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 2025-03-27.

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% 2 6% 4 4 4 3 5% 6% 52%	112788
	Night	11% 7% 3 6% 4 4 4 3 5% 6% 47%	115278
Transparency	Day	32% 6% 11% 20% 18% 13%	112532
	Night	37% 6% 13% 19% 15% 9%	115123
Seeing	Day	11% 6% 19% 30% 25% 10%	14847
	Night	13% 4 18% 40% 23% 3	24248

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	16% 17% 6% 12% 7% 5% 6% 3 5% 5% 18%	3639
	11th to 20th	Day	14% 11% 4 8% 5% 4 5% 3 5% 8% 33%	3640
	21st to end	Day	20% 13% 5% 8% 4 3 2 2 4 4 35%	4004
February	1st to 10th	Day	14% 13% 3 9% 5% 5% 4 4 5% 7% 31%	1723
	11th to 20th	Day	14% 9% 3 8% 5% 6% 4 4 6% 6% 34%	1950
	21st to end	Day	10% 10% 3 6% 6% 4 6% 3 7% 8% 36%	1650
March	1st to 10th	Day	8% 12% 4 8% 5% 5% 5% 5% 6% 8% 33%	3238
	11th to 20th	Day	8% 7% 2 5% 3 3 4 3 4 5% 57%	3403
	21st to end	Day	9% 8% 3 8% 5% 5% 5% 5% 8% 9% 33%	4158
April	1st to 10th	Day	9% 9% 2 6% 5% 5% 4 5% 6% 7% 41%	2280
	11th to 20th	Day	6% 6% 2 7% 4 5% 5% 4 6% 7% 48%	2270
	21st to end	Day	8% 6% 2 6% 5% 4 4 3 5% 7% 49%	2470
May	1st to 10th	Day	7% 7% 2 5% 3 4 4 3 5% 7% 52%	4110
	11th to 20th	Day	6% 3 1 3 3 2 2 2 5% 6% 66%	4335
	21st to end	Day	5% 5% 2 5% 4 4 4 4 6% 9% 52%	4813
June	1st to 10th	Day	8% 6% 2 5% 5% 4 5% 4 8% 8% 45%	2660
	11th to 20th	Day	6% 4 2 4 3 3 3 3 5% 7% 59%	2660
	21st to end	Day	2 3 1 3 3 3 3 2 4 6% 70%	2660
July	1st to 10th	Day	2 1 2 2 1 2 2 3 3 82%	4420
	11th to 20th	Day	2 1 1 1 1 2 2 2 3 4 80%	4420
	21st to end	Day	1 1 1 2 2 2 2 2 3 5% 78%	4790
August	1st to 10th	Day	4 3 2 4 3 3 4 3 3 6% 65%	4325
	11th to 20th	Day	2 1 1 3 2 2 2 2 4 6% 78%	3997
	21st to end	Day	2 2 1 2 2 2 2 2 3 4 77%	4180
September	1st to 10th	Day	3 2 1 2 2 2 2 3 4 6% 74%	2280
	11th to 20th	Day	4 3 1 4 3 3 4 3 5% 6% 64%	2140
	21st to end	Day	5% 3 1 4 3 3 4 2 4 6% 65%	2090
October	1st to 10th	Day	4 3 1 4 3 3 3 2 4 5% 68%	3469
	11th to 20th	Day	8% 4 2 5% 3 4 4 3 5% 6% 56%	3012
	21st to end	Day	9% 6% 3 7% 4 4 4 4 6% 6% 47%	3101
November	1st to 10th	Day	14% 7% 2 6% 4 4 4 4 6% 7% 41%	1764
	11th to 20th	Day	15% 9% 3 7% 4 4 5% 4 5% 7% 38%	1800
	21st to end	Day	12% 9% 4 9% 6% 5% 5% 4 5% 8% 33%	1685
December	1st to 10th	Day	11% 8% 5% 10% 6% 5% 5% 4 6% 7% 32%	2620
	11th to 20th	Day	23% 14% 5% 13% 7% 5% 4 3 5% 5% 15%	3028
	21st to end	Day	16% 13% 5% 12% 7% 5% 6% 5% 5% 5% 21%	4004
January	1st to 10th	Night	20% 15% 5% 11% 7% 5% 4 4 5% 5% 20%	6306
	11th to 20th	Night	15% 10% 3 8% 5% 4 3 3 4 7% 36%	6320
	21st to end	Night	19% 11% 4 7% 3 3 3 2 4 5% 39%	6952
February	1st to 10th	Night	15% 12% 3 9% 5% 4 4 4 5% 5% 33%	2675
	11th to 20th	Night	14% 10% 3 7% 5% 3 5% 4 5% 7% 37%	2338
	21st to end	Night	11% 10% 3 8% 5% 6% 5% 4 7% 6% 33%	1980
March	1st to 10th	Night	10% 12% 3 9% 5% 5% 4 3 5% 7% 37%	3856
