Seawall Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Seawall Campground clear sky chart from 2005-11-06 to 2024-11-11.

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	19% 9% 3 6% 4 4 4 3 5% 7% 36%	101274
	Night	20% 9% 3 7% 4 4 4 3 5% 6% 34%	97925
Transparency	Day	47% 6% 13% 21% 13% 1	104827
	Night	49% 5% 12% 20% 12% 1	102463
Seeing	Day	23% 11% 28% 26% 10% 2	15899
	Night	25% 13% 27% 24% 10% 1	24172

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	19% 10% 3 6% 5% 5% 3 3 5% 7% 36%	2517
	11th to 20th	Day	19% 8% 2 5% 4 4 4 3 4 6% 40%	2520
	21st to end	Day	18% 11% 3 7% 4 4 4 3 5% 7% 34%	2906
February	1st to 10th	Day	18% 13% 3 6% 6% 5% 4 4 5% 8% 28%	1710
	11th to 20th	Day	15% 9% 3 8% 5% 4 5% 4 6% 8% 33%	1748
	21st to end	Day	14% 10% 3 7% 6% 5% 5% 4 6% 6% 35%	1570
March	1st to 10th	Day	25% 12% 3 6% 4 4 3 3 4 5% 30%	3174
	11th to 20th	Day	19% 8% 3 6% 4 4 4 3 5% 6% 37%	3480
	21st to end	Day	28% 9% 3 4 4 4 4 4 5% 6% 29%	3816
April	1st to 10th	Day	21% 9% 2 6% 5% 3 3 3 4 6% 37%	2224
	11th to 20th	Day	21% 8% 2 4 3 4 3 3 5% 8% 40%	2434
	21st to end	Day	20% 7% 3 6% 5% 4 4 3 4 6% 37%	2470
May	1st to 10th	Day	18% 9% 4 7% 5% 4 4 4 6% 6% 34%	4106
	11th to 20th	Day	17% 8% 2 7% 5% 4 4 4 5% 7% 37%	4081
	21st to end	Day	18% 11% 4 6% 4 4 4 4 5% 7% 34%	4880
June	1st to 10th	Day	22% 10% 3 7% 4 4 4 3 5% 7% 32%	2850
	11th to 20th	Day	19% 8% 2 5% 4 4 3 4 6% 8% 37%	2850
	21st to end	Day	26% 11% 3 6% 4 4 3 4 5% 6% 30%	2850
July	1st to 10th	Day	20% 11% 3 7% 4 5% 5% 4 5% 6% 30%	4600
	11th to 20th	Day	16% 8% 2 6% 5% 4 4 4 5% 9% 37%	4440
	21st to end	Day	20% 8% 3 5% 4 4 5% 4 5% 8% 35%	4662
August	1st to 10th	Day	21% 11% 3 7% 4 4 4 4 5% 6% 32%	4105
	11th to 20th	Day	17% 10% 3 7% 5% 4 4 3 5% 7% 35%	4045
	21st to end	Day	10% 6% 2 6% 3 3 4 3 5% 7% 51%	4532
September	1st to 10th	Day	12% 6% 2 5% 3 4 4 3 5% 8% 47%	2178
	11th to 20th	Day	13% 7% 2 4 3 4 3 2 3 6% 52%	2090
	21st to end	Day	18% 8% 2 6% 3 3 4 3 4 7% 43%	2090
October	1st to 10th	Day	17% 7% 2 5% 4 3 4 3 6% 6% 42%	2020
	11th to 20th	Day	17% 7% 2 6% 4 4 4 3 4 7% 43%	1900
	21st to end	Day	22% 9% 2 5% 3 3 4 3 5% 5% 40%	1903
November	1st to 10th	Day	17% 7% 2 6% 5% 3 4 3 5% 6% 42%	1761
	11th to 20th	Day	20% 6% 2 6% 3 3 4 3 5% 8% 40%	1658
	21st to end	Day	20% 10% 3 6% 3 3 4 3 6% 6% 37%	1520
December	1st to 10th	Day	24% 10% 2 6% 5% 4 4 3 5% 6% 32%	1476
	11th to 20th	Day	24% 9% 3 6% 5% 4 4 4 6% 6% 29%	1668
	21st to end	Day	26% 8% 2 7% 4 3 4 3 4 6% 32%	2440
January	1st to 10th	Night	15% 10% 3 8% 5% 4 4 3 5% 7% 36%	4429
	11th to 20th	Night	14% 11% 4 10% 5% 4 4 4 5% 5% 32%	4440
	21st to end	Night	19% 11% 4 9% 4 4 4 3 5% 6% 30%	4748
February	1st to 10th	Night	19% 10% 4 8% 6% 5% 4 4 6% 7% 27%	2470
	11th to 20th	Night	15% 11% 3 7% 5% 4 4 4 7% 6% 35%	2314
	21st to end	Night	16% 10% 3 7% 5% 4 5% 3 5% 6% 37%	1884
