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 2024-12-24.

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	4 4 1 4 3 3 4 4 6% 7% 61%	104732
	Night	5% 4 1 4 3 3 4 3 5% 7% 61%	104083
Transparency	Day	20% 6% 9% 18% 26% 22%	104497
	Night	21% 5% 8% 16% 27% 23%	103909
Seeing	Day	7% 13% 26% 30% 19% 5%	14761
	Night	6% 8% 28% 35% 19% 3	25113

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	4 3 1 5% 5% 6% 6% 5% 8% 10% 46%	4110
	11th to 20th	Day	2 2 1 4 4 6% 8% 7% 10% 12% 45%	4110
	21st to end	Day	7% 4 1 6% 4 6% 7% 7% 10% 12% 36%	4454
August	1st to 10th	Day	3 2 1 4 4 6% 7% 7% 9% 11% 46%	3784
	11th to 20th	Day	2 3 1 4 4 5% 6% 6% 8% 10% 51%	3726
	21st to end	Day	3 3 1 5% 5% 6% 7% 6% 9% 13% 42%	4180
September	1st to 10th	Day	7% 5% 2 5% 5% 5% 6% 5% 8% 8% 45%	2280
	11th to 20th	Day	7% 3 1 4 4 5% 4 4 6% 6% 55%	2280
	21st to end	Day	4 2 1 3 2 3 3 3 5% 7% 66%	2091
October	1st to 10th	Day	3 2 1 3 2 2 3 2 5% 6% 72%	3170
	11th to 20th	Day	3 2 1 3 2 3 3 2 4 5% 71%	3150
	21st to end	Day	2 1 1 1 1 1 2 2 3 84%	3438
November	1st to 10th	Day	3 3 1 3 2 3 3 2 3 6% 71%	1959
	11th to 20th	Day	4 2 1 3 2 2 3 2 5% 6% 69%	1864
	21st to end	Day	7% 4 1 3 3 3 4 3 5% 8% 59%	1800
December	1st to 10th	Day	8% 5% 1 3 2 2 3 3 4 8% 61%	1800
	11th to 20th	Day	7% 6% 2 5% 3 3 3 3 5% 7% 56%	2041
	21st to end	Day	7% 5% 1 3 2 3 3 2 4 6% 64%	3051
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	2 4 2 7% 5% 5% 7% 6% 7% 10% 44%	2860
	11th to 20th	Night	2 2 1 4 4 5% 5% 4 7% 11% 54%	2860
	21st to end	Night	5% 4 2 5% 4 5% 7% 7% 11% 11% 39%	3109
August	1st to 10th	Night	2 3 1 3 4 4 5% 5% 8% 15% 50%	3154
	11th to 20th	Night	3 2 1 3 3 4 4 4 8% 11% 57%	3113
	21st to end	Night	3 4 2 6% 5% 6% 8% 6% 9% 11% 39%	3487
September	1st to 10th	Night	4 3 2 5% 5% 4 5% 5% 7% 8% 51%	1900
	11th to 20th	Night	6% 3 1 4 4 3 5% 4 5% 6% 58%	1900
	21st to end	Night	4 2 1 4 3 3 4 3 4 6% 65%	2085
October	1st to 10th	Night	3 2 1 2 2 2 2 2 4 5% 76%	3800
	11th to 20th	Night	8% 3 1 3 2 3 3 2 3 4 67%	3778
	21st to end	Night	4 2 1 2 2 2 1 1 2 4 78%	4120
November	1st to 10th	Night	4 3 1 2 2 2 3 3 4 7% 70%	2340
	11th to 20th	Night	3 2 1 2 2 2 3 3 5% 7% 69%	2512
	21st to end	Night	8% 4 2 4 4 3 3 3 4 6% 61%	2600
December	1st to 10th	Night	8% 4 1 3 3 2 3 3 5% 7% 60%	2600
	11th to 20th	Night	6% 5% 2 5% 3 3 4 3 5% 7% 56%	3371
	21st to end	Night	8% 5% 1 4 3 3 4 2 4 5% 63%	4700

