Weiser Memorial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Weiser Memorial Park clear sky chart from 2005-11-06 to 2026-07-31.

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% 6% 2 5% 4 4 4 3 5% 6% 54%	146892
	Night	10% 7% 2 6% 4 4 4 3 5% 7% 48%	143430
Transparency	Day	31% 6% 11% 21% 20% 12%	141643
	Night	35% 6% 13% 20% 16% 9%	139681
Seeing	Day	10% 5% 19% 31% 25% 10%	16621
	Night	13% 4 18% 40% 22% 3	25817

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	18% 17% 5% 12% 6% 5% 5% 4 5% 5% 19%	4722
	11th to 20th	Day	11% 9% 3 10% 6% 5% 6% 4 5% 8% 33%	4740
	21st to end	Day	16% 11% 5% 9% 5% 4 4 3 4 4 35%	5187
February	1st to 10th	Day	14% 13% 3 9% 5% 5% 4 4 5% 7% 32%	1809
	11th to 20th	Day	14% 9% 4 8% 6% 6% 4 4 6% 6% 34%	2050
	21st to end	Day	11% 10% 3 6% 5% 4 6% 3 7% 8% 37%	1730
March	1st to 10th	Day	7% 10% 4 10% 6% 5% 5% 5% 6% 8% 34%	4618
	11th to 20th	Day	7% 8% 3 6% 4 4 5% 3 5% 7% 49%	4835
	21st to end	Day	8% 9% 3 8% 6% 5% 5% 5% 7% 10% 34%	5981
April	1st to 10th	Day	9% 8% 2 6% 4 5% 4 5% 6% 7% 43%	2520
	11th to 20th	Day	7% 6% 2 7% 4 5% 5% 4 6% 7% 48%	2512
	21st to end	Day	8% 6% 2 6% 5% 4 4 4 5% 7% 50%	2730
May	1st to 10th	Day	4 4 1 3 3 3 4 3 4 7% 63%	7626
	11th to 20th	Day	5% 3 1 3 3 2 3 3 5% 7% 65%	8081
	21st to end	Day	3 3 1 4 3 3 4 4 6% 8% 60%	8992
June	1st to 10th	Day	7% 5% 2 5% 4 4 5% 4 7% 8% 47%	2940
	11th to 20th	Day	6% 4 1 4 3 3 3 3 5% 7% 59%	2940
	21st to end	Day	3 3 1 3 3 3 3 3 5% 6% 69%	2940
July	1st to 10th	Day	2 1 1 2 1 1 2 2 3 4 81%	6459
	11th to 20th	Day	2 1 1 1 1 2 2 2 3 3 83%	6460
	21st to end	Day	2 2 1 2 2 2 3 2 4 7% 73%	7021
August	1st to 10th	Day	3 3 1 4 3 3 3 4 5% 8% 64%	6111
	11th to 20th	Day	2 1 1 3 2 2 2 2 3 5% 79%	5754
	21st to end	Day	3 3 1 3 3 3 3 2 3 5% 70%	5984
September	1st to 10th	Day	3 2 1 2 2 2 2 3 4 6% 73%	2400
	11th to 20th	Day	4 3 1 4 3 3 4 3 5% 6% 64%	2252
	21st to end	Day	5% 3 1 4 3 3 4 2 4 5% 65%	2200
October	1st to 10th	Day	4 3 1 4 3 3 3 2 4 5% 68%	3578
	11th to 20th	Day	7% 4 2 5% 3 4 4 3 5% 6% 57%	3107
	21st to end	Day	9% 6% 3 7% 4 4 4 4 6% 6% 48%	3200
November	1st to 10th	Day	14% 7% 2 6% 4 4 4 4 6% 8% 42%	1854
	11th to 20th	Day	14% 9% 3 7% 5% 4 5% 4 5% 7% 37%	1890
	21st to end	Day	11% 9% 4 9% 6% 5% 5% 4 5% 8% 33%	1769
December	1st to 10th	Day	12% 8% 5% 10% 6% 5% 6% 4 6% 7% 31%	2700
	11th to 20th	Day	23% 13% 5% 13% 7% 5% 5% 3 5% 5% 15%	3108
	21st to end	Day	17% 13% 5% 12% 7% 5% 6% 4 5% 5% 21%	4092
January	1st to 10th	Night	19% 15% 5% 11% 6% 5% 4 4 5% 6% 19%	8172
	11th to 20th	Night	12% 8% 3 7% 5% 4 4 4 6% 11% 37%	8220
	21st to end	Night	16% 9% 4 7% 4 3 4 3 5% 7% 38%	8994
February	1st to 10th	Night	15% 12% 3 9% 5% 4 4 4 5% 6% 33%	2809
	11th to 20th	Night	14% 10% 3 7% 5% 3 5% 4 5% 7% 36%	2458
	21st to end	Night	11% 10% 3 8% 5% 6% 5% 4 7% 6% 33%	2076
