West Jordan
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the West Jordan clear sky chart from 2005-11-06 to 2025-10-04.

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% 7% 2 6% 4 4 4 4 5% 6% 54%	134823
	Night	6% 8% 3 6% 4 4 4 3 5% 7% 52%	132019
Transparency	Day	28% 7% 10% 19% 20% 14%	129557
	Night	30% 7% 12% 20% 19% 11%	128288
Seeing	Day	10% 18% 33% 28% 9% 2	16058
	Night	10% 10% 25% 34% 18% 3	26582

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	7% 16% 5% 12% 5% 5% 5% 4 6% 8% 29%	4098
	11th to 20th	Day	6% 17% 5% 13% 6% 5% 5% 3 5% 6% 30%	4100
	21st to end	Day	6% 11% 4 8% 4 4 4 3 4 5% 46%	4510
February	1st to 10th	Day	9% 14% 4 9% 6% 5% 4 4 5% 5% 35%	1800
	11th to 20th	Day	8% 14% 4 10% 5% 4 5% 4 5% 7% 34%	1834
	21st to end	Day	5% 14% 6% 10% 6% 4 5% 4 5% 7% 35%	1650
March	1st to 10th	Day	3 14% 5% 12% 5% 5% 4 3 5% 6% 38%	4819
	11th to 20th	Day	4 11% 3 7% 5% 5% 6% 4 6% 7% 42%	5000
	21st to end	Day	6% 13% 4 11% 7% 6% 6% 5% 6% 6% 31%	5486
April	1st to 10th	Day	9% 8% 4 6% 5% 4 4 5% 6% 8% 43%	2213
	11th to 20th	Day	8% 10% 3 7% 4 4 4 5% 6% 6% 43%	2533
	21st to end	Day	8% 8% 2 6% 4 4 4 4 6% 8% 47%	2600
May	1st to 10th	Day	7% 7% 2 5% 3 4 4 4 6% 8% 50%	5880
	11th to 20th	Day	6% 4 2 5% 4 4 4 4 6% 8% 51%	5841
	21st to end	Day	4 4 2 4 3 4 4 4 6% 7% 58%	6423
June	1st to 10th	Day	3 4 1 4 3 4 4 4 6% 9% 57%	2600
	11th to 20th	Day	4 3 1 4 3 3 3 3 5% 6% 65%	2680
	21st to end	Day	2 1 1 2 3 2 3 3 4 5% 73%	2600
July	1st to 10th	Day	1 1 1 3 2 3 3 3 4 5% 75%	5879
	11th to 20th	Day	2 2 1 3 3 3 5% 4 7% 8% 63%	5880
	21st to end	Day	1 2 1 3 2 3 3 3 5% 6% 71%	6401
August	1st to 10th	Day	1 1 1 3 2 3 4 3 5% 6% 72%	5779
	11th to 20th	Day	1 1 1 3 3 3 4 3 5% 6% 70%	5798
	21st to end	Day	2 3 1 4 4 4 4 4 6% 7% 62%	6429
September	1st to 10th	Day	3 2 3 2 2 3 3 6% 6% 70%	2249
	11th to 20th	Day	4 2 1 3 3 4 4 3 5% 6% 65%	2200
	21st to end	Day	6% 3 1 2 2 2 2 2 4 6% 70%	2200
October	1st to 10th	Day	4 3 1 4 2 2 3 2 3 4 70%	3373
	11th to 20th	Day	7% 5% 1 4 3 2 3 2 4 7% 62%	3150
	21st to end	Day	7% 7% 2 4 2 3 3 3 4 5% 60%	3415
November	1st to 10th	Day	8% 8% 2 6% 4 4 5% 3 5% 7% 49%	1764
	11th to 20th	Day	11% 8% 3 5% 5% 4 3 4 5% 7% 47%	1800
	21st to end	Day	7% 11% 3 7% 5% 4 3 3 5% 6% 46%	1683
December	1st to 10th	Day	5% 7% 2 6% 2 3 3 3 6% 7% 56%	2620
	11th to 20th	Day	7% 9% 4 9% 5% 4 5% 5% 7% 8% 38%	3026
	21st to end	Day	7% 14% 6% 12% 5% 4 4 4 5% 7% 31%	4510
January	1st to 10th	Night	7% 16% 6% 11% 5% 4 4 3 5% 7% 34%	5867
	11th to 20th	Night	10% 17% 5% 10% 5% 5% 5% 4 5% 6% 29%	5880
	21st to end	Night	5% 11% 3 7% 4 4 5% 3 5% 6% 48%	6468
February	1st to 10th	Night	9% 12% 4 8% 5% 5% 5% 4 5% 7% 36%	2600
	11th to 20th	Night	7% 13% 4 8% 4 5% 4 3 4 7% 40%	2450
	21st to end	Night	6% 13% 4 8% 6% 3 4 3 5% 7% 41%	1980
March	1st to 10th	Night	5% 12% 4 10% 5% 5% 5% 4 6% 6% 38%	5073
