Oliver Lee Memorial State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oliver Lee Memorial State Park clear sky chart from 2005-11-06 to 2024-07-16.

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	5% 4 1 4 3 3 4 3 5% 7% 60%	89433
	Night	5% 4 1 4 3 3 4 3 5% 7% 61%	90198
Transparency	Day	20% 7% 9% 16% 26% 23%	89161
	Night	20% 6% 8% 15% 27% 23%	89993
Seeing	Day	7% 13% 26% 30% 20% 5%	14212
	Night	6% 8% 28% 35% 19% 3	24506

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	3 10% 2 4 3 3 3 3 5% 6% 57%	2858
	11th to 20th	Day	4 3 1 4 2 2 3 3 4 6% 68%	2860
	21st to end	Day	12% 8% 2 4 3 3 5% 4 6% 6% 49%	3146
February	1st to 10th	Day	6% 5% 1 4 3 2 3 2 4 4 66%	1851
	11th to 20th	Day	7% 6% 2 4 3 2 3 2 4 7% 60%	1849
	21st to end	Day	6% 5% 2 4 3 2 2 2 3 5% 66%	1570
March	1st to 10th	Day	5% 5% 2 4 3 3 4 3 4 6% 62%	3337
	11th to 20th	Day	5% 6% 2 5% 3 2 3 3 5% 6% 60%	3490
	21st to end	Day	4 8% 3 6% 4 4 4 3 5% 6% 53%	3946
April	1st to 10th	Day	4 3 1 3 2 2 3 3 5% 7% 67%	2280
	11th to 20th	Day	3 3 1 3 2 2 2 2 2 5% 73%	2251
	21st to end	Day	3 3 1 2 2 2 3 2 4 5% 73%	2280
May	1st to 10th	Day	2 2 1 2 2 2 2 2 3 3 80%	3800
	11th to 20th	Day	1 2 1 2 3 3 4 3 5% 6% 71%	3765
	21st to end	Day	2 1 1 1 1 2 2 2 5% 83%	4311
June	1st to 10th	Day	2 3 1 3 3 3 4 3 6% 8% 64%	2660
	11th to 20th	Day	3 2 1 2 2 3 3 3 4 6% 71%	2660
	21st to end	Day	4 3 1 4 4 5% 5% 6% 8% 9% 51%	2530
July	1st to 10th	Day	6% 4 2 5% 6% 7% 7% 7% 9% 10% 38%	2470
	11th to 20th	Day	3 2 1 5% 5% 7% 9% 7% 10% 12% 40%	2407
	21st to end	Day	5% 4 1 6% 6% 8% 8% 8% 12% 12% 30%	2545
August	1st to 10th	Day	4 4 2 6% 5% 6% 6% 6% 10% 11% 40%	2149
	11th to 20th	Day	4 5% 2 6% 6% 7% 8% 7% 9% 11% 36%	2123
	21st to end	Day	4 4 2 6% 5% 7% 6% 6% 8% 12% 40%	2376
September	1st to 10th	Day	7% 5% 2 5% 5% 5% 6% 5% 8% 8% 44%	2160
	11th to 20th	Day	7% 3 1 4 4 5% 4 4 6% 6% 54%	2160
	21st to end	Day	4 2 1 3 2 3 3 3 6% 7% 65%	1982
October	1st to 10th	Day	5% 3 1 5% 3 3 4 2 6% 7% 61%	1800
	11th to 20th	Day	3 3 1 3 2 2 3 2 3 5% 71%	1800
	21st to end	Day	3 2 1 2 2 2 2 2 3 4 76%	1980
November	1st to 10th	Day	2 3 1 3 2 3 3 2 3 6% 71%	1859
	11th to 20th	Day	4 2 1 3 2 2 3 2 5% 6% 68%	1771
	21st to end	Day	7% 4 1 3 3 3 4 3 5% 8% 59%	1710
December	1st to 10th	Day	8% 5% 1 3 3 2 3 2 5% 8% 60%	1710
	11th to 20th	Day	7% 6% 2 6% 3 3 3 3 6% 7% 55%	1960
	21st to end	Day	7% 5% 1 3 2 3 3 2 4 6% 64%	3027
January	1st to 10th	Night	3 9% 3 4 3 3 3 3 4 6% 58%	4097
	11th to 20th	Night	4 4 1 3 2 3 4 3 4 4 68%	4110
	21st to end	Night	11% 8% 2 4 4 3 5% 4 5% 6% 48%	4521
February	1st to 10th	Night	6% 6% 1 3 2 3 3 2 5% 6% 62%	2326
	11th to 20th	Night	10% 5% 2 3 3 3 3 2 4 5% 61%	2218
	21st to end	Night	7% 5% 1 3 3 3 3 3 5% 6% 61%	1884
March	1st to 10th	Night	6% 6% 2 4 2 2 2 3 4 6% 64%	3531