March	1st to 10th	Night	8% 11% 3 8% 5% 5% 4 3 5% 7% 40%	5496
	11th to 20th	Night	12% 11% 3 7% 4 4 3 3 4 5% 45%	5384
	21st to end	Night	9% 8% 3 9% 6% 6% 6% 5% 7% 8% 33%	5221
April	1st to 10th	Night	10% 7% 3 6% 4 4 5% 4 5% 6% 46%	2100
	11th to 20th	Night	9% 7% 2 7% 4 4 5% 4 5% 5% 48%	2055
	21st to end	Night	7% 6% 1 6% 3 4 4 4 6% 7% 52%	1890
May	1st to 10th	Night	7% 3 1 3 2 3 3 3 5% 6% 63%	5321
	11th to 20th	Night	4 5% 1 4 3 3 3 3 6% 7% 60%	4767
	21st to end	Night	5% 5% 2 6% 4 3 4 3 4 6% 58%	5181
June	1st to 10th	Night	8% 4 2 5% 4 5% 4 4 6% 8% 50%	1680
	11th to 20th	Night	7% 4 1 5% 3 4 4 3 5% 6% 59%	1680
	21st to end	Night	3 3 2 3 4 2 3 3 5% 6% 66%	1680
July	1st to 10th	Night	2 1 1 2 2 2 2 2 4 5% 76%	3720
	11th to 20th	Night	1 1 1 1 2 2 3 5% 84%	3720
	21st to end	Night	2 2 1 3 3 3 4 4 5% 7% 66%	4050
August	1st to 10th	Night	2 2 1 4 4 4 5% 3 6% 8% 61%	3671
	11th to 20th	Night	1 2 1 2 2 2 2 2 4 5% 77%	4094
	21st to end	Night	5% 3 1 3 2 2 3 2 4 6% 68%	5015
September	1st to 10th	Night	3 2 1 3 2 2 2 2 4 6% 74%	2000
	11th to 20th	Night	4 3 1 4 3 4 3 3 5% 6% 65%	2147
	21st to end	Night	7% 3 1 3 2 2 3 2 3 6% 66%	2200
October	1st to 10th	Night	5% 3 2 4 2 2 3 2 3 4 71%	3620
	11th to 20th	Night	6% 4 2 4 3 3 4 3 5% 6% 60%	4045
	21st to end	Night	9% 5% 2 5% 4 4 4 4 6% 8% 49%	4600
November	1st to 10th	Night	14% 7% 2 6% 4 4 4 4 5% 7% 43%	2665
	11th to 20th	Night	17% 7% 2 7% 5% 4 5% 4 5% 6% 38%	2730
	21st to end	Night	13% 9% 2 6% 4 3 4 3 5% 8% 42%	2847
December	1st to 10th	Night	10% 7% 3 8% 4 3 4 4 8% 12% 35%	4700
	11th to 20th	Night	20% 13% 5% 12% 6% 5% 5% 4 5% 6% 19%	5316
	21st to end	Night	18% 13% 4 9% 5% 5% 5% 5% 6% 7% 23%	7106

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	67% 9% 13% 10% 2	4723
	11th to 20th	Day	47% 10% 21% 19% 3	4740
	21st to end	Day	53% 8% 12% 19% 6% 2	5187
February	1st to 10th	Day	53% 11% 17% 14% 4	1809
	11th to 20th	Day	49% 11% 15% 18% 6%	2060
	21st to end	Day	44% 10% 18% 18% 9% 1	1730
March	1st to 10th	Day	45% 9% 16% 19% 11%	4618
	11th to 20th	Day	35% 5% 14% 32% 13%	4835
	21st to end	Day	42% 9% 19% 21% 7% 1	5981
April	1st to 10th	Day	38% 7% 16% 26% 12% 2	2520
	11th to 20th	Day	34% 7% 14% 25% 17% 4	2515
	21st to end	Day	33% 5% 13% 28% 19% 2	2730
May	1st to 10th	Day	21% 4 7% 28% 34% 6%	7626
	11th to 20th	Day	19% 4 8% 31% 29% 9%	8084
	21st to end	Day	21% 6% 10% 30% 27% 6%	8994
June	1st to 10th	Day	32% 8% 13% 22% 23% 3	2940
	11th to 20th	Day	24% 5% 10% 22% 27% 11%	2940
	21st to end	Day	17% 4 7% 20% 32% 20%	2940
July	1st to 10th	Day	9% 2 2 10% 28% 48%	6391
	11th to 20th	Day	9% 2 2 6% 23% 58%	6385
	21st to end	Day	12% 2 3 16% 34% 33%	6822
August	1st to 10th	Day	21% 4 5% 11% 28% 32%	4447
	11th to 20th	Day	11% 3 3 17% 37% 29%	4165
	21st to end	Day	14% 2 5% 23% 34% 23%	4311
September	1st to 10th	Day	13% 3 6% 21% 32% 26%	2400