	11th to 20th	Night	6% 12% 4 8% 5% 4 5% 4 5% 7% 41%	5000
	21st to end	Night	6% 14% 4 8% 5% 4 4 4 6% 6% 41%	5489
April	1st to 10th	Night	11% 10% 2 5% 4 3 4 3 4 7% 48%	2185
	11th to 20th	Night	6% 7% 2 6% 5% 4 4 5% 5% 7% 48%	1811
	21st to end	Night	9% 7% 2 5% 4 4 5% 4 5% 6% 48%	1800
May	1st to 10th	Night	6% 9% 2 5% 3 3 4 4 6% 7% 51%	4100
	11th to 20th	Night	5% 3 2 4 3 4 3 4 6% 8% 57%	4074
	21st to end	Night	6% 4 1 4 3 3 4 3 5% 7% 59%	4474
June	1st to 10th	Night	5% 4 2 4 4 3 4 4 5% 8% 58%	1796
	11th to 20th	Night	4 3 1 4 2 3 2 3 4 7% 66%	1659
	21st to end	Night	2 3 1 3 3 2 3 3 6% 7% 68%	1800
July	1st to 10th	Night	1 2 1 4 4 4 3 2 4 4 71%	4100
	11th to 20th	Night	2 2 1 5% 4 5% 5% 4 7% 9% 57%	4100
	21st to end	Night	1 2 1 4 3 3 4 3 6% 6% 67%	4472
August	1st to 10th	Night	2 1 1 3 2 3 4 3 5% 8% 69%	4033
	11th to 20th	Night	1 2 1 4 3 4 4 4 4 5% 67%	4051
	21st to end	Night	2 3 1 5% 4 5% 5% 4 6% 6% 59%	4548
September	1st to 10th	Night	3 3 1 4 3 3 3 4 4 6% 68%	2149
	11th to 20th	Night	4 3 1 2 2 3 3 3 5% 6% 67%	2200
	21st to end	Night	5% 3 1 3 2 2 2 2 4 4 71%	2200
October	1st to 10th	Night	4 3 1 3 2 2 3 2 3 5% 72%	3668
	11th to 20th	Night	7% 4 1 4 2 3 3 2 4 6% 63%	3778
	21st to end	Night	7% 6% 2 4 2 2 3 3 5% 7% 58%	4140
November	1st to 10th	Night	7% 9% 2 5% 4 3 4 3 5% 7% 51%	2535
	11th to 20th	Night	9% 7% 2 5% 3 4 3 4 5% 8% 50%	2600
	21st to end	Night	7% 10% 2 5% 4 3 3 4 6% 6% 49%	2692
December	1st to 10th	Night	5% 7% 2 5% 3 3 4 4 10% 9% 49%	4570
	11th to 20th	Night	8% 11% 4 7% 4 4 3 3 5% 8% 45%	5181
	21st to end	Night	8% 13% 5% 10% 5% 5% 4 4 5% 7% 34%	6496

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	50% 9% 16% 16% 8% 1	4099
	11th to 20th	Day	51% 8% 14% 19% 5% 2	4100
	21st to end	Day	38% 8% 15% 24% 14% 1	4510
February	1st to 10th	Day	51% 9% 13% 15% 10% 1	1800
	11th to 20th	Day	48% 10% 14% 17% 11% 1	1843
	21st to end	Day	47% 10% 12% 19% 11% 1	1650
March	1st to 10th	Day	40% 11% 12% 20% 14% 3	4819
	11th to 20th	Day	33% 10% 12% 33% 12% 1	5000
	21st to end	Day	48% 12% 16% 16% 8% 1	5486
April	1st to 10th	Day	39% 10% 13% 19% 15% 5%	2213
	11th to 20th	Day	38% 9% 13% 20% 18% 2	2536
	21st to end	Day	34% 9% 12% 24% 20% 2	2600
May	1st to 10th	Day	30% 9% 11% 22% 23% 6%	5880
	11th to 20th	Day	25% 8% 9% 25% 28% 4	5844
	21st to end	Day	22% 7% 9% 24% 33% 6%	6424
June	1st to 10th	Day	22% 8% 9% 22% 30% 9%	2600
	11th to 20th	Day	20% 5% 7% 17% 30% 21%	2680
	21st to end	Day	13% 4 6% 11% 33% 34%	2600
July	1st to 10th	Day	12% 4 4 6% 15% 59%	5816
	11th to 20th	Day	15% 5% 6% 10% 25% 39%	5811
	21st to end	Day	12% 5% 6% 7% 21% 49%	6217
August	1st to 10th	Day	15% 5% 7% 17% 28% 29%	4208
	11th to 20th	Day	16% 5% 7% 13% 34% 26%	4197
	21st to end	Day	14% 5% 6% 15% 29% 32%	4636
September	1st to 10th	Day	14% 7% 7% 16% 29% 28%	2249
