Harold A Campbell Public Use Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Harold A Campbell Public Use Area clear sky chart from 2005-11-06 to 2024-01-14.

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	8% 6% 3 7% 8% 5% 7% 7% 7% 9% 33%	74882
	Night	7% 5% 2 5% 6% 4 5% 6% 7% 10% 44%	74876
Transparency	Day	46% 6% 15% 18% 12% 3	74605
	Night	35% 6% 18% 22% 14% 3	74672
Seeing	Day	7% 4 14% 26% 26% 23%	14771
	Night	8% 3 13% 33% 31% 12%	24929

By Month

Percentage Cloud Cover SE (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% 5% 3 6% 6% 4 6% 5% 6% 9% 44%	1706
	11th to 20th	Day	8% 5% 3 6% 6% 4 7% 5% 6% 10% 40%	1647
	21st to end	Day	8% 7% 3 6% 5% 4 6% 6% 6% 9% 41%	1832
February	1st to 10th	Day	9% 6% 3 5% 7% 3 6% 5% 6% 9% 41%	1800
	11th to 20th	Day	6% 4 2 4 4 3 5% 5% 6% 9% 53%	1824
	21st to end	Day	5% 5% 2 6% 6% 3 7% 5% 5% 8% 46%	1628
March	1st to 10th	Day	3 3 2 5% 7% 4 6% 5% 7% 10% 48%	1980
	11th to 20th	Day	6% 4 2 5% 7% 5% 6% 6% 7% 9% 45%	1980
	21st to end	Day	5% 3 3 5% 6% 4 6% 7% 6% 7% 48%	2178
April	1st to 10th	Day	4 3 2 4 7% 5% 7% 7% 8% 10% 44%	1980
	11th to 20th	Day	8% 4 3 6% 7% 3 6% 7% 6% 9% 40%	2021
	21st to end	Day	6% 3 2 6% 6% 4 6% 6% 6% 10% 45%	2160
May	1st to 10th	Day	4 3 2 4 6% 4 7% 6% 6% 8% 49%	2160
	11th to 20th	Day	9% 7% 3 7% 8% 5% 6% 7% 7% 9% 31%	2197
	21st to end	Day	10% 6% 4 8% 8% 5% 8% 7% 6% 8% 29%	2531
June	1st to 10th	Day	14% 9% 5% 10% 10% 7% 7% 7% 6% 8% 16%	2340
	11th to 20th	Day	8% 7% 4 9% 10% 6% 9% 9% 8% 10% 20%	2340
	21st to end	Day	9% 6% 4 10% 10% 7% 10% 6% 8% 9% 21%	2340
July	1st to 10th	Day	7% 8% 4 9% 10% 7% 10% 8% 8% 10% 19%	2340
	11th to 20th	Day	10% 8% 4 9% 10% 6% 7% 8% 9% 9% 19%	2340
	21st to end	Day	6% 8% 4 9% 11% 5% 9% 7% 7% 10% 22%	2547
August	1st to 10th	Day	8% 7% 4 9% 9% 6% 9% 8% 9% 11% 20%	2319
	11th to 20th	Day	6% 5% 3 8% 9% 6% 10% 10% 9% 12% 22%	2124
	21st to end	Day	10% 8% 4 9% 10% 7% 8% 8% 9% 9% 19%	2178
September	1st to 10th	Day	8% 7% 4 10% 10% 6% 10% 8% 9% 9% 19%	1980
	11th to 20th	Day	9% 8% 4 9% 11% 7% 8% 8% 7% 9% 22%	1980
	21st to end	Day	11% 9% 4 9% 9% 6% 9% 8% 7% 8% 20%	1980
October	1st to 10th	Day	8% 6% 3 9% 9% 6% 8% 8% 7% 11% 26%	1913
	11th to 20th	Day	9% 6% 3 7% 8% 5% 8% 9% 8% 8% 31%	1800
	21st to end	Day	10% 5% 3 6% 7% 4 6% 7% 7% 9% 37%	1980
November	1st to 10th	Day	7% 4 3 5% 7% 5% 7% 7% 7% 9% 41%	1857
	11th to 20th	Day	10% 7% 3 7% 6% 4 6% 6% 6% 9% 35%	1900
	21st to end	Day	6% 5% 3 6% 6% 4 7% 7% 6% 9% 41%	1900
December	1st to 10th	Day	7% 6% 3 6% 6% 3 6% 5% 6% 8% 43%	1823
	11th to 20th	Day	8% 5% 3 6% 6% 4 6% 6% 6% 8% 43%	2153
	21st to end	Day	10% 6% 3 7% 7% 4 7% 7% 7% 10% 32%	3124
January	1st to 10th	Night	7% 6% 2 4 4 3 5% 5% 5% 9% 50%	2459
	11th to 20th	Night	7% 6% 3 5% 5% 3 5% 6% 7% 9% 44%	2386
	21st to end	Night	6% 5% 3 6% 6% 3 5% 6% 6% 9% 46%	2520
February	1st to 10th	Night	9% 6% 2 4 5% 3 5% 4 7% 8% 46%	2160
