Argyle
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Argyle clear sky chart from 2005-11-06 to 2025-08-05.

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	23% 12% 4 9% 5% 4 4 3 4 6% 27%	126135
	Night	22% 13% 4 11% 5% 4 4 3 4 5% 25%	121961
Transparency	Day	38% 38% 6% 11% 6% 1	129710
	Night	39% 38% 6% 10% 6%	126473
Seeing	Day	31% 17% 30% 16% 5% 1	17809
	Night	30% 15% 27% 21% 6% 1	25543

By Month

Percentage Cloud Cover NE (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	18% 21% 7% 23% 5% 4 3 2 3 3 11%	3275
	11th to 20th	Day	17% 17% 9% 20% 7% 5% 4 3 4 3 11%	4027
	21st to end	Day	18% 16% 6% 19% 9% 4 3 2 4 4 15%	4466
February	1st to 10th	Day	20% 17% 6% 14% 8% 5% 4 4 4 4 14%	1800
	11th to 20th	Day	17% 14% 5% 17% 8% 6% 4 3 3 4 18%	1753
	21st to end	Day	13% 13% 6% 12% 8% 4 4 5% 5% 6% 24%	1605
March	1st to 10th	Day	26% 13% 5% 11% 9% 4 3 2 4 5% 18%	4834
	11th to 20th	Day	18% 13% 4 9% 5% 4 4 3 5% 5% 28%	4980
	21st to end	Day	28% 11% 5% 11% 5% 4 3 3 4 5% 21%	5466
April	1st to 10th	Day	25% 13% 3 7% 4 4 4 3 4 4 30%	2300
	11th to 20th	Day	20% 10% 3 6% 5% 3 3 4 4 5% 37%	2542
	21st to end	Day	23% 9% 2 5% 3 3 4 3 5% 6% 37%	2600
May	1st to 10th	Day	28% 15% 4 8% 5% 4 3 3 4 6% 22%	5886
	11th to 20th	Day	20% 11% 4 8% 5% 5% 4 3 5% 6% 29%	6043
	21st to end	Day	21% 13% 4 8% 5% 4 4 3 4 5% 28%	6948
June	1st to 10th	Day	27% 8% 2 5% 4 4 3 3 4 6% 32%	2840
	11th to 20th	Day	22% 7% 3 6% 4 3 3 4 4 6% 38%	3000
	21st to end	Day	27% 10% 3 7% 4 4 4 3 5% 6% 28%	3000
July	1st to 10th	Day	32% 12% 4 6% 3 3 3 3 5% 5% 24%	6820
	11th to 20th	Day	31% 12% 3 8% 4 4 3 3 4 6% 22%	6285
	21st to end	Day	16% 10% 3 8% 5% 4 4 3 5% 7% 35%	6425
August	1st to 10th	Day	33% 11% 3 5% 3 4 4 3 4 5% 24%	4157
	11th to 20th	Day	19% 8% 3 7% 5% 4 5% 4 5% 7% 33%	4045
	21st to end	Day	13% 6% 2 5% 4 4 4 3 6% 7% 46%	4468
September	1st to 10th	Day	16% 7% 2 7% 3 3 3 3 5% 6% 43%	2266
	11th to 20th	Day	18% 7% 2 6% 3 3 3 3 3 6% 45%	2090
	21st to end	Day	19% 8% 2 7% 3 3 3 3 4 6% 41%	2090
October	1st to 10th	Day	19% 7% 3 6% 4 4 4 3 6% 7% 38%	1919
	11th to 20th	Day	20% 8% 2 6% 4 5% 4 3 7% 6% 35%	1900
	21st to end	Day	20% 10% 4 8% 5% 4 4 3 5% 6% 31%	2057
November	1st to 10th	Day	22% 8% 3 8% 5% 4 3 4 5% 5% 33%	1736
	11th to 20th	Day	21% 14% 5% 9% 6% 5% 3 4 4 6% 23%	1600
	21st to end	Day	21% 17% 5% 10% 6% 4 4 4 5% 6% 18%	1600
