Springdale
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Springdale clear sky chart from 2005-11-06 to 2026-07-16.

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	20% 14% 4 9% 5% 5% 4 3 5% 6% 24%	138527
	Night	19% 13% 4 10% 5% 5% 5% 4 5% 6% 24%	134472
Transparency	Day	62% 5% 11% 16% 6% 1	141944
	Night	62% 5% 11% 15% 7% 1	139167
Seeing	Day	29% 17% 29% 18% 6% 2	20464
	Night	28% 15% 30% 20% 6% 1	27277

By Month

Percentage Cloud Cover NE (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	17% 20% 6% 14% 5% 4 4 3 4 4 18%	4217
	11th to 20th	Day	20% 14% 7% 15% 6% 6% 6% 3 4 5% 14%	4681
	21st to end	Day	6% 14% 5% 11% 9% 9% 6% 4 6% 6% 25%	5157
February	1st to 10th	Day	15% 13% 4 13% 8% 6% 5% 4 7% 5% 19%	1680
	11th to 20th	Day	16% 20% 5% 11% 6% 5% 5% 4 5% 4 19%	1886
	21st to end	Day	11% 15% 5% 11% 7% 5% 6% 4 5% 5% 24%	1730
March	1st to 10th	Day	15% 16% 5% 12% 7% 8% 5% 4 5% 5% 20%	4574
	11th to 20th	Day	21% 18% 7% 12% 6% 4 3 2 3 4 20%	4851
	21st to end	Day	26% 18% 6% 10% 5% 4 3 2 3 4 18%	5949
April	1st to 10th	Day	19% 19% 6% 12% 7% 4 4 3 4 5% 17%	2520
	11th to 20th	Day	19% 18% 5% 9% 4 4 4 3 5% 4 25%	2649
	21st to end	Day	24% 18% 5% 7% 5% 4 3 3 4 4 23%	2730
May	1st to 10th	Day	28% 19% 6% 9% 4 4 3 2 4 4 17%	8114
	11th to 20th	Day	23% 14% 4 9% 5% 4 4 3 4 5% 24%	8333
	21st to end	Day	23% 18% 3 6% 4 3 3 3 4 5% 27%	9682
June	1st to 10th	Day	32% 13% 3 7% 5% 5% 4 3 4 5% 19%	3150
	11th to 20th	Day	27% 12% 3 7% 5% 4 5% 4 4 6% 24%	3150
	21st to end	Day	23% 11% 3 8% 5% 5% 4 4 5% 6% 26%	3150
July	1st to 10th	Day	17% 12% 4 7% 6% 5% 5% 4 6% 6% 27%	6950
	11th to 20th	Day	14% 8% 3 8% 6% 6% 6% 4 7% 8% 30%	6668
	21st to end	Day	19% 9% 3 7% 5% 5% 5% 4 6% 7% 31%	6927
August	1st to 10th	Day	21% 8% 3 8% 5% 5% 5% 4 5% 7% 28%	4564
	11th to 20th	Day	21% 7% 2 6% 4 4 3 3 4 6% 39%	4270
	21st to end	Day	20% 8% 3 7% 5% 4 4 3 6% 7% 32%	4591
September	1st to 10th	Day	22% 7% 3 7% 4 4 4 4 4 7% 34%	2400
	11th to 20th	Day	24% 10% 4 7% 6% 4 5% 3 5% 6% 26%	2233
	21st to end	Day	18% 10% 4 8% 5% 5% 5% 3 6% 8% 29%	2200
October	1st to 10th	Day	20% 9% 3 8% 4 4 5% 3 5% 6% 32%	2162
	11th to 20th	Day	22% 15% 3 8% 5% 5% 5% 4 5% 7% 23%	1800
	21st to end	Day	22% 14% 3 10% 5% 5% 4 3 5% 6% 22%	1980
November	1st to 10th	Day	24% 15% 4 9% 5% 5% 5% 4 5% 6% 18%	1850
	11th to 20th	Day	21% 16% 5% 8% 6% 4 4 3 5% 6% 23%	1626
	21st to end	Day	23% 16% 5% 9% 6% 4 4 4 4 5% 20%	1470
