Weeping Water
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Weeping Water clear sky chart from 2005-11-06 to 2024-11-05.

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	11% 7% 3 7% 4 4 4 4 5% 7% 44%	101072
	Night	10% 7% 2 6% 4 3 4 3 5% 7% 48%	98071
Transparency	Day	38% 3 13% 27% 17% 2	104749
	Night	36% 3 12% 27% 19% 3	102521
Seeing	Day	14% 8% 30% 30% 15% 3	15789
	Night	13% 8% 33% 34% 11% 1	25637

By Month

Percentage Cloud Cover SE (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	10% 13% 6% 13% 9% 6% 4 3 4 6% 27%	2847
	11th to 20th	Day	9% 11% 4 10% 5% 5% 6% 3 5% 7% 35%	2850
	21st to end	Day	8% 13% 6% 14% 5% 5% 5% 3 4 6% 31%	3135
February	1st to 10th	Day	10% 12% 5% 9% 6% 4 4 3 6% 7% 34%	1710
	11th to 20th	Day	10% 9% 2 8% 6% 4 4 4 5% 7% 41%	1702
	21st to end	Day	11% 8% 2 6% 5% 5% 4 3 5% 7% 43%	1570
March	1st to 10th	Day	13% 8% 4 6% 3 2 3 2 4 5% 49%	3397
	11th to 20th	Day	11% 7% 3 6% 3 4 3 3 4 6% 49%	3480
	21st to end	Day	19% 12% 4 8% 5% 4 4 4 5% 7% 28%	3814
April	1st to 10th	Day	16% 7% 3 6% 4 3 4 3 5% 6% 45%	2142
	11th to 20th	Day	15% 8% 3 6% 4 4 4 4 5% 5% 41%	2356
	21st to end	Day	20% 7% 2 7% 3 4 4 4 5% 7% 38%	2470
May	1st to 10th	Day	14% 8% 3 7% 5% 4 4 4 6% 7% 37%	4082
	11th to 20th	Day	14% 8% 3 7% 4 4 4 3 5% 6% 44%	4082
	21st to end	Day	14% 6% 3 6% 4 4 4 4 6% 8% 40%	4559
June	1st to 10th	Day	7% 4 2 5% 4 4 4 4 7% 8% 50%	2660
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 6% 9% 47%	2660
	21st to end	Day	7% 4 2 5% 5% 5% 5% 5% 6% 7% 48%	2657
July	1st to 10th	Day	13% 5% 2 5% 4 4 5% 4 6% 8% 45%	4120
	11th to 20th	Day	7% 3 2 5% 4 4 4 4 7% 8% 54%	4120
	21st to end	Day	4 3 1 4 3 4 4 4 7% 10% 55%	4465
August	1st to 10th	Day	6% 4 2 6% 4 5% 5% 5% 7% 10% 47%	4104
	11th to 20th	Day	13% 6% 2 5% 4 4 5% 4 6% 8% 43%	4041
	21st to end	Day	7% 4 2 6% 4 4 5% 4 6% 8% 50%	4445
September	1st to 10th	Day	13% 4 2 4 3 3 3 3 4 7% 54%	2204
	11th to 20th	Day	11% 5% 1 5% 4 4 3 3 5% 7% 53%	2090
	21st to end	Day	11% 4 1 4 3 3 4 2 5% 5% 58%	2090
October	1st to 10th	Day	14% 5% 1 5% 3 3 4 3 4 6% 52%	1947
	11th to 20th	Day	10% 6% 2 4 4 2 3 2 4 5% 57%	1900
	21st to end	Day	12% 8% 3 6% 4 3 4 3 5% 5% 48%	2090
November	1st to 10th	Day	10% 5% 2 5% 3 4 3 3 4 6% 55%	1742
	11th to 20th	Day	9% 8% 3 7% 4 4 4 3 5% 6% 48%	1668