	11th to 20th	Night	9% 6% 2 4 3 3 4 3 6% 6% 55%	3490
	21st to end	Night	5% 10% 2 4 3 3 4 3 4 7% 54%	3701
April	1st to 10th	Night	3 3 1 4 3 3 3 3 5% 6% 66%	1900
	11th to 20th	Night	6% 3 2 3 3 2 3 3 4 6% 64%	1877
	21st to end	Night	4 3 1 3 2 2 3 3 4 5% 71%	1900
May	1st to 10th	Night	3 2 1 2 1 1 3 1 3 5% 80%	3170
	11th to 20th	Night	3 2 1 3 3 3 3 3 4 6% 69%	3140
	21st to end	Night	2 1 1 1 1 2 2 2 3 4 82%	3249
June	1st to 10th	Night	2 3 2 5% 5% 4 4 5% 7% 7% 57%	1520
	11th to 20th	Night	3 2 1 3 3 3 3 3 6% 7% 69%	1520
	21st to end	Night	2 5% 2 6% 6% 5% 6% 4 8% 9% 47%	1640
July	1st to 10th	Night	3 5% 2 5% 5% 5% 6% 5% 8% 11% 46%	1710
	11th to 20th	Night	3 3 1 5% 4 5% 5% 5% 8% 11% 49%	1674
	21st to end	Night	3 4 1 5% 5% 5% 6% 7% 11% 12% 41%	1773
August	1st to 10th	Night	3 4 2 4 5% 6% 7% 7% 10% 15% 39%	1789
	11th to 20th	Night	5% 3 2 5% 4 5% 5% 6% 10% 12% 43%	1778
	21st to end	Night	3 3 2 5% 5% 5% 7% 5% 7% 10% 48%	1980
September	1st to 10th	Night	4 4 2 6% 5% 4 5% 5% 7% 9% 50%	1800
	11th to 20th	Night	7% 3 2 5% 4 3 5% 4 5% 6% 57%	1800
	21st to end	Night	4 2 1 4 3 3 4 3 4 7% 64%	1974
October	1st to 10th	Night	5% 4 1 4 3 3 3 3 6% 7% 59%	2160
	11th to 20th	Night	4 3 1 3 2 3 3 2 3 5% 72%	2160
	21st to end	Night	5% 3 1 2 3 2 2 1 3 3 75%	2376
November	1st to 10th	Night	3 3 1 2 2 2 3 3 4 7% 70%	2220
	11th to 20th	Night	3 2 1 2 2 3 3 3 5% 6% 69%	2386
	21st to end	Night	8% 4 2 4 4 3 3 3 4 6% 61%	2470
December	1st to 10th	Night	9% 4 1 3 3 2 3 3 5% 7% 59%	2470
	11th to 20th	Night	6% 6% 2 5% 3 3 4 3 5% 7% 55%	3233
	21st to end	Night	8% 5% 1 4 3 3 4 2 4 5% 63%	4651

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	21% 7% 9% 15% 35% 13%	2859
	11th to 20th	Day	14% 5% 5% 20% 41% 14%	2860
	21st to end	Day	29% 7% 9% 19% 25% 11%	3146
February	1st to 10th	Day	21% 4 6% 16% 27% 26%	1851
	11th to 20th	Day	24% 5% 5% 15% 29% 23%	1859
	21st to end	Day	21% 4 4 9% 32% 32%	1570
March	1st to 10th	Day	20% 5% 6% 10% 35% 25%	3337
	11th to 20th	Day	20% 7% 7% 21% 29% 17%	3490
	21st to end	Day	20% 10% 8% 14% 30% 19%	3946
April	1st to 10th	Day	15% 3 6% 15% 31% 29%	2280
	11th to 20th	Day	15% 3 4 11% 29% 38%	2254
	21st to end	Day	13% 3 5% 13% 32% 33%	2280
May	1st to 10th	Day	9% 3 3 8% 24% 53%	3800
	11th to 20th	Day	11% 6% 7% 13% 28% 35%	3768
	21st to end	Day	6% 2 4 10% 18% 60%	4311
June	1st to 10th	Day	16% 5% 10% 18% 26% 25%	2660
	11th to 20th	Day	12% 3 6% 12% 24% 43%	2660
	21st to end	Day	23% 9% 13% 18% 19% 18%	2530
July	1st to 10th	Day	32% 12% 16% 16% 16% 9%	2406
	11th to 20th	Day	26% 14% 18% 22% 16% 4	2338
	21st to end	Day	31% 17% 24% 18% 9% 1	2404
August	1st to 10th	Day	29% 13% 19% 26% 10% 3	2136
	11th to 20th	Day	32% 13% 18% 19% 13% 4	2123
	21st to end	Day	29% 14% 18% 20% 16% 3	2376
September	1st to 10th	Day	31% 9% 14% 17% 19% 11%	2160
