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 2024-01-12.

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% 9% 4 7% 6% 3 5% 5% 5% 7% 33%	74765
	Night	18% 11% 4 7% 6% 3 4 4 5% 6% 33%	74944
Transparency	Day	50% 7% 12% 19% 10% 1	74470
	Night	52% 7% 12% 18% 10% 1	74773
Seeing	Day	23% 20% 27% 19% 9% 2	13717
	Night	23% 18% 27% 24% 8% 1	22872

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	15% 15% 7% 10% 7% 3 5% 5% 5% 5% 24%	1517
	11th to 20th	Day	17% 13% 5% 9% 8% 3 6% 5% 5% 6% 23%	1448
	21st to end	Day	12% 15% 7% 9% 7% 4 5% 5% 5% 6% 25%	1619
February	1st to 10th	Day	17% 14% 6% 9% 8% 4 5% 5% 6% 5% 21%	1620
	11th to 20th	Day	13% 15% 7% 11% 7% 4 5% 4 4 6% 25%	1739
	21st to end	Day	18% 15% 5% 10% 7% 3 5% 4 3 4 26%	1480
March	1st to 10th	Day	16% 12% 5% 9% 6% 4 4 4 5% 6% 29%	1797
	11th to 20th	Day	17% 13% 7% 9% 5% 3 3 4 4 5% 31%	1860
	21st to end	Day	20% 12% 4 7% 4 3 4 3 4 5% 34%	2376
April	1st to 10th	Day	19% 12% 5% 7% 6% 3 4 4 4 5% 33%	2160
	11th to 20th	Day	16% 9% 3 6% 6% 3 5% 4 5% 5% 36%	2134
	21st to end	Day	22% 10% 3 6% 5% 3 4 4 5% 6% 30%	2258
May	1st to 10th	Day	24% 9% 4 6% 5% 2 4 5% 4 6% 30%	2362
	11th to 20th	Day	19% 7% 3 5% 4 3 5% 5% 5% 7% 37%	2478
	21st to end	Day	14% 6% 3 5% 6% 3 5% 5% 6% 9% 38%	2725
June	1st to 10th	Day	19% 7% 3 6% 6% 4 6% 5% 7% 8% 31%	2520
	11th to 20th	Day	19% 6% 3 4 6% 3 5% 6% 6% 8% 33%	2520
	21st to end	Day	18% 6% 3 6% 6% 3 6% 6% 6% 8% 32%	2520
July	1st to 10th	Day	14% 5% 3 5% 5% 3 5% 6% 7% 9% 38%	2520
	11th to 20th	Day	12% 5% 3 5% 6% 3 5% 6% 6% 9% 39%	2520
	21st to end	Day	14% 5% 2 7% 6% 4 6% 6% 6% 7% 36%	2744
August	1st to 10th	Day	12% 5% 2 6% 6% 4 5% 7% 7% 9% 37%	2489
	11th to 20th	Day	14% 7% 2 6% 6% 3 6% 6% 7% 7% 35%	2145
	21st to end	Day	14% 5% 3 5% 5% 3 5% 5% 7% 8% 40%	2376
September	1st to 10th	Day	15% 5% 1 5% 6% 2 6% 5% 5% 7% 43%	2160
	11th to 20th	Day	16% 7% 2 3 4 2 4 4 5% 7% 47%	2066
	21st to end	Day	17% 6% 2 5% 4 3 4 4 5% 8% 43%	1980
October	1st to 10th	Day	22% 9% 3 5% 6% 3 3 4 4 4 36%	1900
	11th to 20th	Day	16% 8% 3 6% 5% 3 5% 4 6% 7% 36%	1792
	21st to end	Day	26% 11% 4 7% 5% 3 4 3 5% 6% 27%	1782
November	1st to 10th	Day	15% 10% 3 5% 5% 3 3 4 4 7% 42%	1671
	11th to 20th	Day	17% 13% 3 7% 5% 3 4 4 4 6% 35%	1710
	21st to end	Day	18% 11% 4 8% 5% 3 5% 5% 5% 6% 30%	1579
December	1st to 10th	Day	17% 16% 7% 9% 6% 4 4 5% 5% 4 22%	1520
	11th to 20th	Day	20% 15% 6% 8% 5% 2 3 3 3 5% 30%	1906
	21st to end	Day	23% 15% 8% 9% 5% 3 5% 3 3 4 21%	2772
January	1st to 10th	Night	15% 15% 5% 10% 7% 4 5% 4 4 5% 27%	2649
	11th to 20th	Night	16% 16% 5% 11% 8% 4 4 4 5% 6% 22%	2541