	11th to 20th	Day	21% 5% 10% 24% 29% 12%	2252
	21st to end	Day	21% 4 9% 29% 29% 8%	2200
October	1st to 10th	Day	21% 4 7% 23% 37% 7%	3578
	11th to 20th	Day	29% 4 15% 31% 18% 3	3107
	21st to end	Day	37% 5% 13% 30% 13% 1	3200
November	1st to 10th	Day	41% 8% 18% 24% 9%	1854
	11th to 20th	Day	46% 10% 19% 19% 5% 1	1890
	21st to end	Day	48% 9% 20% 17% 6%	1769
December	1st to 10th	Day	48% 11% 21% 17% 2	2700
	11th to 20th	Day	69% 10% 12% 7% 2	3108
	21st to end	Day	62% 10% 15% 11% 3	4092
January	1st to 10th	Night	63% 9% 16% 9% 2	8172
	11th to 20th	Night	39% 6% 24% 24% 8%	8220
	21st to end	Night	46% 7% 17% 19% 8% 4	8994
February	1st to 10th	Night	51% 9% 19% 16% 4 1	2809
	11th to 20th	Night	46% 8% 19% 19% 8%	2459
	21st to end	Night	47% 9% 13% 20% 9% 2	2076
March	1st to 10th	Night	41% 8% 14% 25% 12% 1	5496
	11th to 20th	Night	43% 4 8% 29% 15% 1	5384
	21st to end	Night	44% 10% 17% 23% 6% 1	5221
April	1st to 10th	Night	37% 7% 12% 26% 16% 2	2100
	11th to 20th	Night	36% 6% 11% 26% 17% 3	2055
	21st to end	Night	30% 7% 12% 24% 24% 2	1890
May	1st to 10th	Night	21% 4 6% 23% 38% 8%	5319
	11th to 20th	Night	22% 5% 8% 29% 32% 4	4767
	21st to end	Night	27% 5% 8% 33% 23% 5%	5182
June	1st to 10th	Night	32% 7% 13% 23% 22% 2	1680
	11th to 20th	Night	26% 5% 10% 22% 28% 9%	1680
	21st to end	Night	18% 4 8% 19% 33% 19%	1680
July	1st to 10th	Night	12% 3 3 10% 22% 51%	3680
	11th to 20th	Night	6% 2 2 8% 22% 61%	3672
	21st to end	Night	17% 3 3 14% 30% 32%	3937
August	1st to 10th	Night	22% 4 5% 10% 26% 32%	2666
	11th to 20th	Night	10% 3 4 13% 30% 39%	2958
	21st to end	Night	15% 2 4 16% 33% 31%	3608
September	1st to 10th	Night	14% 2 5% 17% 31% 31%	2000
	11th to 20th	Night	21% 4 7% 21% 25% 21%	2147
	21st to end	Night	20% 4 6% 23% 32% 16%	2200
October	1st to 10th	Night	19% 3 6% 19% 33% 20%	3620
	11th to 20th	Night	26% 4 12% 27% 28% 4	4045
	21st to end	Night	33% 6% 11% 31% 17% 1	4600
November	1st to 10th	Night	40% 7% 15% 25% 13% 1	2665
	11th to 20th	Night	46% 7% 17% 22% 7%	2730
	21st to end	Night	41% 7% 22% 21% 9% 1	2847
December	1st to 10th	Night	38% 7% 28% 24% 4	4700
	11th to 20th	Night	63% 9% 18% 8% 2	5316
	21st to end	Night	56% 10% 18% 12% 4	7106

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	29% 6% 15% 28% 16% 6%	220
	11th to 20th	Day	17% 5% 12% 33% 25% 8%	220
	21st to end	Day	19% 3 12% 36% 23% 7%	242
February	1st to 10th	Day	19% 5% 19% 33% 19% 6%	329
	11th to 20th	Day	18% 5% 19% 35% 18% 5%	535
	21st to end	Day	15% 5% 23% 33% 19% 5%	446
March	1st to 10th	Day	17% 6% 23% 37% 16% 2	540
	11th to 20th	Day	15% 7% 19% 34% 18% 7%	540
	21st to end	Day	14% 7% 23% 34% 16% 5%	594
April	1st to 10th	Day	12% 10% 24% 24% 22% 9%	540
	11th to 20th	Day	10% 13% 28% 27% 16% 7%	532
	21st to end	Day	8% 11% 28% 27% 21% 5%	540
May	1st to 10th	Day	7% 11% 27% 26% 22% 8%	543