	11th to 20th	Day	18% 8% 8% 17% 28% 21%	2200
	21st to end	Day	17% 5% 7% 21% 33% 17%	2200
October	1st to 10th	Day	19% 5% 5% 14% 37% 21%	3373
	11th to 20th	Day	23% 5% 8% 27% 28% 8%	3150
	21st to end	Day	26% 6% 11% 31% 22% 3	3415
November	1st to 10th	Day	34% 8% 14% 21% 19% 4	1764
	11th to 20th	Day	36% 8% 12% 28% 15% 1	1800
	21st to end	Day	40% 7% 12% 24% 14% 1	1683
December	1st to 10th	Day	27% 7% 22% 35% 8% 1	2620
	11th to 20th	Day	38% 9% 18% 26% 9%	3024
	21st to end	Day	46% 10% 15% 19% 10%	4510
January	1st to 10th	Night	48% 8% 16% 19% 9%	5867
	11th to 20th	Night	51% 10% 14% 19% 5% 1	5880
	21st to end	Night	35% 9% 17% 28% 10% 1	6468
February	1st to 10th	Night	46% 9% 15% 19% 10% 1	2600
	11th to 20th	Night	44% 8% 12% 20% 16% 2	2451
	21st to end	Night	41% 9% 12% 22% 14% 2	1980
March	1st to 10th	Night	41% 10% 9% 23% 15% 2	5073
	11th to 20th	Night	37% 9% 12% 27% 14% 1	5000
	21st to end	Night	37% 12% 17% 22% 12% 1	5489
April	1st to 10th	Night	36% 7% 13% 22% 16% 6%	2185
	11th to 20th	Night	32% 9% 12% 21% 23% 3	1811
	21st to end	Night	35% 8% 13% 22% 21% 2	1800
May	1st to 10th	Night	26% 11% 13% 21% 26% 4	4097
	11th to 20th	Night	20% 7% 9% 27% 31% 6%	4075
	21st to end	Night	21% 6% 9% 23% 37% 3	4474
June	1st to 10th	Night	24% 6% 9% 21% 29% 11%	1796
	11th to 20th	Night	18% 5% 9% 17% 29% 21%	1659
	21st to end	Night	16% 4 6% 9% 29% 37%	1800
July	1st to 10th	Night	16% 3 4 7% 13% 56%	4055
	11th to 20th	Night	19% 5% 6% 9% 22% 39%	4046
	21st to end	Night	16% 5% 6% 9% 22% 43%	4344
August	1st to 10th	Night	15% 5% 8% 14% 27% 30%	2928
	11th to 20th	Night	18% 7% 7% 13% 29% 25%	2928
	21st to end	Night	15% 5% 7% 10% 29% 34%	3272
September	1st to 10th	Night	18% 4 6% 16% 24% 31%	2149
	11th to 20th	Night	19% 5% 8% 18% 28% 24%	2200
	21st to end	Night	18% 5% 5% 16% 33% 23%	2200
October	1st to 10th	Night	16% 4 6% 15% 35% 24%	3668
	11th to 20th	Night	22% 5% 6% 28% 30% 10%	3778
	21st to end	Night	24% 5% 9% 34% 23% 4	4140
November	1st to 10th	Night	32% 6% 11% 24% 21% 5%	2535
	11th to 20th	Night	32% 6% 14% 27% 18% 3	2600
	21st to end	Night	35% 7% 11% 26% 17% 3	2692
December	1st to 10th	Night	26% 9% 25% 30% 9% 2	4570
	11th to 20th	Night	37% 6% 24% 24% 9%	5182
	21st to end	Night	46% 9% 18% 17% 10%	6496

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% 18% 29% 22% 10%	300
	11th to 20th	Day	13% 21% 33% 20% 10% 3	300
	21st to end	Day	11% 20% 33% 25% 8% 2	330
February	1st to 10th	Day	18% 29% 31% 16% 6%	300
	11th to 20th	Day	16% 25% 35% 18% 5% 1	379
	21st to end	Day	13% 28% 36% 17% 4 1	414
March	1st to 10th	Day	15% 25% 36% 18% 4 1	500
	11th to 20th	Day	12% 24% 38% 22% 4	500
	21st to end	Day	17% 28% 35% 18% 3	550
April	1st to 10th	Day	15% 25% 30% 23% 7% 1	500
	11th to 20th	Day	16% 28% 31% 18% 6% 1	492
	21st to end	Day	14% 28% 28% 23% 7% 1	500
May	1st to 10th	Day	12% 25% 34% 18% 9% 1	503
