Springville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Springville clear sky chart from 2005-11-06 to 2026-01-02.

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	5% 4 1 3 2 2 3 2 4 5% 68%	135504
	Night	6% 4 1 3 2 2 3 3 4 5% 66%	133338
Transparency	Day	19% 5% 7% 18% 28% 23%	130577
	Night	21% 5% 8% 20% 26% 20%	129239
Seeing	Day	8% 12% 30% 35% 12% 3	16835
	Night	9% 4 20% 38% 26% 4	26500

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% 8% 3 5% 3 3 4 4 5% 7% 52%	3647
	11th to 20th	Day	5% 5% 1 5% 3 3 3 5% 6% 6% 57%	3892
	21st to end	Day	10% 8% 2 5% 4 4 4 5% 6% 8% 44%	4533
February	1st to 10th	Day	13% 9% 2 5% 3 2 3 4 4 7% 48%	2000
	11th to 20th	Day	11% 10% 2 5% 3 4 4 4 5% 7% 47%	1950
	21st to end	Day	14% 10% 3 7% 4 3 4 2 4 6% 43%	1650
March	1st to 10th	Day	14% 14% 3 8% 5% 4 4 3 4 6% 35%	4518
	11th to 20th	Day	10% 9% 2 6% 4 4 4 4 5% 7% 45%	4766
	21st to end	Day	11% 11% 3 7% 5% 4 4 3 5% 6% 40%	5959
April	1st to 10th	Day	9% 7% 2 5% 4 3 3 2 4 6% 52%	2400
	11th to 20th	Day	9% 7% 2 5% 4 3 3 4 5% 6% 53%	2369
	21st to end	Day	7% 7% 1 5% 3 3 3 3 5% 7% 56%	2400
May	1st to 10th	Day	4 6% 1 3 3 2 3 2 3 4 69%	5646
	11th to 20th	Day	3 3 1 3 2 2 2 2 4 4 73%	5841
	21st to end	Day	3 1 1 2 1 2 2 2 3 4 80%	6612
June	1st to 10th	Day	3 3 1 3 2 3 3 2 5% 6% 69%	2800
	11th to 20th	Day	1 1 1 1 1 1 1 2 2 4 85%	2800
	21st to end	Day	1 1 1 2 1 1 1 1 3 3 85%	2800
July	1st to 10th	Day	1 1 1 1 1 2 2 92%	6319
	11th to 20th	Day	1 1 1 1 1 2 2 2 3 87%	6320
	21st to end	Day	1 1 1 1 1 1 1 2 4 88%	6493
August	1st to 10th	Day	1 1 2 1 1 1 1 2 3 87%	5346
	11th to 20th	Day	1 1 1 1 1 2 93%	5364
	21st to end	Day	1 1 1 1 1 1 2 1 3 3 86%	5984
September	1st to 10th	Day	1 1 1 1 1 2 2 2 5% 84%	2400
	11th to 20th	Day	1 2 1 2 1 2 2 2 2 3 83%	2300
	21st to end	Day	1 1 2 2 1 2 2 3 4 81%	2200
October	1st to 10th	Day	3 2 1 2 2 1 2 2 4 5% 77%	3546
	11th to 20th	Day	2 3 1 3 2 3 2 2 3 3 76%	3261
	21st to end	Day	6% 3 1 4 3 3 3 3 5% 6% 63%	3475
November	1st to 10th	Day	5% 6% 1 4 3 3 3 3 4 6% 62%	1854
	11th to 20th	Day	7% 4 1 3 3 2 3 3 6% 6% 60%	1890
	21st to end	Day	8% 6% 1 4 4 3 4 3 5% 7% 56%	1890
December	1st to 10th	Day	6% 3 1 4 3 3 3 3 6% 6% 63%	3040
	11th to 20th	Day	13% 7% 2 4 3 3 4 5% 6% 8% 46%	3147
	21st to end	Day	13% 7% 2 6% 4 4 7% 5% 7% 9% 37%	4092
January	1st to 10th	Night	9% 7% 3 4 3 2 3 4 5% 7% 51%	6320
	11th to 20th	Night	8% 6% 2 4 2 3 3 3 4 7% 58%	6077
	21st to end	Night	12% 7% 2 5% 3 3 4 4 5% 7% 47%	6443
February	1st to 10th	Night	13% 10% 2 5% 4 3 3 3 4 6% 47%	2400
	11th to 20th	Night	12% 8% 2 4 3 2 3 3 4 7% 52%	2338
	21st to end	Night	12% 10% 2 5% 3 3 3 2 4 7% 49%	1980
March	1st to 10th	Night	13% 13% 3 5% 4 4 4 4 5% 6% 39%	5376
