Wray
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wray 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	7% 5% 2 4 3 3 4 3 5% 7% 57%	105026
	Night	7% 6% 2 5% 4 4 4 4 5% 7% 53%	102705
Transparency	Day	25% 5% 12% 26% 23% 8%	104768
	Night	29% 6% 12% 25% 21% 7%	102554
Seeing	Day	10% 6% 27% 32% 19% 5%	15680
	Night	9% 6% 33% 40% 11% 1	25614

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	6% 7% 3 5% 2 2 2 3 5% 7% 58%	2538
	11th to 20th	Day	4 10% 3 7% 4 3 4 3 5% 6% 51%	2540
	21st to end	Day	2 5% 2 5% 4 4 4 3 5% 8% 59%	2891
February	1st to 10th	Day	5% 8% 3 7% 5% 5% 5% 4 4 6% 48%	1873
	11th to 20th	Day	3 9% 3 6% 4 4 4 4 4 7% 52%	1849
	21st to end	Day	4 8% 3 5% 3 3 3 2 5% 6% 57%	1570
March	1st to 10th	Day	8% 6% 2 3 3 3 3 3 5% 7% 58%	3130
	11th to 20th	Day	8% 6% 1 3 2 3 3 2 4 5% 62%	3284
	21st to end	Day	7% 6% 1 5% 3 3 4 4 6% 8% 52%	4091
April	1st to 10th	Day	8% 6% 2 4 3 3 4 3 5% 8% 54%	2280
	11th to 20th	Day	13% 5% 2 5% 3 4 3 4 5% 8% 48%	2251
	21st to end	Day	11% 7% 2 4 4 4 4 4 6% 7% 47%	2389
May	1st to 10th	Day	9% 5% 2 6% 4 4 5% 4 7% 7% 47%	4120
	11th to 20th	Day	10% 4 2 5% 3 4 4 4 6% 9% 51%	4082
	21st to end	Day	8% 4 1 5% 3 3 4 3 6% 8% 54%	4765
June	1st to 10th	Day	6% 3 1 3 3 3 4 5% 7% 9% 58%	2660
	11th to 20th	Day	7% 4 2 4 3 4 3 4 6% 8% 58%	2660
	21st to end	Day	4 2 1 3 3 3 5% 5% 7% 8% 59%	2660
July	1st to 10th	Day	6% 4 1 4 3 4 4 4 6% 7% 56%	4430
	11th to 20th	Day	2 2 1 2 2 3 5% 4 7% 11% 60%	4430
	21st to end	Day	3 2 1 3 2 3 4 4 6% 9% 63%	4802
August	1st to 10th	Day	12% 5% 2 3 3 3 4 3 7% 9% 49%	4117
	11th to 20th	Day	6% 4 2 4 3 4 4 3 5% 8% 56%	3736
	21st to end	Day	4 3 1 4 2 3 3 3 5% 7% 64%	4180
September	1st to 10th	Day	6% 4 1 4 2 3 3 3 4 7% 63%	2280
	11th to 20th	Day	7% 3 1 3 3 3 3 3 4 7% 63%	2128
	21st to end	Day	9% 3 1 3 2 2 2 3 4 6% 66%	2090
October	1st to 10th	Day	7% 2 1 2 2 1 2 2 2 4 76%	3480
	11th to 20th	Day	7% 4 1 2 2 2 3 2 4 6% 66%	3160
	21st to end	Day	7% 4 1 3 2 2 2 2 4 7% 65%	3091
November	1st to 10th	Day	3 4 1 5% 3 3 3 3 5% 7% 64%	1709
	11th to 20th	Day	6% 5% 1 4 3 3 2 2 4 5% 66%	1710
	21st to end	Day	6% 7% 2 4 3 2 3 2 4 6% 61%	1710
December	1st to 10th	Day	4 6% 2 6% 3 3 3 3 5% 7% 57%	1620
	11th to 20th	Day	5% 6% 2 4 4 3 3 4 6% 9% 54%	1926
	21st to end	Day	12% 10% 3 6% 4 3 3 3 4 6% 47%	2794
January	1st to 10th	Night	5% 8% 3 7% 3 3 3 3 4 6% 55%	4417
	11th to 20th	Night	2 6% 2 6% 6% 4 5% 3 5% 8% 52%	4430
	21st to end	Night	3 6% 3 7% 5% 4 4 3 5% 6% 55%	4805
February	1st to 10th	Night	7% 9% 4 9% 3 4 3 3 4 6% 48%	2304
	11th to 20th	Night	3 8% 3 7% 6% 4 4 3 6% 7% 49%	2218
	21st to end	Night	4 7% 2 6% 4 4 4 3 5% 6% 53%	1884
March	1st to 10th	Night	7% 8% 2 4 3 3 3 3 4 5% 58%	3734
	11th to 20th	Night	9% 8% 2 5% 3 3 3 2 4 5% 55%	3682
	21st to end	Night	9% 7% 2 5% 4 4 5% 4 5% 9% 46%	3546
