night	15% 15% 4 8% 6% 5% 5% 4 6% 7% 25%	2730
	11th to 20th	Night	14% 11% 3 8% 6% 5% 5% 3 6% 7% 32%	2662
	21st to end	Night	12% 13% 3 9% 6% 5% 5% 4 6% 8% 30%	2092
March	1st to 10th	Night	7% 9% 3 9% 6% 6% 7% 5% 8% 9% 31%	5496
	11th to 20th	Night	10% 9% 3 8% 6% 5% 5% 4 5% 6% 40%	5110
	21st to end	Night	11% 10% 3 8% 7% 7% 8% 6% 7% 8% 25%	5341
April	1st to 10th	Night	10% 8% 3 7% 5% 5% 6% 6% 6% 9% 36%	2100
	11th to 20th	Night	8% 6% 2 6% 5% 5% 5% 4 6% 7% 45%	2079
	21st to end	Night	6% 5% 2 5% 4 4 5% 5% 9% 9% 46%	1936
May	1st to 10th	Night	7% 5% 1 4 3 3 3 3 4 7% 58%	4723
	11th to 20th	Night	3 4 2 5% 4 4 4 4 6% 8% 55%	4700
	21st to end	Night	6% 3 1 4 3 3 4 4 6% 10% 56%	5181
June	1st to 10th	Night	8% 6% 2 6% 4 5% 5% 4 6% 6% 48%	1680
	11th to 20th	Night	4 4 1 4 4 3 4 3 5% 9% 60%	1680
	21st to end	Night	2 3 1 3 3 3 4 3 5% 6% 67%	1680
July	1st to 10th	Night	1 1 1 1 2 2 2 3 5% 83%	4740
	11th to 20th	Night	2 1 1 2 2 2 2 2 3 3 79%	4740
	21st to end	Night	2 2 2 1 1 1 2 3 4 81%	5153
August	1st to 10th	Night	2 2 1 2 2 2 2 2 3 6% 76%	4833
	11th to 20th	Night	3 2 1 3 2 3 3 3 4 5% 70%	5292
	21st to end	Night	3 3 1 3 3 2 3 2 4 6% 70%	6458
September	1st to 10th	Night	2 2 1 3 2 2 3 3 3 6% 72%	2100
	11th to 20th	Night	4 3 2 4 3 4 4 3 4 5% 64%	2100
	21st to end	Night	6% 3 1 4 3 4 4 3 5% 6% 61%	2343
October	1st to 10th	Night	5% 4 1 4 3 3 3 3 5% 8% 61%	3920
	11th to 20th	Night	7% 5% 2 6% 5% 5% 5% 5% 7% 8% 45%	3897
	21st to end	Night	11% 7% 3 7% 5% 5% 6% 5% 6% 7% 37%	4469
November	1st to 10th	Night	17% 8% 4 9% 4 5% 6% 5% 7% 6% 30%	2695
	11th to 20th	Night	18% 12% 4 8% 6% 5% 6% 4 5% 6% 25%	2940
	21st to end	Night	14% 11% 3 9% 6% 6% 6% 4 5% 6% 28%	2940
December	1st to 10th	Night	11% 10% 4 12% 5% 5% 5% 3 5% 6% 34%	4700
	11th to 20th	Night	26% 17% 5% 14% 7% 6% 5% 3 4 4 9%	5316
	21st to end	Night	24% 17% 5% 10% 7% 5% 4 3 4 5% 15%	7106

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	78% 5% 7% 9% 2	4723
	11th to 20th	Day	50% 4 17% 21% 7% 2	4740
	21st to end	Day	63% 4 8% 17% 8%	5384
February	1st to 10th	Day	61% 8% 16% 12% 3	1890
	11th to 20th	Day	53% 8% 17% 17% 5%	1854
	21st to end	Day	51% 9% 16% 15% 9%	1713
March	1st to 10th	Day	48% 8% 12% 20% 11%	4618
	11th to 20th	Day	47% 5% 13% 28% 6%	5109
	21st to end	Day	54% 6% 15% 20% 4	5875
April	1st to 10th	Day	44% 8% 18% 22% 8%	2520
	11th to 20th	Day	39% 7% 18% 21% 12% 2	2492
	21st to end	Day	31% 7% 20% 26% 13% 2	2682
May	1st to 10th	Day	27% 3 8% 34% 24% 3	8195
	11th to 20th	Day	26% 3 18% 35% 16% 2	8163
	21st to end	Day	28% 4 21% 34% 12% 1	8994
June	1st to 10th	Day	32% 5% 15% 30% 15% 3	2940
	11th to 20th	Day	25% 4 15% 37% 16% 3	2940
	21st to end	Day	19% 3 16% 35% 20% 8%	2940
July	1st to 10th	Day	9% 1 7% 28% 32% 22%	8151
	11th to 20th	Day	10% 1 3 17% 30% 39%	8145
	21st to end	Day	10% 1 6% 31% 37% 13%	8723
August	1st to 10th	Day	11% 1 4 19% 37% 28%	6300
