Parker
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Parker clear sky chart from 2005-11-06 to 2026-09-14.

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	5% 5% 2 5% 4 4 4 4 6% 8% 55%	157728
	Night	5% 6% 2 5% 3 3 4 3 5% 7% 56%	150962
Transparency	Day	26% 5% 10% 22% 24% 12%	152701
	Night	27% 5% 11% 24% 25% 9%	147009
Seeing	Day	7% 7% 25% 32% 21% 7%	18166
	Night	7% 3 30% 44% 14% 1	28076

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	1 6% 3 7% 3 3 3 2 4 8% 59%	4720
	11th to 20th	Day	1 5% 2 7% 4 3 3 3 4 6% 63%	4858
	21st to end	Day	1 4 2 8% 4 4 3 3 5% 6% 60%	5844
February	1st to 10th	Day	2 9% 3 7% 3 3 4 3 5% 7% 55%	1893
	11th to 20th	Day	1 4 3 6% 4 4 4 4 6% 8% 57%	2049
	21st to end	Day	2 7% 3 5% 3 3 3 3 5% 5% 62%	1730
March	1st to 10th	Day	2 10% 3 5% 3 3 3 2 5% 5% 59%	4600
	11th to 20th	Day	4 8% 3 6% 4 4 4 3 5% 8% 51%	5003
	21st to end	Day	4 7% 2 4 3 4 4 3 6% 8% 53%	5983
April	1st to 10th	Day	6% 7% 2 5% 3 3 4 4 6% 6% 53%	2520
	11th to 20th	Day	8% 9% 3 5% 4 4 4 3 6% 7% 48%	2491
	21st to end	Day	9% 8% 2 4 3 4 5% 4 7% 9% 46%	2520
May	1st to 10th	Day	11% 7% 2 5% 4 4 4 4 6% 7% 47%	7474
	11th to 20th	Day	11% 7% 2 5% 4 4 5% 4 6% 7% 45%	8072
	21st to end	Day	8% 5% 2 5% 4 5% 5% 5% 7% 9% 45%	9026
June	1st to 10th	Day	5% 4 1 4 4 4 5% 5% 8% 9% 50%	2940
	11th to 20th	Day	5% 4 1 4 3 4 4 5% 7% 8% 54%	2940
	21st to end	Day	4 3 2 5% 4 5% 5% 5% 8% 9% 51%	2940
July	1st to 10th	Day	3 2 1 3 3 3 5% 4 6% 8% 59%	8249
	11th to 20th	Day	3 2 1 4 3 4 5% 4 7% 10% 58%	8250
	21st to end	Day	5% 3 2 5% 5% 5% 6% 5% 8% 9% 46%	8844
August	1st to 10th	Day	7% 3 2 4 4 5% 6% 5% 7% 9% 48%	7465
	11th to 20th	Day	4 2 1 4 4 5% 5% 5% 7% 9% 54%	7003
	21st to end	Day	6% 3 2 6% 4 5% 5% 5% 8% 11% 46%	7751
September	1st to 10th	Day	5% 3 1 4 3 3 4 3 5% 7% 61%	2520
	11th to 20th	Day	6% 3 1 4 3 4 3 4 6% 6% 60%	2397
	21st to end	Day	5% 4 2 4 2 2 3 3 5% 6% 65%	2200
October	1st to 10th	Day	4 3 1 2 2 1 2 1 3 4 76%	3339
	11th to 20th	Day	4 4 2 5% 3 3 3 3 4 7% 62%	3250
	21st to end	Day	5% 6% 1 3 2 2 3 2 4 5% 66%	3397
November	1st to 10th	Day	2 6% 1 3 2 3 2 3 6% 7% 64%	1853
	11th to 20th	Day	2 6% 2 4 3 3 3 3 4 7% 63%	1890
	21st to end	Day	3 6% 2 5% 3 2 2 3 5% 6% 62%	1819
December	1st to 10th	Day	1 6% 2 4 3 3 2 2 4 6% 68%	2700
	11th to 20th	Day	1 4 2 4 3 3 3 2 4 6% 67%	3106
	21st to end	Day	2 7% 3 7% 4 4 4 3 6% 7% 54%	4092
January	1st to 10th	Night	2 9% 3 7% 3 3 3 3 5% 7% 56%	8201
	11th to 20th	Night	2 5% 3 7% 4 3 3 3 4 5% 61%	8190
	21st to end	Night	2 5% 3 6% 4 3 3 3 4 5% 62%	8370
February	1st to 10th	Night	2 8% 3 5% 4 3 4 3 4 7% 56%	2725
	11th to 20th	Night	2 9% 3 6% 5% 4 3 3 5% 7% 52%	2458
	21st to end	Night	3 7% 2 5% 3 2 3 3 4 6% 61%	2076
March	1st to 10th	Night	4 10% 3 5% 3 3 3 3 5% 5% 58%	5494
	11th to 20th	Night	6% 9% 2 5% 3 4 4 3 4 6% 54%	5209