April	1st to 10th	Night	9% 8% 2 5% 4 3 3 3 5% 7% 50%	1900
	11th to 20th	Night	14% 6% 2 4 4 4 4 3 5% 6% 47%	1877
	21st to end	Night	14% 7% 2 5% 3 4 4 4 5% 8% 45%	1790
May	1st to 10th	Night	11% 7% 3 7% 5% 4 6% 4 6% 9% 38%	2850
	11th to 20th	Night	10% 6% 2 5% 4 5% 5% 5% 7% 8% 44%	2823
	21st to end	Night	12% 5% 2 6% 4 4 4 4 7% 9% 41%	2805
June	1st to 10th	Night	6% 4 1 4 5% 4 4 5% 6% 11% 50%	1520
	11th to 20th	Night	7% 4 2 4 4 4 4 4 6% 8% 53%	1520
	21st to end	Night	3 4 1 5% 5% 6% 7% 5% 8% 9% 48%	1520
July	1st to 10th	Night	6% 4 2 6% 4 6% 5% 5% 7% 9% 46%	2540
	11th to 20th	Night	4 4 2 5% 4 4 6% 5% 8% 11% 49%	2540
	21st to end	Night	3 3 1 5% 4 4 5% 4 8% 9% 55%	2761
August	1st to 10th	Night	9% 5% 3 7% 5% 6% 6% 5% 9% 10% 37%	2822
	11th to 20th	Night	9% 7% 2 7% 5% 5% 6% 4 7% 8% 40%	3100
	21st to end	Night	3 4 1 6% 4 4 5% 5% 6% 8% 54%	3487
September	1st to 10th	Night	5% 4 2 4 4 4 4 4 5% 8% 57%	1900
	11th to 20th	Night	7% 3 1 3 2 3 4 3 5% 7% 61%	2052
	21st to end	Night	7% 3 1 4 2 3 3 3 4 6% 63%	2090
October	1st to 10th	Night	6% 2 1 2 2 2 2 2 3 5% 72%	3480
	11th to 20th	Night	9% 4 1 3 2 3 3 2 4 6% 63%	3732
	21st to end	Night	5% 5% 2 4 3 3 3 3 3 5% 63%	4467
November	1st to 10th	Night	3 4 1 4 3 3 4 3 4 7% 64%	2470
	11th to 20th	Night	5% 5% 2 4 3 3 3 3 5% 7% 61%	2470
	21st to end	Night	5% 6% 1 5% 3 3 3 3 4 6% 60%	2470
December	1st to 10th	Night	5% 6% 2 7% 3 3 3 3 5% 6% 57%	2555
	11th to 20th	Night	4 6% 2 4 3 3 3 4 5% 8% 56%	3271
	21st to end	Night	10% 10% 3 5% 3 3 4 3 5% 7% 47%	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	28% 4 11% 32% 20% 6%	2539
	11th to 20th	Day	34% 5% 15% 23% 19% 4	2540
	21st to end	Day	24% 6% 17% 33% 17% 3	2891
February	1st to 10th	Day	37% 5% 12% 24% 17% 6%	1873
	11th to 20th	Day	32% 5% 10% 26% 22% 5%	1859
	21st to end	Day	28% 4 10% 23% 24% 10%	1570
March	1st to 10th	Day	26% 4 10% 20% 30% 10%	3130
	11th to 20th	Day	25% 4 13% 30% 24% 4	3284
	21st to end	Day	27% 7% 15% 35% 13% 2	4091
April	1st to 10th	Day	28% 5% 13% 25% 23% 6%	2280
	11th to 20th	Day	33% 5% 15% 22% 18% 6%	2254
	21st to end	Day	33% 6% 12% 28% 18% 3	2389
May	1st to 10th	Day	31% 9% 14% 26% 13% 8%	4120
	11th to 20th	Day	28% 8% 16% 28% 17% 2	4086
	21st to end	Day	26% 7% 17% 26% 19% 5%	4765
June	1st to 10th	Day	20% 9% 18% 33% 16% 4	2660
	11th to 20th	Day	24% 7% 11% 25% 23% 10%	2660
	21st to end	Day	20% 7% 11% 26% 27% 10%	2660
July	1st to 10th	Day	25% 6% 10% 22% 28% 9%	4361
	11th to 20th	Day	16% 5% 16% 29% 24% 10%	4355
	21st to end	Day	16% 6% 13% 24% 24% 17%	4651
August	1st to 10th	Day	31% 7% 14% 28% 15% 5%	4103
	11th to 20th	Day	28% 5% 14% 21% 27% 5%	3772
	21st to end	Day	20% 4 16% 24% 21% 15%	4179
September	1st to 10th	Day	21% 5% 7% 25% 27% 14%	2280
	11th to 20th	Day	21% 5% 7% 24% 31% 12%	2128
