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 2025-03-12.

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	20% 14% 4 9% 6% 5% 4 3 5% 6% 24%	108593
	Night	19% 12% 4 10% 6% 5% 5% 4 5% 6% 25%	110617
Transparency	Day	62% 5% 11% 15% 6% 1	112055
	Night	61% 5% 11% 15% 6% 1	115341
Seeing	Day	29% 17% 28% 18% 7% 2	18474
	Night	28% 15% 30% 20% 6% 1	25516

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	16% 21% 7% 12% 5% 4 4 3 4 4 18%	3245
	11th to 20th	Day	16% 15% 8% 16% 7% 7% 5% 3 4 5% 15%	3591
	21st to end	Day	6% 11% 5% 11% 10% 9% 6% 4 5% 6% 27%	3982
February	1st to 10th	Day	15% 12% 4 13% 9% 7% 5% 4 7% 5% 19%	1600
	11th to 20th	Day	16% 20% 5% 11% 7% 5% 5% 4 5% 4 20%	1793
	21st to end	Day	11% 15% 5% 11% 7% 5% 7% 3 6% 5% 24%	1650
March	1st to 10th	Day	13% 17% 4 11% 7% 7% 5% 4 5% 5% 22%	3214
	11th to 20th	Day	21% 20% 8% 14% 6% 5% 4 3 3 4 12%	3326
	21st to end	Day	26% 16% 5% 10% 5% 4 3 2 3 4 21%	4059
April	1st to 10th	Day	20% 20% 6% 11% 7% 4 4 3 4 5% 16%	2280
	11th to 20th	Day	19% 19% 5% 9% 4 4 4 3 5% 5% 25%	2394
	21st to end	Day	24% 18% 5% 7% 5% 4 3 3 3 4 23%	2470
May	1st to 10th	Day	29% 21% 7% 9% 4 3 3 2 3 4 16%	4359
	11th to 20th	Day	21% 15% 5% 10% 6% 4 3 3 4 5% 24%	4459
	21st to end	Day	29% 16% 3 7% 5% 4 3 3 4 5% 21%	5173
June	1st to 10th	Day	33% 13% 3 7% 5% 5% 4 3 4 6% 17%	2850
	11th to 20th	Day	27% 12% 3 7% 5% 4 5% 4 5% 6% 24%	2850
	21st to end	Day	24% 11% 3 7% 5% 4 4 4 5% 6% 26%	2850
July	1st to 10th	Day	19% 12% 4 8% 6% 5% 5% 4 6% 6% 24%	4750
	11th to 20th	Day	15% 8% 3 8% 6% 6% 6% 4 6% 7% 29%	4608
	21st to end	Day	17% 7% 2 6% 4 5% 5% 4 6% 8% 35%	4815
August	1st to 10th	Day	21% 8% 3 8% 5% 5% 5% 4 5% 7% 27%	4424
	11th to 20th	Day	21% 7% 2 6% 4 4 4 3 4 6% 39%	4137
	21st to end	Day	20% 8% 3 7% 5% 4 4 3 6% 6% 33%	4450
September	1st to 10th	Day	23% 8% 3 7% 4 4 4 3 5% 6% 33%	2280
	11th to 20th	Day	25% 10% 4 7% 6% 4 4 3 5% 6% 27%	2122
	21st to end	Day	18% 11% 3 8% 5% 5% 5% 3 6% 8% 28%	2090
October	1st to 10th	Day	21% 10% 3 8% 4 4 5% 3 5% 6% 32%	2055
	11th to 20th	Day	22% 14% 2 8% 5% 5% 5% 4 4 7% 23%	1710
	21st to end	Day	23% 14% 3 10% 5% 5% 4 3 5% 6% 22%	1881
November	1st to 10th	Day	25% 15% 4 8% 5% 5% 5% 4 5% 6% 18%	1760
	11th to 20th	Day	20% 16% 5% 8% 6% 4 3 3 5% 6% 24%	1550
	21st to end	Day	24% 17% 5% 9% 6% 4 4 3 4 5% 20%	1400
December	1st to 10th	Day	13% 14% 5% 9% 6% 6% 6% 5% 7% 6% 24%	2290
	11th to 20th	Day	24% 15% 4 9% 5% 5% 4 4 6% 6% 18%	2628
	21st to end	Day	18% 14% 5% 14% 6% 4 4 4 6% 7% 19%	3498
January	1st to 10th	Night	16% 18% 7% 12% 7% 5% 4 3 5% 5% 19%	6718
	11th to 20th	Night	12% 13% 7% 16% 7% 6% 6% 4 5% 6% 18%	6314
	21st to end	Night	7% 10% 4 11% 7% 7% 8% 5% 6% 8% 27%	6996
February	1st to 10th	Night	15% 11% 4 12% 8% 7% 6% 5% 5% 6% 20%	2800
	11th to 20th	Night	15% 17% 4 10% 7% 5% 6% 4 6% 5% 22%	2488
