Shades State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shades State Park clear sky chart from 2005-11-06 to 2024-08-30.

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	14% 9% 3 7% 5% 4 4 4 6% 7% 36%	95555
	Night	15% 10% 4 7% 4 4 4 3 5% 7% 37%	93510
Transparency	Day	46% 6% 12% 22% 12% 2	95310
	Night	47% 5% 11% 21% 14% 2	93362
Seeing	Day	17% 10% 28% 24% 15% 6%	15392
	Night	18% 10% 29% 29% 13% 1	25190

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	15% 14% 9% 14% 4 4 4 3 5% 5% 22%	2527
	11th to 20th	Day	14% 12% 7% 13% 7% 6% 6% 8% 6% 5% 16%	2530
	21st to end	Day	26% 22% 6% 10% 4 2 3 2 3 5% 17%	2861
February	1st to 10th	Day	16% 13% 5% 10% 7% 6% 4 2 4 5% 27%	1890
	11th to 20th	Day	15% 11% 4 10% 6% 4 4 4 5% 6% 30%	1848
	21st to end	Day	18% 15% 5% 9% 4 3 3 2 4 6% 31%	1570
March	1st to 10th	Day	20% 18% 4 7% 4 3 3 3 3 4 30%	3120
	11th to 20th	Day	13% 8% 3 7% 4 4 4 3 5% 7% 42%	3285
	21st to end	Day	15% 11% 5% 8% 5% 5% 4 4 5% 7% 29%	4096
April	1st to 10th	Day	15% 12% 3 7% 5% 4 4 4 5% 7% 35%	2280
	11th to 20th	Day	17% 9% 2 6% 4 4 4 3 5% 7% 38%	2254
	21st to end	Day	21% 8% 3 7% 4 4 4 3 5% 7% 35%	2394
May	1st to 10th	Day	18% 9% 3 7% 5% 5% 5% 5% 6% 8% 28%	4082
	11th to 20th	Day	19% 7% 3 6% 4 4 4 4 6% 7% 35%	4081
	21st to end	Day	10% 6% 2 6% 5% 5% 4 5% 6% 9% 42%	4726
June	1st to 10th	Day	10% 6% 3 6% 5% 4 5% 4 7% 8% 42%	2660
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 4 6% 9% 46%	2660
	21st to end	Day	10% 6% 3 6% 6% 5% 5% 4 6% 10% 40%	2660
July	1st to 10th	Day	14% 6% 3 7% 4 4 4 4 6% 10% 38%	4440
	11th to 20th	Day	6% 5% 2 6% 4 4 5% 5% 7% 12% 43%	4440
	21st to end	Day	10% 6% 2 6% 5% 5% 6% 5% 7% 10% 38%	4796
August	1st to 10th	Day	8% 5% 2 6% 4 5% 5% 4 6% 10% 47%	2457
	11th to 20th	Day	10% 5% 2 5% 4 5% 5% 4 7% 10% 43%	2263
	21st to end	Day	6% 4 2 5% 4 4 5% 5% 6% 9% 51%	2485
September	1st to 10th	Day	11% 7% 2 5% 4 4 5% 3 6% 7% 44%	2160
	11th to 20th	Day	9% 6% 2 5% 4 4 6% 4 7% 7% 48%	1992
	21st to end	Day	12% 5% 2 5% 3 4 4 3 6% 7% 49%	1980
October	1st to 10th	Day	12% 5% 2 5% 4 5% 4 2 6% 8% 47%	1980
	11th to 20th	Day	16% 7% 2 6% 4 5% 4 4 5% 6% 41%	1819
	21st to end	Day	18% 11% 3 7% 4 5% 5% 3 4 6% 34%	1782
November	1st to 10th	Day	11% 7% 2 5% 4 2 4 3 5% 7% 50%	1672
	11th to 20th	Day	18% 11% 3 7% 3 4 3 3 5% 5% 38%	1710
	21st to end	Day	18% 10% 3 8% 5% 3 3 3 5% 5% 36%	1710
December	1st to 10th	Day	17% 15% 4 9% 6% 3 3 3 5% 5% 28%	1644
	11th to 20th	Day	15% 14% 5% 13% 5% 4 3 3 4 5% 28%	1918
	21st to end	Day	21% 21% 7% 12% 5% 4 4 2 4 4 15%	2783
January	1st to 10th	Night	17% 16% 8% 12% 5% 4 4 3 4 4 25%	4428
	11th to 20th	Night	13% 20% 6% 13% 7% 5% 6% 4 4 3 19%	4440
	21st to end	Night	25% 18% 7% 8% 4 3 3 2 3 4 22%	4788
February	1st to 10th	Night	18% 13% 5% 9% 5% 5% 4 3 4 6% 29%	2287
	11th to 20th	Night	14% 11% 5% 10% 5% 4 4 3 5% 7% 33%	2218
