Fairfield Lake State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fairfield Lake State Park clear sky chart from 2005-11-06 to 2024-01-22.

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	11% 5% 2 5% 5% 3 4 4 5% 8% 47%	75027
	Night	11% 5% 2 4 4 2 3 4 5% 7% 54%	74933
Transparency	Day	36% 5% 11% 22% 19% 7%	74752
	Night	32% 4 11% 21% 22% 10%	74728
Seeing	Day	13% 7% 21% 27% 24% 9%	13933
	Night	14% 7% 26% 34% 18% 2	23938

By Month

Percentage Cloud Cover SE (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% 7% 3 4 4 3 3 3 4 6% 51%	1707
	11th to 20th	Day	17% 7% 3 3 4 1 3 3 4 7% 46%	1710
	21st to end	Day	16% 7% 3 5% 4 2 3 3 4 5% 48%	1791
February	1st to 10th	Day	20% 9% 3 6% 3 2 3 3 4 5% 42%	1701
	11th to 20th	Day	21% 7% 2 5% 5% 3 3 3 4 6% 41%	1749
	21st to end	Day	22% 6% 2 5% 4 2 3 2 3 5% 47%	1568
March	1st to 10th	Day	19% 7% 2 5% 5% 3 3 3 5% 7% 41%	1980
	11th to 20th	Day	18% 6% 3 5% 6% 3 5% 4 3 5% 42%	1980
	21st to end	Day	15% 7% 3 5% 4 3 4 4 4 5% 46%	2178
April	1st to 10th	Day	13% 7% 3 6% 5% 3 4 4 5% 7% 41%	1980
	11th to 20th	Day	14% 6% 2 7% 5% 3 4 5% 6% 9% 39%	2078
	21st to end	Day	11% 6% 2 5% 4 4 4 5% 5% 7% 47%	2169
May	1st to 10th	Day	12% 6% 3 6% 5% 3 5% 5% 5% 7% 42%	2340
	11th to 20th	Day	11% 6% 3 6% 6% 3 5% 5% 6% 7% 43%	2302
	21st to end	Day	11% 6% 3 5% 6% 4 6% 6% 7% 9% 37%	2531
June	1st to 10th	Day	5% 3 2 4 5% 3 6% 5% 7% 12% 48%	2340
	11th to 20th	Day	5% 3 2 4 5% 3 6% 6% 8% 11% 49%	2340
	21st to end	Day	5% 3 2 5% 5% 3 6% 6% 8% 10% 46%	2340
July	1st to 10th	Day	7% 4 3 5% 7% 4 6% 6% 8% 10% 39%	2340
	11th to 20th	Day	4 3 2 4 4 3 5% 6% 7% 11% 52%	2340
	21st to end	Day	4 3 2 4 5% 4 5% 6% 7% 11% 48%	2546
August	1st to 10th	Day	4 2 1 3 3 2 4 4 6% 11% 60%	2328
	11th to 20th	Day	6% 3 2 4 4 3 5% 5% 7% 10% 50%	2300
	21st to end	Day	5% 3 1 5% 7% 4 6% 6% 8% 9% 45%	2306
September	1st to 10th	Day	9% 5% 2 5% 4 3 5% 5% 5% 8% 48%	1980
	11th to 20th	Day	11% 5% 2 5% 5% 3 4 6% 6% 8% 44%	1980
	21st to end	Day	6% 4 2 4 5% 3 4 5% 5% 7% 56%	1980
October	1st to 10th	Day	6% 3 1 4 4 2 4 4 4 8% 60%	1898
	11th to 20th	Day	13% 5% 2 4 3 2 3 3 3 6% 57%	1800
	21st to end	Day	14% 5% 2 4 2 2 3 3 3 4 58%	1980
November	1st to 10th	Day	12% 5% 3 4 4 2 4 3 4 6% 52%	1858
	11th to 20th	Day	9% 7% 2 5% 4 2 3 4 4 5% 54%	1891