	21st to end	Night	11% 14% 4 9% 6% 5% 6% 4 5% 6% 30%	1980
March	1st to 10th	Night	17% 13% 4 10% 8% 6% 5% 4 6% 6% 21%	3846
	11th to 20th	Night	18% 19% 7% 13% 7% 6% 5% 4 4 4 14%	3661
	21st to end	Night	23% 15% 5% 10% 5% 4 3 3 4 5% 23%	3571
April	1st to 10th	Night	23% 17% 5% 10% 5% 4 3 3 4 5% 22%	1900
	11th to 20th	Night	21% 16% 4 8% 4 4 4 3 4 6% 27%	1736
	21st to end	Night	25% 16% 4 6% 4 3 4 3 4 5% 26%	1710
May	1st to 10th	Night	30% 18% 5% 9% 4 3 3 3 4 6% 16%	2589
	11th to 20th	Night	23% 14% 5% 12% 4 4 4 3 5% 5% 21%	2445
	21st to end	Night	29% 12% 3 6% 4 4 4 3 5% 6% 25%	2412
June	1st to 10th	Night	33% 12% 3 8% 6% 4 3 3 5% 6% 17%	1330
	11th to 20th	Night	26% 9% 3 5% 5% 4 4 4 5% 7% 28%	1330
	21st to end	Night	26% 10% 3 8% 4 5% 4 4 4 6% 26%	1330
July	1st to 10th	Night	22% 9% 3 8% 4 4 5% 4 5% 7% 29%	2220
	11th to 20th	Night	16% 10% 3 7% 5% 4 5% 4 6% 7% 32%	2359
	21st to end	Night	16% 7% 3 7% 4 4 4 3 4 6% 42%	2750
August	1st to 10th	Night	14% 8% 3 7% 5% 5% 5% 4 6% 7% 35%	2516
	11th to 20th	Night	18% 8% 2 6% 3 3 4 3 5% 6% 42%	2700
	21st to end	Night	20% 6% 2 5% 3 3 4 3 5% 8% 40%	3211
September	1st to 10th	Night	21% 9% 2 5% 4 4 3 3 5% 6% 39%	1900
	11th to 20th	Night	24% 9% 3 6% 5% 4 4 2 5% 5% 34%	2057
	21st to end	Night	20% 9% 3 6% 4 4 5% 4 6% 7% 33%	2090
October	1st to 10th	Night	21% 10% 3 7% 5% 4 4 3 5% 6% 30%	2122
	11th to 20th	Night	21% 11% 3 7% 4 5% 5% 4 6% 5% 29%	2470
	21st to end	Night	26% 11% 3 6% 4 4 4 3 5% 6% 27%	2717
November	1st to 10th	Night	22% 13% 4 8% 6% 5% 5% 5% 6% 6% 22%	2538
	11th to 20th	Night	25% 13% 5% 8% 6% 5% 4 4 5% 6% 20%	2850
	21st to end	Night	21% 16% 5% 10% 5% 5% 4 4 5% 5% 19%	3000
December	1st to 10th	Night	13% 12% 5% 10% 6% 6% 5% 4 6% 6% 25%	4900
	11th to 20th	Night	24% 12% 5% 10% 5% 4 4 4 4 6% 21%	5581
	21st to end	Night	17% 12% 6% 14% 6% 5% 4 4 6% 6% 20%	7480

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	68% 4 7% 15% 5% 2	3246
	11th to 20th	Day	72% 6% 10% 8% 4	3620
	21st to end	Day	58% 6% 9% 16% 8% 3	3982
February	1st to 10th	Day	64% 6% 10% 11% 7% 1	1600
	11th to 20th	Day	70% 6% 8% 10% 6% 1	1800
	21st to end	Day	62% 6% 6% 14% 11% 1	1650
March	1st to 10th	Day	66% 5% 8% 12% 8% 2	3218
	11th to 20th	Day	77% 5% 4 8% 5%	3326
	21st to end	Day	67% 6% 6% 14% 6% 1	4059
April	1st to 10th	Day	72% 5% 8% 9% 5% 1	2280
	11th to 20th	Day	63% 5% 7% 15% 9% 1	2394
	21st to end	Day	65% 5% 7% 14% 9% 1	2470
May	1st to 10th	Day	73% 5% 9% 9% 4	4374
	11th to 20th	Day	65% 3 13% 13% 6%	4463
	21st to end	Day	66% 5% 8% 15% 7%	5173
June	1st to 10th	Day	70% 5% 8% 12% 5%	2850
	11th to 20th	Day	62% 5% 11% 17% 5%	2850
	21st to end	Day	59% 6% 12% 16% 7% 1	2850
July	1st to 10th	Day	58% 5% 13% 17% 6%	4675
	11th to 20th	Day	51% 7% 14% 21% 6%	4526
	21st to end	Day	45% 6% 17% 26% 5% 1	4662
August	1st to 10th	Day	57% 6% 14% 20% 4	4410