	21st to end	Day	13% 8% 3 6% 4 4 4 3 4 7% 45%	1520
December	1st to 10th	Day	9% 7% 3 7% 5% 4 4 3 5% 7% 46%	1520
	11th to 20th	Day	8% 10% 3 9% 6% 5% 3 4 6% 7% 38%	1918
	21st to end	Day	15% 11% 5% 15% 6% 5% 4 3 4 6% 26%	2915
January	1st to 10th	Night	8% 10% 4 16% 8% 5% 4 4 5% 6% 30%	4108
	11th to 20th	Night	9% 10% 4 8% 4 4 7% 4 6% 7% 38%	4120
	21st to end	Night	11% 13% 6% 11% 4 4 4 3 5% 6% 35%	4532
February	1st to 10th	Night	11% 11% 3 8% 5% 5% 4 3 5% 5% 39%	2470
	11th to 20th	Night	9% 8% 3 8% 5% 5% 4 4 6% 7% 43%	2383
	21st to end	Night	10% 7% 3 6% 4 4 3 3 4 5% 51%	1884
March	1st to 10th	Night	11% 6% 2 6% 4 3 3 3 4 6% 52%	3458
	11th to 20th	Night	11% 6% 2 5% 2 3 3 2 4 5% 58%	3480
	21st to end	Night	18% 9% 3 7% 5% 4 4 4 6% 7% 33%	3817
April	1st to 10th	Night	12% 7% 2 5% 5% 3 3 3 6% 6% 47%	2037
	11th to 20th	Night	11% 7% 2 6% 4 4 4 3 4 7% 47%	1772
	21st to end	Night	17% 6% 3 5% 4 4 4 3 4 6% 45%	1710
May	1st to 10th	Night	19% 6% 2 4 4 3 3 3 5% 6% 45%	2823
	11th to 20th	Night	13% 5% 2 6% 3 3 4 2 4 8% 50%	2823
	21st to end	Night	16% 6% 2 5% 4 3 4 3 6% 7% 45%	3004
June	1st to 10th	Night	5% 4 2 3 5% 4 4 3 6% 9% 54%	1520
	11th to 20th	Night	6% 4 2 3 4 4 5% 4 7% 9% 51%	1520
	21st to end	Night	3 3 1 4 4 4 4 4 7% 9% 57%	1520
July	1st to 10th	Night	8% 5% 2 5% 4 4 4 4 5% 8% 51%	2846
	11th to 20th	Night	5% 3 1 3 3 2 3 3 5% 9% 64%	2850
	21st to end	Night	3 2 1 3 3 4 5% 4 6% 10% 59%	3098
August	1st to 10th	Night	4 3 2 4 3 4 4 3 5% 10% 59%	2836
	11th to 20th	Night	12% 5% 2 5% 3 4 3 3 5% 7% 51%	2798
	21st to end	Night	7% 4 2 5% 2 3 3 3 5% 8% 57%	3218
September	1st to 10th	Night	9% 3 2 4 3 3 3 2 5% 6% 60%	1972
	11th to 20th	Night	9% 3 1 4 3 3 4 3 5% 8% 58%	2090
	21st to end	Night	9% 4 1 3 3 3 3 3 4 5% 60%	2090
October	1st to 10th	Night	11% 5% 2 4 3 3 4 4 5% 6% 52%	2213
	11th to 20th	Night	11% 6% 1 4 2 3 3 2 4 6% 57%	2280
	21st to end	Night	13% 6% 2 4 3 3 4 3 5% 5% 52%	2508
November	1st to 10th	Night	9% 4 1 4 3 3 4 3 5% 7% 57%	2436
	11th to 20th	Night	9% 7% 2 6% 3 3 3 3 4 6% 53%	2508
	21st to end	Night	12% 8% 2 5% 4 3 2 3 4 6% 52%	2660
December	1st to 10th	Night	9% 7% 3 7% 5% 4 4 4 5% 6% 47%	2660
	11th to 20th	Night	9% 8% 3 6% 4 3 4 3 5% 6% 49%	3279
	21st to end	Night	17% 14% 5% 13% 4 3 2 3 4 5% 32%	4748