	11th to 20th	Day	27% 6% 11% 19% 25% 12%	2160
	21st to end	Day	17% 6% 9% 21% 32% 15%	1982
October	1st to 10th	Day	21% 6% 9% 17% 26% 20%	1800
	11th to 20th	Day	17% 3 6% 12% 31% 32%	1800
	21st to end	Day	14% 2 6% 19% 34% 26%	1980
November	1st to 10th	Day	16% 3 6% 20% 31% 24%	1859
	11th to 20th	Day	15% 4 6% 20% 27% 26%	1771
	21st to end	Day	22% 5% 8% 16% 31% 18%	1710
December	1st to 10th	Day	22% 4 7% 21% 31% 15%	1710
	11th to 20th	Day	28% 4 10% 16% 29% 13%	1958
	21st to end	Day	20% 4 6% 17% 31% 22%	3027
January	1st to 10th	Night	22% 6% 8% 15% 32% 16%	4097
	11th to 20th	Night	15% 6% 7% 15% 44% 14%	4110
	21st to end	Night	31% 7% 8% 15% 27% 11%	4521
February	1st to 10th	Night	20% 4 7% 15% 25% 27%	2326
	11th to 20th	Night	25% 4 5% 13% 29% 25%	2218
	21st to end	Night	21% 5% 5% 9% 27% 32%	1884
March	1st to 10th	Night	20% 5% 6% 12% 34% 24%	3531
	11th to 20th	Night	22% 9% 9% 17% 26% 17%	3490
	21st to end	Night	21% 9% 7% 14% 31% 18%	3701
April	1st to 10th	Night	17% 5% 5% 11% 34% 28%	1900
	11th to 20th	Night	19% 4 6% 12% 25% 33%	1877
	21st to end	Night	16% 4 5% 13% 32% 30%	1900
May	1st to 10th	Night	9% 2 3 7% 22% 56%	3170
	11th to 20th	Night	12% 6% 9% 14% 23% 35%	3141
	21st to end	Night	8% 2 4 8% 18% 59%	3250
June	1st to 10th	Night	21% 7% 9% 17% 19% 28%	1520
	11th to 20th	Night	14% 4 5% 13% 21% 44%	1520
	21st to end	Night	26% 10% 13% 17% 16% 18%	1640
July	1st to 10th	Night	28% 9% 15% 21% 19% 9%	1665
	11th to 20th	Night	23% 10% 16% 24% 21% 6%	1620
	21st to end	Night	25% 15% 22% 23% 12% 2	1674
August	1st to 10th	Night	26% 14% 20% 26% 10% 4	1779
	11th to 20th	Night	26% 12% 19% 25% 14% 4	1778
	21st to end	Night	27% 10% 17% 24% 19% 4	1980
September	1st to 10th	Night	27% 9% 13% 16% 21% 13%	1800
	11th to 20th	Night	24% 8% 11% 18% 24% 15%	1800
	21st to end	Night	18% 6% 10% 17% 32% 16%	1974
October	1st to 10th	Night	21% 6% 11% 15% 26% 21%	2160
	11th to 20th	Night	16% 4 5% 14% 26% 36%	2160
	21st to end	Night	16% 3 4 16% 32% 30%	2376
November	1st to 10th	Night	14% 4 5% 17% 34% 27%	2220
	11th to 20th	Night	14% 4 8% 16% 32% 27%	2386
	21st to end	Night	24% 5% 6% 14% 31% 20%	2470
December	1st to 10th	Night	24% 5% 7% 17% 28% 20%	2470
	11th to 20th	Night	26% 5% 9% 18% 25% 17%	3234
	21st to end	Night	22% 5% 6% 15% 33% 19%	4651

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	11% 19% 31% 30% 8% 1	270
	11th to 20th	Day	11% 18% 31% 29% 10% 1	270
	21st to end	Day	6% 24% 29% 29% 11% 1	297
February	1st to 10th	Day	13% 15% 33% 27% 10% 1	270
	11th to 20th	Day	13% 19% 39% 23% 5% 1	270
	21st to end	Day	14% 32% 32% 18% 4	225
March	1st to 10th	Day	11% 24% 41% 19% 4 1	387
	11th to 20th	Day	12% 24% 31% 25% 6% 2	460
	21st to end	Day	12% 33% 33% 17% 4 1	506
April	1st to 10th	Day	8% 26% 37% 22% 5% 1	460
	11th to 20th	Day	8% 29% 40% 18% 4	452