	11th to 20th	Night	9% 8% 2 5% 3 4 4 3 5% 6% 50%	5230
	21st to end	Night	11% 10% 3 6% 4 4 5% 3 4 7% 44%	5016
April	1st to 10th	Night	9% 6% 2 4 3 3 3 3 4 6% 57%	2000
	11th to 20th	Night	9% 4 1 4 3 2 4 3 4 6% 61%	1979
	21st to end	Night	7% 5% 1 3 2 2 2 2 4 7% 65%	2000
May	1st to 10th	Night	6% 4 1 3 2 2 2 1 3 4 71%	4340
	11th to 20th	Night	4 2 2 2 1 2 2 3 5% 78%	4074
	21st to end	Night	2 1 2 1 1 1 1 2 2 86%	4258
June	1st to 10th	Night	4 2 1 2 2 1 2 2 4 6% 74%	1600
	11th to 20th	Night	1 1 1 2 2 1 1 2 2 3 84%	1600
	21st to end	Night	1 1 1 1 1 1 2 3 89%	1600
July	1st to 10th	Night	1 1 1 2 94%	3640
	11th to 20th	Night	1 1 1 1 1 1 1 2 2 89%	3640
	21st to end	Night	1 1 1 1 1 1 1 2 3 88%	4367
August	1st to 10th	Night	1 1 1 1 1 1 1 3 3 86%	4486
	11th to 20th	Night	1 1 1 2 95%	4506
	21st to end	Night	1 1 1 2 2 2 3 87%	5015
September	1st to 10th	Night	1 1 1 1 1 1 1 1 2 90%	2000
	11th to 20th	Night	1 2 1 1 2 2 2 3 3 84%	2100
	21st to end	Night	1 1 2 1 2 2 2 3 3 83%	2200
October	1st to 10th	Night	2 2 1 2 2 2 2 2 2 83%	3651
	11th to 20th	Night	2 1 1 2 1 2 3 2 3 4 78%	3897
	21st to end	Night	4 3 1 3 2 2 3 2 3 4 74%	4331
November	1st to 10th	Night	6% 5% 1 4 2 2 3 3 4 5% 65%	2665
	11th to 20th	Night	6% 5% 1 5% 3 3 2 3 5% 7% 60%	2730
	21st to end	Night	8% 5% 2 4 3 3 4 4 5% 6% 56%	2730
December	1st to 10th	Night	5% 3 1 4 3 3 3 3 5% 6% 63%	4370
	11th to 20th	Night	11% 6% 2 5% 4 4 4 4 7% 9% 44%	5273
	21st to end	Night	8% 7% 3 7% 5% 6% 9% 5% 7% 9% 35%	7106

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% 6% 19% 25% 20% 2	3647
	11th to 20th	Day	24% 7% 10% 19% 22% 19%	3892
	21st to end	Day	33% 6% 11% 17% 26% 7%	4533
February	1st to 10th	Day	35% 6% 9% 22% 20% 9%	2000
	11th to 20th	Day	34% 7% 10% 19% 22% 8%	1960
	21st to end	Day	42% 6% 9% 23% 16% 4	1650
March	1st to 10th	Day	43% 9% 9% 16% 18% 6%	4518
	11th to 20th	Day	32% 10% 16% 28% 9% 5%	4766
	21st to end	Day	37% 11% 14% 22% 14% 2	5959
April	1st to 10th	Day	31% 7% 12% 26% 19% 5%	2400
	11th to 20th	Day	29% 6% 12% 25% 22% 6%	2372
	21st to end	Day	26% 7% 9% 35% 21% 2	2400
May	1st to 10th	Day	18% 6% 8% 27% 35% 7%	5646
	11th to 20th	Day	14% 5% 5% 30% 43% 3	5844
	21st to end	Day	9% 3 4 28% 51% 5%	6613
June	1st to 10th	Day	15% 5% 10% 23% 37% 11%	2800
	11th to 20th	Day	6% 3 5% 17% 44% 26%	2800
	21st to end	Day	7% 3 2 9% 39% 40%	2800
July	1st to 10th	Day	3 1 1 5% 19% 71%	6251
	11th to 20th	Day	6% 2 1 6% 23% 62%	6245
	21st to end	Day	5% 2 2 12% 40% 40%	6305
August	1st to 10th	Day	7% 2 2 6% 37% 45%	3890
	11th to 20th	Day	3 1 1 6% 27% 60%	3880
	21st to end	Day	4 1 1 10% 30% 52%	4311
September	1st to 10th	Day	6% 3 3 10% 34% 44%	2400
	11th to 20th	Day	8% 3 3 19% 41% 27%	2300
	21st to end	Day	8% 3 3 20% 37% 28%	2200