	11th to 20th	Night	10% 8% 2 5% 3 4 3 2 5% 5% 53%	3796
	21st to end	Night	10% 8% 3 8% 6% 5% 5% 5% 7% 8% 33%	3630
April	1st to 10th	Night	11% 7% 3 6% 5% 4 5% 4 5% 6% 45%	1900
	11th to 20th	Night	9% 7% 2 7% 4 4 5% 4 5% 5% 48%	1857
	21st to end	Night	7% 6% 1 6% 3 4 4 4 7% 7% 51%	1710
May	1st to 10th	Night	10% 5% 2 5% 4 4 5% 4 6% 7% 48%	2860
	11th to 20th	Night	4 3 1 4 3 3 3 3 5% 6% 63%	2556
	21st to end	Night	8% 7% 2 6% 4 4 4 4 5% 7% 50%	2762
June	1st to 10th	Night	8% 5% 2 6% 5% 5% 4 4 6% 8% 47%	1520
	11th to 20th	Night	8% 4 1 4 3 4 4 3 5% 6% 58%	1520
	21st to end	Night	2 3 1 3 4 2 3 3 6% 6% 66%	1520
July	1st to 10th	Night	1 1 1 2 2 2 2 3 4 82%	2540
	11th to 20th	Night	1 1 2 2 2 4 6% 81%	2540
	21st to end	Night	3 2 1 3 2 2 3 3 4 5% 72%	2761
August	1st to 10th	Night	3 3 2 5% 4 4 4 3 6% 7% 60%	2592
	11th to 20th	Night	1 1 2 2 2 2 2 5% 5% 76%	2840
	21st to end	Night	4 3 1 2 2 2 2 2 2 4 77%	3498
September	1st to 10th	Night	3 2 1 3 2 2 2 2 4 5% 75%	1900
	11th to 20th	Night	4 3 1 4 3 4 3 3 5% 5% 65%	2039
	21st to end	Night	7% 3 1 3 2 3 3 3 3 6% 66%	2090
October	1st to 10th	Night	5% 3 2 4 2 2 2 2 3 4 71%	3509
	11th to 20th	Night	6% 4 2 4 3 3 4 3 5% 6% 60%	3920
	21st to end	Night	9% 5% 2 5% 4 4 4 4 6% 8% 49%	4457
November	1st to 10th	Night	14% 7% 2 6% 4 4 4 4 4 7% 44%	2535
	11th to 20th	Night	17% 7% 2 7% 5% 4 4 4 5% 6% 39%	2600
	21st to end	Night	13% 9% 2 6% 4 3 4 3 5% 7% 42%	2711
December	1st to 10th	Night	10% 7% 3 8% 4 3 4 4 8% 12% 36%	4560
	11th to 20th	Night	20% 14% 5% 12% 6% 5% 5% 4 4 6% 19%	5176
	21st to end	Night	18% 13% 4 9% 5% 5% 5% 5% 6% 7% 23%	6952

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% 12% 10% 2	3639
	11th to 20th	Day	49% 8% 18% 20% 3	3640
	21st to end	Day	55% 8% 10% 18% 6% 2	4004
February	1st to 10th	Day	54% 11% 16% 14% 4	1723
	11th to 20th	Day	48% 11% 16% 19% 6%	1960
	21st to end	Day	44% 10% 19% 18% 9% 1	1650
March	1st to 10th	Day	45% 11% 15% 19% 9%	3238
	11th to 20th	Day	30% 5% 13% 38% 14%	3403
	21st to end	Day	41% 11% 19% 20% 7% 2	4158
April	1st to 10th	Day	40% 7% 16% 23% 12% 2	2280
	11th to 20th	Day	34% 7% 15% 25% 16% 4	2273
	21st to end	Day	34% 5% 13% 26% 19% 2	2470
May	1st to 10th	Day	30% 6% 10% 26% 24% 4	4110
	11th to 20th	Day	19% 5% 8% 28% 29% 11%	4338
	21st to end	Day	25% 8% 16% 32% 18% 3	4814
June	1st to 10th	Day	34% 9% 14% 22% 20% 1	2660
	11th to 20th	Day	25% 5% 11% 23% 26% 10%	2660
	21st to end	Day	16% 4 7% 19% 33% 21%	2660
July	1st to 10th	Day	9% 2 3 8% 21% 57%	4351
	11th to 20th	Day	10% 2 3 7% 21% 58%	4345
	21st to end	Day	10% 2 3 9% 30% 46%	4639
August	1st to 10th	Day	21% 4 5% 10% 28% 33%	4309
	11th to 20th	Day	11% 3 3 18% 37% 29%	4036
	21st to end	Day	13% 2 5% 22% 35% 23%	4179
September	1st to 10th	Day	13% 3 6% 20% 32% 27%	2280
	11th to 20th	Day	21% 5% 10% 23% 29% 12%	2140