	11th to 20th	Day	14% 2 10% 44% 24% 6%	5962
	21st to end	Day	20% 2 10% 33% 29% 6%	6104
September	1st to 10th	Day	15% 2 10% 34% 26% 12%	2520
	11th to 20th	Day	24% 4 16% 28% 22% 6%	2520
	21st to end	Day	29% 4 14% 31% 18% 5%	2228
October	1st to 10th	Day	26% 4 12% 32% 23% 3	3280
	11th to 20th	Day	40% 5% 18% 23% 13% 1	3261
	21st to end	Day	48% 6% 12% 26% 8% 1	3335
November	1st to 10th	Day	56% 8% 14% 17% 4	1822
	11th to 20th	Day	62% 9% 13% 12% 3	1680
	21st to end	Day	61% 7% 16% 11% 5%	1680
December	1st to 10th	Day	60% 5% 13% 19% 4	2700
	11th to 20th	Day	80% 4 8% 6% 1	3108
	21st to end	Day	79% 4 8% 7% 1	4092
January	1st to 10th	Night	76% 5% 9% 9% 1	8172
	11th to 20th	Night	43% 4 16% 28% 8% 1	8220
	21st to end	Night	58% 4 8% 21% 9%	8806
February	1st to 10th	Night	56% 9% 18% 13% 3	2730
	11th to 20th	Night	49% 8% 18% 19% 5% 1	2664
	21st to end	Night	48% 9% 16% 19% 7% 1	2092
March	1st to 10th	Night	46% 7% 14% 23% 10%	5496
	11th to 20th	Night	44% 5% 16% 28% 7%	5110
	21st to end	Night	53% 7% 19% 19% 3	5341
April	1st to 10th	Night	40% 8% 20% 24% 7% 1	2100
	11th to 20th	Night	36% 6% 20% 24% 11% 2	2079
	21st to end	Night	31% 8% 18% 29% 12% 2	1936
May	1st to 10th	Night	26% 3 8% 36% 25% 2	4721
	11th to 20th	Night	25% 5% 18% 35% 15% 2	4700
	21st to end	Night	23% 4 27% 33% 13%	5182
June	1st to 10th	Night	35% 5% 14% 33% 11% 2	1680
	11th to 20th	Night	21% 4 19% 38% 17% 1	1680
	21st to end	Night	18% 3 14% 37% 22% 6%	1680
July	1st to 10th	Night	8% 1 8% 29% 34% 20%	4700
	11th to 20th	Night	13% 1 5% 15% 34% 33%	4692
	21st to end	Night	10% 1 7% 33% 37% 13%	5040
August	1st to 10th	Night	10% 1 4 17% 38% 29%	3815
	11th to 20th	Night	16% 2 12% 39% 25% 5%	4169
	21st to end	Night	15% 2 12% 36% 29% 6%	5064
September	1st to 10th	Night	14% 3 13% 31% 27% 13%	2100
	11th to 20th	Night	22% 5% 13% 30% 20% 10%	2100
	21st to end	Night	23% 3 15% 31% 22% 5%	2343
October	1st to 10th	Night	22% 3 12% 37% 24% 1	3920
	11th to 20th	Night	35% 5% 20% 25% 13% 1	3897
	21st to end	Night	43% 7% 13% 26% 10% 1	4469
November	1st to 10th	Night	51% 8% 15% 20% 6%	2695
	11th to 20th	Night	58% 8% 14% 15% 4	2940
	21st to end	Night	54% 9% 16% 16% 5% 1	2940
December	1st to 10th	Night	51% 6% 14% 26% 3	4700
	11th to 20th	Night	78% 6% 9% 6% 1	5316
	21st to end	Night	71% 6% 10% 11% 2	7106

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	33% 16% 16% 20% 11% 3	220
	11th to 20th	Day	30% 9% 19% 27% 12% 3	220
	21st to end	Day	22% 9% 24% 26% 17% 2	309
February	1st to 10th	Day	25% 16% 25% 21% 12% 2	430
	11th to 20th	Day	27% 15% 24% 24% 9% 1	425
	21st to end	Day	23% 18% 25% 25% 7% 2	438
March	1st to 10th	Day	24% 17% 26% 23% 9% 2	540
	11th to 20th	Day	23% 17% 23% 22% 11% 3	540
	21st to end	Day	23% 20% 27% 20% 9% 1	594
April	1st to 10th	Day	23% 20% 26% 18% 11% 2	540
	11th to 20th	Day	17% 26% 27% 18% 8% 4	532
	21st to end	Day	15% 22% 32% 20% 9% 2	540
