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 2025-01-22.

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	14% 9% 3 7% 5% 4 4 4 6% 8% 36%	104937
	Night	15% 10% 4 7% 4 4 4 3 5% 7% 37%	104487
Transparency	Day	44% 6% 12% 23% 14% 2	108560
	Night	45% 5% 11% 22% 15% 2	109005
Seeing	Day	17% 11% 28% 24% 15% 6%	15870
	Night	18% 10% 29% 29% 13% 1	25801

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%	2607
	11th to 20th	Day	14% 12% 8% 13% 7% 6% 6% 7% 6% 5% 17%	2610
	21st to end	Day	26% 22% 6% 10% 4 2 3 3 3 5% 17%	2869
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% 1 6% 3 4 5% 4 6% 9% 49%	4104
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 4 7% 11% 41%	3759
	21st to end	Day	6% 4 2 5% 4 4 4 4 6% 10% 52%	4180
September	1st to 10th	Day	10% 6% 2 5% 4 4 5% 4 6% 7% 46%	2280
	11th to 20th	Day	9% 5% 2 5% 3 3 6% 4 7% 7% 50%	2102
	21st to end	Day	13% 5% 2 6% 4 4 4 4 6% 7% 46%	2090
October	1st to 10th	Day	12% 5% 2 5% 4 5% 4 2 6% 7% 48%	2090
	11th to 20th	Day	15% 7% 2 6% 4 5% 4 4 5% 6% 42%	1919
	21st to end	Day	18% 10% 3 7% 4 5% 5% 3 4 6% 35%	1881
November	1st to 10th	Day	11% 7% 2 5% 4 3 4 3 5% 7% 49%	1762
	11th to 20th	Day	18% 11% 3 7% 4 4 4 4 5% 4 38%	1800
	21st to end	Day	18% 11% 3 8% 5% 3 3 3 5% 5% 35%	1800
December	1st to 10th	Day	12% 12% 4 8% 5% 3 3 3 5% 5% 41%	2812
	11th to 20th	Day	15% 15% 5% 12% 5% 5% 4 4 6% 6% 23%	3008
	21st to end	Day	26% 18% 6% 11% 5% 4 4 3 5% 4 15%	3982
January	1st to 10th	Night	17% 16% 8% 12% 5% 4 4 3 4 4 25%	4568
	11th to 20th	Night	13% 20% 6% 13% 7% 5% 6% 4 4 3 20%	4580
	21st to end	Night	25% 18% 7% 8% 4 3 3 2 3 4 22%	4803
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	9% 5% 1 4 3 3 4 3 6% 9% 52%	2825
	11th to 20th	Night	7% 5% 2 6% 5% 4 6% 4 6% 8% 46%	3066
	21st to end	Night	5% 5% 2 5% 3 3 3 3 5% 9% 56%	3476
September	1st to 10th	Night	11% 6% 2 5% 4 3 3 2 6% 6% 51%	1900
	11th to 20th	Night	7% 4 2 3 3 4 4 3 5% 9% 56%	2057
	21st to end	Night	12% 5% 2 5% 4 4 5% 3 6% 6% 48%	2090
October	1st to 10th	Night	9% 4 2 5% 4 3 4 3 6% 5% 55%	2090
	11th to 20th	Night	16% 6% 2 5% 3 3 4 3 4 6% 48%	2258
	21st to end	Night	17% 8% 3 7% 4 3 4 4 4 7% 39%	2717
November	1st to 10th	Night	12% 7% 2 5% 4 3 4 3 4 7% 50%	2536
	11th to 20th	Night	13% 10% 4 7% 4 4 4 4 5% 6% 40%	2600
	21st to end	Night	19% 13% 4 7% 4 4 3 3 4 5% 33%	2600
December	1st to 10th	Night	13% 10% 4 7% 5% 3 4 3 5% 5% 41%	4367
	11th to 20th	Night	17% 14% 5% 11% 5% 4 4 3 4 5% 29%	5199
	21st to end	Night	26% 19% 6% 9% 5% 4 3 3 4 5% 15%	6996