	11th to 20th	Day	48% 4 13% 20% 11% 4	4179
	21st to end	Day	51% 4 13% 25% 6%	4450
September	1st to 10th	Day	50% 6% 11% 23% 9% 1	2280
	11th to 20th	Day	59% 6% 12% 17% 6%	2122
	21st to end	Day	54% 6% 15% 17% 7% 1	2090
October	1st to 10th	Day	57% 6% 12% 16% 7% 1	3407
	11th to 20th	Day	63% 5% 11% 16% 5%	2832
	21st to end	Day	61% 3 12% 14% 9% 1	3092
November	1st to 10th	Day	67% 7% 11% 10% 4 1	1760
	11th to 20th	Day	63% 5% 11% 14% 6% 1	1550
	21st to end	Day	68% 6% 9% 10% 6% 1	1400
December	1st to 10th	Day	57% 5% 12% 19% 7%	2290
	11th to 20th	Day	66% 5% 17% 7% 4	2627
	21st to end	Day	66% 4 10% 16% 4	3498
January	1st to 10th	Night	71% 4 7% 11% 6% 2	6718
	11th to 20th	Night	66% 10% 9% 10% 5%	6360
	21st to end	Night	57% 5% 12% 12% 12% 2	6996
February	1st to 10th	Night	66% 6% 9% 11% 7% 1	2800
	11th to 20th	Night	65% 6% 11% 12% 6%	2492
	21st to end	Night	56% 5% 9% 19% 10% 1	1980
March	1st to 10th	Night	64% 6% 8% 15% 6% 1	3855
	11th to 20th	Night	75% 5% 6% 9% 5% 1	3662
	21st to end	Night	63% 7% 9% 14% 6%	3571
April	1st to 10th	Night	68% 4 5% 13% 9% 1	1900
	11th to 20th	Night	62% 3 8% 17% 8% 1	1736
	21st to end	Night	62% 4 8% 15% 10% 1	1710
May	1st to 10th	Night	73% 3 9% 11% 3 1	2594
	11th to 20th	Night	68% 4 9% 14% 4	2446
	21st to end	Night	62% 5% 10% 17% 5%	2413
June	1st to 10th	Night	69% 5% 11% 10% 5%	1330
	11th to 20th	Night	57% 6% 15% 16% 6%	1330
	21st to end	Night	59% 6% 11% 15% 8% 1	1330
July	1st to 10th	Night	55% 4 15% 21% 4	2186
	11th to 20th	Night	51% 7% 16% 19% 6%	2317
	21st to end	Night	46% 4 16% 29% 5%	2663
August	1st to 10th	Night	47% 7% 19% 23% 4	2505
	11th to 20th	Night	44% 5% 17% 21% 10% 2	2724
	21st to end	Night	43% 5% 18% 28% 5%	3210
September	1st to 10th	Night	48% 5% 13% 25% 9% 1	1900
	11th to 20th	Night	55% 5% 14% 17% 9% 1	2057
	21st to end	Night	51% 6% 15% 20% 7% 1	2090
October	1st to 10th	Night	60% 6% 14% 14% 5%	3551
	11th to 20th	Night	57% 5% 15% 15% 8%	4097
	21st to end	Night	57% 4 13% 17% 8% 1	4467
November	1st to 10th	Night	63% 7% 11% 13% 5%	2538
	11th to 20th	Night	66% 6% 11% 13% 4	2850
	21st to end	Night	68% 6% 9% 11% 6%	3000
December	1st to 10th	Night	57% 5% 8% 19% 10%	4900
	11th to 20th	Night	68% 4 14% 10% 4	5583
	21st to end	Night	68% 5% 9% 15% 2	7480

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% 4 1	400
	11th to 20th	Day	24% 21% 32% 19% 5% 1	400
	21st to end	Day	25% 21% 33% 18% 4	440
February	1st to 10th	Day	25% 23% 33% 14% 6% 1	400
	11th to 20th	Day	28% 23% 35% 12% 1 1	396
	21st to end	Day	22% 21% 34% 15% 5% 2	331
March	1st to 10th	Day	23% 27% 32% 12% 6% 1	400
	11th to 20th	Day	29% 19% 26% 16% 8% 2	373
	21st to end	Day	31% 22% 27% 15% 4 1	475
April	1st to 10th	Day	31% 23% 28% 13% 3 1	460
	11th to 20th	Day	33% 16% 27% 18% 6% 1	592
	21st to end	Day	32% 19% 27% 17% 5% 1	650
