Wheatland
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wheatland clear sky chart from 2005-11-06 to 2025-04-26.

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	6% 6% 2 5% 4 4 4 4 6% 7% 53%	117609
	Night	6% 7% 2 5% 4 3 4 3 5% 7% 54%	119881
Transparency	Day	30% 3 10% 26% 21% 9%	117351
	Night	31% 3 11% 28% 20% 7%	119729
Seeing	Day	11% 11% 28% 29% 17% 5%	16324
	Night	10% 11% 33% 35% 11% 1	26486

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	3 11% 4 10% 5% 4 4 3 4 6% 46%	3638
	11th to 20th	Day	3 12% 3 8% 6% 5% 4 4 6% 7% 42%	3640
	21st to end	Day	2 7% 2 6% 4 4 2 2 4 6% 62%	4372
February	1st to 10th	Day	4 9% 4 7% 6% 3 3 4 6% 8% 45%	1800
	11th to 20th	Day	3 10% 4 8% 5% 5% 4 4 5% 7% 45%	1875
	21st to end	Day	4 7% 3 7% 4 3 4 2 6% 6% 54%	1650
March	1st to 10th	Day	6% 9% 3 6% 3 4 4 3 4 8% 51%	4500
	11th to 20th	Day	6% 7% 3 7% 4 4 4 4 5% 6% 50%	4880
	21st to end	Day	7% 8% 3 6% 5% 5% 5% 4 6% 8% 43%	5837
April	1st to 10th	Day	9% 9% 3 5% 4 4 4 3 6% 7% 47%	2400
	11th to 20th	Day	12% 9% 3 6% 4 5% 5% 5% 6% 7% 38%	2371
	21st to end	Day	11% 7% 2 6% 5% 4 5% 4 5% 7% 43%	2347
May	1st to 10th	Day	17% 8% 2 6% 4 4 4 4 6% 7% 39%	4261
	11th to 20th	Day	12% 4 2 5% 4 5% 6% 4 8% 8% 42%	4388
	21st to end	Day	9% 5% 2 4 4 4 5% 5% 7% 8% 47%	4825
June	1st to 10th	Day	5% 3 1 4 4 4 5% 6% 8% 11% 49%	2660
	11th to 20th	Day	7% 3 1 4 3 4 5% 4 6% 9% 52%	2660
	21st to end	Day	4 2 1 4 3 4 5% 4 7% 8% 57%	2660
July	1st to 10th	Day	4 2 1 3 3 3 4 4 7% 7% 60%	4430
	11th to 20th	Day	2 2 1 3 4 4 5% 5% 9% 10% 55%	4430
	21st to end	Day	3 2 1 4 3 4 4 4 7% 8% 59%	4802
August	1st to 10th	Day	7% 3 1 4 4 4 5% 5% 7% 9% 51%	4202
	11th to 20th	Day	3 2 1 5% 4 4 6% 4 6% 7% 56%	3815
	21st to end	Day	3 3 1 4 4 4 4 4 6% 6% 62%	4180
September	1st to 10th	Day	6% 3 1 3 3 3 4 3 5% 6% 63%	2280
	11th to 20th	Day	7% 3 1 3 3 3 3 3 5% 7% 64%	2257
	21st to end	Day	6% 3 2 3 3 3 2 3 4 7% 65%	2090
October	1st to 10th	Day	5% 3 1 3 2 2 2 2 3 4 75%	3179
	11th to 20th	Day	10% 4 2 4 3 3 3 3 3 5% 60%	3150
	21st to end	Day	8% 7% 2 4 2 3 3 3 4 6% 58%	3222
November	1st to 10th	Day	4 6% 2 5% 4 3 3 4 6% 8% 56%	1763
	11th to 20th	Day	4 5% 2 4 3 3 3 3 6% 8% 61%	1795
	21st to end	Day	3 8% 3 6% 3 3 3 3 7% 7% 54%	1600
December	1st to 10th	Day	2 6% 3 4 3 3 3 3 4 6% 63%	2620
	11th to 20th	Day	3 7% 3 6% 3 3 3 3 5% 8% 57%	3026
	21st to end	Day	6% 9% 3 8% 5% 3 4 3 5% 7% 48%	4004
January	1st to 10th	Night	4 11% 4 8% 4 4 4 3 5% 6% 47%	6327
	11th to 20th	Night	2 10% 5% 8% 5% 5% 4 4 5% 6% 47%	6340
	21st to end	Night	2 6% 3 8% 4 3 3 3 4 5% 58%	6635
February	1st to 10th	Night	4 9% 3 8% 4 4 5% 4 6% 8% 46%	2600
	11th to 20th	Night	4 11% 4 7% 5% 4 5% 3 6% 6% 46%	2410
	21st to end	Night	2 8% 3 7% 4 3 4 3 5% 7% 53%	1980
March	1st to 10th	Night	7% 10% 2 4 2 3 3 3 4 8% 54%	5374