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	60% 2 12% 18% 8% 1	2848
	11th to 20th	Day	50% 2 16% 22% 10%	2850
	21st to end	Day	55% 2 13% 19% 11%	3135
February	1st to 10th	Day	50% 4 15% 20% 10% 2	1710
	11th to 20th	Day	43% 4 11% 25% 14% 3	1711
	21st to end	Day	40% 3 13% 25% 16% 3	1570
March	1st to 10th	Day	39% 2 9% 28% 18% 3	3397
	11th to 20th	Day	37% 3 11% 30% 18% 1	3480
	21st to end	Day	56% 3 20% 16% 5% 1	3814
April	1st to 10th	Day	41% 3 13% 27% 14% 2	2142
	11th to 20th	Day	44% 3 13% 23% 14% 3	2356
	21st to end	Day	46% 3 11% 25% 13% 1	2470
May	1st to 10th	Day	45% 4 10% 25% 13% 2	4120
	11th to 20th	Day	43% 3 10% 26% 18% 1	4086
	21st to end	Day	41% 4 12% 27% 14% 1	4572
June	1st to 10th	Day	31% 5% 17% 30% 15% 2	2660
	11th to 20th	Day	34% 4 13% 31% 16% 2	2660
	21st to end	Day	33% 5% 14% 31% 14% 4	2657
July	1st to 10th	Day	37% 4 14% 29% 14% 2	4056
	11th to 20th	Day	29% 4 12% 33% 19% 3	4051
	21st to end	Day	23% 6% 18% 32% 20% 2	4325
August	1st to 10th	Day	31% 5% 16% 28% 18% 2	4090
	11th to 20th	Day	38% 5% 14% 25% 16% 1	4080
	21st to end	Day	32% 5% 14% 27% 17% 5%	4444
September	1st to 10th	Day	32% 3 10% 30% 20% 5%	2204
	11th to 20th	Day	31% 3 12% 32% 20% 2	2090
	21st to end	Day	30% 3 9% 32% 26% 1	2090
October	1st to 10th	Day	21% 2 7% 19% 48% 3	3233
	11th to 20th	Day	21% 2 11% 31% 28% 7%	3140
	21st to end	Day	34% 3 10% 29% 22% 3	3428
November	1st to 10th	Day	31% 2 13% 30% 20% 3	1742
	11th to 20th	Day	37% 3 12% 27% 20% 1	1668
	21st to end	Day	40% 3 10% 31% 15% 1	1520
December	1st to 10th	Day	38% 3 15% 29% 14% 1	1520
	11th to 20th	Day	44% 3 17% 30% 7%	1915
	21st to end	Day	61% 2 10% 19% 7%	2915
January	1st to 10th	Night	55% 2 11% 19% 12%	4108
	11th to 20th	Night	45% 2 13% 28% 11% 1	4120
	21st to end	Night	51% 2 14% 20% 11% 1	4532
February	1st to 10th	Night	47% 3 12% 21% 13% 3	2470
	11th to 20th	Night	39% 4 13% 25% 16% 3	2384
	21st to end	Night	37% 3 10% 25% 21% 5%	1884
March	1st to 10th	Night	34% 2 8% 29% 23% 3	3458
	11th to 20th	Night	32% 2 9% 30% 22% 6%	3480
	21st to end	Night	51% 3 21% 19% 6% 1	3817
April	1st to 10th	Night	38% 3 9% 28% 19% 3	2037
	11th to 20th	Night	38% 3 10% 28% 17% 3	1772
	21st to end	Night	42% 3 12% 24% 19% 1	1710
May	1st to 10th	Night	42% 3 11% 23% 19% 2	2850
	11th to 20th	Night	36% 3 12% 26% 23% 1	2824
	21st to end	Night	41% 2 13% 22% 19% 2	3012
June	1st to 10th	Night	26% 5% 15% 34% 17% 3	1520
	11th to 20th	Night	27% 6% 15% 29% 20% 4	1520
	21st to end	Night	23% 4 16% 32% 22% 3	1520
July	1st to 10th	Night	32% 4 13% 29% 18% 3	2801
	11th to 20th	Night	20% 4 14% 36% 22% 3	2796
	21st to end	Night	19% 6% 17% 31% 24% 2	2999
August	1st to 10th	Night	21% 4 17% 34% 21% 3	2826
	11th to 20th	Night	34% 4 13% 29% 19% 2	2825
	21st to end	Night	26% 4 16% 28% 18% 8%	3218
September	1st to 10th	Night	26% 3 10% 30% 23% 8%	1972
	11th to 20th	Night	27% 3 11% 34% 22% 4	2090
	21st to end	Night	27% 3 8% 29% 29% 4	2090
October	1st to 10th	Night	20% 2 7% 18% 47% 6%	3694
	11th to 20th	Night	21% 2 7% 30% 30% 9%	3779
	21st to end	Night	34% 2 8% 30% 24% 2	4120
November	1st to 10th	Night	27% 3 14% 27% 24% 5%	2436
	11th to 20th	Night	33% 3 10% 31% 20% 3	2508
	21st to end	Night	35% 2 12% 28% 21% 2	2660
December	1st to 10th	Night	37% 3 13% 31% 15% 1	2660
	11th to 20th	Night	37% 2 12% 37% 11% 1	3281
	21st to end	Night	58% 2 10% 22% 8% 1	4748

