Grafton Lakes State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Grafton Lakes State Park clear sky chart from 2005-11-06 to 2024-11-05.

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	17% 10% 3 8% 5% 4 5% 4 5% 7% 32%	101388
	Night	17% 12% 4 8% 5% 4 4 3 5% 6% 31%	97661
Transparency	Day	50% 7% 13% 19% 10% 1	104897
	Night	52% 7% 12% 18% 10% 1	102241
Seeing	Day	23% 19% 28% 19% 8% 2	14845
	Night	23% 18% 27% 24% 8% 1	23863

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	14% 17% 5% 11% 6% 4 4 4 4 4 26%	2517
	11th to 20th	Day	15% 14% 7% 12% 8% 4 5% 4 4 5% 22%	2520
	21st to end	Day	19% 21% 7% 9% 5% 4 4 3 4 4 21%	2835
February	1st to 10th	Day	16% 15% 5% 10% 7% 5% 5% 5% 6% 4 24%	1710
	11th to 20th	Day	13% 15% 6% 13% 7% 5% 4 3 4 6% 25%	1838
	21st to end	Day	17% 17% 4 11% 6% 4 4 3 3 4 27%	1570
March	1st to 10th	Day	23% 15% 4 9% 5% 4 3 2 3 5% 26%	3116
	11th to 20th	Day	14% 18% 5% 9% 4 4 4 3 4 5% 29%	3276
	21st to end	Day	21% 12% 3 11% 4 3 4 3 3 4 32%	4166
April	1st to 10th	Day	19% 14% 4 8% 5% 3 4 3 3 5% 32%	2280
	11th to 20th	Day	16% 10% 3 8% 5% 4 5% 3 5% 5% 35%	2254
	21st to end	Day	21% 11% 3 7% 5% 4 4 4 4 6% 31%	2384
May	1st to 10th	Day	26% 10% 3 7% 4 3 4 3 5% 6% 28%	4156
	11th to 20th	Day	18% 9% 3 8% 5% 5% 4 4 6% 7% 32%	4398
	21st to end	Day	12% 6% 2 6% 5% 5% 4 4 7% 9% 41%	4837
June	1st to 10th	Day	18% 7% 3 6% 5% 5% 6% 4 7% 8% 31%	2660
	11th to 20th	Day	18% 7% 3 5% 6% 4 5% 5% 7% 8% 32%	2660
	21st to end	Day	18% 7% 3 7% 5% 5% 6% 5% 6% 8% 32%	2660
July	1st to 10th	Day	12% 6% 3 7% 5% 5% 5% 5% 8% 10% 36%	4440
	11th to 20th	Day	9% 6% 3 8% 6% 6% 6% 5% 8% 9% 36%	4440
	21st to end	Day	14% 7% 2 9% 5% 5% 5% 5% 7% 7% 34%	4814
August	1st to 10th	Day	16% 8% 3 7% 5% 5% 5% 4 6% 8% 32%	4393
	11th to 20th	Day	13% 8% 3 8% 5% 4 6% 5% 7% 8% 34%	3762
	21st to end	Day	12% 6% 3 6% 4 5% 5% 4 7% 8% 39%	4180
September	1st to 10th	Day	14% 5% 1 5% 5% 4 5% 3 6% 7% 44%	2280
	11th to 20th	Day	15% 7% 2 4 3 3 4 3 5% 7% 47%	2180
	21st to end	Day	16% 7% 2 6% 3 4 4 4 6% 8% 41%	2090
October	1st to 10th	Day	21% 9% 3 7% 5% 4 4 3 4 4 36%	2005
	11th to 20th	Day	16% 9% 3 7% 4 4 5% 3 6% 7% 38%	1891
	21st to end	Day	24% 11% 3 8% 4 4 4 3 5% 6% 29%	1881
November	1st to 10th	Day	14% 11% 2 7% 3 4 4 3 4 6% 41%	1708
	11th to 20th	Day	17% 14% 3 7% 4 4 4 3 4 5% 35%	1710
	21st to end	Day	17% 12% 4 8% 5% 4 5% 4 5% 6% 30%	1579
December	1st to 10th	Day	17% 19% 6% 9% 6% 5% 4 4 5% 4 22%	1520
	11th to 20th	Day	20% 16% 5% 9% 4 3 2 3 3 5% 30%	1906
	21st to end	Day	23% 16% 7% 10% 4 4 4 2 4 4 21%	2772
January	1st to 10th	Night	14% 16% 5% 10% 5% 5% 3 3 4 5% 30%	4429
	11th to 20th	Night	12% 16% 6% 15% 8% 5% 4 3 5% 5% 22%	4440
	21st to end	Night	23% 15% 5% 11% 7% 5% 4 3 3 3 22%	4820
February	1st to 10th	Night	15% 14% 4 12% 8% 5% 5% 4 5% 5% 24%	2470
	11th to 20th	Night	13% 14% 6% 12% 7% 5% 5% 4 5% 5% 25%	2226
