Ogden
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ogden clear sky chart from 2005-11-06 to 2025-11-03.

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% 8% 2 5% 3 3 4 3 5% 6% 53%	135684
	Night	9% 9% 3 6% 4 3 4 3 5% 6% 50%	131801
Transparency	Day	31% 6% 10% 19% 20% 14%	130405
	Night	34% 6% 11% 20% 18% 11%	128083
Seeing	Day	10% 8% 24% 34% 20% 3	16488
	Night	13% 4 20% 40% 21% 2	26470

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	12% 21% 4 8% 4 4 4 3 5% 6% 29%	4098
	11th to 20th	Day	9% 16% 4 10% 6% 6% 5% 3 4 4 32%	4100
	21st to end	Day	8% 15% 5% 8% 4 3 3 3 7% 7% 37%	4510
February	1st to 10th	Day	16% 16% 3 8% 4 4 4 4 5% 6% 30%	1800
	11th to 20th	Day	13% 16% 4 8% 6% 4 4 4 5% 6% 30%	1820
	21st to end	Day	10% 16% 6% 9% 6% 4 3 3 5% 6% 31%	1650
March	1st to 10th	Day	7% 19% 5% 10% 4 4 4 3 4 5% 36%	4799
	11th to 20th	Day	7% 13% 3 6% 5% 4 4 4 5% 6% 42%	5000
	21st to end	Day	13% 16% 5% 10% 5% 4 4 3 5% 5% 29%	5486
April	1st to 10th	Day	14% 10% 3 6% 5% 4 4 5% 6% 6% 39%	2220
	11th to 20th	Day	11% 10% 2 6% 4 5% 5% 4 5% 7% 41%	2547
	21st to end	Day	10% 9% 3 6% 4 4 4 3 6% 7% 44%	2600
May	1st to 10th	Day	7% 8% 2 6% 4 4 5% 4 5% 6% 48%	5880
	11th to 20th	Day	9% 6% 2 5% 4 3 5% 4 6% 8% 48%	5841
	21st to end	Day	6% 4 1 5% 3 3 4 3 5% 7% 59%	6423
June	1st to 10th	Day	5% 4 1 4 3 3 3 4 6% 8% 57%	2745
	11th to 20th	Day	6% 4 2 4 3 3 3 3 5% 8% 60%	2814
	21st to end	Day	3 2 1 3 2 2 2 2 4 5% 72%	2892
July	1st to 10th	Day	2 2 1 3 2 2 2 2 4 5% 75%	6109
	11th to 20th	Day	2 3 1 3 2 2 3 3 5% 6% 71%	5880
	21st to end	Day	2 2 1 2 2 2 2 3 5% 6% 72%	6401
August	1st to 10th	Day	3 2 1 3 3 2 2 2 3 5% 73%	5779
	11th to 20th	Day	2 2 1 3 2 2 3 3 4 5% 72%	5798
	21st to end	Day	4 3 1 4 3 3 4 4 6% 7% 62%	6451
September	1st to 10th	Day	3 2 1 3 3 2 3 3 4 5% 71%	2257
	11th to 20th	Day	4 3 1 4 3 3 4 3 4 5% 66%	2200
	21st to end	Day	6% 3 1 3 2 3 3 2 4 5% 68%	2200
October	1st to 10th	Day	7% 3 1 3 3 3 3 3 3 5% 66%	3440
	11th to 20th	Day	8% 5% 2 4 3 3 3 3 5% 6% 57%	3250
	21st to end	Day	7% 7% 2 6% 3 3 3 3 4 6% 57%	3491
November	1st to 10th	Day	12% 10% 2 6% 4 3 4 4 5% 6% 45%	1782
	11th to 20th	Day	15% 9% 2 5% 3 3 4 2 5% 9% 44%	1800
	21st to end	Day	11% 12% 3 5% 4 4 3 3 6% 6% 43%	1626
December	1st to 10th	Day	7% 8% 2 6% 3 3 3 2 4 6% 55%	2620
	11th to 20th	Day	12% 14% 4 8% 4 4 4 4 5% 9% 31%	3026
	21st to end	Day	16% 15% 4 7% 5% 5% 5% 4 6% 6% 27%	4349
January	1st to 10th	Night	11% 17% 4 8% 5% 3 3 3 4 6% 36%	5867
	11th to 20th	Night	13% 14% 6% 9% 5% 4 4 3 5% 5% 34%	5880
	21st to end	Night	10% 14% 3 7% 3 3 3 3 6% 6% 41%	6468
February	1st to 10th	Night	15% 15% 3 7% 5% 4 4 4 5% 6% 33%	2600
	11th to 20th	Night	13% 13% 3 8% 4 4 3 3 5% 6% 40%	2462
	21st to end	Night	9% 15% 4 9% 6% 4 3 4 5% 5% 37%	1980
March	1st to 10th	Night	13% 16% 3 7% 4 4 4 4 4 5% 36%	5081