	21st to end	Day	21% 4 9% 29% 29% 8%	2090
October	1st to 10th	Day	21% 4 7% 23% 38% 7%	3469
	11th to 20th	Day	29% 4 15% 31% 18% 3	3012
	21st to end	Day	37% 6% 12% 31% 13% 1	3101
November	1st to 10th	Day	41% 8% 18% 24% 9%	1764
	11th to 20th	Day	46% 10% 19% 19% 6% 1	1800
	21st to end	Day	48% 9% 20% 16% 6%	1685
December	1st to 10th	Day	47% 11% 22% 17% 2	2620
	11th to 20th	Day	70% 11% 12% 6% 1	3028
	21st to end	Day	62% 10% 15% 10% 3	4004
January	1st to 10th	Night	63% 10% 14% 10% 3	6306
	11th to 20th	Night	47% 7% 18% 20% 7%	6320
	21st to end	Night	49% 7% 14% 19% 8% 3	6952
February	1st to 10th	Night	52% 9% 18% 16% 4 1	2675
	11th to 20th	Night	45% 8% 20% 19% 8%	2339
	21st to end	Night	47% 10% 14% 19% 9% 2	1980
March	1st to 10th	Night	44% 9% 14% 22% 9% 1	3856
	11th to 20th	Night	35% 5% 9% 36% 16%	3796
	21st to end	Night	42% 11% 18% 21% 7%	3630
April	1st to 10th	Night	39% 7% 12% 24% 16% 2	1900
	11th to 20th	Night	37% 7% 11% 25% 17% 3	1857
	21st to end	Night	31% 7% 13% 24% 24% 2	1710
May	1st to 10th	Night	30% 7% 11% 25% 24% 4	2860
	11th to 20th	Night	18% 5% 10% 27% 33% 6%	2556
	21st to end	Night	32% 7% 10% 34% 15% 2	2762
June	1st to 10th	Night	34% 8% 14% 24% 19% 1	1520
	11th to 20th	Night	27% 5% 11% 23% 28% 8%	1520
	21st to end	Night	17% 4 8% 19% 33% 19%	1520
July	1st to 10th	Night	8% 2 3 10% 20% 57%	2500
	11th to 20th	Night	7% 2 3 9% 21% 59%	2492
	21st to end	Night	15% 3 3 7% 27% 45%	2674
August	1st to 10th	Night	22% 4 5% 9% 26% 33%	2584
	11th to 20th	Night	10% 3 4 13% 30% 39%	2867
	21st to end	Night	14% 2 4 16% 33% 31%	3498
September	1st to 10th	Night	13% 2 5% 17% 31% 32%	1900
	11th to 20th	Night	21% 4 7% 21% 25% 22%	2039
	21st to end	Night	20% 4 6% 23% 32% 15%	2090
October	1st to 10th	Night	19% 3 6% 18% 33% 21%	3509
	11th to 20th	Night	26% 4 12% 27% 28% 4	3920
	21st to end	Night	34% 6% 11% 30% 17% 1	4457
November	1st to 10th	Night	40% 7% 14% 25% 13% 1	2535
	11th to 20th	Night	46% 7% 17% 23% 8%	2600
	21st to end	Night	41% 7% 22% 21% 9% 1	2711
December	1st to 10th	Night	37% 7% 28% 24% 4	4560
	11th to 20th	Night	64% 9% 17% 8% 2	5176
	21st to end	Night	56% 10% 17% 12% 5%	6952

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	28% 5% 16% 29% 16% 7%	200
	11th to 20th	Day	19% 5% 13% 33% 23% 7%	200
	21st to end	Day	21% 3 12% 35% 20% 8%	220
February	1st to 10th	Day	19% 5% 20% 32% 18% 5%	303
	11th to 20th	Day	19% 5% 19% 34% 18% 5%	495
	21st to end	Day	14% 6% 22% 32% 20% 5%	414
March	1st to 10th	Day	18% 6% 22% 36% 16% 2	500
	11th to 20th	Day	16% 6% 19% 33% 19% 7%	500
	21st to end	Day	14% 8% 23% 33% 18% 5%	531
April	1st to 10th	Day	14% 11% 24% 24% 20% 7%	460
	11th to 20th	Day	8% 13% 31% 26% 16% 7%	452
	21st to end	Day	8% 11% 30% 26% 20% 4	460
May	1st to 10th	Day	8% 12% 27% 26% 21% 7%	463