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%	2608
	11th to 20th	Day	67% 4 11% 11% 6%	2610
	21st to end	Day	72% 3 8% 13% 3 1	2869
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	31% 7% 16% 31% 15% 1	4091
	11th to 20th	Day	35% 7% 13% 30% 15% 1	3796
	21st to end	Day	27% 6% 15% 31% 17% 4	4179
September	1st to 10th	Day	36% 6% 12% 24% 17% 4	2280
	11th to 20th	Day	32% 7% 11% 24% 22% 3	2102
	21st to end	Day	36% 5% 10% 25% 20% 3	2090
October	1st to 10th	Day	24% 4 8% 29% 32% 3	3480
	11th to 20th	Day	32% 4 9% 25% 29% 1	3161
	21st to end	Day	42% 3 8% 23% 21% 1	3081
November	1st to 10th	Day	35% 4 14% 25% 17% 4	1762
	11th to 20th	Day	48% 4 10% 21% 13% 4	1800
	21st to end	Day	51% 5% 9% 22% 12% 1	1800
December	1st to 10th	Day	46% 3 11% 28% 12%	2812
	11th to 20th	Day	61% 4 10% 19% 5%	3005
	21st to end	Day	73% 4 9% 10% 4	3982
January	1st to 10th	Night	63% 4 10% 16% 6%	4568
	11th to 20th	Night	69% 3 8% 13% 6% 1	4580
	21st to end	Night	67% 3 8% 14% 8%	4803
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	29% 6% 17% 33% 14% 1	2814
	11th to 20th	Night	34% 6% 13% 28% 17% 1	3095
	21st to end	Night	26% 5% 12% 32% 20% 4	3476
September	1st to 10th	Night	33% 5% 12% 25% 19% 6%	1900
	11th to 20th	Night	25% 6% 11% 26% 27% 5%	2057
	21st to end	Night	36% 6% 10% 22% 22% 4	2090
October	1st to 10th	Night	20% 4 7% 28% 40% 2	3480
	11th to 20th	Night	28% 3 9% 24% 34% 2	3755
	21st to end	Night	37% 3 8% 23% 25% 5%	4467
November	1st to 10th	Night	36% 4 9% 27% 20% 4	2536
	11th to 20th	Night	45% 3 10% 22% 17% 3	2600
	21st to end	Night	54% 4 9% 22% 11%	2600
December	1st to 10th	Night	46% 3 12% 26% 12%	4367
	11th to 20th	Night	58% 3 12% 17% 10% 1	5201
	21st to end	Night	73% 4 9% 10% 4	6996

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	25% 18% 31% 20% 6%	300
	11th to 20th	Day	21% 22% 37% 17% 3 1	300
	21st to end	Day	24% 19% 34% 19% 3	300
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% 32% 12%	539
September	1st to 10th	Day	12% 4 18% 30% 28% 8%	490
	11th to 20th	Day	9% 4 15% 29% 31% 12%	490
	21st to end	Day	14% 9% 23% 23% 21% 9%	490
October	1st to 10th	Day	10% 6% 29% 30% 19% 6%	490
	11th to 20th	Day	15% 15% 34% 22% 12% 2	352
	21st to end	Day	29% 17% 32% 20% 3	330
November	1st to 10th	Day	13% 15% 36% 23% 11% 2	300
	11th to 20th	Day	25% 17% 31% 18% 7% 2	300
	21st to end	Day	26% 13% 37% 22% 2	300
December	1st to 10th	Day	19% 21% 39% 15% 5% 1	300
	11th to 20th	Day	21% 16% 40% 18% 5% 1	300
	21st to end	Day	28% 18% 35% 17% 2	330
January	1st to 10th	Night	21% 17% 34% 24% 4	1000
	11th to 20th	Night	23% 15% 37% 20% 4	1000
	21st to end	Night	22% 15% 36% 25% 3	1051
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	627
September	1st to 10th	Night	13% 2 15% 37% 29% 4	570
	11th to 20th	Night	8% 3 15% 37% 34% 3	727
	21st to end	Night	15% 5% 20% 31% 26% 2	760
October	1st to 10th	Night	10% 6% 24% 38% 19% 4	760
	11th to 20th	Night	20% 11% 27% 27% 14% 1	760
	21st to end	Night	22% 12% 33% 26% 7%	836
November	1st to 10th	Night	15% 9% 39% 27% 9% 1	780
	11th to 20th	Night	18% 16% 33% 26% 7%	800
	21st to end	Night	25% 14% 30% 25% 6%	800
December	1st to 10th	Night	23% 11% 39% 22% 4	865
	11th to 20th	Night	25% 10% 34% 25% 6% 1	1000
	21st to end	Night	30% 15% 31% 21% 3	1100

Page generated at 2025-01-19 03:06:45. Version ac07

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