	11th to 20th	Night	8% 12% 3 7% 4 4 4 5% 6% 7% 40%	5000
	21st to end	Night	12% 14% 3 7% 5% 4 5% 3 5% 6% 38%	5489
April	1st to 10th	Night	13% 11% 3 6% 4 3 4 3 4 4 45%	2180
	11th to 20th	Night	10% 9% 4 6% 5% 4 3 3 5% 5% 45%	1796
	21st to end	Night	11% 8% 2 7% 4 4 3 3 5% 6% 47%	1800
May	1st to 10th	Night	9% 8% 2 5% 4 4 3 3 5% 6% 51%	4100
	11th to 20th	Night	8% 5% 2 4 3 3 4 4 5% 7% 54%	4074
	21st to end	Night	8% 4 2 6% 3 3 4 3 5% 7% 54%	4474
June	1st to 10th	Night	5% 4 2 5% 3 3 4 4 7% 7% 56%	1645
	11th to 20th	Night	6% 3 1 4 3 2 3 3 4 7% 63%	1573
	21st to end	Night	3 2 1 4 2 3 3 3 4 6% 69%	1498
July	1st to 10th	Night	2 3 1 4 3 3 3 3 4 5% 70%	3824
	11th to 20th	Night	2 3 2 5% 3 4 4 4 5% 7% 60%	4100
	21st to end	Night	2 3 2 4 3 3 4 4 6% 7% 63%	4472
August	1st to 10th	Night	3 2 1 3 3 4 4 4 5% 7% 64%	4033
	11th to 20th	Night	2 4 1 5% 3 4 4 3 5% 6% 62%	4051
	21st to end	Night	3 3 2 6% 4 4 4 4 5% 5% 60%	4526
September	1st to 10th	Night	4 3 1 3 3 3 3 3 5% 5% 67%	2140
	11th to 20th	Night	6% 3 1 3 3 3 3 3 4 5% 64%	2200
	21st to end	Night	6% 3 1 4 2 2 3 3 3 4 69%	2200
October	1st to 10th	Night	6% 3 1 3 2 2 3 2 3 4 70%	3754
	11th to 20th	Night	10% 6% 2 4 2 3 3 3 4 6% 57%	3898
	21st to end	Night	8% 6% 2 5% 3 3 4 3 4 7% 55%	4304
November	1st to 10th	Night	12% 8% 2 4 4 3 3 3 5% 6% 49%	2561
	11th to 20th	Night	12% 7% 2 7% 4 3 3 3 5% 7% 47%	2600
	21st to end	Night	11% 10% 2 5% 5% 4 4 3 4 6% 46%	2750
December	1st to 10th	Night	8% 7% 2 5% 3 2 3 2 4 6% 57%	4570
	11th to 20th	Night	15% 12% 3 6% 4 3 4 3 5% 6% 40%	5181
	21st to end	Night	15% 13% 3 8% 5% 4 4 3 5% 7% 31%	6670

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	54% 9% 16% 12% 7% 1	4099
	11th to 20th	Day	49% 11% 17% 15% 5% 3	4100
	21st to end	Day	44% 10% 15% 19% 12% 1	4510
February	1st to 10th	Day	55% 8% 15% 14% 8% 1	1800
	11th to 20th	Day	52% 8% 15% 15% 8% 1	1829
	21st to end	Day	51% 8% 13% 16% 10% 1	1650
March	1st to 10th	Day	47% 9% 9% 23% 10% 3	4799
	11th to 20th	Day	38% 8% 11% 31% 11% 1	5000
	21st to end	Day	52% 9% 14% 18% 5% 1	5486
April	1st to 10th	Day	42% 8% 13% 20% 13% 4	2220
	11th to 20th	Day	40% 8% 10% 21% 19% 2	2550
	21st to end	Day	37% 6% 10% 25% 20% 2	2600
May	1st to 10th	Day	31% 7% 11% 23% 24% 4	5880
	11th to 20th	Day	29% 7% 9% 26% 24% 5%	5844
	21st to end	Day	22% 6% 8% 26% 35% 3	6424
June	1st to 10th	Day	23% 5% 10% 23% 31% 8%	2745
	11th to 20th	Day	22% 4 7% 17% 29% 21%	2814
	21st to end	Day	15% 2 4 11% 31% 36%	2892
July	1st to 10th	Day	12% 3 4 8% 17% 57%	6045
	11th to 20th	Day	13% 3 4 8% 27% 45%	5811
	21st to end	Day	12% 3 5% 7% 27% 46%	6217
August	1st to 10th	Day	17% 4 5% 13% 29% 31%	4208
	11th to 20th	Day	16% 4 5% 12% 35% 27%	4197
	21st to end	Day	13% 4 5% 15% 32% 31%	4646
September	1st to 10th	Day	16% 4 6% 15% 31% 28%	2257