	21st to end	Night	16% 15% 4 11% 4 4 5% 3 4 6% 27%	1884
March	1st to 10th	Night	22% 11% 4 10% 5% 4 4 4 5% 6% 26%	3724
	11th to 20th	Night	14% 18% 4 8% 5% 4 5% 3 4 5% 30%	3666
	21st to end	Night	19% 16% 4 11% 4 3 3 3 3 4 30%	3466
April	1st to 10th	Night	20% 13% 3 7% 4 4 4 4 5% 6% 29%	1900
	11th to 20th	Night	19% 11% 3 7% 4 4 3 4 5% 7% 33%	1875
	21st to end	Night	21% 10% 3 6% 4 4 3 3 5% 6% 35%	1796
May	1st to 10th	Night	27% 10% 3 7% 4 4 4 3 5% 5% 29%	2813
	11th to 20th	Night	17% 9% 3 9% 6% 5% 6% 4 6% 6% 29%	2495
	21st to end	Night	14% 7% 2 7% 5% 5% 5% 4 6% 8% 37%	2738
June	1st to 10th	Night	21% 7% 2 5% 5% 5% 4 3 5% 7% 36%	1520
	11th to 20th	Night	18% 5% 2 6% 4 4 4 5% 6% 7% 40%	1520
	21st to end	Night	14% 6% 2 6% 4 4 6% 4 6% 8% 40%	1520
July	1st to 10th	Night	12% 7% 3 8% 6% 6% 5% 4 6% 8% 36%	2520
	11th to 20th	Night	13% 8% 3 8% 5% 4 5% 4 5% 7% 37%	2520
	21st to end	Night	13% 8% 3 7% 5% 4 5% 3 6% 7% 38%	2739
August	1st to 10th	Night	21% 8% 3 7% 4 4 4 3 5% 7% 33%	2506
	11th to 20th	Night	14% 7% 3 8% 6% 6% 5% 4 6% 7% 35%	3061
	21st to end	Night	12% 6% 2 6% 4 4 4 4 6% 8% 43%	3476
September	1st to 10th	Night	16% 7% 3 6% 4 3 4 3 5% 6% 43%	1900
	11th to 20th	Night	15% 5% 1 4 3 4 3 2 4 7% 51%	2000
	21st to end	Night	15% 7% 2 6% 5% 4 4 3 5% 6% 43%	2090
October	1st to 10th	Night	21% 8% 3 6% 5% 4 4 4 4 6% 35%	2171
	11th to 20th	Night	16% 9% 2 6% 5% 4 4 4 5% 6% 38%	2289
	21st to end	Night	24% 10% 3 7% 4 4 4 3 6% 7% 29%	2717
November	1st to 10th	Night	15% 11% 3 7% 4 4 4 3 5% 4 39%	2470
	11th to 20th	Night	16% 12% 3 7% 5% 5% 5% 4 4 6% 33%	2470
	21st to end	Night	15% 14% 4 8% 6% 4 5% 4 4 5% 33%	2598
December	1st to 10th	Night	19% 17% 5% 10% 6% 5% 3 3 5% 5% 23%	2660
	11th to 20th	Night	22% 14% 5% 8% 5% 4 4 3 5% 5% 25%	3288
	21st to end	Night	24% 17% 6% 9% 4 3 4 3 4 5% 22%	4884

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	58% 9% 12% 17% 4	2518
	11th to 20th	Day	64% 9% 11% 12% 4 1	2520
	21st to end	Day	67% 5% 10% 13% 4 1	2835
February	1st to 10th	Day	61% 7% 12% 14% 6%	1710
	11th to 20th	Day	60% 6% 9% 16% 8% 1	1847
	21st to end	Day	60% 6% 10% 14% 9%	1570
March	1st to 10th	Day	62% 5% 12% 12% 8% 1	3119
	11th to 20th	Day	54% 10% 15% 12% 8% 1	3276
	21st to end	Day	55% 6% 7% 14% 17% 2	4166
April	1st to 10th	Day	55% 5% 8% 20% 9% 2	2280
	11th to 20th	Day	50% 6% 11% 18% 14% 1	2254
	21st to end	Day	53% 6% 9% 17% 11% 3	2384
May	1st to 10th	Day	56% 7% 11% 17% 9% 1	4170
	11th to 20th	Day	49% 9% 14% 19% 8% 1	4402
	21st to end	Day	38% 9% 14% 24% 13% 1	4837
June	1st to 10th	Day	49% 8% 15% 18% 9%	2660
	11th to 20th	Day	47% 8% 13% 19% 12% 1	2660
	21st to end	Day	48% 9% 14% 19% 10%	2660
July	1st to 10th	Day	42% 7% 13% 24% 12% 1	4370
	11th to 20th	Day	43% 6% 16% 24% 10%	4365
	21st to end	Day	47% 6% 15% 20% 11%	4661
August	1st to 10th	Day	50% 7% 14% 21% 8%	4379
	11th to 20th	Day	46% 7% 16% 25% 5%	3799