	21st to end	Day	22% 3 6% 23% 34% 11%	2090
October	1st to 10th	Day	16% 2 5% 18% 34% 25%	3480
	11th to 20th	Day	20% 3 8% 32% 26% 9%	3160
	21st to end	Day	22% 2 9% 27% 31% 10%	3091
November	1st to 10th	Day	21% 4 13% 27% 26% 10%	1709
	11th to 20th	Day	22% 3 8% 29% 29% 9%	1710
	21st to end	Day	26% 2 9% 25% 29% 9%	1710
December	1st to 10th	Day	27% 4 11% 29% 25% 4	1620
	11th to 20th	Day	27% 4 9% 29% 28% 3	1924
	21st to end	Day	39% 4 10% 28% 15% 4	2794
January	1st to 10th	Night	30% 4 11% 31% 21% 2	4417
	11th to 20th	Night	30% 6% 13% 24% 21% 6%	4430
	21st to end	Night	30% 5% 12% 34% 17% 2	4805
February	1st to 10th	Night	38% 5% 12% 21% 18% 6%	2304
	11th to 20th	Night	34% 5% 12% 28% 18% 4	2218
	21st to end	Night	31% 4 9% 24% 24% 8%	1884
March	1st to 10th	Night	28% 4 9% 19% 26% 15%	3734
	11th to 20th	Night	31% 4 12% 22% 26% 6%	3682
	21st to end	Night	31% 9% 18% 30% 11% 1	3546
April	1st to 10th	Night	33% 6% 12% 24% 19% 7%	1900
	11th to 20th	Night	36% 5% 13% 23% 18% 4	1877
	21st to end	Night	37% 6% 12% 25% 18% 2	1790
May	1st to 10th	Night	38% 9% 18% 21% 10% 4	2850
	11th to 20th	Night	33% 10% 20% 25% 10% 2	2824
	21st to end	Night	35% 10% 17% 24% 10% 3	2806
June	1st to 10th	Night	27% 9% 23% 24% 13% 3	1520
	11th to 20th	Night	28% 7% 14% 22% 20% 8%	1520
	21st to end	Night	27% 10% 13% 22% 20% 7%	1520
July	1st to 10th	Night	32% 7% 13% 22% 23% 2	2500
	11th to 20th	Night	28% 6% 17% 20% 24% 6%	2492
	21st to end	Night	22% 7% 17% 23% 19% 12%	2674
August	1st to 10th	Night	37% 9% 14% 23% 14% 3	2813
	11th to 20th	Night	40% 8% 13% 21% 15% 3	3130
	21st to end	Night	27% 6% 13% 27% 17% 10%	3487
September	1st to 10th	Night	25% 6% 10% 23% 24% 13%	1900
	11th to 20th	Night	22% 7% 10% 24% 25% 12%	2052
	21st to end	Night	22% 4 8% 24% 31% 11%	2090
October	1st to 10th	Night	17% 4 7% 17% 35% 21%	3480
	11th to 20th	Night	23% 3 7% 27% 28% 11%	3732
	21st to end	Night	25% 3 10% 24% 29% 9%	4467
November	1st to 10th	Night	20% 4 10% 27% 27% 12%	2470
	11th to 20th	Night	23% 4 10% 26% 27% 9%	2470
	21st to end	Night	26% 3 9% 24% 27% 10%	2470
December	1st to 10th	Night	28% 4 11% 29% 21% 6%	2555
	11th to 20th	Night	25% 4 10% 30% 27% 4	3272
	21st to end	Night	35% 5% 12% 30% 17% 2	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	8% 8% 34% 33% 15% 2	270
	11th to 20th	Day	15% 7% 36% 32% 7% 2	270
	21st to end	Day	7% 7% 47% 27% 8% 3	297
February	1st to 10th	Day	13% 10% 45% 27% 4 2	270
	11th to 20th	Day	8% 10% 43% 27% 10% 3	270
	21st to end	Day	8% 13% 44% 25% 9% 1	225
March	1st to 10th	Day	11% 7% 33% 30% 16% 3	270
	11th to 20th	Day	14% 7% 32% 27% 17% 2	270
	21st to end	Day	13% 12% 36% 28% 11% 1	458
April	1st to 10th	Day	12% 16% 35% 25% 9% 3	460
	11th to 20th	Day	17% 13% 32% 25% 10% 2	452
	21st to end	Day	15% 12% 33% 26% 11% 2	569
