Pierre
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pierre clear sky chart from 2005-11-06 to 2024-11-12.

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% 6% 2 6% 4 4 4 3 5% 7% 48%	104810
	Night	8% 7% 2 6% 4 4 4 4 6% 7% 47%	103015
Transparency	Day	34% 6% 14% 27% 16% 3	104553
	Night	34% 6% 14% 26% 16% 3	102862
Seeing	Day	12% 7% 27% 32% 17% 4	15986
	Night	11% 7% 31% 39% 12% 1	25913

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	4 8% 4 14% 8% 6% 4 3 6% 6% 38%	2538
	11th to 20th	Day	3 9% 4 11% 6% 8% 7% 5% 11% 7% 30%	2540
	21st to end	Day	4 8% 4 12% 7% 6% 5% 4 6% 6% 38%	2794
February	1st to 10th	Day	7% 14% 4 8% 5% 5% 5% 4 5% 7% 36%	1653
	11th to 20th	Day	7% 9% 3 7% 7% 4 4 4 7% 7% 42%	1849
	21st to end	Day	8% 11% 3 8% 5% 4 5% 3 6% 6% 41%	1570
March	1st to 10th	Day	8% 7% 3 7% 5% 4 4 3 4 6% 50%	3130
	11th to 20th	Day	7% 6% 2 5% 4 4 4 4 6% 8% 50%	3404
	21st to end	Day	22% 11% 3 7% 5% 4 3 4 6% 8% 28%	3907
April	1st to 10th	Day	14% 9% 3 6% 4 4 4 3 5% 6% 42%	2280
	11th to 20th	Day	16% 8% 3 8% 5% 4 4 3 5% 6% 39%	2344
	21st to end	Day	15% 8% 2 7% 5% 4 4 3 6% 6% 42%	2470
May	1st to 10th	Day	18% 6% 2 5% 4 4 4 3 5% 7% 41%	4120
	11th to 20th	Day	10% 5% 2 5% 4 3 3 4 6% 7% 51%	4171
	21st to end	Day	14% 6% 2 6% 4 3 4 3 5% 7% 45%	4825
June	1st to 10th	Day	10% 4 2 5% 4 3 4 4 6% 8% 51%	2660
	11th to 20th	Day	9% 5% 2 4 4 4 4 5% 7% 8% 49%	2660
	21st to end	Day	6% 3 2 5% 4 2 4 3 5% 8% 57%	2660
July	1st to 10th	Day	7% 4 2 5% 4 3 4 4 6% 9% 51%	4430
	11th to 20th	Day	4 3 1 4 3 3 4 3 5% 7% 63%	4430
	21st to end	Day	4 3 1 4 4 4 4 4 6% 9% 58%	4802
August	1st to 10th	Day	7% 6% 2 6% 4 4 3 3 5% 7% 53%	4202
	11th to 20th	Day	12% 6% 3 6% 4 4 5% 4 6% 7% 44%	4041
	21st to end	Day	5% 3 1 4 2 3 4 4 5% 8% 62%	4323
September	1st to 10th	Day	8% 4 1 4 3 3 4 3 3 6% 62%	2266
	11th to 20th	Day	9% 3 2 3 3 2 3 3 5% 7% 60%	2090
	21st to end	Day	11% 4 1 3 3 2 2 2 5% 6% 60%	2090
October	1st to 10th	Day	9% 3 1 2 2 2 2 2 4 6% 67%	3480
	11th to 20th	Day	8% 6% 2 6% 4 3 3 2 3 7% 56%	2980
	21st to end	Day	11% 7% 2 6% 4 4 4 3 5% 7% 45%	3091
November	1st to 10th	Day	10% 6% 3 5% 4 3 4 4 5% 7% 48%	1763
	11th to 20th	Day	6% 7% 3 7% 6% 4 4 4 5% 7% 48%	1719
	21st to end	Day	6% 9% 3 6% 5% 4 4 3 5% 8% 47%	1680
December	1st to 10th	Day	7% 10% 3 8% 5% 5% 6% 4 7% 7% 38%	1330
	11th to 20th	Day	4 8% 4 8% 5% 5% 5% 4 7% 8% 41%	1724
	21st to end	Day	15% 12% 3 9% 5% 5% 5% 3 4 6% 34%	2794
January	1st to 10th	Night	5% 10% 4 12% 6% 5% 5% 6% 7% 9% 31%	4417
	11th to 20th	Night	4 9% 3 9% 6% 8% 7% 4 10% 8% 33%	4430
	21st to end	Night	4 7% 4 12% 6% 5% 4 4 6% 7% 41%	4873
February	1st to 10th	Night	8% 12% 4 9% 5% 6% 6% 4 5% 7% 35%	2531
	11th to 20th	Night	6% 9% 4 8% 4 6% 4 5% 6% 7% 42%	2228
	21st to end	Night	8% 8% 3 7% 4 4 5% 4 6% 6% 44%	1884
March	1st to 10th	Night	8% 8% 4 7% 4 5% 5% 4 6% 7% 44%	3734