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	28% 7% 17% 18% 18% 11%	4046
	11th to 20th	Day	25% 8% 18% 31% 16% 3	4041
	21st to end	Day	32% 10% 18% 29% 10% 1	4314
August	1st to 10th	Day	27% 7% 15% 34% 14% 2	3772
	11th to 20th	Day	24% 8% 13% 28% 24% 3	3762
	21st to end	Day	29% 8% 19% 29% 12% 2	4179
September	1st to 10th	Day	31% 9% 13% 16% 20% 11%	2280
	11th to 20th	Day	26% 6% 11% 19% 26% 13%	2280
	21st to end	Day	17% 5% 9% 20% 32% 17%	2091
October	1st to 10th	Day	15% 4 5% 13% 30% 33%	3170
	11th to 20th	Day	17% 2 7% 13% 35% 26%	3150
	21st to end	Day	9% 1 3 14% 37% 35%	3438
November	1st to 10th	Day	16% 3 6% 20% 31% 24%	1959
	11th to 20th	Day	15% 4 6% 19% 28% 27%	1864
	21st to end	Day	22% 5% 8% 16% 31% 19%	1800
December	1st to 10th	Day	22% 4 7% 21% 32% 15%	1800
	11th to 20th	Day	27% 4 10% 16% 30% 13%	2039
	21st to end	Day	20% 4 6% 17% 31% 22%	3051
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	33% 6% 14% 21% 17% 10%	2815
	11th to 20th	Night	23% 6% 14% 26% 24% 7%	2806
	21st to end	Night	33% 9% 19% 26% 12% 1	3011
August	1st to 10th	Night	21% 8% 14% 32% 21% 4	3144
	11th to 20th	Night	20% 7% 12% 25% 33% 4	3143
	21st to end	Night	35% 6% 15% 25% 17% 2	3487
September	1st to 10th	Night	27% 9% 13% 16% 21% 14%	1900
	11th to 20th	Night	24% 8% 11% 18% 24% 16%	1900
	21st to end	Night	18% 6% 9% 17% 32% 18%	2085
October	1st to 10th	Night	13% 3 6% 10% 29% 39%	3800
	11th to 20th	Night	23% 2 5% 9% 29% 32%	3778
	21st to end	Night	14% 2 3 14% 31% 38%	4120
November	1st to 10th	Night	15% 4 4 17% 33% 26%	2340
	11th to 20th	Night	14% 3 7% 15% 32% 28%	2512
	21st to end	Night	24% 5% 6% 14% 30% 21%	2600
December	1st to 10th	Night	23% 4 7% 17% 29% 20%	2600
	11th to 20th	Night	26% 5% 8% 17% 26% 18%	3372
	21st to end	Night	22% 5% 6% 15% 33% 19%	4700

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% 45% 12%	484
	21st to end	Day	4 1 9% 26% 47% 15%	531
August	1st to 10th	Day	2 7% 30% 45% 15%	487
	11th to 20th	Day	4 2 13% 33% 38% 10%	477
	21st to end	Day	4 2 9% 30% 41% 13%	539
September	1st to 10th	Day	8% 2 15% 37% 31% 7%	490
	11th to 20th	Day	7% 2 17% 41% 27% 7%	490
	21st to end	Day	5% 6% 22% 40% 19% 7%	310
October	1st to 10th	Day	7% 4 27% 33% 24% 4	300
	11th to 20th	Day	6% 9% 24% 36% 19% 6%	300
	21st to end	Day	8% 12% 27% 28% 18% 6%	330
November	1st to 10th	Day	6% 17% 35% 24% 14% 3	300
	11th to 20th	Day	7% 11% 28% 32% 18% 4	300
	21st to end	Day	9% 18% 36% 23% 12% 1	300
December	1st to 10th	Day	13% 16% 31% 28% 10% 2	300
	11th to 20th	Day	6% 23% 35% 28% 8%	300
	21st to end	Day	13% 20% 36% 25% 6%	306
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 12% 38% 40% 5%	552
	21st to end	Night	4 2 10% 37% 40% 7%	624
August	1st to 10th	Night	3 1 8% 31% 46% 10%	567
	11th to 20th	Night	4 3 11% 31% 42% 9%	564
	21st to end	Night	3 2 12% 36% 41% 6%	627
September	1st to 10th	Night	5% 1 16% 38% 34% 6%	570
	11th to 20th	Night	7% 2 12% 45% 32% 2	570
	21st to end	Night	4 4 22% 42% 25% 3	575
October	1st to 10th	Night	6% 3 28% 40% 21% 3	760
	11th to 20th	Night	5% 6% 27% 38% 21% 3	760
	21st to end	Night	6% 7% 25% 32% 25% 5%	836
November	1st to 10th	Night	5% 9% 26% 32% 23% 4	780
	11th to 20th	Night	5% 8% 24% 39% 21% 3	912
	21st to end	Night	9% 10% 29% 31% 18% 3	1000
December	1st to 10th	Night	10% 10% 29% 35% 15% 1	1000
	11th to 20th	Night	9% 11% 38% 29% 13% 1	1000
	21st to end	Night	11% 11% 32% 33% 11% 2	932

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