	21st to end	Night	13% 14% 6% 10% 8% 4 6% 4 4 5% 27%	2736
February	1st to 10th	Night	16% 14% 5% 11% 9% 4 6% 5% 4 5% 23%	2340
	11th to 20th	Night	14% 12% 6% 10% 8% 4 6% 5% 5% 5% 25%	2105
	21st to end	Night	16% 15% 5% 10% 6% 3 5% 5% 4 6% 26%	1776
March	1st to 10th	Night	17% 14% 5% 9% 6% 3 4 4 4 5% 29%	2150
	11th to 20th	Night	17% 13% 5% 8% 7% 3 5% 4 4 5% 30%	2096
	21st to end	Night	20% 11% 3 6% 5% 2 4 4 4 5% 35%	1980
April	1st to 10th	Night	20% 12% 4 6% 5% 3 4 5% 5% 6% 30%	1800
	11th to 20th	Night	20% 10% 3 5% 6% 2 4 4 5% 7% 34%	1775
	21st to end	Night	21% 10% 3 6% 5% 2 4 4 5% 6% 34%	1702
May	1st to 10th	Night	23% 12% 4 7% 4 3 4 4 4 6% 30%	1613
	11th to 20th	Night	19% 8% 3 6% 6% 3 5% 5% 6% 6% 34%	1415
	21st to end	Night	15% 5% 2 6% 5% 4 5% 6% 7% 7% 38%	1550
June	1st to 10th	Night	21% 6% 2 5% 5% 3 5% 4 5% 7% 36%	1440
	11th to 20th	Night	19% 5% 2 5% 4 3 4 5% 5% 7% 40%	1440
	21st to end	Night	14% 5% 2 5% 4 2 6% 6% 6% 8% 41%	1440
July	1st to 10th	Night	13% 5% 3 5% 5% 3 5% 4 6% 10% 40%	1440
	11th to 20th	Night	14% 6% 3 5% 5% 3 5% 6% 6% 7% 40%	1440
	21st to end	Night	13% 6% 2 5% 5% 2 5% 5% 6% 8% 43%	1574
August	1st to 10th	Night	11% 4 2 4 5% 4 4 5% 7% 10% 43%	1432
	11th to 20th	Night	14% 6% 3 5% 6% 4 6% 6% 7% 8% 36%	1751
	21st to end	Night	16% 5% 3 5% 5% 3 4 4 5% 8% 43%	1980
September	1st to 10th	Night	16% 7% 3 5% 4 3 4 4 5% 6% 42%	1800
	11th to 20th	Night	16% 5% 2 4 4 3 3 2 4 6% 51%	1894
	21st to end	Night	15% 7% 1 5% 6% 2 5% 4 5% 5% 44%	1980
October	1st to 10th	Night	22% 7% 3 5% 5% 3 4 4 4 5% 36%	2056
	11th to 20th	Night	16% 8% 3 5% 6% 3 5% 5% 5% 6% 37%	2168
	21st to end	Night	26% 9% 3 6% 5% 3 4 4 5% 7% 28%	2574
November	1st to 10th	Night	15% 11% 3 7% 5% 3 5% 4 5% 4 39%	2407
	11th to 20th	Night	17% 11% 4 6% 6% 4 5% 5% 4 6% 33%	2470
	21st to end	Night	16% 13% 5% 7% 6% 3 5% 4 4 5% 33%	2598
December	1st to 10th	Night	19% 15% 7% 9% 7% 4 3 4 5% 5% 23%	2660
	11th to 20th	Night	22% 14% 6% 8% 5% 3 4 4 5% 6% 25%	3288
	21st to end	Night	24% 16% 7% 7% 6% 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	60% 7% 11% 16% 7%	1518
	11th to 20th	Day	62% 8% 10% 12% 6% 2	1448
	21st to end	Day	58% 6% 13% 13% 7% 2	1619
February	1st to 10th	Day	62% 7% 12% 12% 5%	1620
	11th to 20th	Day	61% 6% 9% 16% 8% 1	1748
	21st to end	Day	61% 6% 10% 13% 9%	1480
March	1st to 10th	Day	56% 5% 13% 15% 9% 2	1800
	11th to 20th	Day	55% 5% 11% 13% 13% 3	1860
	21st to end	Day	54% 5% 8% 15% 15% 3	2376
April	1st to 10th	Day	55% 5% 8% 21% 10% 2	2160
	11th to 20th	Day	49% 6% 11% 18% 15% 1	2134
	21st to end	Day	54% 6% 9% 17% 11% 3	2258
May	1st to 10th	Day	55% 6% 9% 18% 10% 2	2362
	11th to 20th	Day	46% 6% 10% 22% 14% 2	2482