	11th to 20th	Day	14% 9% 24% 24% 21% 8%	488
	21st to end	Day	8% 7% 16% 30% 26% 13%	529
June	1st to 10th	Day	7% 6% 23% 30% 22% 12%	490
	11th to 20th	Day	10% 11% 24% 27% 23% 6%	490
	21st to end	Day	3 4 21% 34% 29% 9%	490
July	1st to 10th	Day	2 2 17% 39% 31% 9%	486
	11th to 20th	Day	3 3 16% 40% 30% 8%	484
	21st to end	Day	2 2 14% 36% 35% 11%	531
August	1st to 10th	Day	4 2 15% 31% 36% 12%	487
	11th to 20th	Day	1 2 13% 31% 33% 19%	477
	21st to end	Day	4 2 14% 28% 32% 19%	539
September	1st to 10th	Day	4 2 13% 23% 37% 20%	490
	11th to 20th	Day	6% 4 16% 23% 35% 16%	490
	21st to end	Day	6% 4 16% 29% 29% 16%	490
October	1st to 10th	Day	8% 6% 14% 27% 28% 16%	490
	11th to 20th	Day	10% 4 17% 27% 28% 15%	405
	21st to end	Day	13% 7% 21% 34% 18% 7%	330
November	1st to 10th	Day	17% 4 19% 32% 24% 4	300
	11th to 20th	Day	18% 4 17% 36% 21% 4	300
	21st to end	Day	21% 3 15% 31% 25% 5%	243
December	1st to 10th	Day	26% 2 15% 26% 20% 13%	200
	11th to 20th	Day	27% 5% 18% 31% 18% 3	200
	21st to end	Day	21% 4 18% 30% 22% 5%	220
January	1st to 10th	Night	22% 4 17% 34% 20% 4	800
	11th to 20th	Night	20% 2 16% 36% 20% 6%	800
	21st to end	Night	20% 2 14% 36% 25% 4	880
February	1st to 10th	Night	21% 3 20% 37% 17% 2	800
	11th to 20th	Night	20% 3 17% 40% 19% 2	784
	21st to end	Night	15% 3 23% 40% 16% 2	660
March	1st to 10th	Night	16% 5% 19% 41% 17% 2	800
	11th to 20th	Night	17% 5% 16% 38% 22% 2	800
	21st to end	Night	16% 6% 21% 42% 14% 1	862
April	1st to 10th	Night	14% 5% 19% 40% 21% 2	760
	11th to 20th	Night	13% 7% 24% 35% 20% 2	729
	21st to end	Night	10% 5% 26% 39% 18% 1	570
May	1st to 10th	Night	7% 8% 24% 42% 18% 2	570
	11th to 20th	Night	9% 6% 22% 31% 27% 4	401
	21st to end	Night	9% 7% 18% 38% 23% 4	411
June	1st to 10th	Night	9% 4 23% 36% 25% 3	380
	11th to 20th	Night	10% 9% 27% 31% 22% 2	380
	21st to end	Night	3 4 22% 46% 24% 1	380
July	1st to 10th	Night	1 4 22% 49% 22% 2	370
	11th to 20th	Night	3 27% 51% 18% 1	368
	21st to end	Night	2 2 18% 49% 28% 1	416
August	1st to 10th	Night	4 2 19% 45% 28% 2	415
	11th to 20th	Night	2 1 16% 47% 31% 3	580
	21st to end	Night	5% 3 15% 41% 33% 4	836
September	1st to 10th	Night	4 2 13% 43% 35% 4	760
	11th to 20th	Night	5% 2 13% 39% 36% 6%	760
	21st to end	Night	8% 3 14% 36% 31% 8%	760
October	1st to 10th	Night	9% 2 16% 40% 29% 4	760
	11th to 20th	Night	10% 3 15% 40% 27% 5%	760
	21st to end	Night	10% 3 18% 42% 23% 4	836
November	1st to 10th	Night	16% 3 15% 40% 24% 2	780
	11th to 20th	Night	20% 3 17% 40% 19% 2	800
	21st to end	Night	18% 3 15% 37% 22% 5%	800
December	1st to 10th	Night	20% 2 16% 37% 21% 4	800
	11th to 20th	Night	25% 2 14% 40% 17% 2	800
	21st to end	Night	26% 3 17% 38% 14% 2	880

Page generated at 2025-03-24 07:04:32. Version ac07

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