December	1st to 10th	Day	25% 15% 7% 14% 4 4 4 3 4 5% 14%	2610
	11th to 20th	Day	28% 14% 4 10% 6% 5% 5% 3 4 5% 16%	2996
	21st to end	Day	22% 14% 6% 12% 5% 4 3 3 4 5% 23%	3706
January	1st to 10th	Night	15% 21% 8% 25% 6% 4 3 2 3 3 11%	6676
	11th to 20th	Night	17% 14% 8% 18% 8% 6% 5% 3 3 4 13%	5858
	21st to end	Night	14% 16% 6% 20% 8% 6% 5% 3 4 4 14%	6490
February	1st to 10th	Night	21% 16% 6% 15% 8% 5% 4 3 3 4 15%	2600
	11th to 20th	Night	19% 14% 6% 13% 8% 6% 5% 4 4 4 17%	2533
	21st to end	Night	14% 13% 5% 11% 7% 6% 5% 4 5% 6% 25%	2020
March	1st to 10th	Night	24% 13% 4 12% 9% 5% 4 2 4 4 19%	5005
	11th to 20th	Night	18% 14% 5% 10% 4 5% 4 4 5% 6% 26%	4979
	21st to end	Night	30% 12% 4 8% 3 3 3 3 4 5% 26%	5466
April	1st to 10th	Night	24% 13% 3 7% 5% 3 3 3 4 6% 29%	2100
	11th to 20th	Night	23% 10% 3 6% 4 3 4 3 5% 7% 33%	1803
	21st to end	Night	24% 9% 2 6% 4 4 4 3 4 7% 32%	1800
May	1st to 10th	Night	31% 13% 3 6% 4 3 3 2 4 6% 24%	4054
	11th to 20th	Night	23% 12% 3 7% 4 4 3 3 5% 6% 30%	3843
	21st to end	Night	22% 15% 3 7% 4 4 3 2 4 6% 30%	3948
June	1st to 10th	Night	27% 10% 3 7% 3 3 4 4 5% 7% 27%	1575
	11th to 20th	Night	19% 11% 4 6% 5% 4 4 3 5% 5% 34%	1400
	21st to end	Night	29% 13% 3 6% 4 4 3 3 4 6% 25%	1400
July	1st to 10th	Night	35% 13% 3 7% 4 3 3 3 5% 5% 18%	3160
	11th to 20th	Night	34% 15% 3 7% 4 3 4 2 3 4 20%	3618
	21st to end	Night	19% 13% 4 7% 4 3 3 3 4 6% 33%	4428
August	1st to 10th	Night	32% 14% 3 6% 4 3 3 2 3 5% 25%	2862
	11th to 20th	Night	22% 12% 3 10% 4 3 3 3 5% 6% 29%	2782
	21st to end	Night	14% 10% 3 6% 3 3 3 3 4 6% 43%	3188
September	1st to 10th	Night	19% 8% 2 5% 3 4 4 4 6% 6% 40%	1911
	11th to 20th	Night	21% 7% 2 5% 3 4 3 3 4 6% 42%	2090
	21st to end	Night	22% 8% 3 6% 4 3 3 4 4 6% 37%	2090
October	1st to 10th	Night	20% 7% 2 6% 4 4 3 3 5% 7% 38%	2261
	11th to 20th	Night	18% 8% 2 6% 4 3 3 3 6% 7% 40%	2280
	21st to end	Night	24% 9% 3 7% 4 4 3 3 5% 6% 33%	2537
November	1st to 10th	Night	18% 9% 3 7% 5% 4 4 4 5% 7% 35%	2562
	11th to 20th	Night	20% 13% 4 9% 6% 5% 4 4 5% 6% 24%	2800
	21st to end	Night	21% 15% 5% 9% 5% 5% 4 3 5% 5% 23%	2800
December	1st to 10th	Night	18% 15% 6% 15% 7% 6% 5% 4 5% 5% 14%	4580
	11th to 20th	Night	22% 14% 4 10% 6% 5% 5% 4 5% 6% 19%	5213
	21st to end	Night	23% 15% 5% 12% 4 4 3 2 3 4 24%	7249