	11th to 20th	Night	8% 6% 2 6% 3 3 4 4 5% 8% 50%	3557
	21st to end	Night	18% 12% 4 8% 5% 4 4 3 5% 6% 31%	3712
April	1st to 10th	Night	13% 7% 2 6% 4 4 4 3 5% 8% 43%	1900
	11th to 20th	Night	16% 7% 2 4 4 4 4 4 4 7% 43%	1783
	21st to end	Night	15% 8% 2 6% 4 4 4 2 5% 7% 43%	1710
May	1st to 10th	Night	12% 6% 2 6% 4 4 5% 4 6% 8% 44%	2850
	11th to 20th	Night	11% 4 2 4 3 3 4 4 5% 6% 55%	2732
	21st to end	Night	13% 5% 2 6% 4 4 5% 4 6% 8% 43%	2762
June	1st to 10th	Night	9% 4 1 4 3 3 4 4 5% 9% 53%	1520
	11th to 20th	Night	8% 5% 2 5% 4 4 4 5% 8% 8% 48%	1520
	21st to end	Night	6% 3 1 4 4 4 4 3 5% 8% 59%	1520
July	1st to 10th	Night	6% 3 2 4 4 5% 6% 4 7% 10% 50%	2540
	11th to 20th	Night	3 2 1 3 2 2 3 3 6% 7% 68%	2540
	21st to end	Night	3 2 1 5% 3 3 4 4 6% 9% 59%	2761
August	1st to 10th	Night	5% 4 2 5% 4 5% 6% 4 7% 8% 51%	2735
	11th to 20th	Night	9% 6% 2 5% 3 4 4 4 6% 8% 50%	2798
	21st to end	Night	4 4 1 5% 4 4 4 3 6% 7% 58%	3327
September	1st to 10th	Night	6% 4 1 4 2 3 3 3 4 6% 63%	1914
	11th to 20th	Night	7% 3 1 5% 3 3 3 4 5% 7% 58%	2090
	21st to end	Night	11% 4 2 4 3 3 3 2 5% 5% 59%	2090
October	1st to 10th	Night	9% 3 1 3 2 2 2 2 4 5% 69%	3480
	11th to 20th	Night	8% 5% 2 5% 3 4 4 3 5% 8% 53%	3909
	21st to end	Night	9% 7% 2 6% 4 3 4 4 5% 8% 47%	4467
November	1st to 10th	Night	7% 7% 2 5% 4 4 4 4 5% 7% 50%	2535
	11th to 20th	Night	7% 8% 2 7% 5% 5% 5% 3 5% 7% 47%	2484
	21st to end	Night	6% 8% 3 5% 4 4 4 3 6% 8% 50%	2491
December	1st to 10th	Night	6% 10% 3 8% 5% 6% 4 4 5% 6% 42%	2850
	11th to 20th	Night	5% 9% 3 7% 4 4 4 4 6% 8% 46%	3468
	21st to end	Night	16% 11% 3 8% 4 3 4 3 4 6% 37%	4873

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	46% 6% 13% 26% 8% 1	2539
	11th to 20th	Day	46% 7% 15% 20% 10% 1	2540
	21st to end	Day	44% 8% 17% 22% 9%	2794
February	1st to 10th	Day	46% 8% 15% 21% 10%	1653
	11th to 20th	Day	40% 7% 17% 21% 14% 2	1859
	21st to end	Day	42% 7% 16% 22% 12% 2	1570
March	1st to 10th	Day	35% 7% 11% 26% 18% 2	3130
	11th to 20th	Day	30% 6% 16% 32% 15% 1	3404
	21st to end	Day	53% 8% 18% 15% 5%	3907
April	1st to 10th	Day	42% 6% 12% 27% 11% 2	2280
	11th to 20th	Day	46% 6% 12% 22% 12% 2	2347
	21st to end	Day	42% 6% 13% 27% 10% 1	2470
May	1st to 10th	Day	40% 7% 12% 25% 14% 2	4120
	11th to 20th	Day	31% 7% 15% 28% 16% 3	4175
	21st to end	Day	36% 8% 14% 29% 12%	4825
June	1st to 10th	Day	29% 9% 18% 30% 12% 3	2660
	11th to 20th	Day	31% 9% 16% 28% 14% 2	2660
	21st to end	Day	25% 7% 15% 30% 19% 4	2660
July	1st to 10th	Day	28% 8% 16% 30% 16% 2	4361
	11th to 20th	Day	20% 5% 12% 32% 26% 6%	4355
	21st to end	Day	22% 6% 14% 30% 23% 5%	4651
August	1st to 10th	Day	30% 6% 11% 25% 22% 5%	4187
	11th to 20th	Day	38% 6% 15% 25% 14% 2	4080
	21st to end	Day	21% 5% 15% 30% 23% 6%	4322
September	1st to 10th	Day	25% 5% 10% 29% 26% 6%	2266