	21st to end	Day	16% 7% 3 5% 4 2 4 4 4 5% 45%	1710
December	1st to 10th	Day	14% 7% 2 5% 4 2 3 3 4 6% 48%	1710
	11th to 20th	Day	18% 7% 3 4 4 2 4 4 5% 6% 43%	2161
	21st to end	Day	15% 8% 3 6% 5% 2 3 3 3 5% 46%	3135
January	1st to 10th	Night	14% 6% 2 4 3 2 2 3 4 6% 53%	2458
	11th to 20th	Night	17% 6% 2 4 4 2 3 3 4 5% 51%	2470
	21st to end	Night	15% 6% 2 4 5% 2 3 4 4 5% 50%	2600
February	1st to 10th	Night	17% 6% 3 5% 4 2 3 3 4 5% 47%	2272
	11th to 20th	Night	18% 7% 3 5% 4 3 3 3 3 5% 46%	2098
	21st to end	Night	20% 5% 2 4 4 2 4 3 4 5% 47%	1686
March	1st to 10th	Night	16% 5% 3 5% 5% 2 4 3 6% 7% 43%	1980
	11th to 20th	Night	14% 6% 3 4 5% 2 3 5% 5% 6% 47%	1980
	21st to end	Night	11% 5% 2 4 3 2 4 3 5% 8% 52%	2178
April	1st to 10th	Night	11% 4 2 4 4 3 4 4 5% 7% 53%	1980
	11th to 20th	Night	13% 5% 2 4 4 2 4 4 6% 7% 49%	1829
	21st to end	Night	10% 4 2 5% 4 3 3 4 5% 7% 53%	1785
May	1st to 10th	Night	8% 5% 3 5% 5% 3 4 3 6% 9% 50%	1620
	11th to 20th	Night	10% 4 2 5% 5% 2 4 4 6% 9% 50%	1593
	21st to end	Night	8% 4 1 4 4 3 3 5% 6% 10% 52%	1745
June	1st to 10th	Night	5% 2 2 3 3 3 4 5% 6% 9% 60%	1620
	11th to 20th	Night	3 2 1 2 3 2 3 4 5% 9% 66%	1620
	21st to end	Night	5% 4 2 3 4 2 5% 3 7% 9% 57%	1620
July	1st to 10th	Night	5% 4 1 4 4 3 5% 5% 7% 12% 50%	1620
	11th to 20th	Night	2 1 1 2 2 2 5% 4 5% 10% 66%	1620
	21st to end	Night	3 2 1 3 4 3 5% 5% 8% 12% 54%	1772
August	1st to 10th	Night	2 1 1 1 2 2 2 3 5% 10% 68%	1611
	11th to 20th	Night	6% 4 2 4 4 2 4 5% 6% 10% 53%	1600
	21st to end	Night	4 3 2 4 4 2 3 5% 7% 12% 53%	2044
September	1st to 10th	Night	7% 4 2 4 4 3 4 4 5% 8% 54%	1980
	11th to 20th	Night	11% 5% 2 4 4 2 3 3 5% 8% 52%	1980
	21st to end	Night	7% 3 2 3 3 2 3 4 4 7% 62%	1980
October	1st to 10th	Night	5% 2 2 3 3 1 3 3 5% 7% 65%	2042
	11th to 20th	Night	12% 4 1 3 3 3 2 3 5% 5% 60%	2160
	21st to end	Night	13% 5% 2 3 3 2 2 3 3 4 60%	2376
November	1st to 10th	Night	11% 4 1 4 3 2 3 3 3 5% 60%	2220
	11th to 20th	Night	8% 5% 2 5% 4 3 4 4 4 5% 57%	2286
	21st to end	Night	15% 6% 2 4 4 3 3 3 5% 5% 50%	2470
December	1st to 10th	Night	14% 6% 2 4 3 2 3 4 4 6% 51%	2470
	11th to 20th	Night	15% 7% 3 6% 5% 3 3 3 4 6% 47%	3036
	21st to end	Night	15% 7% 2 5% 4 2 3 3 4 4 52%	4532