December	1st to 10th	Day	13% 14% 5% 9% 6% 6% 6% 5% 7% 6% 24%	2360
	11th to 20th	Day	24% 14% 4 9% 5% 5% 5% 4 6% 6% 18%	2698
	21st to end	Day	18% 14% 5% 14% 6% 4 4 4 6% 6% 19%	3575
January	1st to 10th	Night	15% 17% 7% 12% 7% 5% 5% 3 5% 6% 18%	8705
	11th to 20th	Night	14% 14% 6% 15% 7% 6% 6% 4 5% 6% 16%	8234
	21st to end	Night	6% 12% 5% 11% 7% 7% 9% 5% 6% 7% 24%	9056
February	1st to 10th	Night	15% 12% 4 13% 8% 7% 5% 4 5% 6% 20%	2940
	11th to 20th	Night	14% 17% 5% 11% 7% 6% 6% 4 5% 5% 21%	2615
	21st to end	Night	12% 13% 4 9% 6% 5% 6% 4 5% 5% 29%	2076
March	1st to 10th	Night	18% 11% 3 9% 7% 7% 6% 5% 6% 7% 21%	5486
	11th to 20th	Night	18% 16% 6% 13% 7% 6% 5% 3 4 4 19%	5327
	21st to end	Night	21% 17% 6% 12% 5% 4 3 3 4 5% 19%	5223
April	1st to 10th	Night	22% 17% 5% 10% 5% 4 3 3 4 4 23%	2100
	11th to 20th	Night	21% 15% 4 7% 4 4 4 3 4 6% 27%	1921
	21st to end	Night	25% 16% 5% 7% 4 3 4 2 4 5% 26%	1890
May	1st to 10th	Night	33% 17% 4 8% 3 3 3 2 5% 5% 16%	4812
	11th to 20th	Night	23% 13% 4 9% 4 4 4 4 5% 6% 24%	4557
	21st to end	Night	23% 16% 5% 6% 4 3 3 3 5% 6% 27%	4524
June	1st to 10th	Night	32% 11% 3 7% 5% 4 3 3 5% 6% 21%	1470
	11th to 20th	Night	26% 10% 3 5% 5% 4 4 4 5% 7% 28%	1470
	21st to end	Night	25% 10% 3 8% 4 5% 4 4 5% 6% 26%	1470
July	1st to 10th	Night	22% 10% 3 8% 4 5% 4 4 5% 7% 28%	3249
	11th to 20th	Night	14% 9% 3 8% 5% 4 5% 4 6% 7% 34%	3407
	21st to end	Night	22% 9% 3 7% 4 4 4 3 4 6% 35%	3948
August	1st to 10th	Night	13% 8% 3 7% 5% 5% 5% 4 6% 7% 37%	2596
	11th to 20th	Night	18% 8% 2 6% 3 3 4 3 5% 6% 43%	2787
	21st to end	Night	20% 6% 2 5% 4 3 4 3 5% 8% 40%	3312
September	1st to 10th	Night	20% 8% 2 5% 4 4 3 3 5% 7% 39%	2000
	11th to 20th	Night	23% 9% 3 7% 5% 4 4 2 5% 6% 33%	2166
	21st to end	Night	19% 9% 3 6% 4 4 5% 4 6% 7% 33%	2200
October	1st to 10th	Night	21% 10% 3 7% 5% 4 4 3 5% 6% 31%	2235
	11th to 20th	Night	21% 11% 3 6% 4 5% 5% 4 6% 5% 29%	2600
	21st to end	Night	25% 11% 3 6% 4 4 4 3 5% 6% 28%	2860
November	1st to 10th	Night	22% 13% 4 9% 6% 5% 5% 4 6% 5% 21%	2668
	11th to 20th	Night	25% 13% 5% 8% 6% 5% 4 4 5% 6% 19%	2992
	21st to end	Night	21% 16% 5% 10% 5% 5% 4 3 5% 6% 19%	3150
December	1st to 10th	Night	13% 12% 5% 11% 6% 6% 5% 4 6% 6% 25%	5050
	11th to 20th	Night	24% 12% 5% 10% 5% 5% 5% 4 4 6% 21%	5731
	21st to end	Night	17% 13% 6% 14% 6% 5% 5% 4 5% 6% 20%	7645