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	63% 25% 7% 5%	3276
	11th to 20th	Day	60% 27% 5% 6% 2	4060
	21st to end	Day	55% 28% 5% 5% 6%	4466
February	1st to 10th	Day	28% 62% 3 4 3	1800
	11th to 20th	Day	27% 61% 3 6% 3	1761
	21st to end	Day	21% 63% 4 7% 4 1	1605
March	1st to 10th	Day	54% 29% 5% 7% 4 1	4838
	11th to 20th	Day	43% 29% 11% 13% 5%	4980
	21st to end	Day	53% 28% 3 9% 6% 1	5466
April	1st to 10th	Day	26% 61% 3 6% 4	2300
	11th to 20th	Day	19% 63% 5% 9% 4 1	2542
	21st to end	Day	19% 61% 3 8% 7% 1	2600
May	1st to 10th	Day	50% 28% 6% 13% 3	5897
	11th to 20th	Day	44% 29% 8% 13% 5% 1	6047
	21st to end	Day	47% 28% 6% 9% 9% 1	6948
June	1st to 10th	Day	19% 62% 3 9% 7%	2840
	11th to 20th	Day	17% 62% 5% 9% 7% 1	3000
	21st to end	Day	21% 61% 4 9% 6% 1	3000
July	1st to 10th	Day	46% 28% 7% 11% 8% 1	6745
	11th to 20th	Day	45% 27% 6% 15% 6%	6205
	21st to end	Day	31% 29% 11% 18% 10% 1	6242
August	1st to 10th	Day	41% 38% 4 10% 6% 1	4144
	11th to 20th	Day	30% 42% 9% 17% 3	4084
	21st to end	Day	19% 39% 8% 18% 15% 2	4468
September	1st to 10th	Day	16% 60% 5% 11% 7% 1	2266
	11th to 20th	Day	19% 60% 4 9% 7% 1	2090
	21st to end	Day	17% 60% 4 11% 8% 1	2090
October	1st to 10th	Day	28% 40% 7% 17% 7% 1	3192
	11th to 20th	Day	24% 38% 5% 16% 16% 1	3140
	21st to end	Day	26% 37% 8% 19% 7% 3	3371
November	1st to 10th	Day	24% 57% 6% 8% 3 1	1736
	11th to 20th	Day	29% 56% 4 6% 3 1	1600
	21st to end	Day	31% 57% 4 7% 1	1600
December	1st to 10th	Day	45% 39% 8% 8% 1	2610
	11th to 20th	Day	47% 32% 10% 8% 3	2995
	21st to end	Day	47% 27% 11% 9% 6%	3706
January	1st to 10th	Night	62% 26% 4 7% 1	6676
	11th to 20th	Night	55% 29% 5% 9% 3	5900
	21st to end	Night	53% 29% 7% 7% 5%	6490
February	1st to 10th	Night	30% 61% 3 3 3	2600
	11th to 20th	Night	26% 60% 3 7% 3	2536
	21st to end	Night	23% 62% 4 6% 5%	2020
March	1st to 10th	Night	53% 29% 4 6% 7%	5014
	11th to 20th	Night	45% 28% 11% 12% 4	4980
	21st to end	Night	49% 28% 5% 11% 7% 1	5466
April	1st to 10th	Night	23% 61% 3 6% 5% 2	2100
	11th to 20th	Night	21% 62% 3 9% 3 1	1803
	21st to end	Night	21% 62% 3 7% 5% 1	1800
May	1st to 10th	Night	49% 28% 8% 10% 5%	4060
	11th to 20th	Night	43% 28% 7% 15% 6% 2	3844
	21st to end	Night	43% 29% 7% 16% 6%	3949
June	1st to 10th	Night	19% 62% 3 10% 5%	1575
	11th to 20th	Night	17% 62% 5% 10% 6%	1400
	21st to end	Night	21% 61% 3 8% 7% 1	1400
July	1st to 10th	Night	53% 27% 5% 9% 6%	3125
	11th to 20th	Night	50% 27% 6% 8% 9% 1	3575
	21st to end	Night	37% 28% 7% 16% 10% 2	4297
August	1st to 10th	Night	42% 38% 5% 10% 5%	2850
	11th to 20th	Night	34% 41% 11% 13% 1	2809
	21st to end	Night	22% 40% 6% 17% 13% 1	3187
September	1st to 10th	Night	16% 61% 3 12% 7% 1	1911
	11th to 20th	Night	19% 59% 4 11% 6% 1	2090
	21st to end	Night	18% 60% 2 12% 7%	2090
October	1st to 10th	Night	31% 39% 8% 12% 8% 1	3768
	11th to 20th	Night	19% 37% 8% 18% 17% 1	3779
	21st to end	Night	25% 37% 8% 20% 10% 1	4173
November	1st to 10th	Night	24% 57% 7% 9% 4	2562
	11th to 20th	Night	27% 57% 5% 8% 4	2800
	21st to end	Night	28% 57% 6% 6% 3	2800
December	1st to 10th	Night	42% 39% 7% 10% 2	4580
	11th to 20th	Night	42% 34% 9% 10% 5%	5215
	21st to end	Night	48% 26% 7% 10% 7% 1	7249