	11th to 20th	Night	7% 3 2 3 4 2 4 5% 5% 8% 56%	2020
	21st to end	Night	4 2 1 4 4 3 4 5% 5% 9% 58%	1628
March	1st to 10th	Night	3 3 2 3 3 3 4 5% 5% 9% 61%	1980
	11th to 20th	Night	7% 3 2 3 4 3 4 3 6% 9% 57%	1980
	21st to end	Night	4 3 2 4 4 3 5% 5% 6% 8% 57%	2178
April	1st to 10th	Night	5% 3 1 3 4 2 3 5% 6% 10% 58%	1980
	11th to 20th	Night	6% 3 2 5% 4 3 5% 6% 7% 9% 51%	1886
	21st to end	Night	6% 3 2 4 4 3 4 5% 5% 9% 55%	1800
May	1st to 10th	Night	3 2 2 4 3 2 4 5% 6% 11% 59%	1800
	11th to 20th	Night	7% 4 3 5% 6% 3 6% 6% 7% 10% 42%	1709
	21st to end	Night	6% 5% 3 5% 6% 3 5% 6% 7% 13% 41%	1744
June	1st to 10th	Night	12% 6% 3 7% 8% 5% 7% 8% 9% 10% 25%	1620
	11th to 20th	Night	6% 7% 3 5% 7% 5% 7% 7% 9% 11% 33%	1620
	21st to end	Night	7% 5% 3 7% 7% 5% 7% 7% 9% 12% 33%	1620
July	1st to 10th	Night	6% 5% 3 7% 6% 4 7% 6% 9% 13% 33%	1620
	11th to 20th	Night	5% 5% 3 6% 6% 5% 7% 8% 9% 10% 36%	1620
	21st to end	Night	4 4 3 6% 7% 6% 7% 8% 9% 11% 35%	1771
August	1st to 10th	Night	6% 4 3 6% 6% 3 5% 8% 9% 13% 37%	1611
	11th to 20th	Night	5% 5% 3 5% 6% 5% 7% 7% 8% 13% 35%	1761
	21st to end	Night	7% 7% 3 7% 7% 5% 6% 7% 9% 12% 30%	2174
September	1st to 10th	Night	7% 3 3 6% 7% 5% 8% 8% 10% 13% 30%	1980
	11th to 20th	Night	7% 7% 3 8% 8% 5% 6% 7% 8% 11% 30%	1980
	21st to end	Night	9% 6% 3 9% 9% 5% 8% 7% 8% 11% 26%	1980
October	1st to 10th	Night	8% 6% 3 7% 7% 5% 6% 6% 8% 9% 36%	2046
	11th to 20th	Night	8% 5% 2 5% 5% 3 6% 5% 7% 10% 45%	2160
	21st to end	Night	9% 5% 2 6% 7% 3 5% 5% 6% 9% 44%	2376
November	1st to 10th	Night	9% 3 3 4 5% 3 4 5% 5% 9% 50%	2221
	11th to 20th	Night	9% 5% 3 6% 6% 4 6% 6% 6% 9% 41%	2280
	21st to end	Night	8% 5% 3 5% 4 3 5% 5% 6% 8% 48%	2280
December	1st to 10th	Night	5% 4 2 5% 5% 3 5% 5% 6% 8% 51%	2352
	11th to 20th	Night	11% 5% 2 4 4 3 4 4 6% 8% 49%	3042
	21st to end	Night	9% 8% 3 7% 7% 4 5% 6% 7% 8% 36%	4532

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	37% 4 11% 21% 19% 8%	1707
	11th to 20th	Day	40% 4 10% 23% 17% 5%	1647
	21st to end	Day	40% 4 9% 20% 20% 6%	1832
February	1st to 10th	Day	39% 5% 9% 25% 17% 6%	1800
	11th to 20th	Day	29% 3 8% 28% 23% 9%	1834
	21st to end	Day	35% 4 9% 18% 25% 9%	1628
March	1st to 10th	Day	32% 3 9% 26% 24% 6%	1980
	11th to 20th	Day	35% 3 8% 28% 20% 6%	1980
	21st to end	Day	34% 3 10% 23% 22% 7%	2178
April	1st to 10th	Day	33% 4 15% 27% 17% 4	1980
	11th to 20th	Day	39% 5% 13% 23% 18% 3	2021
	21st to end	Day	36% 4 9% 24% 22% 5%	2160
May	1st to 10th	Day	33% 4 9% 25% 21% 8%	2160
	11th to 20th	Day	49% 4 14% 23% 10%	2201
	21st to end	Day	53% 5% 12% 16% 13%	2531
June	1st to 10th	Day	66% 5% 15% 11% 4	2340
	11th to 20th	Day	56% 8% 19% 14% 2	2340
	21st to end	Day	58% 8% 22% 10% 1	2340
July	1st to 10th	Day	58% 9% 25% 7%	2275
	11th to 20th	Day	58% 9% 22% 11%	2271
	21st to end	Day	55% 9% 25% 11%	2405