	21st to end	Night	7% 9% 3 5% 4 4 4 3 5% 6% 50%	5217
April	1st to 10th	Night	5% 8% 2 5% 4 4 3 3 4 7% 54%	2100
	11th to 20th	Night	10% 8% 2 5% 3 3 3 3 5% 6% 50%	2077
	21st to end	Night	12% 8% 2 5% 4 3 4 3 4 7% 47%	2100
May	1st to 10th	Night	14% 9% 2 6% 3 4 4 4 5% 6% 45%	5472
	11th to 20th	Night	10% 7% 2 5% 4 4 4 4 6% 7% 47%	4816
	21st to end	Night	10% 6% 2 5% 4 3 4 3 5% 6% 49%	5181
June	1st to 10th	Night	6% 3 1 4 3 3 3 3 7% 11% 55%	1680
	11th to 20th	Night	5% 3 1 3 3 3 3 3 6% 7% 61%	1680
	21st to end	Night	4 4 2 4 4 4 4 4 7% 9% 55%	1680
July	1st to 10th	Night	4 2 1 4 3 4 4 4 6% 7% 61%	4740
	11th to 20th	Night	3 2 2 4 3 4 5% 4 6% 9% 58%	4740
	21st to end	Night	4 3 2 6% 4 5% 7% 6% 9% 10% 44%	5261
August	1st to 10th	Night	6% 4 1 5% 4 4 5% 4 6% 7% 54%	5345
	11th to 20th	Night	5% 3 2 5% 5% 5% 6% 5% 8% 11% 47%	5853
	21st to end	Night	6% 4 2 6% 4 5% 5% 5% 8% 11% 43%	6465
September	1st to 10th	Night	6% 5% 1 4 3 3 4 4 6% 7% 57%	2100
	11th to 20th	Night	7% 3 1 3 3 3 4 3 6% 6% 61%	2068
	21st to end	Night	7% 4 1 4 3 2 3 3 4 6% 63%	2200
October	1st to 10th	Night	5% 3 1 3 2 2 3 2 4 4 69%	3845
	11th to 20th	Night	6% 4 2 4 3 3 3 3 5% 7% 59%	3898
	21st to end	Night	3 7% 2 3 2 2 3 2 3 5% 66%	4369
November	1st to 10th	Night	3 3 1 4 3 3 3 3 4 7% 66%	2665
	11th to 20th	Night	2 5% 2 4 2 3 3 3 4 6% 65%	2730
	21st to end	Night	4 7% 2 5% 3 3 3 2 5% 7% 60%	2798
December	1st to 10th	Night	1 4 2 4 2 2 2 2 4 5% 72%	4710
	11th to 20th	Night	1 4 2 5% 3 3 3 3 4 7% 65%	5321
	21st to end	Night	4 8% 3 7% 4 4 4 3 5% 7% 53%	7128

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	25% 3 7% 29% 27% 9%	4723
	11th to 20th	Day	23% 3 9% 26% 29% 10%	4858
	21st to end	Day	25% 3 8% 26% 26% 12%	5844
February	1st to 10th	Day	29% 3 11% 26% 21% 10%	1893
	11th to 20th	Day	25% 4 8% 27% 27% 8%	2059
	21st to end	Day	24% 3 8% 21% 29% 16%	1730
March	1st to 10th	Day	26% 3 7% 15% 32% 18%	4600
	11th to 20th	Day	30% 4 10% 21% 27% 7%	5003
	21st to end	Day	27% 6% 10% 35% 20% 3	5983
April	1st to 10th	Day	28% 6% 12% 24% 21% 9%	2520
	11th to 20th	Day	34% 5% 10% 20% 20% 11%	2494
	21st to end	Day	32% 7% 12% 23% 21% 5%	2520
May	1st to 10th	Day	34% 5% 11% 27% 19% 5%	7474
	11th to 20th	Day	35% 7% 9% 19% 23% 7%	8076
	21st to end	Day	31% 8% 14% 24% 16% 8%	9027
June	1st to 10th	Day	27% 8% 14% 22% 18% 10%	2940
	11th to 20th	Day	25% 7% 10% 17% 23% 18%	2940
	21st to end	Day	25% 6% 12% 18% 24% 14%	2940
July	1st to 10th	Day	20% 5% 8% 16% 29% 23%	8181
	11th to 20th	Day	19% 5% 11% 20% 22% 23%	8175
	21st to end	Day	30% 7% 15% 21% 15% 12%	8647
August	1st to 10th	Day	30% 7% 12% 19% 18% 15%	5916
	11th to 20th	Day	26% 8% 16% 21% 20% 10%	5519
	21st to end	Day	25% 6% 16% 25% 20% 8%	6078
September	1st to 10th	Day	22% 4 8% 22% 26% 18%	2520
	11th to 20th	Day	23% 4 9% 19% 28% 18%	2397