March	1st to 10th	Night	28% 13% 3 6% 3 4 3 3 4 4 30%	3664
	11th to 20th	Night	13% 11% 3 7% 5% 5% 6% 5% 6% 9% 30%	3479
	21st to end	Night	28% 9% 3 6% 5% 4 4 4 4 4 29%	3816
April	1st to 10th	Night	23% 11% 2 6% 4 4 4 3 4 5% 34%	1952
	11th to 20th	Night	21% 10% 3 6% 4 3 4 3 6% 7% 34%	1695
	21st to end	Night	24% 10% 3 6% 4 4 3 4 5% 6% 33%	1710
May	1st to 10th	Night	23% 8% 3 8% 4 3 4 3 5% 7% 30%	2834
	11th to 20th	Night	19% 7% 3 8% 5% 5% 6% 4 7% 8% 29%	2813
	21st to end	Night	16% 11% 3 7% 6% 4 4 4 5% 7% 34%	2729
June	1st to 10th	Night	27% 9% 2 7% 3 3 5% 3 5% 7% 28%	1330
	11th to 20th	Night	20% 8% 3 6% 4 3 3 4 6% 7% 36%	1330
	21st to end	Night	27% 11% 3 6% 4 3 3 3 5% 6% 30%	1330
July	1st to 10th	Night	19% 12% 4 9% 4 4 5% 4 6% 7% 25%	2359
	11th to 20th	Night	20% 9% 2 7% 3 4 5% 4 5% 8% 33%	2520
	21st to end	Night	17% 10% 2 6% 5% 4 5% 5% 6% 7% 33%	2859
August	1st to 10th	Night	24% 13% 4 8% 4 4 4 3 5% 6% 27%	2825
	11th to 20th	Night	19% 10% 4 6% 4 5% 6% 4 5% 7% 30%	2782
	21st to end	Night	10% 6% 3 7% 4 4 4 3 4 7% 46%	3124
September	1st to 10th	Night	14% 6% 2 5% 3 4 4 3 5% 7% 48%	1999
	11th to 20th	Night	16% 8% 2 4 3 2 3 3 4 6% 50%	2090
	21st to end	Night	17% 7% 2 5% 4 3 4 3 5% 6% 45%	2090
October	1st to 10th	Night	20% 6% 2 5% 3 3 4 3 5% 6% 41%	2159
	11th to 20th	Night	17% 7% 2 6% 3 3 4 3 6% 7% 43%	2280
	21st to end	Night	24% 8% 2 5% 4 3 4 3 4 7% 37%	2693
November	1st to 10th	Night	18% 7% 2 5% 4 3 4 3 5% 6% 42%	2537
	11th to 20th	Night	18% 8% 2 6% 4 4 5% 3 6% 7% 38%	2526
	21st to end	Night	18% 9% 3 5% 5% 4 4 3 6% 7% 36%	2660
December	1st to 10th	Night	25% 10% 3 8% 4 4 4 3 6% 6% 28%	2702
	11th to 20th	Night	25% 9% 2 5% 4 3 4 4 6% 6% 33%	3531
	21st to end	Night	25% 10% 3 6% 3 3 3 3 5% 6% 33%	5222

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	50% 5% 17% 22% 6% 1	2518
	11th to 20th	Day	46% 5% 14% 21% 11% 2	2520
	21st to end	Day	51% 7% 16% 18% 8%	2906
February	1st to 10th	Day	55% 6% 14% 14% 10% 2	1710
	11th to 20th	Day	49% 7% 14% 16% 12% 1	1756
	21st to end	Day	48% 6% 13% 19% 10% 5%	1570
March	1st to 10th	Day	57% 5% 10% 13% 13% 3	3178
	11th to 20th	Day	46% 5% 14% 19% 13% 2	3480
	21st to end	Day	56% 3 9% 13% 15% 4	3816
April	1st to 10th	Day	49% 5% 9% 17% 16% 3	2224
	11th to 20th	Day	43% 5% 10% 24% 15% 2	2434
	21st to end	Day	48% 5% 9% 18% 17% 3	2470
May	1st to 10th	Day	48% 7% 14% 21% 8% 1	4120
	11th to 20th	Day	44% 8% 15% 23% 9% 1	4085
	21st to end	Day	48% 6% 14% 18% 13% 1	4880
June	1st to 10th	Day	52% 6% 11% 21% 10%	2850
	11th to 20th	Day	45% 7% 11% 19% 15% 3	2850
	21st to end	Day	55% 5% 10% 17% 11% 2	2850
July	1st to 10th	Day	53% 6% 9% 20% 11%	4530
	11th to 20th	Day	44% 5% 16% 23% 11%	4365
	21st to end	Day	47% 7% 12% 21% 12% 1	4513
August	1st to 10th	Day	53% 5% 11% 23% 8%	4092
	11th to 20th	Day	49% 4 17% 20% 10%	4084