August	1st to 10th	Day	55% 8% 25% 11% 1	2306
	11th to 20th	Day	51% 10% 26% 11%	2124
	21st to end	Day	59% 9% 22% 8% 2	2178
September	1st to 10th	Day	56% 10% 20% 13%	1980
	11th to 20th	Day	57% 9% 21% 11% 3	1980
	21st to end	Day	60% 7% 15% 10% 5% 1	1980
October	1st to 10th	Day	51% 6% 14% 15% 11% 3	1913
	11th to 20th	Day	48% 6% 11% 19% 13% 3	1800
	21st to end	Day	44% 4 9% 18% 20% 6%	1980
November	1st to 10th	Day	39% 5% 11% 17% 20% 9%	1857
	11th to 20th	Day	46% 5% 7% 20% 16% 6%	1900
	21st to end	Day	38% 5% 11% 19% 22% 3	1900
December	1st to 10th	Day	39% 3 11% 24% 20% 3	1823
	11th to 20th	Day	40% 3 9% 19% 21% 8%	2150
	21st to end	Day	46% 3 13% 19% 16% 3	3124
January	1st to 10th	Night	32% 4 13% 27% 20% 5%	2459
	11th to 20th	Night	36% 5% 12% 27% 16% 4	2386
	21st to end	Night	34% 4 12% 25% 17% 7%	2520
February	1st to 10th	Night	34% 4 13% 26% 18% 4	2160
	11th to 20th	Night	26% 3 9% 31% 24% 8%	2021
	21st to end	Night	24% 4 11% 25% 30% 7%	1628
March	1st to 10th	Night	21% 3 12% 32% 24% 7%	1980
	11th to 20th	Night	25% 4 15% 33% 18% 5%	1980
	21st to end	Night	25% 4 11% 30% 24% 6%	2178
April	1st to 10th	Night	22% 4 19% 35% 17% 4	1980
	11th to 20th	Night	28% 5% 17% 25% 21% 4	1886
	21st to end	Night	27% 3 14% 30% 22% 5%	1800
May	1st to 10th	Night	20% 4 14% 36% 20% 6%	1800
	11th to 20th	Night	35% 6% 21% 25% 13%	1710
	21st to end	Night	36% 6% 18% 27% 13%	1745
June	1st to 10th	Night	50% 8% 22% 15% 3	1620
	11th to 20th	Night	40% 11% 28% 19% 2	1620
	21st to end	Night	42% 12% 30% 13% 2	1620
July	1st to 10th	Night	39% 13% 34% 13% 1	1575
	11th to 20th	Night	39% 10% 37% 14% 1	1566
	21st to end	Night	37% 13% 34% 13% 2	1672
August	1st to 10th	Night	36% 10% 35% 17% 1	1600
	11th to 20th	Night	38% 12% 38% 12%	1761
	21st to end	Night	44% 11% 32% 12% 2	2174
September	1st to 10th	Night	41% 15% 28% 14% 1	1980
	11th to 20th	Night	46% 12% 27% 13% 2	1980
	21st to end	Night	51% 11% 19% 13% 6%	1980
October	1st to 10th	Night	42% 8% 20% 18% 11% 2	2046
	11th to 20th	Night	34% 6% 18% 23% 18% 2	2160
	21st to end	Night	38% 4 10% 22% 18% 7%	2376
November	1st to 10th	Night	33% 4 13% 21% 21% 8%	2221
	11th to 20th	Night	39% 5% 9% 25% 17% 5%	2280
	21st to end	Night	35% 4 12% 22% 23% 4	2280
December	1st to 10th	Night	31% 5% 12% 29% 19% 4	2352
	11th to 20th	Night	34% 3 10% 22% 22% 9%	3044
	21st to end	Night	46% 3 14% 19% 16% 3	4532

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	10% 7% 32% 35% 14% 3	270
	11th to 20th	Day	10% 8% 27% 35% 14% 4	249
	21st to end	Day	11% 12% 35% 32% 8% 2	264
February	1st to 10th	Day	8% 7% 28% 35% 17% 6%	240
	11th to 20th	Day	6% 3 25% 34% 24% 8%	316
	21st to end	Day	5% 7% 18% 35% 30% 5%	346
March	1st to 10th	Day	5% 6% 25% 38% 24% 2	420
	11th to 20th	Day	7% 6% 23% 34% 26% 5%	420
	21st to end	Day	3 3 23% 33% 31% 7%	462
April	1st to 10th	Day	3 4 27% 34% 25% 7%	420