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	42% 24% 27% 6% 2	202
	11th to 20th	Day	35% 21% 28% 13% 3	400
	21st to end	Day	28% 25% 33% 11% 2	440
February	1st to 10th	Day	38% 19% 30% 11% 3	400
	11th to 20th	Day	35% 29% 24% 10% 2	396
	21st to end	Day	31% 24% 29% 14% 2	391
March	1st to 10th	Day	35% 21% 32% 10% 2	500
	11th to 20th	Day	36% 22% 28% 9% 5%	500
	21st to end	Day	33% 24% 26% 11% 4 1	550
April	1st to 10th	Day	41% 24% 23% 9% 3	500
	11th to 20th	Day	34% 21% 33% 9% 3	492
	21st to end	Day	32% 21% 31% 11% 5% 1	500
May	1st to 10th	Day	34% 23% 29% 12% 3 1	503
	11th to 20th	Day	27% 21% 28% 19% 5% 1	605
	21st to end	Day	31% 14% 31% 18% 6% 1	790
June	1st to 10th	Day	32% 16% 27% 20% 6% 1	730
	11th to 20th	Day	25% 15% 32% 21% 7% 1	730
	21st to end	Day	36% 12% 27% 18% 6% 1	730
July	1st to 10th	Day	29% 9% 30% 21% 9% 1	720
	11th to 20th	Day	28% 9% 31% 22% 8% 2	630
	21st to end	Day	23% 11% 39% 19% 7% 1	576
August	1st to 10th	Day	24% 9% 35% 24% 7% 2	502
	11th to 20th	Day	25% 12% 34% 17% 10% 2	479
	21st to end	Day	24% 13% 29% 20% 11% 4	539
September	1st to 10th	Day	19% 14% 34% 23% 8% 2	490
	11th to 20th	Day	25% 11% 30% 21% 8% 4	490
	21st to end	Day	22% 14% 32% 21% 7% 4	490
October	1st to 10th	Day	25% 13% 28% 22% 10% 3	400
	11th to 20th	Day	26% 17% 28% 19% 7% 3	390
	21st to end	Day	29% 20% 30% 16% 6%	429
November	1st to 10th	Day	28% 20% 28% 16% 7% 1	395
	11th to 20th	Day	38% 20% 26% 12% 5% 1	400
	21st to end	Day	35% 21% 30% 11% 3 1	400
December	1st to 10th	Day	36% 20% 30% 12% 2	400
	11th to 20th	Day	42% 25% 21% 10% 2 1	400
	21st to end	Day	40% 23% 23% 10% 3 1	320
January	1st to 10th	Night	34% 22% 29% 13% 3	877
	11th to 20th	Night	36% 16% 28% 17% 3	800
	21st to end	Night	27% 24% 30% 16% 3	880
February	1st to 10th	Night	36% 18% 28% 17% 1	800
	11th to 20th	Night	34% 24% 26% 13% 3	783
	21st to end	Night	25% 20% 34% 17% 5%	660
March	1st to 10th	Night	30% 20% 31% 16% 4	800
	11th to 20th	Night	28% 18% 28% 20% 6% 1	800
	21st to end	Night	28% 18% 30% 17% 6% 1	880
April	1st to 10th	Night	35% 17% 29% 17% 2	700
	11th to 20th	Night	29% 18% 32% 18% 3	594
	21st to end	Night	31% 14% 28% 20% 7%	600
May	1st to 10th	Night	30% 14% 31% 21% 4 1	600
	11th to 20th	Night	29% 10% 32% 22% 6%	592
	21st to end	Night	27% 10% 31% 26% 4 1	649
June	1st to 10th	Night	32% 8% 29% 23% 7%	575
	11th to 20th	Night	23% 7% 31% 32% 7% 1	400
	21st to end	Night	34% 5% 23% 29% 9%	400
July	1st to 10th	Night	30% 5% 25% 29% 11%	390
	11th to 20th	Night	28% 6% 25% 30% 11% 1	497
	21st to end	Night	25% 9% 27% 31% 8%	656
August	1st to 10th	Night	26% 6% 25% 32% 10% 1	581
	11th to 20th	Night	28% 8% 22% 29% 12%	562
	21st to end	Night	22% 5% 26% 30% 15% 1	627
September	1st to 10th	Night	22% 8% 27% 31% 12% 1	581
	11th to 20th	Night	25% 9% 24% 24% 16% 2	760
	21st to end	Night	27% 9% 26% 25% 12% 2	760
October	1st to 10th	Night	26% 9% 26% 26% 12% 1	760
	11th to 20th	Night	25% 15% 27% 23% 8% 2	760
	21st to end	Night	31% 15% 26% 23% 5%	836
November	1st to 10th	Night	28% 12% 28% 23% 8% 1	793
	11th to 20th	Night	33% 18% 25% 18% 6%	900
	21st to end	Night	33% 21% 23% 17% 5%	900
December	1st to 10th	Night	36% 17% 27% 16% 4	900
	11th to 20th	Night	36% 22% 25% 13% 3	900
	21st to end	Night	35% 21% 23% 18% 3	990

Page generated at 2025-08-02 02:32:22. Version ac07

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