	21st to end	Night	18% 12% 4 9% 5% 4 4 3 4 5% 32%	1884
March	1st to 10th	Night	19% 15% 4 6% 4 3 3 3 4 6% 33%	3733
	11th to 20th	Night	13% 7% 2 6% 4 4 4 3 5% 6% 46%	3674
	21st to end	Night	19% 9% 4 8% 5% 4 4 3 5% 7% 34%	3562
April	1st to 10th	Night	13% 10% 3 6% 4 4 3 4 5% 7% 39%	1900
	11th to 20th	Night	17% 8% 2 6% 4 3 3 4 5% 7% 40%	1875
	21st to end	Night	18% 7% 2 6% 6% 4 5% 4 6% 5% 36%	1785
May	1st to 10th	Night	17% 11% 3 8% 4 5% 4 3 6% 9% 31%	2813
	11th to 20th	Night	18% 7% 3 6% 4 3 4 4 6% 8% 38%	2812
	21st to end	Night	10% 6% 2 6% 5% 5% 5% 4 5% 8% 44%	2834
June	1st to 10th	Night	9% 5% 3 6% 4 3 4 3 6% 6% 50%	1520
	11th to 20th	Night	8% 5% 2 6% 4 4 4 4 6% 9% 48%	1520
	21st to end	Night	8% 5% 2 6% 4 4 5% 4 8% 11% 43%	1520
July	1st to 10th	Night	11% 5% 1 5% 4 4 4 4 7% 9% 46%	2530
	11th to 20th	Night	5% 4 1 3 3 3 5% 4 7% 9% 55%	2530
	21st to end	Night	8% 7% 3 8% 5% 4 5% 3 6% 10% 42%	2762
August	1st to 10th	Night	8% 4 2 4 4 4 5% 4 6% 9% 51%	1701
	11th to 20th	Night	6% 4 2 6% 5% 4 6% 5% 7% 8% 47%	1854
	21st to end	Night	7% 5% 2 4 3 3 3 3 6% 9% 56%	2080
September	1st to 10th	Night	11% 7% 2 5% 4 3 3 3 7% 6% 49%	1800
	11th to 20th	Night	8% 4 2 4 3 4 4 3 5% 9% 55%	1948
	21st to end	Night	12% 5% 2 5% 3 4 4 3 6% 6% 50%	1980
October	1st to 10th	Night	9% 4 2 6% 4 3 4 3 6% 5% 54%	1980
	11th to 20th	Night	17% 7% 2 5% 3 3 4 3 4 6% 47%	2138
	21st to end	Night	18% 9% 3 7% 4 3 4 4 4 6% 39%	2574
November	1st to 10th	Night	12% 7% 2 5% 3 3 4 3 4 7% 50%	2406
	11th to 20th	Night	13% 10% 3 7% 4 4 4 4 5% 6% 40%	2470
	21st to end	Night	19% 12% 4 7% 4 4 3 3 4 5% 34%	2470
December	1st to 10th	Night	16% 13% 5% 8% 7% 4 5% 3 5% 5% 30%	2531
	11th to 20th	Night	16% 14% 4 10% 4 4 4 3 4 5% 32%	3279
	21st to end	Night	23% 20% 7% 10% 5% 4 3 3 3 4 17%	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	64% 4 8% 18% 6%	2528
	11th to 20th	Day	68% 4 11% 11% 6%	2530
	21st to end	Day	72% 3 8% 13% 3 1	2861
February	1st to 10th	Day	61% 3 9% 17% 8% 2	1890
	11th to 20th	Day	55% 4 11% 20% 9% 1	1858
	21st to end	Day	56% 4 10% 21% 7% 2	1570
March	1st to 10th	Day	59% 4 7% 18% 11% 2	3120
	11th to 20th	Day	40% 5% 12% 29% 14% 1	3285
	21st to end	Day	53% 6% 13% 23% 4 1	4096
April	1st to 10th	Day	47% 6% 14% 19% 14% 1	2280
	11th to 20th	Day	46% 5% 11% 24% 11% 3	2254
	21st to end	Day	49% 5% 12% 21% 11% 3	2394
May	1st to 10th	Day	51% 7% 13% 22% 6%	4120
	11th to 20th	Day	45% 7% 13% 26% 9%	4085
	21st to end	Day	37% 8% 12% 21% 20% 3	4739
June	1st to 10th	Day	36% 8% 13% 25% 15% 3	2660
	11th to 20th	Day	33% 6% 12% 24% 22% 3	2660
	21st to end	Day	38% 7% 16% 19% 16% 4	2660
July	1st to 10th	Day	41% 5% 11% 26% 14% 2	4371
	11th to 20th	Day	31% 7% 15% 29% 17% 1	4365
	21st to end	Day	39% 8% 16% 20% 14% 3	4645
August	1st to 10th	Day	32% 8% 15% 29% 14% 1	2444
	11th to 20th	Day	36% 7% 14% 27% 15% 1	2263