	21st to end	Day	33% 5% 12% 28% 21% 1	4532
September	1st to 10th	Day	34% 6% 13% 26% 19% 1	2178
	11th to 20th	Day	34% 5% 11% 26% 20% 2	2090
	21st to end	Day	41% 5% 10% 26% 17% 1	2090
October	1st to 10th	Day	45% 4 14% 23% 12% 1	3358
	11th to 20th	Day	32% 3 9% 34% 22%	3140
	21st to end	Day	35% 3 17% 24% 18% 3	3115
November	1st to 10th	Day	43% 5% 15% 23% 12% 1	1761
	11th to 20th	Day	44% 5% 11% 21% 17% 2	1658
	21st to end	Day	49% 6% 17% 20% 7% 1	1520
December	1st to 10th	Day	55% 7% 13% 17% 8% 1	1476
	11th to 20th	Day	56% 5% 14% 16% 8% 1	1668
	21st to end	Day	54% 7% 14% 16% 7% 2	2440
January	1st to 10th	Night	48% 5% 15% 23% 7% 1	4429
	11th to 20th	Night	52% 6% 16% 17% 9% 1	4440
	21st to end	Night	55% 6% 14% 17% 8%	4748
February	1st to 10th	Night	56% 6% 13% 14% 10% 2	2470
	11th to 20th	Night	49% 7% 10% 19% 13% 2	2317
	21st to end	Night	48% 4 11% 20% 12% 4	1884
March	1st to 10th	Night	59% 4 9% 13% 11% 3	3673
	11th to 20th	Night	48% 7% 17% 16% 11% 1	3480
	21st to end	Night	59% 3 7% 14% 15% 2	3816
April	1st to 10th	Night	53% 4 8% 14% 17% 4	1952
	11th to 20th	Night	50% 4 8% 21% 15% 2	1695
	21st to end	Night	52% 5% 9% 17% 14% 3	1710
May	1st to 10th	Night	51% 6% 16% 18% 8% 1	2840
	11th to 20th	Night	49% 9% 16% 17% 7% 1	2814
	21st to end	Night	49% 8% 14% 18% 11% 1	2730
June	1st to 10th	Night	55% 7% 9% 21% 8% 1	1330
	11th to 20th	Night	47% 7% 12% 21% 12% 2	1330
	21st to end	Night	56% 6% 8% 19% 9% 2	1330
July	1st to 10th	Night	56% 6% 10% 16% 10% 1	2320
	11th to 20th	Night	49% 5% 13% 22% 10%	2472
	21st to end	Night	48% 6% 13% 19% 13% 1	2768
August	1st to 10th	Night	60% 4 11% 18% 7%	2813
	11th to 20th	Night	52% 5% 14% 20% 9%	2809
	21st to end	Night	38% 4 11% 25% 21% 1	3124
September	1st to 10th	Night	36% 6% 13% 27% 18% 1	1999
	11th to 20th	Night	38% 4 11% 26% 20% 2	2090
	21st to end	Night	40% 4 9% 28% 18% 1	2090
October	1st to 10th	Night	41% 4 13% 25% 15% 1	3601
	11th to 20th	Night	32% 4 11% 28% 25% 1	3779
	21st to end	Night	40% 3 10% 29% 16% 3	4431
November	1st to 10th	Night	43% 5% 12% 25% 14% 1	2537
	11th to 20th	Night	47% 5% 13% 19% 14% 2	2526
	21st to end	Night	48% 5% 16% 17% 12% 1	2660
December	1st to 10th	Night	57% 6% 12% 15% 9%	2702
	11th to 20th	Night	51% 5% 15% 16% 12% 1	3532
	21st to end	Night	53% 6% 14% 16% 10% 1	5222

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	26% 32% 25% 13% 4	180
	11th to 20th	Day	29% 25% 28% 15% 2 1	180
	21st to end	Day	20% 21% 35% 18% 6%	280
February	1st to 10th	Day	26% 22% 31% 16% 5%	370
	11th to 20th	Day	23% 26% 37% 12% 2	406
	21st to end	Day	24% 19% 33% 21% 3	382
March	1st to 10th	Day	25% 19% 35% 18% 3	460
	11th to 20th	Day	22% 20% 35% 19% 4	460
	21st to end	Day	28% 17% 30% 17% 6% 1	506
April	1st to 10th	Day	28% 17% 32% 17% 4 1	460
	11th to 20th	Day	26% 14% 34% 19% 6% 1	452
	21st to end	Day	24% 8% 38% 22% 7% 1	460