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	19% 13% 35% 23% 8% 2	270
	11th to 20th	Day	20% 15% 36% 23% 6% 1	270
	21st to end	Day	13% 12% 44% 23% 6% 1	297
February	1st to 10th	Day	15% 21% 41% 20% 3	270
	11th to 20th	Day	16% 13% 37% 26% 6% 1	270
	21st to end	Day	14% 16% 43% 22% 4 1	225
March	1st to 10th	Day	16% 13% 40% 25% 5%	270
	11th to 20th	Day	30% 7% 36% 19% 7% 1	270
	21st to end	Day	31% 15% 35% 16% 2	297
April	1st to 10th	Day	20% 18% 38% 21% 4	322
	11th to 20th	Day	20% 15% 34% 25% 6%	554
	21st to end	Day	24% 13% 33% 20% 9% 2	650
May	1st to 10th	Day	20% 10% 35% 24% 10% 1	653
	11th to 20th	Day	17% 8% 32% 29% 12% 2	675
	21st to end	Day	19% 7% 28% 28% 14% 2	734
June	1st to 10th	Day	7% 6% 21% 35% 26% 5%	680
	11th to 20th	Day	9% 5% 31% 34% 18% 4	680
	21st to end	Day	6% 7% 35% 35% 14% 3	680
July	1st to 10th	Day	10% 4 16% 33% 28% 9%	671
	11th to 20th	Day	7% 1 21% 40% 23% 7%	668
	21st to end	Day	7% 2 16% 41% 29% 5%	739
August	1st to 10th	Day	7% 3 20% 40% 26% 5%	676
	11th to 20th	Day	10% 2 18% 43% 23% 3	665
	21st to end	Day	10% 3 20% 36% 25% 5%	700
September	1st to 10th	Day	13% 2 25% 38% 16% 6%	414
	11th to 20th	Day	8% 3 28% 34% 19% 7%	300
	21st to end	Day	16% 5% 30% 27% 18% 4	300
October	1st to 10th	Day	21% 6% 23% 28% 14% 7%	300
	11th to 20th	Day	10% 16% 40% 22% 12% 1	300
	21st to end	Day	17% 15% 38% 20% 8% 2	330
November	1st to 10th	Day	17% 10% 37% 26% 9% 2	282
	11th to 20th	Day	14% 14% 43% 22% 7%	270
	21st to end	Day	21% 12% 33% 24% 10%	270
December	1st to 10th	Day	9% 14% 41% 29% 6% 2	270
	11th to 20th	Day	14% 12% 37% 28% 9%	270
	21st to end	Day	20% 17% 39% 20% 3	297
January	1st to 10th	Night	12% 13% 36% 33% 6% 1	950
	11th to 20th	Night	16% 14% 36% 28% 7%	950
	21st to end	Night	15% 9% 39% 30% 6%	1045
February	1st to 10th	Night	17% 11% 40% 27% 5%	950
	11th to 20th	Night	13% 12% 41% 29% 5%	909
	21st to end	Night	15% 13% 43% 25% 5%	628
March	1st to 10th	Night	12% 15% 41% 25% 7% 1	598
	11th to 20th	Night	20% 8% 36% 30% 7%	570
	21st to end	Night	23% 8% 38% 24% 6%	627
April	1st to 10th	Night	17% 15% 38% 25% 5%	570
	11th to 20th	Night	15% 13% 39% 29% 4 1	563
	21st to end	Night	20% 9% 34% 28% 8% 1	570
May	1st to 10th	Night	20% 7% 34% 30% 9% 1	570
	11th to 20th	Night	16% 8% 30% 36% 9% 1	561
	21st to end	Night	17% 6% 29% 33% 14%	617
June	1st to 10th	Night	6% 4 25% 45% 19%	570
	11th to 20th	Night	8% 4 31% 42% 14% 1	570
	21st to end	Night	5% 3 33% 44% 14%	570
July	1st to 10th	Night	8% 1 15% 42% 33% 1	555
	11th to 20th	Night	4 1 18% 49% 26% 1	552
	21st to end	Night	4 1 15% 53% 27% 1	624
August	1st to 10th	Night	6% 1 18% 49% 24% 2	567
	11th to 20th	Night	7% 3 17% 47% 24% 2	564
	21st to end	Night	9% 2 20% 42% 24% 3	627
September	1st to 10th	Night	11% 2 25% 39% 23% 2	570
	11th to 20th	Night	9% 2 27% 42% 18% 2	570
	21st to end	Night	10% 5% 31% 38% 15% 1	570
October	1st to 10th	Night	15% 6% 31% 32% 14% 2	693
	11th to 20th	Night	14% 9% 36% 31% 9%	760
	21st to end	Night	18% 10% 31% 32% 8%	836
November	1st to 10th	Night	10% 11% 32% 36% 10% 1	916
	11th to 20th	Night	13% 12% 39% 29% 7%	950
	21st to end	Night	16% 10% 36% 30% 8% 1	950
December	1st to 10th	Night	13% 12% 37% 32% 5% 1	950
	11th to 20th	Night	15% 10% 35% 33% 6% 1	950
	21st to end	Night	20% 12% 34% 30% 4	1045

Page generated at 2024-11-03 01:11:19. Version ac07

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