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	38% 3 6% 20% 24% 9%	1708
	11th to 20th	Day	39% 4 7% 20% 22% 8%	1710
	21st to end	Day	41% 2 5% 15% 26% 11%	1791
February	1st to 10th	Day	47% 3 5% 15% 20% 11%	1701
	11th to 20th	Day	47% 3 6% 17% 20% 8%	1759
	21st to end	Day	44% 2 6% 15% 18% 15%	1568
March	1st to 10th	Day	45% 3 7% 16% 20% 9%	1980
	11th to 20th	Day	47% 4 7% 14% 22% 7%	1980
	21st to end	Day	42% 4 8% 19% 22% 6%	2178
April	1st to 10th	Day	43% 4 9% 20% 16% 8%	1980
	11th to 20th	Day	41% 5% 10% 17% 19% 9%	2078
	21st to end	Day	37% 5% 9% 22% 21% 6%	2169
May	1st to 10th	Day	41% 5% 9% 22% 17% 6%	2340
	11th to 20th	Day	41% 6% 12% 23% 18% 1	2306
	21st to end	Day	42% 7% 14% 21% 15% 1	2531
June	1st to 10th	Day	30% 6% 16% 33% 13% 2	2340
	11th to 20th	Day	28% 7% 15% 31% 15% 4	2340
	21st to end	Day	30% 8% 14% 29% 17% 2	2340
July	1st to 10th	Day	36% 8% 19% 26% 11%	2276
	11th to 20th	Day	24% 7% 20% 29% 17% 2	2271
	21st to end	Day	27% 7% 22% 30% 12% 1	2405
August	1st to 10th	Day	19% 5% 18% 37% 19% 1	2314
	11th to 20th	Day	28% 7% 18% 28% 16% 3	2300
	21st to end	Day	32% 9% 14% 28% 15% 3	2306
September	1st to 10th	Day	34% 6% 11% 22% 18% 8%	1980
	11th to 20th	Day	36% 8% 14% 19% 16% 8%	1980
	21st to end	Day	28% 5% 9% 22% 23% 13%	1980
October	1st to 10th	Day	25% 4 11% 24% 20% 17%	1898
	11th to 20th	Day	31% 4 6% 17% 26% 17%	1800
	21st to end	Day	32% 2 4 18% 28% 16%	1980
November	1st to 10th	Day	34% 4 7% 20% 24% 9%	1858
	11th to 20th	Day	33% 3 8% 19% 24% 12%	1891
	21st to end	Day	42% 3 6% 19% 20% 10%	1710
December	1st to 10th	Day	39% 2 10% 20% 20% 8%	1710
	11th to 20th	Day	43% 3 6% 16% 23% 9%	2159
	21st to end	Day	43% 2 4 18% 24% 9%	3135
January	1st to 10th	Night	34% 3 5% 19% 25% 13%	2458
	11th to 20th	Night	38% 2 7% 18% 24% 11%	2470
	21st to end	Night	38% 3 5% 16% 23% 15%	2600
February	1st to 10th	Night	40% 4 6% 15% 20% 15%	2272
	11th to 20th	Night	42% 3 6% 15% 22% 12%	2098
	21st to end	Night	42% 3 7% 14% 17% 17%	1686
March	1st to 10th	Night	42% 4 8% 15% 20% 12%	1980
	11th to 20th	Night	39% 5% 9% 14% 25% 8%	1980
	21st to end	Night	32% 5% 11% 19% 23% 10%	2178
April	1st to 10th	Night	31% 6% 10% 22% 19% 12%	1980
	11th to 20th	Night	35% 5% 11% 19% 18% 13%	1829
	21st to end	Night	31% 6% 10% 20% 27% 8%	1785
May	1st to 10th	Night	34% 5% 11% 22% 20% 8%	1620
	11th to 20th	Night	33% 4 14% 27% 18% 3	1594
	21st to end	Night	28% 6% 18% 29% 17% 2	1746
June	1st to 10th	Night	21% 7% 16% 34% 19% 3	1620
	11th to 20th	Night	16% 5% 17% 36% 21% 5%	1620
	21st to end	Night	24% 6% 14% 29% 23% 4	1620
July	1st to 10th	Night	26% 7% 20% 33% 13% 2	1575
	11th to 20th	Night	13% 6% 24% 34% 21% 2	1566
	21st to end	Night	20% 6% 28% 31% 13% 1	1673
August	1st to 10th	Night	12% 5% 19% 38% 22% 3	1601
	11th to 20th	Night	27% 7% 19% 27% 17% 4	1600
	21st to end	Night	24% 6% 18% 33% 15% 4	2044
September	1st to 10th	Night	29% 5% 14% 23% 19% 10%	1980
	11th to 20th	Night	32% 5% 16% 20% 19% 9%	1980
	21st to end	Night	23% 4 10% 23% 26% 14%	1980
October	1st to 10th	Night	20% 5% 9% 26% 22% 18%	2042
	11th to 20th	Night	28% 3 7% 18% 25% 20%	2160
	21st to end	Night	30% 3 5% 17% 24% 21%	2376
November	1st to 10th	Night	29% 3 8% 20% 26% 13%	2220
	11th to 20th	Night	31% 3 7% 19% 25% 14%	2286
	21st to end	Night	38% 3 7% 17% 23% 11%	2470
December	1st to 10th	Night	35% 3 9% 21% 22% 10%	2470
	11th to 20th	Night	41% 3 6% 14% 23% 13%	3037
	21st to end	Night	38% 2 5% 15% 27% 12%	4532