	11th to 20th	Day	20% 5% 7% 18% 33% 18%	2200
	21st to end	Day	18% 4 8% 21% 37% 12%	2200
October	1st to 10th	Day	21% 4 6% 15% 33% 21%	3440
	11th to 20th	Day	26% 5% 8% 29% 25% 7%	3250
	21st to end	Day	28% 5% 11% 35% 19% 2	3491
November	1st to 10th	Day	38% 7% 14% 22% 17% 1	1782
	11th to 20th	Day	38% 6% 18% 25% 12%	1800
	21st to end	Day	41% 7% 18% 22% 12% 1	1626
December	1st to 10th	Day	30% 7% 21% 33% 8% 1	2620
	11th to 20th	Day	49% 7% 21% 19% 3	3024
	21st to end	Day	55% 9% 14% 15% 7%	4349
January	1st to 10th	Night	48% 10% 17% 16% 9%	5867
	11th to 20th	Night	49% 10% 15% 21% 5% 1	5880
	21st to end	Night	42% 9% 15% 22% 11% 1	6468
February	1st to 10th	Night	51% 8% 15% 18% 7% 1	2600
	11th to 20th	Night	46% 6% 13% 21% 14% 1	2463
	21st to end	Night	47% 7% 12% 22% 10% 2	1980
March	1st to 10th	Night	46% 6% 9% 21% 14% 3	5081
	11th to 20th	Night	39% 7% 11% 26% 16% 1	5000
	21st to end	Night	44% 8% 16% 22% 9% 1	5489
April	1st to 10th	Night	41% 4 13% 21% 15% 6%	2180
	11th to 20th	Night	38% 7% 9% 23% 21% 2	1796
	21st to end	Night	37% 6% 11% 24% 20% 2	1800
May	1st to 10th	Night	31% 6% 12% 19% 27% 5%	4097
	11th to 20th	Night	25% 7% 8% 27% 27% 5%	4075
	21st to end	Night	27% 5% 8% 19% 37% 3	4474
June	1st to 10th	Night	24% 6% 10% 20% 31% 9%	1645
	11th to 20th	Night	21% 4 8% 18% 29% 21%	1573
	21st to end	Night	16% 2 6% 11% 27% 38%	1498
July	1st to 10th	Night	17% 3 4 6% 13% 56%	3780
	11th to 20th	Night	21% 4 4 7% 20% 44%	4046
	21st to end	Night	18% 4 6% 7% 22% 42%	4344
August	1st to 10th	Night	21% 4 6% 10% 26% 32%	2928
	11th to 20th	Night	23% 5% 6% 11% 25% 30%	2928
	21st to end	Night	16% 4 6% 10% 24% 40%	3262
September	1st to 10th	Night	19% 3 7% 13% 25% 33%	2140
	11th to 20th	Night	22% 4 6% 15% 31% 23%	2200
	21st to end	Night	20% 3 6% 17% 34% 21%	2200
October	1st to 10th	Night	19% 4 5% 13% 35% 24%	3754
	11th to 20th	Night	29% 3 5% 27% 27% 9%	3898
	21st to end	Night	29% 4 8% 34% 22% 3	4304
November	1st to 10th	Night	35% 4 11% 26% 19% 4	2561
	11th to 20th	Night	37% 4 15% 28% 15% 1	2600
	21st to end	Night	39% 5% 14% 27% 13% 2	2750
December	1st to 10th	Night	30% 5% 17% 38% 9% 1	4570
	11th to 20th	Night	45% 6% 24% 20% 5%	5182
	21st to end	Night	52% 7% 17% 16% 7%	6670

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	20% 12% 26% 28% 12% 4	300
	11th to 20th	Day	18% 10% 21% 32% 16% 2	300
	21st to end	Day	18% 6% 27% 33% 13% 2	330
February	1st to 10th	Day	24% 11% 29% 25% 9% 1	300
	11th to 20th	Day	18% 12% 35% 26% 9% 1	365
	21st to end	Day	13% 12% 36% 28% 10% 1	414
March	1st to 10th	Day	16% 12% 32% 29% 10% 1	500
	11th to 20th	Day	12% 11% 30% 32% 14%	500
	21st to end	Day	19% 14% 32% 26% 9%	550
April	1st to 10th	Day	14% 13% 29% 28% 15% 1	500
	11th to 20th	Day	13% 18% 31% 27% 10% 1	492
	21st to end	Day	13% 13% 31% 25% 17% 2	500
May	1st to 10th	Day	10% 14% 30% 31% 14% 1	503