	11th to 20th	Day	24% 5% 15% 29% 23% 2	2090
	21st to end	Day	26% 4 11% 33% 24% 3	2090
October	1st to 10th	Day	21% 3 9% 24% 36% 7%	3480
	11th to 20th	Day	30% 4 12% 37% 16% 2	2980
	21st to end	Day	38% 5% 13% 26% 16% 2	3091
November	1st to 10th	Day	35% 5% 16% 25% 16% 4	1763
	11th to 20th	Day	35% 5% 17% 29% 13% 2	1719
	21st to end	Day	36% 6% 15% 27% 14% 2	1680
December	1st to 10th	Day	42% 8% 15% 24% 10% 1	1330
	11th to 20th	Day	37% 8% 20% 28% 6% 1	1721
	21st to end	Day	50% 7% 11% 26% 6% 1	2794
January	1st to 10th	Night	45% 7% 14% 25% 8% 1	4417
	11th to 20th	Night	44% 7% 16% 23% 9% 1	4430
	21st to end	Night	39% 8% 20% 22% 10% 1	4873
February	1st to 10th	Night	47% 6% 14% 20% 11% 1	2531
	11th to 20th	Night	40% 7% 14% 23% 14% 3	2228
	21st to end	Night	38% 6% 15% 25% 13% 4	1884
March	1st to 10th	Night	38% 7% 14% 23% 17% 2	3734
	11th to 20th	Night	31% 6% 13% 35% 15% 1	3557
	21st to end	Night	51% 8% 13% 20% 7% 1	3712
April	1st to 10th	Night	41% 5% 13% 25% 14% 3	1900
	11th to 20th	Night	40% 6% 13% 22% 15% 4	1783
	21st to end	Night	40% 6% 12% 27% 13% 1	1710
May	1st to 10th	Night	35% 7% 15% 23% 17% 4	2850
	11th to 20th	Night	27% 7% 12% 32% 22% 1	2733
	21st to end	Night	36% 8% 15% 29% 11% 1	2762
June	1st to 10th	Night	28% 8% 15% 30% 17% 3	1520
	11th to 20th	Night	31% 8% 16% 25% 17% 3	1520
	21st to end	Night	23% 6% 16% 33% 19% 3	1520
July	1st to 10th	Night	27% 7% 20% 22% 22% 2	2500
	11th to 20th	Night	16% 5% 13% 34% 27% 6%	2492
	21st to end	Night	20% 6% 17% 33% 19% 5%	2674
August	1st to 10th	Night	29% 7% 16% 28% 15% 6%	2727
	11th to 20th	Night	31% 7% 20% 26% 14% 2	2825
	21st to end	Night	24% 6% 13% 28% 23% 5%	3327
September	1st to 10th	Night	23% 5% 11% 28% 26% 7%	1914
	11th to 20th	Night	24% 6% 13% 31% 21% 4	2090
	21st to end	Night	28% 5% 9% 28% 26% 4	2090
October	1st to 10th	Night	20% 3 7% 18% 44% 7%	3480
	11th to 20th	Night	30% 4 9% 33% 22% 3	3909
	21st to end	Night	35% 5% 14% 23% 20% 4	4467
November	1st to 10th	Night	33% 5% 13% 25% 18% 5%	2535
	11th to 20th	Night	36% 5% 14% 24% 17% 4	2484
	21st to end	Night	33% 5% 16% 28% 15% 2	2491
December	1st to 10th	Night	42% 5% 13% 27% 11% 2	2850
	11th to 20th	Night	35% 6% 18% 31% 9% 1	3470
	21st to end	Night	48% 6% 13% 24% 9% 1	4873

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	7% 10% 30% 36% 13% 5%	270
	11th to 20th	Day	10% 10% 35% 29% 13% 3	270
	21st to end	Day	11% 9% 36% 28% 12% 4	297
February	1st to 10th	Day	14% 9% 37% 30% 9%	270
	11th to 20th	Day	15% 6% 36% 29% 13% 1	270
	21st to end	Day	15% 10% 30% 31% 12% 1	225
March	1st to 10th	Day	20% 7% 30% 28% 10% 4	270
	11th to 20th	Day	11% 10% 27% 38% 11% 4	270
	21st to end	Day	19% 11% 30% 23% 13% 5%	352
April	1st to 10th	Day	20% 14% 33% 21% 12%	460
	11th to 20th	Day	21% 16% 28% 27% 8% 1	545
	21st to end	Day	17% 9% 31% 27% 14% 2	650