October	1st to 10th	Day	11% 3 4 12% 19% 52%	3546
	11th to 20th	Day	14% 3 4 22% 36% 22%	3261
	21st to end	Day	19% 4 4 15% 33% 25%	3475
November	1st to 10th	Day	22% 6% 7% 19% 27% 18%	1854
	11th to 20th	Day	25% 4 9% 23% 26% 13%	1890
	21st to end	Day	29% 5% 7% 18% 25% 16%	1890
December	1st to 10th	Day	22% 4 8% 30% 25% 11%	3040
	11th to 20th	Day	33% 7% 12% 19% 20% 7%	3147
	21st to end	Day	38% 12% 15% 19% 12% 4	4092
January	1st to 10th	Night	30% 5% 18% 22% 22% 3	6320
	11th to 20th	Night	25% 6% 9% 19% 28% 13%	6077
	21st to end	Night	33% 7% 7% 21% 21% 10%	6443
February	1st to 10th	Night	38% 5% 6% 22% 19% 9%	2400
	11th to 20th	Night	30% 6% 10% 22% 24% 9%	2339
	21st to end	Night	36% 5% 11% 25% 18% 4	1980
March	1st to 10th	Night	39% 9% 10% 16% 21% 5%	5376
	11th to 20th	Night	29% 9% 17% 30% 10% 5%	5230
	21st to end	Night	36% 9% 20% 21% 12% 3	5016
April	1st to 10th	Night	28% 7% 13% 29% 17% 6%	2000
	11th to 20th	Night	23% 8% 12% 29% 22% 6%	1979
	21st to end	Night	22% 5% 13% 38% 21% 2	2000
May	1st to 10th	Night	18% 5% 8% 33% 29% 8%	4337
	11th to 20th	Night	10% 4 5% 36% 44% 2	4075
	21st to end	Night	8% 2 4 31% 51% 4	4258
June	1st to 10th	Night	14% 3 10% 24% 39% 10%	1600
	11th to 20th	Night	7% 3 6% 17% 40% 27%	1600
	21st to end	Night	5% 1 3 10% 45% 37%	1600
July	1st to 10th	Night	2 1 1 4 20% 72%	3600
	11th to 20th	Night	5% 1 2 7% 21% 65%	3592
	21st to end	Night	5% 1 2 11% 37% 43%	4244
August	1st to 10th	Night	7% 2 2 8% 36% 45%	3256
	11th to 20th	Night	2 1 1 9% 25% 62%	3256
	21st to end	Night	4 1 1 9% 31% 53%	3608
September	1st to 10th	Night	5% 2 2 11% 32% 48%	2000
	11th to 20th	Night	8% 3 4 17% 43% 25%	2100
	21st to end	Night	8% 2 3 21% 35% 30%	2200
October	1st to 10th	Night	9% 3 4 12% 22% 51%	3651
	11th to 20th	Night	10% 3 4 24% 40% 19%	3897
	21st to end	Night	14% 4 4 18% 36% 25%	4331
November	1st to 10th	Night	21% 5% 8% 20% 27% 19%	2665
	11th to 20th	Night	23% 5% 10% 20% 26% 17%	2730
	21st to end	Night	28% 6% 8% 17% 26% 15%	2730
December	1st to 10th	Night	22% 5% 10% 28% 24% 10%	4370
	11th to 20th	Night	32% 9% 13% 21% 18% 8%	5273
	21st to end	Night	37% 13% 14% 21% 11% 3	7106

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	21% 12% 33% 26% 8%	202
	11th to 20th	Day	13% 10% 33% 29% 12% 3	309
	21st to end	Day	15% 9% 32% 30% 12% 2	445
February	1st to 10th	Day	17% 13% 33% 25% 10% 2	500
	11th to 20th	Day	17% 15% 37% 24% 6% 2	495
	21st to end	Day	15% 17% 38% 24% 6%	414
March	1st to 10th	Day	19% 19% 35% 21% 5% 1	500
	11th to 20th	Day	16% 20% 33% 24% 6% 1	500
	21st to end	Day	18% 25% 33% 21% 5%	550
April	1st to 10th	Day	14% 19% 31% 27% 8% 2	500
	11th to 20th	Day	15% 22% 31% 25% 6% 1	492
	21st to end	Day	9% 19% 32% 29% 9% 2	500
May	1st to 10th	Day	9% 22% 32% 25% 10% 1	503