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	69% 3 8% 14% 4 1	4218
	11th to 20th	Day	72% 5% 9% 9% 5%	4710
	21st to end	Day	60% 5% 10% 16% 7% 3	5157
February	1st to 10th	Day	65% 6% 11% 11% 6% 1	1680
	11th to 20th	Day	71% 5% 8% 10% 6% 1	1893
	21st to end	Day	63% 6% 6% 14% 11% 1	1730
March	1st to 10th	Day	68% 4 6% 12% 9% 1	4578
	11th to 20th	Day	70% 4 5% 11% 7% 3	4851
	21st to end	Day	70% 5% 6% 12% 7% 1	5949
April	1st to 10th	Day	72% 5% 8% 9% 6% 1	2520
	11th to 20th	Day	63% 5% 8% 15% 9% 1	2649
	21st to end	Day	65% 5% 7% 14% 8% 1	2730
May	1st to 10th	Day	71% 4 9% 12% 3 1	8127
	11th to 20th	Day	64% 3 11% 15% 7%	8337
	21st to end	Day	61% 4 11% 18% 6%	9683
June	1st to 10th	Day	68% 5% 8% 14% 5%	3150
	11th to 20th	Day	62% 5% 11% 17% 5%	3150
	21st to end	Day	59% 5% 12% 16% 7% 1	3150
July	1st to 10th	Day	56% 4 13% 20% 7%	6875
	11th to 20th	Day	49% 6% 15% 24% 6%	6586
	21st to end	Day	51% 5% 16% 23% 5%	6730
August	1st to 10th	Day	55% 6% 14% 20% 5%	4550
	11th to 20th	Day	48% 4 13% 21% 11% 4	4312
	21st to end	Day	51% 4 13% 25% 6%	4591
September	1st to 10th	Day	49% 5% 12% 24% 9% 1	2400
	11th to 20th	Day	60% 6% 12% 16% 6%	2233
	21st to end	Day	54% 5% 15% 18% 7% 1	2200
October	1st to 10th	Day	57% 6% 12% 17% 7% 1	3514
	11th to 20th	Day	63% 5% 11% 16% 5%	2922
	21st to end	Day	61% 3 12% 15% 9% 1	3191
November	1st to 10th	Day	68% 7% 10% 11% 4 1	1850
	11th to 20th	Day	64% 5% 11% 14% 6%	1626
	21st to end	Day	67% 6% 9% 11% 6% 1	1470
December	1st to 10th	Day	56% 5% 12% 19% 8%	2360
	11th to 20th	Day	66% 5% 17% 8% 4	2697
	21st to end	Day	66% 4 10% 16% 4	3575
January	1st to 10th	Night	68% 3 9% 12% 6% 1	8705
	11th to 20th	Night	68% 8% 9% 9% 5%	8280
	21st to end	Night	60% 5% 10% 12% 11% 2	9056
February	1st to 10th	Night	66% 6% 10% 11% 7% 1	2940
	11th to 20th	Night	67% 6% 10% 11% 6%	2619
	21st to end	Night	57% 5% 9% 18% 10% 1	2076
March	1st to 10th	Night	63% 5% 8% 14% 8% 2	5495
	11th to 20th	Night	69% 5% 6% 10% 9% 1	5328
	21st to end	Night	65% 6% 8% 14% 6%	5223
April	1st to 10th	Night	67% 4 5% 13% 9% 1	2100
	11th to 20th	Night	62% 3 9% 18% 8% 1	1921
	21st to end	Night	63% 4 8% 16% 9% 1	1890
May	1st to 10th	Night	71% 3 11% 12% 3	4817
	11th to 20th	Night	64% 3 12% 14% 6% 1	4558
	21st to end	Night	61% 3 10% 20% 5%	4525
June	1st to 10th	Night	66% 5% 11% 12% 6%	1470
	11th to 20th	Night	57% 6% 15% 16% 6%	1470
	21st to end	Night	59% 6% 11% 16% 8%	1470
July	1st to 10th	Night	56% 4 14% 22% 4	3216
	11th to 20th	Night	49% 6% 14% 22% 8%	3365
	21st to end	Night	53% 4 15% 24% 4	3831
August	1st to 10th	Night	45% 7% 19% 24% 5%	2585
	11th to 20th	Night	44% 5% 17% 22% 10% 2	2811
	21st to end	Night	44% 5% 18% 28% 5%	3311
September	1st to 10th	Night	47% 5% 14% 26% 9% 1	2000
	11th to 20th	Night	55% 5% 13% 17% 8% 1	2166
	21st to end	Night	51% 6% 15% 21% 7% 1	2200
October	1st to 10th	Night	60% 6% 14% 14% 5%	3664
	11th to 20th	Night	57% 5% 14% 15% 7%	4227
	21st to end	Night	57% 4 14% 17% 8% 1	4610
November	1st to 10th	Night	64% 7% 10% 14% 5%	2668
	11th to 20th	Night	66% 6% 11% 13% 4	2992
	21st to end	Night	67% 6% 9% 11% 6%	3150
December	1st to 10th	Night	58% 5% 8% 19% 10%	5050
	11th to 20th	Night	68% 4 14% 10% 4	5733
	21st to end	Night	68% 5% 9% 15% 2	7645