	11th to 20th	Night	6% 9% 3 6% 3 3 3 3 5% 7% 52%	5098
	21st to end	Night	11% 12% 3 7% 4 4 4 4 5% 6% 41%	5122
April	1st to 10th	Night	10% 7% 3 5% 3 4 4 4 5% 7% 49%	2000
	11th to 20th	Night	12% 7% 2 6% 5% 3 5% 4 5% 6% 46%	1977
	21st to end	Night	14% 8% 2 6% 4 3 4 3 5% 7% 45%	1946
May	1st to 10th	Night	14% 9% 2 7% 3 4 3 3 5% 6% 45%	2706
	11th to 20th	Night	11% 4 1 5% 3 3 4 3 6% 7% 52%	2517
	21st to end	Night	11% 4 1 4 4 4 4 4 7% 8% 49%	2762
June	1st to 10th	Night	5% 4 1 4 4 3 4 4 7% 9% 55%	1520
	11th to 20th	Night	8% 3 1 3 3 3 4 4 6% 9% 56%	1520
	21st to end	Night	3 2 1 4 3 3 4 4 5% 8% 63%	1520
July	1st to 10th	Night	6% 2 1 4 3 4 5% 5% 7% 7% 56%	2540
	11th to 20th	Night	3 2 1 3 3 4 5% 6% 6% 9% 59%	2540
	21st to end	Night	4 3 1 5% 4 5% 5% 4 7% 9% 55%	2761
August	1st to 10th	Night	11% 3 1 4 3 4 5% 4 7% 9% 49%	2734
	11th to 20th	Night	3 3 1 6% 5% 5% 6% 5% 7% 8% 52%	3022
	21st to end	Night	3 3 1 4 3 3 4 3 6% 9% 61%	3487
September	1st to 10th	Night	7% 4 1 3 3 2 3 3 4 6% 64%	1900
	11th to 20th	Night	7% 3 1 3 3 3 3 3 5% 6% 63%	1922
	21st to end	Night	8% 3 1 3 3 2 3 2 4 5% 65%	2090
October	1st to 10th	Night	6% 3 1 2 1 2 2 2 3 4 75%	3789
	11th to 20th	Night	8% 5% 2 4 3 3 3 2 4 6% 59%	3778
	21st to end	Night	8% 7% 2 4 3 2 3 3 5% 6% 59%	4304
November	1st to 10th	Night	6% 5% 2 5% 4 3 3 3 5% 8% 56%	2535
	11th to 20th	Night	4 7% 2 5% 4 4 4 4 6% 7% 54%	2600
	21st to end	Night	4 8% 2 5% 3 3 3 3 5% 7% 56%	2800
December	1st to 10th	Night	3 6% 2 5% 3 3 3 2 4 5% 64%	4570
	11th to 20th	Night	3 8% 3 5% 4 4 4 3 5% 6% 56%	5181
	21st to end	Night	7% 10% 3 7% 4 4 4 4 6% 7% 45%	6974

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	40% 2 11% 28% 18% 1	3639
	11th to 20th	Day	41% 4 14% 21% 19% 2	3640
	21st to end	Day	27% 2 15% 28% 23% 5%	4372
February	1st to 10th	Day	36% 3 15% 27% 15% 3	1800
	11th to 20th	Day	38% 4 10% 28% 16% 5%	1884
	21st to end	Day	30% 3 16% 27% 18% 6%	1650
March	1st to 10th	Day	33% 2 5% 28% 26% 5%	4500
	11th to 20th	Day	34% 3 12% 29% 20% 2	4880
	21st to end	Day	38% 3 14% 32% 12% 1	5837
April	1st to 10th	Day	35% 5% 14% 24% 17% 5%	2400
	11th to 20th	Day	44% 4 9% 21% 18% 4	2374
	21st to end	Day	39% 4 10% 28% 18% 2	2347
May	1st to 10th	Day	45% 3 9% 24% 14% 6%	4261
	11th to 20th	Day	38% 3 11% 30% 14% 5%	4392
	21st to end	Day	32% 3 13% 30% 17% 5%	4825
June	1st to 10th	Day	26% 4 16% 29% 19% 6%	2660
	11th to 20th	Day	28% 4 11% 23% 20% 14%	2660
	21st to end	Day	23% 4 8% 24% 27% 15%	2660
July	1st to 10th	Day	20% 5% 6% 20% 28% 21%	4361
	11th to 20th	Day	20% 4 7% 24% 24% 20%	4355
	21st to end	Day	21% 3 7% 19% 25% 25%	4651
August	1st to 10th	Day	27% 3 10% 25% 21% 13%	4187
	11th to 20th	Day	26% 3 8% 21% 24% 18%	3853
	21st to end	Day	21% 3 7% 18% 27% 24%	4179
September	1st to 10th	Day	22% 3 5% 19% 30% 21%	2280