	21st to end	Day	40% 6% 14% 29% 9% 1	4180
September	1st to 10th	Day	38% 8% 13% 26% 14% 1	2280
	11th to 20th	Day	37% 6% 11% 24% 20% 1	2180
	21st to end	Day	41% 7% 12% 25% 13% 2	2090
October	1st to 10th	Day	52% 4 8% 21% 14% 1	3330
	11th to 20th	Day	43% 5% 13% 23% 14% 3	3119
	21st to end	Day	42% 5% 13% 27% 11% 2	3081
November	1st to 10th	Day	43% 6% 15% 22% 13% 1	1708
	11th to 20th	Day	52% 6% 11% 17% 12% 1	1710
	21st to end	Day	53% 7% 16% 16% 6% 1	1579
December	1st to 10th	Day	64% 7% 11% 11% 6% 1	1520
	11th to 20th	Day	58% 6% 13% 16% 6% 1	1906
	21st to end	Day	66% 7% 10% 12% 5%	2772
January	1st to 10th	Night	57% 8% 13% 14% 7% 1	4429
	11th to 20th	Night	62% 9% 11% 12% 5% 1	4440
	21st to end	Night	67% 5% 10% 12% 5% 1	4820
February	1st to 10th	Night	61% 6% 12% 14% 6% 1	2470
	11th to 20th	Night	58% 8% 11% 13% 9% 1	2228
	21st to end	Night	58% 6% 12% 15% 7% 2	1884
March	1st to 10th	Night	58% 8% 9% 16% 8% 1	3734
	11th to 20th	Night	55% 8% 12% 18% 6% 1	3667
	21st to end	Night	56% 6% 6% 13% 15% 3	3466
April	1st to 10th	Night	54% 6% 12% 18% 9% 1	1900
	11th to 20th	Night	50% 6% 10% 19% 14% 1	1875
	21st to end	Night	50% 7% 11% 16% 14% 3	1796
May	1st to 10th	Night	55% 8% 11% 15% 10% 1	2819
	11th to 20th	Night	52% 10% 14% 16% 7% 1	2496
	21st to end	Night	42% 10% 13% 19% 15% 2	2739
June	1st to 10th	Night	46% 7% 13% 22% 11% 1	1520
	11th to 20th	Night	42% 8% 15% 23% 11%	1520
	21st to end	Night	41% 8% 15% 23% 12%	1520
July	1st to 10th	Night	45% 6% 16% 19% 14% 1	2480
	11th to 20th	Night	45% 6% 13% 24% 11%	2472
	21st to end	Night	45% 6% 13% 25% 11% 1	2651
August	1st to 10th	Night	51% 6% 14% 21% 7%	2496
	11th to 20th	Night	47% 6% 18% 22% 7%	3090
	21st to end	Night	38% 5% 16% 31% 10% 1	3476
September	1st to 10th	Night	42% 6% 12% 26% 14% 1	1900
	11th to 20th	Night	34% 5% 13% 28% 20% 1	2000
	21st to end	Night	42% 7% 11% 24% 15% 1	2090
October	1st to 10th	Night	53% 5% 10% 20% 11% 1	3626
	11th to 20th	Night	41% 5% 13% 21% 18% 2	3800
	21st to end	Night	44% 5% 13% 29% 9%	4467
November	1st to 10th	Night	46% 7% 12% 19% 14% 2	2470
	11th to 20th	Night	51% 7% 13% 15% 11% 2	2470
	21st to end	Night	54% 7% 15% 17% 7% 1	2598
December	1st to 10th	Night	62% 7% 13% 12% 5%	2660
	11th to 20th	Night	60% 9% 13% 11% 8%	3288
	21st to end	Night	66% 7% 9% 14% 5%	4884

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% 28% 28% 12% 3	180
	11th to 20th	Day	34% 27% 27% 9% 2 1	180
	21st to end	Day	22% 31% 32% 11% 5%	216
February	1st to 10th	Day	32% 36% 26% 4 2	270
	11th to 20th	Day	30% 35% 23% 11% 2	446
	21st to end	Day	29% 27% 28% 13% 2	382
March	1st to 10th	Day	30% 23% 28% 16% 2	460
	11th to 20th	Day	30% 28% 27% 12% 3 1	460
	21st to end	Day	33% 27% 22% 12% 5% 1	506
April	1st to 10th	Day	34% 24% 22% 13% 6% 1	460
	11th to 20th	Day	29% 27% 25% 12% 6% 2	452
	21st to end	Day	29% 20% 31% 13% 4 2	460