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	27% 21% 31% 17% 3 1	430
	11th to 20th	Day	25% 20% 31% 18% 4	430
	21st to end	Day	24% 22% 33% 17% 4	473
February	1st to 10th	Day	25% 22% 32% 14% 6% 1	430
	11th to 20th	Day	30% 23% 33% 12% 2 1	426
	21st to end	Day	23% 21% 34% 15% 5% 2	355
March	1st to 10th	Day	24% 27% 32% 10% 6% 1	430
	11th to 20th	Day	29% 20% 26% 16% 7% 2	430
	21st to end	Day	30% 22% 28% 15% 4 1	556
April	1st to 10th	Day	31% 24% 29% 12% 3 1	540
	11th to 20th	Day	32% 16% 29% 18% 5% 1	687
	21st to end	Day	33% 18% 25% 17% 6% 1	750
May	1st to 10th	Day	40% 15% 21% 16% 5% 2	753
	11th to 20th	Day	32% 14% 25% 18% 7% 3	774
	21st to end	Day	34% 14% 31% 16% 5% 1	845
June	1st to 10th	Day	37% 12% 23% 19% 6% 2	780
	11th to 20th	Day	34% 12% 28% 16% 8% 2	780
	21st to end	Day	27% 13% 29% 18% 10% 4	780
July	1st to 10th	Day	27% 13% 30% 20% 7% 3	770
	11th to 20th	Day	20% 13% 32% 26% 10% 1	743
	21st to end	Day	25% 12% 30% 24% 8% 1	795
August	1st to 10th	Day	23% 9% 30% 26% 9% 3	725
	11th to 20th	Day	23% 10% 24% 27% 13% 3	717
	21st to end	Day	24% 10% 30% 24% 10% 3	758
September	1st to 10th	Day	23% 16% 31% 21% 8% 1	530
	11th to 20th	Day	35% 16% 27% 17% 4 1	437
	21st to end	Day	23% 22% 31% 17% 5% 1	420
October	1st to 10th	Day	22% 20% 35% 18% 4 1	420
	11th to 20th	Day	32% 15% 26% 18% 7% 3	420
	21st to end	Day	28% 19% 27% 16% 8% 2	462
November	1st to 10th	Day	35% 23% 26% 11% 4	425
	11th to 20th	Day	36% 18% 25% 15% 5% 1	430
	21st to end	Day	38% 20% 29% 10% 3	430
December	1st to 10th	Day	28% 20% 30% 16% 6%	430
	11th to 20th	Day	31% 25% 29% 12% 3	430
	21st to end	Day	27% 21% 27% 17% 7% 1	473
January	1st to 10th	Night	26% 20% 30% 17% 5% 1	950
	11th to 20th	Night	24% 23% 32% 17% 4	950
	21st to end	Night	23% 21% 36% 18% 2	1045
February	1st to 10th	Night	24% 21% 32% 19% 4	950
	11th to 20th	Night	27% 21% 32% 15% 2 1	872
	21st to end	Night	21% 14% 37% 20% 7% 2	692
March	1st to 10th	Night	27% 22% 32% 15% 4 1	840
	11th to 20th	Night	24% 18% 30% 22% 6%	738
	21st to end	Night	31% 15% 32% 15% 5% 1	693
April	1st to 10th	Night	31% 20% 29% 15% 4 1	630
	11th to 20th	Night	30% 13% 31% 19% 6% 1	624
	21st to end	Night	34% 12% 29% 19% 5%	630
May	1st to 10th	Night	37% 10% 23% 21% 8% 1	630
	11th to 20th	Night	33% 9% 30% 18% 10%	622
	21st to end	Night	34% 11% 29% 20% 5%	682
June	1st to 10th	Night	38% 10% 22% 23% 6% 1	630
	11th to 20th	Night	33% 10% 25% 21% 10% 1	630
	21st to end	Night	31% 11% 28% 20% 10% 1	630
July	1st to 10th	Night	27% 10% 31% 25% 7% 1	616
	11th to 20th	Night	21% 9% 32% 30% 8%	598
	21st to end	Night	29% 7% 31% 26% 7%	656
August	1st to 10th	Night	23% 7% 27% 32% 10% 1	598
	11th to 20th	Night	28% 6% 28% 27% 10%	592
	21st to end	Night	23% 6% 30% 30% 9% 1	660
September	1st to 10th	Night	26% 9% 35% 25% 6%	600
	11th to 20th	Night	31% 13% 28% 24% 5%	600
	21st to end	Night	28% 14% 36% 17% 5% 1	600
October	1st to 10th	Night	30% 11% 35% 19% 5%	633
	11th to 20th	Night	30% 12% 28% 21% 8% 1	910
	21st to end	Night	31% 14% 29% 19% 6%	1001
November	1st to 10th	Night	31% 19% 29% 17% 4	930
	11th to 20th	Night	32% 17% 30% 15% 5% 1	950
	21st to end	Night	31% 21% 29% 16% 2	950
December	1st to 10th	Night	26% 20% 31% 17% 5%	950
	11th to 20th	Night	31% 21% 30% 15% 3	950
	21st to end	Night	24% 19% 30% 19% 7% 1	1045

Page generated at 2026-07-13 04:14:49. Version ac07

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