	11th to 20th	Day	10% 24% 32% 24% 9% 1	528
	21st to end	Day	9% 18% 34% 26% 11% 3	573
June	1st to 10th	Day	4 16% 37% 31% 8% 4	530
	11th to 20th	Day	5% 19% 33% 29% 12% 1	610
	21st to end	Day	3 15% 38% 35% 7% 2	530
July	1st to 10th	Day	1 9% 37% 43% 9% 2	526
	11th to 20th	Day	3 8% 39% 35% 12% 3	524
	21st to end	Day	3 3 38% 41% 12% 2	575
August	1st to 10th	Day	4 9% 36% 39% 10% 1	527
	11th to 20th	Day	3 9% 35% 40% 11% 2	517
	21st to end	Day	3 11% 31% 38% 11% 4	583
September	1st to 10th	Day	3 9% 32% 36% 16% 3	530
	11th to 20th	Day	5% 15% 33% 35% 11% 2	530
	21st to end	Day	7% 14% 25% 37% 16% 2	530
October	1st to 10th	Day	6% 21% 28% 27% 15% 2	417
	11th to 20th	Day	11% 17% 27% 29% 16% 1	300
	21st to end	Day	11% 19% 34% 26% 9%	330
November	1st to 10th	Day	16% 21% 26% 27% 9% 2	300
	11th to 20th	Day	12% 20% 33% 22% 9% 3	300
	21st to end	Day	16% 14% 28% 29% 11% 2	300
December	1st to 10th	Day	15% 15% 28% 26% 13% 4	300
	11th to 20th	Day	16% 17% 34% 25% 8% 1	300
	21st to end	Day	21% 22% 27% 25% 4	330
January	1st to 10th	Night	16% 11% 26% 28% 16% 4	800
	11th to 20th	Night	13% 12% 26% 30% 15% 5%	800
	21st to end	Night	14% 11% 23% 33% 15% 4	880
February	1st to 10th	Night	13% 13% 31% 30% 11% 3	800
	11th to 20th	Night	13% 13% 29% 31% 12% 3	784
	21st to end	Night	11% 15% 30% 30% 13% 2	660
March	1st to 10th	Night	13% 15% 30% 29% 10% 4	800
	11th to 20th	Night	10% 13% 27% 31% 16% 3	800
	21st to end	Night	12% 18% 27% 31% 10% 2	880
April	1st to 10th	Night	15% 15% 29% 29% 11% 2	785
	11th to 20th	Night	8% 16% 31% 33% 10% 2	593
	21st to end	Night	11% 12% 27% 33% 15% 3	600
May	1st to 10th	Night	9% 11% 30% 34% 15% 2	600
	11th to 20th	Night	7% 9% 27% 31% 21% 4	591
	21st to end	Night	9% 10% 24% 33% 21% 4	650
June	1st to 10th	Night	5% 11% 23% 39% 21% 2	600
	11th to 20th	Night	4 11% 27% 38% 19% 1	600
	21st to end	Night	3 6% 25% 37% 25% 4	600
July	1st to 10th	Night	2 5% 24% 35% 31% 2	585
	11th to 20th	Night	4 4 21% 45% 24% 3	582
	21st to end	Night	3 3 16% 39% 37% 2	657
August	1st to 10th	Night	4 4 24% 40% 26% 2	597
	11th to 20th	Night	3 3 20% 44% 26% 3	594
	21st to end	Night	3 5% 22% 42% 25% 3	660
September	1st to 10th	Night	5% 5% 18% 41% 27% 5%	749
	11th to 20th	Night	4 7% 19% 40% 23% 6%	800
	21st to end	Night	7% 6% 20% 32% 27% 9%	800
October	1st to 10th	Night	7% 8% 25% 35% 20% 5%	772
	11th to 20th	Night	8% 7% 23% 35% 22% 5%	760
	21st to end	Night	9% 11% 25% 31% 19% 5%	836
November	1st to 10th	Night	13% 10% 23% 29% 20% 4	780
	11th to 20th	Night	10% 11% 31% 29% 14% 5%	800
	21st to end	Night	12% 11% 24% 33% 16% 4	892
December	1st to 10th	Night	14% 11% 25% 32% 16% 2	1000
	11th to 20th	Night	18% 11% 28% 32% 10% 2	1000
	21st to end	Night	22% 13% 25% 31% 8% 1	895

Page generated at 2025-09-30 23:39:02. Version ac07

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