	11th to 20th	Day	21% 2 5% 23% 30% 18%	2257
	21st to end	Day	21% 3 6% 27% 33% 11%	2090
October	1st to 10th	Day	17% 2 6% 18% 28% 29%	3179
	11th to 20th	Day	29% 2 9% 28% 26% 7%	3150
	21st to end	Day	28% 3 8% 30% 26% 5%	3222
November	1st to 10th	Day	27% 2 12% 28% 25% 7%	1763
	11th to 20th	Day	23% 2 12% 33% 25% 5%	1795
	21st to end	Day	28% 3 11% 29% 26% 4	1600
December	1st to 10th	Day	23% 3 12% 35% 25% 2	2620
	11th to 20th	Day	27% 3 14% 38% 16% 3	3024
	21st to end	Day	37% 2 10% 34% 14% 2	4004
January	1st to 10th	Night	39% 3 11% 29% 15% 3	6327
	11th to 20th	Night	38% 6% 15% 20% 19% 3	6340
	21st to end	Night	30% 2 16% 31% 18% 3	6635
February	1st to 10th	Night	36% 4 16% 28% 13% 3	2600
	11th to 20th	Night	38% 4 12% 26% 15% 4	2411
	21st to end	Night	31% 3 12% 28% 22% 4	1980
March	1st to 10th	Night	31% 2 5% 32% 24% 6%	5374
	11th to 20th	Night	33% 3 10% 26% 25% 4	5098
	21st to end	Night	44% 2 17% 24% 12% 1	5122
April	1st to 10th	Night	35% 4 12% 27% 17% 5%	2000
	11th to 20th	Night	39% 3 10% 25% 18% 5%	1977
	21st to end	Night	41% 2 9% 27% 19% 2	1946
May	1st to 10th	Night	41% 2 9% 26% 19% 3	2706
	11th to 20th	Night	32% 3 13% 35% 13% 5%	2518
	21st to end	Night	32% 4 15% 27% 18% 4	2762
June	1st to 10th	Night	24% 4 22% 27% 17% 5%	1520
	11th to 20th	Night	25% 3 14% 26% 22% 11%	1520
	21st to end	Night	20% 4 10% 28% 25% 13%	1520
July	1st to 10th	Night	25% 4 10% 22% 21% 18%	2500
	11th to 20th	Night	21% 4 12% 26% 25% 12%	2492
	21st to end	Night	25% 3 11% 21% 25% 15%	2674
August	1st to 10th	Night	32% 3 13% 25% 19% 9%	2726
	11th to 20th	Night	29% 3 12% 24% 18% 14%	3050
	21st to end	Night	21% 3 10% 20% 26% 20%	3487
September	1st to 10th	Night	23% 2 5% 22% 29% 18%	1900
	11th to 20th	Night	22% 2 7% 26% 26% 17%	1922
	21st to end	Night	22% 2 6% 26% 28% 15%	2090
October	1st to 10th	Night	16% 2 6% 20% 28% 28%	3789
	11th to 20th	Night	28% 2 11% 25% 27% 7%	3778
	21st to end	Night	28% 2 9% 30% 23% 9%	4304
November	1st to 10th	Night	27% 3 13% 26% 26% 6%	2535
	11th to 20th	Night	28% 3 9% 31% 22% 6%	2600
	21st to end	Night	29% 3 9% 31% 23% 5%	2800
December	1st to 10th	Night	24% 2 12% 37% 21% 4	4570
	11th to 20th	Night	31% 2 11% 40% 15% 1	5182
	21st to end	Night	38% 3 11% 32% 14% 2	6974

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	12% 16% 33% 27% 9% 2	300
	11th to 20th	Day	14% 20% 38% 23% 5% 1	300
	21st to end	Day	8% 21% 45% 19% 7%	330
February	1st to 10th	Day	11% 24% 44% 18% 3 1	300
	11th to 20th	Day	15% 25% 32% 24% 4	300
	21st to end	Day	20% 22% 31% 20% 7%	249
March	1st to 10th	Day	9% 23% 31% 31% 6%	300
	11th to 20th	Day	17% 15% 33% 25% 9% 1	445
	21st to end	Day	19% 17% 34% 23% 7% 2	550
April	1st to 10th	Day	18% 18% 36% 21% 7%	500
	11th to 20th	Day	22% 16% 37% 17% 7% 2	492
	21st to end	Day	18% 10% 32% 24% 12% 3	487