	21st to end	Day	21% 3 7% 18% 36% 14%	2200
October	1st to 10th	Day	14% 3 5% 15% 37% 26%	3339
	11th to 20th	Day	24% 2 8% 23% 33% 10%	3250
	21st to end	Day	22% 2 6% 21% 37% 13%	3397
November	1st to 10th	Day	18% 4 9% 24% 29% 16%	1853
	11th to 20th	Day	21% 4 6% 24% 34% 11%	1890
	21st to end	Day	24% 3 9% 21% 28% 15%	1819
December	1st to 10th	Day	20% 3 7% 31% 29% 10%	2700
	11th to 20th	Day	18% 4 7% 28% 32% 12%	3104
	21st to end	Day	29% 3 8% 26% 26% 9%	4092
January	1st to 10th	Night	28% 3 6% 28% 28% 6%	8202
	11th to 20th	Night	26% 4 9% 23% 24% 14%	8190
	21st to end	Night	25% 4 9% 22% 28% 12%	8370
February	1st to 10th	Night	28% 4 9% 24% 26% 9%	2725
	11th to 20th	Night	31% 5% 9% 26% 21% 8%	2458
	21st to end	Night	24% 3 6% 24% 28% 15%	2076
March	1st to 10th	Night	29% 3 6% 15% 35% 13%	5494
	11th to 20th	Night	30% 4 11% 13% 29% 13%	5209
	21st to end	Night	33% 5% 10% 32% 18% 2	5217
April	1st to 10th	Night	29% 6% 11% 22% 22% 10%	2100
	11th to 20th	Night	34% 4 11% 23% 20% 8%	2077
	21st to end	Night	37% 5% 11% 24% 18% 5%	2100
May	1st to 10th	Night	38% 6% 12% 27% 12% 5%	5470
	11th to 20th	Night	33% 6% 13% 25% 16% 6%	4817
	21st to end	Night	33% 7% 18% 23% 14% 4	5182
June	1st to 10th	Night	22% 7% 18% 30% 15% 8%	1680
	11th to 20th	Night	20% 6% 13% 22% 23% 16%	1680
	21st to end	Night	23% 8% 11% 24% 24% 10%	1680
July	1st to 10th	Night	20% 6% 10% 21% 36% 8%	4700
	11th to 20th	Night	21% 6% 15% 22% 22% 14%	4692
	21st to end	Night	30% 8% 19% 19% 17% 7%	5146
August	1st to 10th	Night	30% 7% 12% 26% 20% 6%	4229
	11th to 20th	Night	30% 9% 21% 21% 13% 6%	4613
	21st to end	Night	25% 8% 21% 26% 16% 4	5069
September	1st to 10th	Night	25% 5% 10% 22% 26% 12%	2100
	11th to 20th	Night	21% 5% 11% 23% 25% 15%	2068
	21st to end	Night	23% 3 8% 21% 33% 12%	2200
October	1st to 10th	Night	19% 3 8% 18% 32% 20%	3845
	11th to 20th	Night	24% 3 10% 25% 28% 10%	3898
	21st to end	Night	22% 2 5% 25% 32% 14%	4369
November	1st to 10th	Night	18% 4 8% 24% 30% 16%	2665
	11th to 20th	Night	20% 3 7% 26% 32% 11%	2730
	21st to end	Night	26% 3 8% 23% 30% 11%	2798
December	1st to 10th	Night	17% 3 7% 34% 32% 8%	4710
	11th to 20th	Night	19% 3 6% 29% 36% 7%	5322
	21st to end	Night	32% 3 8% 23% 26% 9%	7128

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	3 9% 26% 43% 16% 3	330
	11th to 20th	Day	7% 7% 31% 40% 14% 1	330
	21st to end	Day	4 7% 35% 40% 12% 1	363
February	1st to 10th	Day	3 9% 43% 35% 8% 2	330
	11th to 20th	Day	2 7% 41% 38% 10% 2	330
	21st to end	Day	3 10% 45% 32% 10% 1	273
March	1st to 10th	Day	5% 7% 35% 33% 15% 4	330
	11th to 20th	Day	9% 10% 36% 30% 12% 3	485
	21st to end	Day	12% 16% 32% 26% 11% 3	594
April	1st to 10th	Day	9% 14% 34% 28% 12% 3	540
	11th to 20th	Day	12% 19% 31% 26% 10% 2	532
	21st to end	Day	16% 13% 30% 25% 14% 2	540