May	1st to 10th	Day	14% 10% 28% 31% 13% 3	653
	11th to 20th	Day	16% 5% 27% 31% 16% 4	675
	21st to end	Day	13% 8% 28% 29% 18% 4	734
June	1st to 10th	Day	7% 5% 21% 31% 27% 9%	680
	11th to 20th	Day	8% 6% 28% 36% 20% 2	680
	21st to end	Day	6% 3 24% 38% 22% 6%	680
July	1st to 10th	Day	8% 3 19% 36% 27% 7%	671
	11th to 20th	Day	3 1 16% 39% 32% 9%	668
	21st to end	Day	6% 2 14% 36% 33% 9%	739
August	1st to 10th	Day	9% 2 13% 37% 32% 8%	676
	11th to 20th	Day	6% 2 23% 40% 22% 7%	487
	21st to end	Day	4 2 18% 41% 27% 8%	539
September	1st to 10th	Day	6% 3 19% 36% 26% 10%	490
	11th to 20th	Day	4 4 17% 38% 25% 13%	338
	21st to end	Day	14% 3 18% 28% 27% 10%	300
October	1st to 10th	Day	14% 4 19% 27% 23% 13%	300
	11th to 20th	Day	7% 8% 33% 28% 19% 5%	300
	21st to end	Day	14% 7% 33% 25% 15% 5%	330
November	1st to 10th	Day	5% 7% 34% 32% 17% 5%	282
	11th to 20th	Day	9% 6% 32% 34% 16% 3	270
	21st to end	Day	12% 7% 28% 38% 12% 3	270
December	1st to 10th	Day	6% 10% 36% 36% 10% 2	270
	11th to 20th	Day	13% 10% 33% 29% 15%	270
	21st to end	Day	16% 9% 37% 27% 8% 2	297
January	1st to 10th	Night	7% 9% 36% 34% 13% 1	950
	11th to 20th	Night	8% 9% 36% 37% 8% 1	950
	21st to end	Night	8% 7% 41% 36% 8%	1003
February	1st to 10th	Night	11% 9% 41% 34% 5%	760
	11th to 20th	Night	7% 7% 44% 35% 6% 1	744
	21st to end	Night	7% 9% 45% 35% 4	628
March	1st to 10th	Night	9% 9% 37% 37% 7%	760
	11th to 20th	Night	14% 6% 38% 33% 7% 1	694
	21st to end	Night	14% 9% 36% 35% 6%	627
April	1st to 10th	Night	14% 10% 40% 32% 4	570
	11th to 20th	Night	16% 7% 43% 30% 3	563
	21st to end	Night	18% 9% 32% 35% 7% 1	570
May	1st to 10th	Night	13% 7% 32% 39% 8%	570
	11th to 20th	Night	17% 6% 27% 38% 11% 1	561
	21st to end	Night	15% 7% 35% 32% 12%	617
June	1st to 10th	Night	8% 6% 30% 40% 15% 1	570
	11th to 20th	Night	9% 5% 39% 38% 8%	570
	21st to end	Night	4 4 28% 49% 15%	570
July	1st to 10th	Night	9% 3 23% 51% 14%	555
	11th to 20th	Night	5% 2 20% 55% 17% 1	552
	21st to end	Night	5% 1 19% 50% 23%	624
August	1st to 10th	Night	8% 2 18% 51% 21% 1	567
	11th to 20th	Night	6% 3 24% 52% 14%	564
	21st to end	Night	5% 2 22% 53% 17% 1	627
September	1st to 10th	Night	6% 2 26% 51% 14% 1	570
	11th to 20th	Night	9% 4 28% 43% 15% 1	570
	21st to end	Night	9% 4 28% 43% 16%	570
October	1st to 10th	Night	13% 8% 25% 39% 15% 1	570
	11th to 20th	Night	11% 6% 29% 38% 14% 1	728
	21st to end	Night	10% 8% 32% 36% 13% 1	1045
November	1st to 10th	Night	5% 5% 32% 45% 12% 1	950
	11th to 20th	Night	8% 6% 36% 39% 10%	950
	21st to end	Night	8% 5% 34% 39% 12% 1	950
December	1st to 10th	Night	8% 7% 42% 37% 7%	950
	11th to 20th	Night	7% 8% 36% 40% 8% 1	950
	21st to end	Night	11% 9% 38% 36% 5%	1045

Page generated at 2024-11-03 00:11:18. Version ac07

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