May	1st to 10th	Day	19% 11% 28% 25% 14% 3	653
	11th to 20th	Day	21% 7% 19% 29% 21% 4	675
	21st to end	Day	13% 8% 23% 32% 18% 5%	734
June	1st to 10th	Day	5% 6% 23% 30% 25% 10%	680
	11th to 20th	Day	10% 8% 27% 35% 18% 3	680
	21st to end	Day	6% 3 27% 35% 24% 5%	680
July	1st to 10th	Day	6% 2 16% 37% 29% 10%	671
	11th to 20th	Day	4 3 18% 35% 34% 6%	668
	21st to end	Day	6% 2 15% 34% 34% 8%	739
August	1st to 10th	Day	6% 3 21% 34% 28% 9%	558
	11th to 20th	Day	4 3 24% 31% 27% 12%	477
	21st to end	Day	4 5% 23% 34% 24% 10%	539
September	1st to 10th	Day	7% 5% 22% 34% 23% 9%	490
	11th to 20th	Day	7% 6% 26% 31% 22% 7%	467
	21st to end	Day	8% 7% 23% 33% 17% 13%	300
October	1st to 10th	Day	10% 8% 20% 30% 20% 12%	300
	11th to 20th	Day	12% 13% 25% 28% 14% 8%	300
	21st to end	Day	15% 14% 34% 26% 9% 2	330
November	1st to 10th	Day	11% 10% 35% 32% 10% 3	300
	11th to 20th	Day	13% 18% 36% 25% 8% 1	300
	21st to end	Day	10% 15% 42% 26% 7%	300
December	1st to 10th	Day	9% 19% 40% 21% 9%	300
	11th to 20th	Day	11% 22% 46% 19% 2	300
	21st to end	Day	14% 22% 35% 22% 5% 1	330
January	1st to 10th	Night	10% 20% 40% 23% 7% 1	1000
	11th to 20th	Night	9% 24% 43% 20% 4	1000
	21st to end	Night	10% 16% 44% 25% 4	956
February	1st to 10th	Night	10% 17% 46% 24% 4	800
	11th to 20th	Night	12% 14% 41% 28% 4	784
	21st to end	Night	11% 19% 41% 24% 5%	660
March	1st to 10th	Night	11% 16% 39% 29% 4	800
	11th to 20th	Night	13% 11% 33% 36% 8%	800
	21st to end	Night	15% 11% 35% 33% 6% 1	720
April	1st to 10th	Night	14% 12% 36% 34% 4	600
	11th to 20th	Night	15% 9% 36% 33% 7%	593
	21st to end	Night	18% 7% 30% 35% 10% 1	587
May	1st to 10th	Night	20% 7% 24% 34% 14% 1	570
	11th to 20th	Night	18% 4 19% 40% 17% 2	561
	21st to end	Night	11% 4 28% 40% 17%	617
June	1st to 10th	Night	7% 4 25% 42% 21% 1	570
	11th to 20th	Night	9% 3 31% 48% 8% 1	570
	21st to end	Night	4 2 28% 49% 16% 1	570
July	1st to 10th	Night	6% 3 13% 50% 26% 1	555
	11th to 20th	Night	4 2 19% 52% 22% 1	552
	21st to end	Night	4 1 14% 53% 27% 1	624
August	1st to 10th	Night	7% 1 12% 54% 24% 1	567
	11th to 20th	Night	4 1 18% 54% 23% 1	564
	21st to end	Night	4 2 18% 50% 25% 1	627
September	1st to 10th	Night	9% 2 18% 49% 20% 2	570
	11th to 20th	Night	8% 4 22% 45% 19% 2	570
	21st to end	Night	10% 3 26% 45% 16% 1	570
October	1st to 10th	Night	13% 5% 27% 36% 17% 2	749
	11th to 20th	Night	12% 6% 31% 40% 11% 1	760
	21st to end	Night	13% 9% 34% 35% 8% 1	945
November	1st to 10th	Night	11% 7% 39% 35% 7% 1	975
	11th to 20th	Night	8% 17% 43% 29% 3	1000
	21st to end	Night	9% 12% 43% 32% 5%	1000
December	1st to 10th	Night	11% 21% 40% 24% 4	1000
	11th to 20th	Night	11% 19% 44% 23% 4	1000
	21st to end	Night	13% 20% 41% 21% 4	1100

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