	21st to end	Day	43% 9% 16% 21% 10% 2	2725
June	1st to 10th	Day	49% 8% 15% 18% 9%	2520
	11th to 20th	Day	47% 8% 13% 19% 12% 1	2520
	21st to end	Day	48% 9% 14% 19% 10%	2520
July	1st to 10th	Day	42% 10% 13% 22% 13% 1	2450
	11th to 20th	Day	40% 9% 17% 25% 9%	2445
	21st to end	Day	44% 9% 14% 21% 12% 1	2591
August	1st to 10th	Day	41% 11% 16% 23% 10% 1	2475
	11th to 20th	Day	44% 10% 15% 21% 8% 1	2145
	21st to end	Day	39% 9% 14% 25% 12% 1	2376
September	1st to 10th	Day	39% 8% 13% 25% 13% 1	2160
	11th to 20th	Day	38% 7% 10% 24% 20% 1	2066
	21st to end	Day	40% 7% 12% 26% 13% 2	1980
October	1st to 10th	Day	52% 6% 10% 18% 11% 2	1900
	11th to 20th	Day	45% 9% 15% 23% 8% 1	1792
	21st to end	Day	58% 7% 12% 13% 9% 2	1782
November	1st to 10th	Day	43% 6% 15% 22% 12% 1	1671
	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	61% 6% 11% 12% 9% 1	2649
	11th to 20th	Night	63% 7% 12% 11% 6% 1	2541
	21st to end	Night	59% 6% 11% 15% 9% 2	2736
February	1st to 10th	Night	63% 6% 12% 12% 6% 1	2340
	11th to 20th	Night	58% 8% 11% 13% 9% 1	2107
	21st to end	Night	59% 6% 12% 15% 7% 2	1776
March	1st to 10th	Night	57% 6% 9% 18% 9% 1	2160
	11th to 20th	Night	57% 6% 9% 17% 8% 2	2097
	21st to end	Night	52% 5% 9% 16% 15% 4	1980
April	1st to 10th	Night	54% 6% 12% 18% 9% 1	1800
	11th to 20th	Night	50% 6% 10% 20% 13% 1	1775
	21st to end	Night	50% 7% 11% 16% 13% 3	1702
May	1st to 10th	Night	55% 6% 9% 15% 13% 2	1613
	11th to 20th	Night	49% 6% 12% 18% 12% 2	1416
	21st to end	Night	44% 9% 13% 21% 12% 1	1551
June	1st to 10th	Night	47% 7% 13% 23% 10% 1	1440
	11th to 20th	Night	43% 9% 15% 22% 11%	1440
	21st to end	Night	40% 8% 15% 24% 12%	1440
July	1st to 10th	Night	39% 9% 16% 22% 13% 1	1400
	11th to 20th	Night	40% 9% 15% 26% 10%	1392
	21st to end	Night	35% 9% 17% 25% 12% 2	1486
August	1st to 10th	Night	35% 9% 19% 27% 10% 1	1422
	11th to 20th	Night	42% 10% 16% 23% 9%	1751
	21st to end	Night	38% 7% 14% 26% 14% 1	1980
September	1st to 10th	Night	42% 6% 13% 25% 13% 1	1800
	11th to 20th	Night	35% 5% 13% 26% 20% 1	1894
	21st to end	Night	41% 7% 10% 24% 16% 1	1980
October	1st to 10th	Night	50% 7% 11% 20% 11% 2	2056
	11th to 20th	Night	46% 7% 16% 21% 9% 1	2168
	21st to end	Night	56% 7% 13% 15% 8% 1	2574
November	1st to 10th	Night	46% 7% 12% 19% 14% 2	2407
	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	28% 28% 28% 12% 3	180
	11th to 20th	Day	34% 28% 25% 9% 2 1	162
	21st to end	Day	21% 33% 30% 11% 5%	192
February	1st to 10th	Day	35% 37% 24% 3 2	240
	11th to 20th	Day	29% 36% 23% 11% 2	407
	21st to end	Day	29% 29% 27% 13% 2	346
March	1st to 10th	Day	29% 25% 29% 15% 2	420