May	1st to 10th	Day	41% 14% 19% 17% 6% 2	653
	11th to 20th	Day	31% 14% 25% 19% 8% 3	674
	21st to end	Day	33% 14% 33% 15% 4 1	735
June	1st to 10th	Day	39% 12% 23% 18% 6% 2	680
	11th to 20th	Day	35% 12% 26% 16% 8% 2	680
	21st to end	Day	26% 14% 30% 18% 9% 4	680
July	1st to 10th	Day	28% 13% 30% 20% 6% 3	670
	11th to 20th	Day	20% 12% 32% 26% 10% 1	668
	21st to end	Day	25% 11% 29% 26% 9% 1	740
August	1st to 10th	Day	25% 9% 29% 25% 9% 3	675
	11th to 20th	Day	23% 10% 24% 26% 13% 3	667
	21st to end	Day	23% 10% 29% 24% 11% 3	705
September	1st to 10th	Day	25% 16% 32% 19% 8% 1	490
	11th to 20th	Day	35% 16% 27% 17% 4 1	406
	21st to end	Day	24% 22% 32% 16% 6% 1	390
October	1st to 10th	Day	22% 21% 34% 17% 4 2	390
	11th to 20th	Day	32% 14% 26% 18% 7% 3	390
	21st to end	Day	29% 21% 27% 14% 8% 1	429
November	1st to 10th	Day	35% 23% 26% 11% 5% 1	395
	11th to 20th	Day	34% 19% 25% 16% 5% 1	400
	21st to end	Day	39% 20% 28% 11% 3	400
December	1st to 10th	Day	29% 19% 30% 16% 6% 1	400
	11th to 20th	Day	30% 24% 29% 13% 3	400
	21st to end	Day	26% 21% 28% 16% 7% 2	440
January	1st to 10th	Night	26% 20% 30% 17% 6% 1	900
	11th to 20th	Night	23% 22% 33% 18% 4	900
	21st to end	Night	22% 20% 36% 18% 2	990
February	1st to 10th	Night	24% 21% 33% 18% 4	900
	11th to 20th	Night	27% 22% 33% 15% 2 1	828
	21st to end	Night	20% 14% 37% 20% 7% 2	660
March	1st to 10th	Night	27% 21% 32% 15% 4 1	800
	11th to 20th	Night	22% 18% 30% 24% 6%	675
	21st to end	Night	32% 15% 32% 16% 5% 1	627
April	1st to 10th	Night	32% 20% 28% 16% 4 1	570
	11th to 20th	Night	29% 13% 30% 20% 6% 1	564
	21st to end	Night	34% 12% 30% 19% 4 1	570
May	1st to 10th	Night	35% 10% 23% 22% 9% 1	570
	11th to 20th	Night	34% 9% 29% 18% 10%	562
	21st to end	Night	34% 12% 29% 20% 5%	616
June	1st to 10th	Night	39% 10% 20% 23% 6% 1	570
	11th to 20th	Night	33% 9% 26% 21% 10% 1	570
	21st to end	Night	31% 10% 29% 19% 10% 1	570
July	1st to 10th	Night	26% 10% 31% 24% 8% 1	556
	11th to 20th	Night	21% 9% 33% 30% 8%	552
	21st to end	Night	28% 7% 31% 26% 8%	623
August	1st to 10th	Night	24% 7% 27% 31% 10%	568
	11th to 20th	Night	28% 6% 27% 27% 10%	562
	21st to end	Night	23% 6% 30% 30% 10% 1	627
September	1st to 10th	Night	26% 9% 35% 24% 6%	570
	11th to 20th	Night	31% 13% 28% 24% 5%	570
	21st to end	Night	28% 13% 36% 17% 5% 1	570
October	1st to 10th	Night	30% 11% 35% 18% 5% 1	600
	11th to 20th	Night	28% 13% 29% 21% 8% 1	860
	21st to end	Night	33% 15% 29% 18% 6%	946
November	1st to 10th	Night	30% 19% 30% 16% 4	880
	11th to 20th	Night	32% 17% 30% 15% 5% 1	900
	21st to end	Night	32% 21% 29% 16% 2	900
December	1st to 10th	Night	26% 19% 31% 18% 5%	900
	11th to 20th	Night	31% 20% 31% 15% 3	900
	21st to end	Night	24% 19% 30% 20% 7% 1	990

Page generated at 2025-03-09 09:08:46. Version ac07

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