May	1st to 10th	Day	23% 13% 34% 24% 5% 2	463
	11th to 20th	Day	17% 8% 36% 29% 9% 2	487
	21st to end	Day	27% 6% 30% 25% 11% 1	632
June	1st to 10th	Day	24% 5% 29% 27% 13% 2	680
	11th to 20th	Day	24% 4 21% 31% 15% 4	680
	21st to end	Day	29% 4 22% 33% 10% 2	680
July	1st to 10th	Day	25% 4 19% 34% 15% 3	580
	11th to 20th	Day	20% 4 20% 34% 20% 3	484
	21st to end	Day	19% 2 20% 38% 17% 3	532
August	1st to 10th	Day	15% 3 23% 37% 21% 1	486
	11th to 20th	Day	20% 4 19% 34% 19% 5%	479
	21st to end	Day	16% 4 20% 36% 18% 5%	539
September	1st to 10th	Day	15% 3 24% 38% 17% 3	490
	11th to 20th	Day	20% 7% 26% 26% 15% 7%	490
	21st to end	Day	19% 7% 28% 28% 17% 3	490
October	1st to 10th	Day	17% 11% 25% 30% 15% 3	453
	11th to 20th	Day	18% 12% 30% 26% 12% 2	390
	21st to end	Day	29% 10% 30% 22% 8%	429
November	1st to 10th	Day	19% 19% 29% 26% 5% 2	395
	11th to 20th	Day	27% 20% 30% 17% 5% 1	370
	21st to end	Day	28% 23% 26% 18% 5%	370
December	1st to 10th	Day	28% 16% 36% 16% 3 1	326
	11th to 20th	Day	32% 26% 31% 9% 3	180
	21st to end	Day	29% 21% 30% 17% 3	198
January	1st to 10th	Night	24% 25% 29% 18% 4	760
	11th to 20th	Night	28% 23% 30% 15% 4	760
	21st to end	Night	20% 25% 33% 17% 4	836
February	1st to 10th	Night	25% 22% 34% 16% 3	760
	11th to 20th	Night	23% 28% 30% 16% 3 1	743
	21st to end	Night	24% 18% 36% 18% 4	628
March	1st to 10th	Night	25% 18% 36% 19% 2	760
	11th to 20th	Night	23% 18% 30% 22% 7%	760
	21st to end	Night	25% 14% 33% 21% 6% 1	836
April	1st to 10th	Night	29% 12% 31% 21% 6%	760
	11th to 20th	Night	26% 9% 33% 26% 6%	571
	21st to end	Night	28% 9% 26% 26% 10% 1	570
May	1st to 10th	Night	26% 4 30% 26% 11% 2	570
	11th to 20th	Night	25% 6% 27% 31% 10% 1	562
	21st to end	Night	25% 5% 24% 31% 13% 2	513
June	1st to 10th	Night	31% 5% 18% 32% 12% 2	380
	11th to 20th	Night	24% 3 18% 34% 18% 3	380
	21st to end	Night	35% 2 14% 32% 16% 2	380
July	1st to 10th	Night	23% 3 17% 38% 18% 1	370
	11th to 20th	Night	24% 2 14% 36% 21% 3	368
	21st to end	Night	23% 2 14% 35% 22% 2	486
August	1st to 10th	Night	22% 1 16% 38% 21% 2	568
	11th to 20th	Night	21% 3 16% 36% 23% 2	562
	21st to end	Night	18% 3 16% 34% 25% 5%	627
September	1st to 10th	Night	17% 2 20% 39% 20% 3	740
	11th to 20th	Night	21% 5% 21% 30% 18% 5%	760
	21st to end	Night	19% 6% 24% 29% 18% 3	760
October	1st to 10th	Night	24% 7% 22% 28% 17% 2	760
	11th to 20th	Night	21% 12% 27% 25% 13% 2	760
	21st to end	Night	29% 13% 31% 20% 7%	836
November	1st to 10th	Night	21% 13% 30% 25% 9% 1	780
	11th to 20th	Night	24% 22% 28% 19% 6% 1	787
	21st to end	Night	25% 21% 31% 16% 7%	850
December	1st to 10th	Night	31% 18% 33% 14% 3	850
	11th to 20th	Night	29% 25% 28% 15% 3	850
	21st to end	Night	30% 20% 32% 15% 3	929

Page generated at 2024-11-08 06:44:46. Version ac07

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