	21st to end	Day	8% 28% 34% 25% 5% 1	460
May	1st to 10th	Day	5% 21% 42% 27% 6% 1	463
	11th to 20th	Day	2 16% 37% 32% 11% 2	488
	21st to end	Day	3 15% 42% 31% 8%	543
June	1st to 10th	Day	3 5% 22% 45% 22% 3	680
	11th to 20th	Day	3 6% 26% 38% 24% 2	680
	21st to end	Day	4 2 20% 37% 31% 6%	550
July	1st to 10th	Day	6% 2 11% 34% 35% 13%	486
	11th to 20th	Day	2 1 8% 31% 46% 13%	465
	21st to end	Day	3 1 7% 25% 49% 16%	487
August	1st to 10th	Day	2 6% 28% 47% 16%	447
	11th to 20th	Day	4 3 12% 32% 38% 11%	437
	21st to end	Day	5% 2 6% 29% 44% 14%	495
September	1st to 10th	Day	7% 2 13% 37% 34% 8%	450
	11th to 20th	Day	7% 1 13% 43% 29% 7%	450
	21st to end	Day	4 4 21% 44% 20% 7%	280
October	1st to 10th	Day	8% 4 24% 34% 25% 4	270
	11th to 20th	Day	4 9% 22% 38% 21% 6%	270
	21st to end	Day	6% 13% 27% 28% 20% 7%	297
November	1st to 10th	Day	5% 17% 33% 26% 16% 4	270
	11th to 20th	Day	4 10% 27% 34% 20% 4	270
	21st to end	Day	9% 19% 34% 24% 13% 1	270
December	1st to 10th	Day	12% 15% 31% 29% 11% 2	270
	11th to 20th	Day	7% 24% 33% 27% 8%	270
	21st to end	Day	14% 20% 36% 25% 6%	297
January	1st to 10th	Night	7% 8% 33% 36% 13% 3	760
	11th to 20th	Night	9% 9% 34% 33% 13% 3	760
	21st to end	Night	10% 12% 31% 31% 14% 2	836
February	1st to 10th	Night	8% 12% 33% 32% 13% 2	760
	11th to 20th	Night	11% 11% 40% 30% 8%	744
	21st to end	Night	8% 18% 44% 24% 4 1	628
March	1st to 10th	Night	10% 16% 36% 29% 8% 1	760
	11th to 20th	Night	8% 14% 32% 33% 13% 1	760
	21st to end	Night	6% 17% 38% 29% 9% 1	760
April	1st to 10th	Night	3 14% 47% 28% 7%	570
	11th to 20th	Night	8% 16% 39% 29% 6%	563
	21st to end	Night	7% 14% 41% 31% 6%	570
May	1st to 10th	Night	5% 9% 42% 35% 8%	570
	11th to 20th	Night	3 9% 32% 41% 15% 1	561
	21st to end	Night	3 8% 37% 43% 10% 1	617
June	1st to 10th	Night	2 4 28% 47% 19% 1	570
	11th to 20th	Night	4 5% 27% 45% 19% 1	570
	21st to end	Night	4 3 17% 49% 25% 2	570
July	1st to 10th	Night	4 2 15% 46% 31% 2	555
	11th to 20th	Night	4 1 11% 39% 41% 5%	540
	21st to end	Night	3 2 9% 37% 42% 7%	591
August	1st to 10th	Night	4 1 6% 31% 48% 11%	537
	11th to 20th	Night	4 2 8% 31% 45% 10%	534
	21st to end	Night	3 2 11% 36% 43% 6%	594
September	1st to 10th	Night	5% 1 13% 39% 36% 6%	540
	11th to 20th	Night	7% 1 9% 46% 34% 2	540
	21st to end	Night	4 4 19% 43% 27% 3	544
October	1st to 10th	Night	6% 3 25% 41% 22% 3	720
	11th to 20th	Night	5% 5% 26% 39% 22% 4	720
	21st to end	Night	6% 6% 23% 32% 26% 6%	792
November	1st to 10th	Night	4 8% 25% 34% 25% 5%	740
	11th to 20th	Night	4 6% 24% 41% 22% 3	866
	21st to end	Night	9% 10% 27% 32% 19% 3	950
December	1st to 10th	Night	10% 10% 27% 36% 16% 1	950
	11th to 20th	Night	10% 10% 37% 29% 14% 1	950
	21st to end	Night	12% 11% 32% 33% 11% 2	914

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