May	1st to 10th	Day	15% 19% 30% 21% 11% 3	543
	11th to 20th	Day	21% 17% 30% 17% 13% 4	568
	21st to end	Day	13% 17% 31% 24% 12% 4	617
June	1st to 10th	Day	16% 20% 28% 19% 13% 4	570
	11th to 20th	Day	15% 23% 34% 17% 10% 2	570
	21st to end	Day	7% 16% 35% 25% 14% 4	570
July	1st to 10th	Day	5% 11% 43% 24% 14% 3	566
	11th to 20th	Day	5% 13% 37% 27% 15% 3	564
	21st to end	Day	4 11% 35% 24% 18% 8%	619
August	1st to 10th	Day	6% 9% 30% 24% 21% 10%	567
	11th to 20th	Day	2 10% 31% 27% 20% 10%	557
	21st to end	Day	8% 13% 26% 22% 22% 9%	627
September	1st to 10th	Day	5% 11% 25% 27% 22% 10%	570
	11th to 20th	Day	10% 11% 27% 24% 21% 6%	570
	21st to end	Day	12% 13% 22% 28% 20% 6%	563
October	1st to 10th	Day	13% 14% 23% 25% 16% 9%	530
	11th to 20th	Day	16% 15% 22% 23% 17% 7%	530
	21st to end	Day	19% 15% 23% 22% 15% 4	448
November	1st to 10th	Day	26% 12% 20% 26% 12% 3	313
	11th to 20th	Day	30% 10% 23% 24% 9% 3	220
	21st to end	Day	26% 8% 18% 29% 16% 2	220
December	1st to 10th	Day	25% 10% 22% 25% 13% 5%	220
	11th to 20th	Day	35% 10% 21% 25% 7% 1	220
	21st to end	Day	29% 12% 21% 26% 11% 1	242
January	1st to 10th	Night	30% 9% 21% 28% 11% 1	840
	11th to 20th	Night	26% 8% 18% 31% 14% 2	840
	21st to end	Night	22% 8% 18% 32% 17% 2	924
February	1st to 10th	Night	24% 11% 17% 33% 14% 1	840
	11th to 20th	Night	19% 12% 22% 30% 16% 1	824
	21st to end	Night	21% 14% 21% 33% 11% 1	692
March	1st to 10th	Night	19% 12% 21% 34% 13% 1	840
	11th to 20th	Night	16% 11% 25% 34% 13% 2	840
	21st to end	Night	16% 16% 27% 29% 10% 1	924
April	1st to 10th	Night	14% 16% 26% 30% 14%	840
	11th to 20th	Night	14% 17% 28% 26% 13% 2	831
	21st to end	Night	10% 17% 32% 27% 13% 1	676
May	1st to 10th	Night	10% 14% 30% 31% 15%	420
	11th to 20th	Night	10% 12% 28% 32% 16% 2	414
	21st to end	Night	7% 9% 35% 35% 13% 2	455
June	1st to 10th	Night	12% 14% 32% 27% 14% 1	420
	11th to 20th	Night	9% 18% 38% 27% 8%	420
	21st to end	Night	5% 13% 35% 30% 15% 1	420
July	1st to 10th	Night	3 9% 36% 35% 17%	410
	11th to 20th	Night	2 11% 39% 35% 13% 1	408
	21st to end	Night	2 9% 32% 37% 18% 1	460
August	1st to 10th	Night	2 7% 29% 39% 20% 3	467
	11th to 20th	Night	4 5% 21% 33% 30% 7%	624
	21st to end	Night	3 11% 28% 33% 22% 3	908
September	1st to 10th	Night	3 6% 27% 31% 29% 3	840
	11th to 20th	Night	6% 7% 26% 28% 29% 4	840
	21st to end	Night	8% 7% 21% 34% 27% 3	832
October	1st to 10th	Night	11% 7% 20% 38% 20% 4	800
	11th to 20th	Night	14% 8% 21% 30% 25% 2	800
	21st to end	Night	16% 8% 25% 32% 17% 2	880
November	1st to 10th	Night	20% 9% 21% 36% 13% 1	820
	11th to 20th	Night	25% 10% 22% 30% 12% 1	840
	21st to end	Night	18% 8% 22% 34% 15% 3	840
December	1st to 10th	Night	24% 7% 20% 31% 16% 2	840
	11th to 20th	Night	27% 9% 18% 33% 14% 1	840
	21st to end	Night	27% 11% 21% 31% 9% 1	924

Page generated at 2026-09-26 01:18:44. Version ac07

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