	21st to end	Day	28% 7% 14% 26% 18% 7%	2485
September	1st to 10th	Day	38% 6% 13% 23% 16% 4	2160
	11th to 20th	Day	33% 7% 12% 25% 20% 3	1992
	21st to end	Day	34% 5% 11% 26% 21% 3	1980
October	1st to 10th	Day	37% 5% 11% 25% 18% 4	1980
	11th to 20th	Day	42% 5% 10% 22% 19% 1	1819
	21st to end	Day	50% 5% 9% 22% 12% 1	1782
November	1st to 10th	Day	34% 4 14% 25% 17% 5%	1672
	11th to 20th	Day	48% 4 10% 21% 14% 4	1710
	21st to end	Day	50% 5% 9% 22% 13% 1	1710
December	1st to 10th	Day	59% 4 11% 18% 9%	1644
	11th to 20th	Day	59% 4 7% 24% 6% 1	1915
	21st to end	Day	73% 4 9% 10% 4	2783
January	1st to 10th	Night	63% 4 11% 16% 6%	4428
	11th to 20th	Night	69% 3 8% 13% 6%	4440
	21st to end	Night	67% 3 8% 14% 8%	4788
February	1st to 10th	Night	58% 4 11% 17% 9% 1	2287
	11th to 20th	Night	52% 3 11% 19% 12% 2	2219
	21st to end	Night	55% 5% 10% 18% 10% 2	1884
March	1st to 10th	Night	54% 4 8% 22% 10% 2	3733
	11th to 20th	Night	37% 6% 10% 24% 20% 1	3674
	21st to end	Night	49% 5% 12% 26% 7% 1	3562
April	1st to 10th	Night	45% 5% 11% 23% 14% 2	1900
	11th to 20th	Night	43% 5% 9% 22% 16% 5%	1875
	21st to end	Night	47% 7% 10% 21% 12% 4	1785
May	1st to 10th	Night	50% 8% 12% 21% 8% 1	2840
	11th to 20th	Night	43% 7% 14% 26% 10% 1	2813
	21st to end	Night	36% 8% 12% 21% 19% 4	2842
June	1st to 10th	Night	34% 5% 11% 27% 20% 3	1520
	11th to 20th	Night	33% 6% 11% 24% 21% 5%	1520
	21st to end	Night	33% 8% 15% 22% 17% 5%	1520
July	1st to 10th	Night	33% 7% 13% 27% 17% 5%	2490
	11th to 20th	Night	23% 6% 13% 32% 24% 2	2482
	21st to end	Night	37% 6% 16% 21% 17% 3	2674
August	1st to 10th	Night	28% 8% 14% 30% 18% 2	1690
	11th to 20th	Night	31% 8% 13% 27% 20% 2	1854
	21st to end	Night	25% 6% 13% 28% 21% 7%	2080
September	1st to 10th	Night	34% 5% 12% 25% 18% 6%	1800
	11th to 20th	Night	26% 6% 11% 27% 25% 5%	1948
	21st to end	Night	33% 6% 10% 23% 24% 4	1980
October	1st to 10th	Night	31% 6% 10% 26% 24% 4	1980
	11th to 20th	Night	39% 4 9% 24% 21% 3	2138
	21st to end	Night	47% 4 10% 21% 17% 2	2574
November	1st to 10th	Night	36% 4 9% 26% 20% 5%	2406
	11th to 20th	Night	44% 3 11% 22% 16% 3	2470
	21st to end	Night	53% 4 9% 23% 11%	2470
December	1st to 10th	Night	56% 4 11% 18% 10% 1	2531
	11th to 20th	Night	55% 3 10% 19% 12% 1	3281
	21st to end	Night	71% 5% 8% 10% 6%	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	26% 17% 31% 19% 6%	270
	11th to 20th	Day	22% 20% 37% 17% 3 1	270
	21st to end	Day	25% 19% 33% 20% 3	297
February	1st to 10th	Day	26% 16% 37% 19% 2	270
	11th to 20th	Day	26% 20% 34% 13% 6% 1	270
	21st to end	Day	29% 16% 40% 12% 3	225
March	1st to 10th	Day	24% 25% 37% 10% 4	270
	11th to 20th	Day	28% 19% 35% 14% 4	343
	21st to end	Day	32% 15% 30% 16% 7%	506
April	1st to 10th	Day	22% 19% 31% 21% 7% 2	460
	11th to 20th	Day	22% 17% 29% 20% 10% 3	452
	21st to end	Day	27% 17% 30% 17% 7% 2	460