	11th to 20th	Day	9% 13% 34% 33% 9% 2	528
	21st to end	Day	9% 15% 31% 32% 9% 3	573
June	1st to 10th	Day	3 10% 30% 40% 12% 5%	530
	11th to 20th	Day	1 13% 32% 38% 13% 4	530
	21st to end	Day	1 9% 31% 39% 15% 4	530
July	1st to 10th	Day	1 3 26% 49% 16% 5%	526
	11th to 20th	Day	1 1 14% 56% 20% 7%	524
	21st to end	Day	2 1 16% 57% 18% 6%	575
August	1st to 10th	Day	3 5% 31% 42% 13% 6%	527
	11th to 20th	Day	1 3 28% 48% 15% 6%	517
	21st to end	Day	2 2 27% 48% 15% 5%	583
September	1st to 10th	Day	2 4 29% 45% 15% 4	530
	11th to 20th	Day	3 10% 33% 43% 10% 2	530
	21st to end	Day	2 12% 32% 39% 14% 1	530
October	1st to 10th	Day	4 13% 30% 40% 13% 1	530
	11th to 20th	Day	4 11% 33% 39% 12% 1	530
	21st to end	Day	5% 12% 29% 38% 15% 1	536
November	1st to 10th	Day	6% 13% 28% 32% 18% 2	330
	11th to 20th	Day	11% 10% 33% 28% 15% 3	330
	21st to end	Day	13% 11% 30% 32% 12% 2	330
December	1st to 10th	Day	11% 9% 32% 35% 11% 2	330
	11th to 20th	Day	13% 8% 29% 32% 17% 2	234
	21st to end	Day	24% 12% 31% 23% 9% 1	242
January	1st to 10th	Night	16% 6% 27% 31% 16% 4	804
	11th to 20th	Night	10% 5% 31% 38% 15% 2	800
	21st to end	Night	16% 4 28% 34% 15% 2	880
February	1st to 10th	Night	18% 5% 25% 36% 15% 2	800
	11th to 20th	Night	17% 5% 25% 33% 17% 4	784
	21st to end	Night	17% 6% 25% 37% 13% 2	660
March	1st to 10th	Night	16% 8% 25% 35% 15% 2	800
	11th to 20th	Night	13% 7% 25% 31% 20% 4	800
	21st to end	Night	16% 8% 23% 36% 18% 1	880
April	1st to 10th	Night	12% 5% 24% 39% 18% 2	800
	11th to 20th	Night	10% 7% 24% 34% 23% 2	791
	21st to end	Night	9% 6% 23% 36% 23% 3	800
May	1st to 10th	Night	8% 4 25% 38% 25% 1	710
	11th to 20th	Night	7% 4 20% 40% 26% 2	591
	21st to end	Night	8% 6% 20% 40% 24% 2	564
June	1st to 10th	Night	6% 2 13% 46% 33% 1	400
	11th to 20th	Night	1 1 17% 47% 30% 4	400
	21st to end	Night	1 1 15% 42% 37% 5%	400
July	1st to 10th	Night	1 6% 38% 48% 6%	390
	11th to 20th	Night	1 2 35% 53% 9%	388
	21st to end	Night	1 1 6% 33% 47% 12%	606
August	1st to 10th	Night	2 1 8% 44% 40% 6%	796
	11th to 20th	Night	1 6% 39% 44% 10%	792
	21st to end	Night	1 6% 32% 52% 9%	880
September	1st to 10th	Night	1 1 6% 39% 43% 10%	800
	11th to 20th	Night	2 1 13% 45% 33% 7%	800
	21st to end	Night	2 1 15% 40% 37% 6%	800
October	1st to 10th	Night	4 1 16% 50% 26% 4	800
	11th to 20th	Night	4 2 18% 41% 29% 5%	800
	21st to end	Night	4 2 19% 38% 31% 6%	880
November	1st to 10th	Night	8% 4 17% 39% 27% 5%	820
	11th to 20th	Night	9% 4 22% 39% 22% 3	840
	21st to end	Night	10% 3 25% 40% 19% 4	840
December	1st to 10th	Night	10% 4 27% 37% 19% 3	840
	11th to 20th	Night	16% 4 24% 39% 15% 2	840
	21st to end	Night	17% 6% 28% 35% 11% 2	924

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