	11th to 20th	Day	9% 4 24% 31% 22% 9%	412
	21st to end	Day	6% 4 18% 32% 29% 11%	420
May	1st to 10th	Day	4 1 16% 30% 33% 16%	423
	11th to 20th	Day	11% 4 14% 26% 28% 18%	447
	21st to end	Day	9% 4 7% 21% 28% 31%	485
June	1st to 10th	Day	14% 5% 9% 18% 28% 27%	450
	11th to 20th	Day	7% 3 4 19% 27% 40%	450
	21st to end	Day	5% 2 2 11% 27% 53%	450
July	1st to 10th	Day	4 3 1 9% 23% 60%	445
	11th to 20th	Day	6% 2 2 11% 29% 50%	444
	21st to end	Day	7% 1 2 11% 25% 53%	488
August	1st to 10th	Day	6% 1 2 11% 26% 53%	446
	11th to 20th	Day	5% 2 3 10% 30% 52%	439
	21st to end	Day	8% 2 4 21% 26% 39%	495
September	1st to 10th	Day	9% 2 3 11% 27% 47%	450
	11th to 20th	Day	6% 4 6% 13% 26% 46%	450
	21st to end	Day	10% 2 6% 18% 28% 36%	450
October	1st to 10th	Day	8% 3 10% 31% 35% 13%	450
	11th to 20th	Day	9% 3 12% 32% 29% 15%	450
	21st to end	Day	9% 4 16% 30% 30% 11%	495
November	1st to 10th	Day	9% 3 17% 34% 27% 10%	455
	11th to 20th	Day	11% 3 20% 36% 22% 7%	460
	21st to end	Day	4 3 22% 35% 29% 7%	460
December	1st to 10th	Day	7% 6% 19% 37% 25% 6%	383
	11th to 20th	Day	7% 6% 24% 36% 21% 6%	270
	21st to end	Day	6% 9% 24% 34% 19% 8%	297
January	1st to 10th	Night	9% 6% 20% 40% 23% 1	760
	11th to 20th	Night	9% 4 25% 41% 20% 1	735
	21st to end	Night	7% 5% 29% 43% 15% 1	792
February	1st to 10th	Night	10% 4 22% 44% 19% 1	720
	11th to 20th	Night	8% 2 24% 44% 21% 1	703
	21st to end	Night	5% 2 23% 49% 20% 1	592
March	1st to 10th	Night	4 3 29% 45% 18% 1	720
	11th to 20th	Night	7% 3 22% 46% 20% 2	720
	21st to end	Night	6% 4 22% 46% 21% 1	792
April	1st to 10th	Night	5% 4 18% 49% 23% 1	720
	11th to 20th	Night	6% 4 19% 48% 23% 1	711
	21st to end	Night	7% 3 18% 49% 21% 3	720
May	1st to 10th	Night	3 1 14% 45% 33% 3	720
	11th to 20th	Night	9% 2 11% 42% 31% 4	648
	21st to end	Night	7% 2 4 28% 47% 12%	584
June	1st to 10th	Night	13% 2 4 23% 45% 14%	540
	11th to 20th	Night	6% 2 1 11% 50% 29%	540
	21st to end	Night	6% 1 1 8% 44% 39%	540
July	1st to 10th	Night	7% 1 2 6% 44% 40%	525
	11th to 20th	Night	5% 1 1 7% 43% 43%	522
	21st to end	Night	3 1 1 7% 43% 45%	591
August	1st to 10th	Night	6% 1 1 7% 47% 38%	537
	11th to 20th	Night	6% 2 1 10% 42% 39%	697
	21st to end	Night	9% 2 4 18% 38% 29%	792
September	1st to 10th	Night	8% 1 3 13% 43% 31%	720
	11th to 20th	Night	9% 3 4 15% 40% 30%	720
	21st to end	Night	11% 2 5% 18% 42% 22%	720
October	1st to 10th	Night	10% 3 5% 34% 39% 9%	720
	11th to 20th	Night	10% 3 7% 34% 39% 8%	720
	21st to end	Night	12% 2 13% 38% 30% 6%	792
November	1st to 10th	Night	9% 3 17% 37% 31% 3	740
	11th to 20th	Night	9% 3 16% 40% 27% 4	760
	21st to end	Night	10% 3 16% 44% 26% 1	760
December	1st to 10th	Night	7% 2 15% 43% 31% 3	760
	11th to 20th	Night	10% 3 16% 41% 27% 4	760
	21st to end	Night	7% 5% 18% 41% 27% 3	836

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