May	1st to 10th	Day	19% 9% 27% 27% 16% 3	653
	11th to 20th	Day	17% 7% 26% 31% 14% 6%	675
	21st to end	Day	15% 8% 29% 27% 16% 5%	734
June	1st to 10th	Day	8% 6% 23% 31% 22% 10%	680
	11th to 20th	Day	12% 6% 29% 35% 16% 3	680
	21st to end	Day	8% 6% 25% 37% 21% 3	680
July	1st to 10th	Day	6% 2 20% 41% 27% 4	671
	11th to 20th	Day	6% 4 24% 43% 20% 2	668
	21st to end	Day	5% 3 22% 44% 22% 4	739
August	1st to 10th	Day	9% 3 22% 36% 23% 6%	676
	11th to 20th	Day	9% 4 22% 38% 23% 4	665
	21st to end	Day	8% 4 22% 35% 25% 6%	630
September	1st to 10th	Day	9% 4 24% 33% 23% 7%	476
	11th to 20th	Day	10% 6% 20% 32% 25% 7%	300
	21st to end	Day	17% 8% 27% 28% 19% 2	300
October	1st to 10th	Day	18% 8% 24% 25% 19% 6%	300
	11th to 20th	Day	16% 10% 36% 21% 17% 2	300
	21st to end	Day	16% 13% 31% 26% 12% 2	330
November	1st to 10th	Day	16% 10% 28% 28% 15% 3	300
	11th to 20th	Day	11% 12% 30% 30% 15% 2	273
	21st to end	Day	13% 11% 33% 26% 16% 3	270
December	1st to 10th	Day	13% 10% 33% 30% 11% 2	270
	11th to 20th	Day	11% 9% 41% 27% 10% 1	270
	21st to end	Day	17% 11% 35% 25% 11% 1	297
January	1st to 10th	Night	11% 7% 32% 40% 9% 1	950
	11th to 20th	Night	10% 11% 30% 39% 9% 1	950
	21st to end	Night	11% 8% 36% 34% 11% 1	1045
February	1st to 10th	Night	13% 9% 35% 34% 9% 1	950
	11th to 20th	Night	9% 7% 36% 36% 11% 1	754
	21st to end	Night	13% 5% 33% 38% 10% 1	628
March	1st to 10th	Night	12% 8% 34% 37% 9% 1	760
	11th to 20th	Night	12% 8% 31% 40% 7% 1	621
	21st to end	Night	15% 9% 30% 34% 11% 1	627
April	1st to 10th	Night	17% 9% 33% 35% 7%	570
	11th to 20th	Night	19% 11% 29% 37% 4	563
	21st to end	Night	18% 8% 27% 36% 10% 1	570
May	1st to 10th	Night	11% 6% 32% 37% 14% 1	570
	11th to 20th	Night	17% 4 26% 39% 12% 1	561
	21st to end	Night	13% 6% 32% 35% 12% 1	617
June	1st to 10th	Night	10% 4 26% 41% 18% 2	570
	11th to 20th	Night	9% 5% 34% 42% 9% 1	570
	21st to end	Night	5% 2 27% 50% 16%	570
July	1st to 10th	Night	5% 3 23% 51% 18% 1	555
	11th to 20th	Night	5% 2 26% 51% 15%	552
	21st to end	Night	5% 1 26% 51% 15% 1	624
August	1st to 10th	Night	6% 3 26% 50% 15%	567
	11th to 20th	Night	7% 2 26% 46% 18%	564
	21st to end	Night	6% 3 27% 45% 18%	627
September	1st to 10th	Night	8% 5% 26% 45% 15% 1	570
	11th to 20th	Night	9% 4 29% 42% 16% 1	570
	21st to end	Night	12% 6% 29% 37% 14% 1	570
October	1st to 10th	Night	17% 5% 29% 34% 14%	570
	11th to 20th	Night	14% 9% 29% 36% 13%	827
	21st to end	Night	15% 8% 30% 37% 9% 1	1045
November	1st to 10th	Night	11% 7% 34% 36% 12% 1	975
	11th to 20th	Night	11% 10% 31% 37% 11%	956
	21st to end	Night	9% 8% 34% 38% 11%	950
December	1st to 10th	Night	11% 9% 36% 34% 10%	950
	11th to 20th	Night	11% 7% 34% 39% 10%	950
	21st to end	Night	18% 8% 32% 33% 10%	1045

Page generated at 2024-11-08 21:45:39. Version ac07

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