May	1st to 10th	Day	14% 10% 31% 27% 13% 4	689
	11th to 20th	Day	16% 7% 23% 29% 20% 5%	775
	21st to end	Day	10% 9% 24% 31% 19% 7%	844
June	1st to 10th	Day	6% 5% 20% 32% 25% 12%	780
	11th to 20th	Day	6% 6% 26% 33% 23% 7%	780
	21st to end	Day	5% 4 24% 35% 25% 7%	780
July	1st to 10th	Day	7% 3 14% 28% 36% 12%	771
	11th to 20th	Day	4 2 13% 29% 38% 14%	768
	21st to end	Day	6% 2 13% 25% 40% 15%	812
August	1st to 10th	Day	8% 2 17% 31% 26% 16%	567
	11th to 20th	Day	4 2 15% 34% 27% 17%	557
	21st to end	Day	6% 3 18% 32% 29% 12%	627
September	1st to 10th	Day	6% 3 19% 30% 28% 14%	570
	11th to 20th	Day	5% 5% 22% 29% 29% 11%	503
	21st to end	Day	5% 3 20% 27% 28% 16%	330
October	1st to 10th	Day	10% 5% 19% 24% 26% 15%	330
	11th to 20th	Day	2 8% 25% 35% 21% 8%	330
	21st to end	Day	9% 8% 23% 36% 20% 5%	363
November	1st to 10th	Day	6% 9% 25% 37% 18% 5%	330
	11th to 20th	Day	5% 7% 24% 43% 18% 3	330
	21st to end	Day	7% 4 33% 39% 14% 3	330
December	1st to 10th	Day	4 7% 34% 36% 18% 2	330
	11th to 20th	Day	4 6% 38% 39% 12% 1	330
	21st to end	Day	5% 6% 35% 42% 11% 2	363
January	1st to 10th	Night	4 3 36% 45% 10% 2	1050
	11th to 20th	Night	4 4 36% 46% 8% 1	1029
	21st to end	Night	4 2 35% 47% 10% 1	924
February	1st to 10th	Night	5% 3 43% 42% 6%	840
	11th to 20th	Night	6% 4 42% 42% 7%	824
	21st to end	Night	5% 4 43% 44% 4	692
March	1st to 10th	Night	6% 4 41% 42% 7%	840
	11th to 20th	Night	10% 5% 33% 42% 11%	840
	21st to end	Night	9% 5% 39% 40% 7%	751
April	1st to 10th	Night	9% 5% 40% 40% 6%	630
	11th to 20th	Night	15% 8% 31% 38% 8%	623
	21st to end	Night	17% 6% 31% 37% 9%	630
May	1st to 10th	Night	15% 6% 29% 40% 10% 1	630
	11th to 20th	Night	17% 3 19% 45% 15% 1	621
	21st to end	Night	11% 3 31% 38% 17% 1	683
June	1st to 10th	Night	6% 3 20% 47% 22% 2	630
	11th to 20th	Night	5% 3 28% 48% 16% 1	630
	21st to end	Night	5% 2 22% 48% 22% 2	630
July	1st to 10th	Night	7% 1 15% 46% 28% 2	615
	11th to 20th	Night	3 1 17% 45% 32% 3	612
	21st to end	Night	6% 1 11% 44% 36% 2	690
August	1st to 10th	Night	5% 1 14% 48% 29% 2	627
	11th to 20th	Night	7% 1 15% 52% 23% 1	624
	21st to end	Night	6% 1 18% 49% 24% 2	693
September	1st to 10th	Night	7% 2 17% 48% 23% 3	630
	11th to 20th	Night	7% 2 20% 47% 22% 1	609
	21st to end	Night	8% 2 20% 48% 20% 2	600
October	1st to 10th	Night	10% 3 25% 44% 16% 2	751
	11th to 20th	Night	5% 3 29% 44% 18% 2	800
	21st to end	Night	8% 3 28% 45% 14% 2	948
November	1st to 10th	Night	4 3 31% 48% 13% 1	1025
	11th to 20th	Night	5% 3 34% 47% 10% 1	1050
	21st to end	Night	7% 4 31% 44% 13% 1	1050
December	1st to 10th	Night	4 2 37% 46% 11%	1050
	11th to 20th	Night	5% 3 37% 44% 10% 1	1050
	21st to end	Night	6% 5% 40% 41% 8% 1	1155

Page generated at 2026-09-11 02:11:56. Version ac07

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