	11th to 20th	Day	29% 28% 28% 12% 3 1	420
	21st to end	Day	32% 25% 23% 13% 6% 2	462
April	1st to 10th	Day	33% 25% 23% 13% 6% 1	420
	11th to 20th	Day	26% 27% 26% 12% 6% 2	412
	21st to end	Day	31% 19% 30% 14% 4 2	420
May	1st to 10th	Day	32% 22% 25% 11% 7% 2	423
	11th to 20th	Day	22% 19% 33% 19% 4 2	447
	21st to end	Day	18% 15% 29% 23% 10% 4	485
June	1st to 10th	Day	18% 15% 32% 24% 10% 1	450
	11th to 20th	Day	20% 14% 30% 24% 11% 1	450
	21st to end	Day	18% 16% 32% 22% 11% 2	450
July	1st to 10th	Day	14% 11% 29% 27% 15% 3	445
	11th to 20th	Day	12% 8% 34% 31% 13% 2	444
	21st to end	Day	15% 11% 36% 24% 13% 1	488
August	1st to 10th	Day	13% 10% 27% 32% 13% 5%	446
	11th to 20th	Day	17% 8% 28% 23% 15% 8%	439
	21st to end	Day	15% 14% 25% 26% 15% 6%	495
September	1st to 10th	Day	18% 12% 21% 25% 17% 7%	450
	11th to 20th	Day	18% 14% 24% 20% 14% 10%	450
	21st to end	Day	19% 14% 26% 22% 12% 6%	450
October	1st to 10th	Day	27% 14% 22% 20% 13% 4	450
	11th to 20th	Day	22% 20% 27% 21% 10% 1	446
	21st to end	Day	33% 16% 26% 19% 6% 1	396
November	1st to 10th	Day	21% 21% 24% 21% 11% 1	365
	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% 18% 2	727
	21st to end	Night	19% 26% 32% 20% 2	792
February	1st to 10th	Night	25% 25% 33% 16% 1	720
	11th to 20th	Night	22% 27% 32% 16% 2	703
	21st to end	Night	29% 25% 26% 17% 2	592
March	1st to 10th	Night	27% 23% 31% 17% 2	720
	11th to 20th	Night	26% 28% 28% 17% 2	720
	21st to end	Night	27% 22% 26% 18% 7%	792
April	1st to 10th	Night	28% 21% 28% 21% 3	720
	11th to 20th	Night	25% 22% 26% 20% 7%	711
	21st to end	Night	26% 18% 29% 20% 5%	622
May	1st to 10th	Night	25% 18% 27% 22% 8%	533
	11th to 20th	Night	21% 14% 30% 31% 4 1	354
	21st to end	Night	16% 8% 27% 35% 12% 1	389
June	1st to 10th	Night	22% 8% 27% 30% 13%	360
	11th to 20th	Night	18% 8% 24% 39% 11%	360
	21st to end	Night	14% 7% 24% 45% 10% 1	360
July	1st to 10th	Night	13% 5% 22% 45% 14% 1	350
	11th to 20th	Night	15% 5% 20% 42% 17% 1	348
	21st to end	Night	14% 5% 22% 44% 14% 1	394
August	1st to 10th	Night	13% 3 21% 45% 18% 1	358
	11th to 20th	Night	16% 5% 20% 36% 18% 4	687
	21st to end	Night	15% 7% 21% 36% 19% 2	792
September	1st to 10th	Night	17% 8% 26% 31% 16% 2	720
	11th to 20th	Night	19% 8% 22% 28% 18% 5%	720
	21st to end	Night	18% 10% 25% 29% 15% 3	720
October	1st to 10th	Night	26% 10% 21% 28% 13% 2	720
	11th to 20th	Night	20% 14% 29% 28% 8%	720
	21st to end	Night	31% 17% 27% 22% 4	792
November	1st to 10th	Night	21% 19% 28% 23% 8%	740
	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 2024-01-09 07:14:44. Version ac07

Copyright 2024 Attilla Danko