	11th to 20th	Day	11% 13% 24% 30% 19% 3	528
	21st to end	Day	8% 10% 22% 33% 23% 4	573
June	1st to 10th	Day	4 6% 22% 37% 26% 4	675
	11th to 20th	Day	7% 8% 24% 39% 20% 2	730
	21st to end	Day	4 6% 24% 41% 21% 4	622
July	1st to 10th	Day	1 3 22% 46% 26% 2	526
	11th to 20th	Day	3 3 17% 47% 27% 4	524
	21st to end	Day	4 2 14% 47% 29% 4	575
August	1st to 10th	Day	4 4 18% 46% 24% 4	527
	11th to 20th	Day	3 4 17% 42% 30% 4	517
	21st to end	Day	6% 3 17% 38% 31% 5%	583
September	1st to 10th	Day	3 5% 17% 34% 34% 7%	530
	11th to 20th	Day	6% 5% 25% 32% 26% 6%	530
	21st to end	Day	6% 5% 20% 31% 33% 4	530
October	1st to 10th	Day	11% 7% 23% 29% 26% 5%	435
	11th to 20th	Day	9% 8% 27% 27% 22% 7%	330
	21st to end	Day	7% 12% 21% 37% 21% 1	363
November	1st to 10th	Day	18% 7% 24% 29% 16% 5%	306
	11th to 20th	Day	14% 10% 20% 38% 14% 4	300
	21st to end	Day	16% 6% 22% 30% 21% 5%	300
December	1st to 10th	Day	14% 7% 21% 36% 15% 6%	300
	11th to 20th	Day	18% 7% 25% 38% 9% 1	300
	21st to end	Day	23% 11% 22% 32% 10% 2	330
January	1st to 10th	Night	21% 4 21% 35% 18% 2	800
	11th to 20th	Night	20% 4 18% 39% 16% 3	800
	21st to end	Night	20% 4 21% 38% 13% 3	880
February	1st to 10th	Night	22% 5% 25% 36% 11% 1	800
	11th to 20th	Night	18% 4 26% 39% 13% 1	784
	21st to end	Night	15% 6% 28% 38% 12% 1	660
March	1st to 10th	Night	19% 7% 22% 39% 12% 2	800
	11th to 20th	Night	14% 5% 23% 42% 16% 1	800
	21st to end	Night	20% 6% 23% 38% 12% 1	880
April	1st to 10th	Night	18% 7% 23% 39% 13% 1	780
	11th to 20th	Night	12% 9% 30% 35% 15%	593
	21st to end	Night	13% 6% 24% 37% 20% 1	600
May	1st to 10th	Night	12% 6% 25% 39% 19% 1	600
	11th to 20th	Night	11% 4 22% 34% 27% 2	591
	21st to end	Night	12% 5% 17% 37% 27% 2	650
June	1st to 10th	Night	6% 6% 19% 40% 29% 1	600
	11th to 20th	Night	8% 6% 21% 43% 22%	573
	21st to end	Night	4 3 21% 40% 30% 3	400
July	1st to 10th	Night	4 2 15% 46% 31% 2	466
	11th to 20th	Night	5% 1 14% 51% 29% 1	582
	21st to end	Night	4 1 10% 46% 38% 1	657
August	1st to 10th	Night	5% 2 13% 49% 30% 1	597
	11th to 20th	Night	3 1 14% 46% 35% 1	594
	21st to end	Night	5% 3 13% 41% 35% 2	660
September	1st to 10th	Night	4 3 16% 41% 34% 2	740
	11th to 20th	Night	7% 3 16% 42% 29% 3	800
	21st to end	Night	8% 3 18% 35% 30% 6%	800
October	1st to 10th	Night	10% 5% 18% 42% 24% 1	800
	11th to 20th	Night	14% 5% 17% 37% 26% 2	800
	21st to end	Night	10% 4 23% 39% 22% 2	880
November	1st to 10th	Night	15% 4 18% 41% 19% 2	788
	11th to 20th	Night	14% 4 22% 43% 15% 2	800
	21st to end	Night	15% 4 22% 36% 19% 3	950
December	1st to 10th	Night	17% 4 23% 39% 15% 1	1000
	11th to 20th	Night	22% 5% 21% 39% 13% 1	1000
	21st to end	Night	25% 7% 23% 35% 9% 1	965

Page generated at 2025-10-31 00:02:38. Version ac07

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