May	1st to 10th	Day	32% 22% 26% 11% 7% 2	463
	11th to 20th	Day	22% 18% 33% 20% 5% 2	487
	21st to end	Day	18% 16% 30% 24% 9% 3	529
June	1st to 10th	Day	18% 16% 31% 25% 10% 1	490
	11th to 20th	Day	19% 14% 30% 25% 11% 1	490
	21st to end	Day	21% 16% 31% 20% 10% 1	490
July	1st to 10th	Day	14% 11% 31% 27% 14% 3	485
	11th to 20th	Day	12% 8% 34% 32% 12% 2	484
	21st to end	Day	15% 12% 36% 23% 13% 1	532
August	1st to 10th	Day	14% 11% 27% 31% 12% 5%	486
	11th to 20th	Day	18% 8% 29% 24% 14% 7%	479
	21st to end	Day	14% 14% 26% 27% 14% 6%	539
September	1st to 10th	Day	18% 12% 22% 25% 16% 7%	490
	11th to 20th	Day	16% 13% 23% 21% 16% 11%	490
	21st to end	Day	19% 13% 28% 22% 12% 6%	490
October	1st to 10th	Day	26% 14% 23% 20% 13% 4	490
	11th to 20th	Day	23% 18% 27% 20% 10% 2	485
	21st to end	Day	32% 16% 26% 19% 5% 1	429
November	1st to 10th	Day	22% 21% 25% 20% 11% 1	378
	11th to 20th	Day	26% 28% 25% 14% 5% 1	370
	21st to end	Day	28% 27% 25% 18% 2	239
December	1st to 10th	Day	29% 29% 28% 11% 3 1	180
	11th to 20th	Day	34% 26% 28% 10% 2	180
	21st to end	Day	30% 27% 30% 11% 3	198
January	1st to 10th	Night	23% 28% 32% 15% 2	760
	11th to 20th	Night	27% 25% 28% 17% 2	760
	21st to end	Night	20% 26% 32% 20% 2	836
February	1st to 10th	Night	23% 25% 34% 16% 1	760
	11th to 20th	Night	23% 27% 33% 16% 2	743
	21st to end	Night	29% 24% 27% 17% 2	628
March	1st to 10th	Night	28% 23% 30% 17% 2	760
	11th to 20th	Night	25% 28% 28% 17% 2	760
	21st to end	Night	28% 22% 25% 18% 6%	836
April	1st to 10th	Night	29% 21% 28% 21% 3	760
	11th to 20th	Night	26% 22% 26% 19% 6%	751
	21st to end	Night	26% 19% 29% 21% 5%	656
May	1st to 10th	Night	26% 18% 27% 22% 7%	562
	11th to 20th	Night	20% 14% 30% 32% 4 1	374
	21st to end	Night	16% 9% 28% 35% 12% 1	411
June	1st to 10th	Night	22% 8% 28% 31% 12%	380
	11th to 20th	Night	17% 9% 25% 38% 11%	380
	21st to end	Night	14% 8% 24% 43% 10% 1	380
July	1st to 10th	Night	14% 5% 22% 45% 14% 1	370
	11th to 20th	Night	15% 5% 21% 41% 16% 1	368
	21st to end	Night	14% 6% 23% 43% 14% 1	416
August	1st to 10th	Night	14% 2 21% 44% 17% 1	378
	11th to 20th	Night	16% 5% 21% 35% 19% 4	726
	21st to end	Night	15% 7% 21% 36% 19% 2	836
September	1st to 10th	Night	18% 8% 26% 31% 16% 2	760
	11th to 20th	Night	19% 8% 21% 29% 19% 5%	760
	21st to end	Night	19% 9% 25% 30% 14% 3	760
October	1st to 10th	Night	26% 10% 22% 28% 13% 1	760
	11th to 20th	Night	21% 14% 29% 28% 9%	760
	21st to end	Night	30% 17% 28% 22% 4	836
November	1st to 10th	Night	21% 20% 28% 23% 8%	760
	11th to 20th	Night	23% 21% 29% 19% 7% 1	760
	21st to end	Night	24% 23% 28% 20% 5% 1	760
December	1st to 10th	Night	28% 26% 27% 14% 4	760
	11th to 20th	Night	28% 24% 27% 18% 3	760
	21st to end	Night	28% 27% 28% 15% 2	836

Page generated at 2024-11-03 02:11:17. Version ac07

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