	11th to 20th	Day	13% 10% 25% 25% 20% 8%	568
	21st to end	Day	7% 6% 17% 31% 26% 13%	617
June	1st to 10th	Day	7% 6% 24% 30% 21% 12%	570
	11th to 20th	Day	9% 10% 24% 28% 23% 5%	570
	21st to end	Day	3 4 20% 35% 29% 9%	570
July	1st to 10th	Day	2 2 17% 39% 31% 9%	566
	11th to 20th	Day	3 3 16% 40% 30% 8%	564
	21st to end	Day	2 2 14% 36% 34% 12%	616
August	1st to 10th	Day	4 3 16% 30% 35% 13%	527
	11th to 20th	Day	1 3 13% 31% 33% 19%	517
	21st to end	Day	5% 2 14% 28% 31% 20%	583
September	1st to 10th	Day	4 2 13% 23% 37% 21%	530
	11th to 20th	Day	5% 3 15% 23% 35% 18%	530
	21st to end	Day	6% 4 16% 28% 31% 16%	530
October	1st to 10th	Day	8% 6% 15% 27% 28% 16%	530
	11th to 20th	Day	10% 4 18% 27% 28% 14%	440
	21st to end	Day	12% 6% 20% 34% 20% 7%	363
November	1st to 10th	Day	16% 4 20% 32% 23% 4	330
	11th to 20th	Day	17% 4 17% 36% 21% 5%	330
	21st to end	Day	20% 3 15% 33% 25% 5%	267
December	1st to 10th	Day	25% 3 14% 28% 18% 12%	220
	11th to 20th	Day	26% 5% 18% 30% 18% 3	220
	21st to end	Day	21% 5% 18% 29% 21% 6%	242
January	1st to 10th	Night	22% 4 18% 34% 19% 4	840
	11th to 20th	Night	19% 2 16% 37% 20% 6%	840
	21st to end	Night	19% 2 14% 37% 24% 4	924
February	1st to 10th	Night	21% 4 20% 37% 17% 2	840
	11th to 20th	Night	19% 3 17% 39% 19% 2	824
	21st to end	Night	15% 3 24% 40% 15% 2	692
March	1st to 10th	Night	15% 5% 20% 41% 16% 2	840
	11th to 20th	Night	17% 4 19% 37% 21% 2	840
	21st to end	Night	16% 6% 22% 41% 14% 1	924
April	1st to 10th	Night	13% 5% 20% 41% 20% 2	840
	11th to 20th	Night	13% 7% 24% 35% 18% 2	807
	21st to end	Night	9% 5% 26% 41% 17% 1	630
May	1st to 10th	Night	7% 8% 23% 43% 17% 2	630
	11th to 20th	Night	9% 6% 25% 31% 25% 4	443
	21st to end	Night	8% 6% 19% 40% 23% 4	455
June	1st to 10th	Night	8% 5% 23% 37% 24% 3	420
	11th to 20th	Night	9% 9% 28% 32% 20% 1	420
	21st to end	Night	3 4 22% 47% 23% 1	420
July	1st to 10th	Night	1 4 22% 51% 21% 1	410
	11th to 20th	Night	2 26% 52% 18%	408
	21st to end	Night	2 2 18% 50% 27% 1	458
August	1st to 10th	Night	4 2 19% 46% 27% 2	437
	11th to 20th	Night	2 1 15% 48% 30% 3	611
	21st to end	Night	5% 3 15% 41% 32% 4	880
September	1st to 10th	Night	4 2 13% 44% 34% 4	800
	11th to 20th	Night	5% 2 13% 40% 35% 6%	800
	21st to end	Night	8% 3 14% 36% 31% 8%	800
October	1st to 10th	Night	10% 2 17% 40% 28% 4	800
	11th to 20th	Night	10% 3 17% 40% 26% 5%	800
	21st to end	Night	10% 3 18% 42% 23% 3	880
November	1st to 10th	Night	16% 3 15% 40% 23% 1	820
	11th to 20th	Night	20% 3 16% 41% 18% 2	840
	21st to end	Night	18% 3 15% 37% 21% 4	840
December	1st to 10th	Night	20% 3 17% 36% 20% 4	840
	11th to 20th	Night	24% 2 15% 41% 16% 2	840
	21st to end	Night	26% 3 18% 38% 14% 2	924

Page generated at 2026-07-28 01:25:22. Version ac07

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