May	1st to 10th	Day	22% 13% 29% 25% 8% 2	463
	11th to 20th	Day	21% 8% 27% 27% 13% 4	487
	21st to end	Day	11% 7% 29% 26% 18% 9%	675
June	1st to 10th	Day	12% 7% 29% 28% 19% 6%	680
	11th to 20th	Day	12% 4 29% 32% 18% 5%	680
	21st to end	Day	11% 7% 32% 27% 17% 6%	680
July	1st to 10th	Day	12% 3 18% 28% 23% 16%	671
	11th to 20th	Day	7% 4 20% 31% 25% 12%	668
	21st to end	Day	10% 2 18% 33% 27% 9%	734
August	1st to 10th	Day	8% 2 18% 27% 30% 14%	486
	11th to 20th	Day	12% 5% 18% 29% 24% 11%	479
	21st to end	Day	6% 3 13% 33% 33% 12%	532
September	1st to 10th	Day	13% 4 18% 29% 27% 9%	450
	11th to 20th	Day	10% 4 15% 28% 31% 12%	450
	21st to end	Day	12% 9% 23% 24% 22% 10%	450
October	1st to 10th	Day	10% 6% 30% 30% 17% 5%	450
	11th to 20th	Day	16% 16% 35% 22% 10% 1	320
	21st to end	Day	31% 18% 32% 18% 2	297
November	1st to 10th	Day	13% 14% 36% 23% 13% 2	270
	11th to 20th	Day	25% 18% 29% 19% 8% 2	270
	21st to end	Day	25% 11% 38% 24% 2	270
December	1st to 10th	Day	20% 21% 36% 16% 5% 1	270
	11th to 20th	Day	21% 16% 40% 17% 5% 1	270
	21st to end	Day	27% 19% 36% 16% 2	297
January	1st to 10th	Night	22% 17% 34% 24% 4	950
	11th to 20th	Night	24% 15% 37% 21% 4	950
	21st to end	Night	22% 15% 35% 25% 3	1045
February	1st to 10th	Night	25% 12% 37% 24% 3	767
	11th to 20th	Night	18% 16% 40% 21% 4	743
	21st to end	Night	25% 15% 36% 21% 3	628
March	1st to 10th	Night	23% 14% 35% 24% 4	760
	11th to 20th	Night	20% 13% 37% 24% 6% 1	760
	21st to end	Night	24% 10% 36% 25% 5% 1	684
April	1st to 10th	Night	16% 15% 36% 27% 6%	570
	11th to 20th	Night	20% 12% 31% 29% 8%	563
	21st to end	Night	20% 10% 37% 25% 8% 1	570
May	1st to 10th	Night	19% 8% 34% 28% 9%	570
	11th to 20th	Night	18% 8% 25% 32% 16% 1	561
	21st to end	Night	12% 4 23% 38% 22% 1	617
June	1st to 10th	Night	11% 4 22% 44% 18%	570
	11th to 20th	Night	11% 3 21% 45% 18% 1	570
	21st to end	Night	8% 3 24% 41% 25%	570
July	1st to 10th	Night	9% 2 14% 38% 32% 6%	555
	11th to 20th	Night	6% 4 17% 38% 32% 3	552
	21st to end	Night	6% 3 14% 43% 32% 3	624
August	1st to 10th	Night	8% 2 10% 44% 31% 4	567
	11th to 20th	Night	7% 2 14% 42% 31% 4	564
	21st to end	Night	8% 3 14% 32% 40% 4	624
September	1st to 10th	Night	14% 2 15% 37% 28% 4	540
	11th to 20th	Night	8% 3 16% 36% 34% 3	688
	21st to end	Night	14% 5% 20% 31% 28% 2	720
October	1st to 10th	Night	10% 6% 24% 37% 19% 4	720
	11th to 20th	Night	21% 11% 27% 27% 13% 1	720
	21st to end	Night	23% 12% 33% 26% 6%	792
November	1st to 10th	Night	15% 9% 39% 27% 10% 1	740
	11th to 20th	Night	17% 16% 32% 27% 8%	760
	21st to end	Night	24% 13% 30% 26% 6%	760
December	1st to 10th	Night	23% 12% 38% 23% 4	821
	11th to 20th	Night	25% 10% 34% 25% 6% 1	950
	21st to end	Night	29% 15% 31% 22% 4	1045

Page generated at 2024-08-27 09:49:40. Version ac07

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