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	23% 13% 34% 23% 6% 1	270
	11th to 20th	Day	23% 18% 33% 18% 7% 1	270
	21st to end	Day	21% 15% 40% 17% 6%	267
February	1st to 10th	Day	24% 15% 37% 20% 5%	240
	11th to 20th	Day	32% 20% 29% 17% 3	240
	21st to end	Day	32% 19% 36% 10% 4	198
March	1st to 10th	Day	25% 14% 38% 16% 6%	240
	11th to 20th	Day	22% 17% 37% 18% 5% 1	240
	21st to end	Day	19% 17% 41% 15% 9% 1	264
April	1st to 10th	Day	20% 15% 41% 19% 3 1	240
	11th to 20th	Day	21% 13% 31% 25% 9% 1	356
	21st to end	Day	15% 14% 33% 27% 9% 2	429
May	1st to 10th	Day	11% 12% 33% 34% 9% 1	603
	11th to 20th	Day	14% 6% 27% 33% 16% 4	625
	21st to end	Day	11% 5% 23% 33% 23% 5%	679
June	1st to 10th	Day	6% 2 14% 37% 31% 11%	630
	11th to 20th	Day	5% 2 16% 40% 28% 10%	630
	21st to end	Day	5% 3 12% 32% 33% 15%	630
July	1st to 10th	Day	6% 2 8% 33% 35% 15%	621
	11th to 20th	Day	3 1 5% 31% 45% 16%	618
	21st to end	Day	4 1 4 29% 47% 16%	684
August	1st to 10th	Day	4 5% 25% 51% 15%	626
	11th to 20th	Day	6% 1 6% 27% 46% 15%	614
	21st to end	Day	9% 1 4 15% 40% 32%	425
September	1st to 10th	Day	9% 1 5% 22% 33% 31%	270
	11th to 20th	Day	5% 3 8% 21% 41% 22%	270
	21st to end	Day	10% 2 9% 27% 34% 17%	270
October	1st to 10th	Day	3 3 15% 35% 35% 10%	270
	11th to 20th	Day	11% 7% 27% 27% 20% 9%	270
	21st to end	Day	24% 12% 22% 22% 16% 4	297
November	1st to 10th	Day	17% 7% 27% 33% 13% 3	270
	11th to 20th	Day	18% 11% 28% 26% 15% 3	270
	21st to end	Day	21% 14% 31% 21% 10% 1	270
December	1st to 10th	Day	21% 10% 32% 20% 14% 3	270
	11th to 20th	Day	27% 16% 29% 21% 7%	270
	21st to end	Day	22% 14% 39% 18% 6% 2	297
January	1st to 10th	Night	19% 11% 34% 28% 8%	950
	11th to 20th	Night	22% 11% 32% 27% 7%	950
	21st to end	Night	18% 11% 35% 30% 5%	1000
February	1st to 10th	Night	23% 11% 32% 29% 5%	832
	11th to 20th	Night	23% 12% 39% 23% 3	704
	21st to end	Night	25% 13% 36% 23% 3	502
March	1st to 10th	Night	20% 12% 37% 27% 5%	540
	11th to 20th	Night	17% 10% 39% 26% 7%	540
	21st to end	Night	14% 11% 42% 27% 6% 1	594
April	1st to 10th	Night	13% 10% 42% 29% 6%	540
	11th to 20th	Night	16% 11% 39% 25% 9%	533
	21st to end	Night	14% 7% 42% 25% 10% 1	540
May	1st to 10th	Night	10% 9% 40% 31% 10% 1	540
	11th to 20th	Night	11% 5% 34% 33% 15% 1	531
	21st to end	Night	8% 3 28% 40% 20% 2	584
June	1st to 10th	Night	5% 2 15% 41% 33% 3	540
	11th to 20th	Night	3 1 19% 50% 24% 2	540
	21st to end	Night	5% 2 12% 41% 34% 6%	540
July	1st to 10th	Night	5% 1 9% 44% 35% 5%	525
	11th to 20th	Night	2 8% 44% 39% 6%	522
	21st to end	Night	4 1 6% 45% 41% 4	591
August	1st to 10th	Night	2 5% 46% 42% 4	537
	11th to 20th	Night	8% 1 7% 42% 37% 5%	534
	21st to end	Night	5% 1 6% 36% 46% 7%	594
September	1st to 10th	Night	8% 1 9% 35% 40% 7%	540
	11th to 20th	Night	13% 2 8% 29% 44% 5%	540
	21st to end	Night	9% 1 11% 34% 39% 5%	540
October	1st to 10th	Night	7% 1 14% 46% 26% 5%	602
	11th to 20th	Night	13% 4 22% 38% 19% 3	720
	21st to end	Night	15% 7% 28% 32% 17% 2	792
November	1st to 10th	Night	13% 3 27% 38% 18% 1	740
	11th to 20th	Night	11% 8% 29% 39% 13%	766
	21st to end	Night	19% 9% 29% 29% 13% 1	950
December	1st to 10th	Night	18% 9% 31% 33% 9% 1	950
	11th to 20th	Night	22% 10% 29% 33% 6%	950
	21st to end	Night	21% 10% 31% 31% 7%	1045

Page generated at 2024-01-19 08:28:33. Version ac07

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