High Cliff State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the High Cliff State Park clear sky chart from 2005-11-06 to 2024-01-13.

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	13% 8% 3 7% 6% 3 5% 5% 5% 7% 37%	74789
	Night	13% 9% 4 7% 6% 3 4 4 5% 6% 38%	74955
Transparency	Day	45% 7% 13% 23% 11% 1	74490
	Night	46% 6% 12% 22% 12% 1	74775
Seeing	Day	16% 10% 30% 26% 13% 4	14770
	Night	17% 9% 32% 30% 11% 1	24773

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	11% 12% 4 9% 8% 4 6% 5% 5% 5% 30%	1517
	11th to 20th	Day	13% 15% 6% 12% 9% 4 5% 4 5% 6% 21%	1456
	21st to end	Day	12% 14% 7% 12% 7% 3 5% 5% 5% 5% 25%	1584
February	1st to 10th	Day	10% 11% 6% 10% 7% 3 6% 5% 5% 6% 31%	1602
	11th to 20th	Day	12% 11% 4 8% 5% 3 5% 4 4 6% 37%	1715
	21st to end	Day	14% 11% 5% 8% 7% 4 5% 4 5% 6% 31%	1480
March	1st to 10th	Day	13% 10% 4 7% 5% 3 5% 4 5% 7% 37%	1800
	11th to 20th	Day	13% 8% 4 6% 7% 3 5% 5% 5% 7% 37%	1855
	21st to end	Day	18% 9% 5% 7% 6% 3 5% 5% 5% 7% 31%	2376
April	1st to 10th	Day	14% 13% 4 7% 5% 3 5% 5% 5% 7% 30%	2160
	11th to 20th	Day	20% 9% 3 5% 5% 3 5% 4 5% 6% 34%	2134
	21st to end	Day	18% 9% 3 7% 6% 3 4 5% 5% 7% 33%	2295
May	1st to 10th	Day	15% 8% 3 7% 6% 4 6% 6% 6% 7% 34%	2389
	11th to 20th	Day	15% 6% 3 5% 5% 3 5% 5% 5% 8% 39%	2479
	21st to end	Day	12% 5% 2 5% 6% 4 6% 5% 6% 9% 40%	2725
June	1st to 10th	Day	10% 6% 3 5% 5% 3 4 5% 6% 9% 44%	2520
	11th to 20th	Day	13% 6% 2 4 4 3 5% 5% 5% 10% 42%	2520
	21st to end	Day	9% 5% 3 6% 4 3 4 5% 6% 10% 44%	2520
July	1st to 10th	Day	7% 3 1 4 5% 3 5% 6% 8% 11% 48%	2520
	11th to 20th	Day	8% 4 2 4 4 3 5% 5% 8% 9% 48%	2520
	21st to end	Day	8% 4 2 5% 5% 3 5% 5% 6% 9% 49%	2743
August	1st to 10th	Day	7% 5% 2 5% 6% 3 5% 6% 7% 10% 44%	2507
	11th to 20th	Day	10% 6% 2 5% 4 3 6% 5% 6% 9% 44%	2226
	21st to end	Day	12% 6% 2 4 5% 3 5% 5% 5% 7% 45%	2376
September	1st to 10th	Day	12% 5% 3 6% 5% 3 4 5% 5% 8% 44%	2160
	11th to 20th	Day	12% 5% 2 5% 4 3 4 3 5% 9% 48%	2062
	21st to end	Day	12% 8% 3 6% 6% 3 4 5% 6% 7% 40%	1980
October	1st to 10th	Day	15% 7% 2 6% 4 3 4 4 5% 6% 44%	1895
	11th to 20th	Day	20% 10% 4 7% 6% 3 4 4 6% 7% 28%	1762
	21st to end	Day	17% 11% 3 7% 6% 3 4 5% 4 5% 35%	1782
November	1st to 10th	Day	13% 8% 3 5% 5% 3 5% 5% 4 7% 41%	1672
	11th to 20th	Day	12% 11% 6% 9% 7% 4 5% 5% 6% 6% 30%	1710
	21st to end	Day	16% 11% 4 8% 5% 3 5% 5% 3 6% 34%	1526
December	1st to 10th	Day	13% 10% 6% 9% 9% 4 6% 6% 6% 6% 25%	1520
	11th to 20th	Day	12% 13% 5% 11% 8% 4 7% 5% 5% 6% 25%	1918
	21st to end	Day	18% 15% 7% 13% 10% 4 5% 4 3 4 16%	2783
January	1st to 10th	Night	11% 13% 5% 9% 8% 3 5% 3 3 4 34%	2648
	11th to 20th	Night	14% 13% 6% 10% 7% 3 5% 5% 4 6% 27%	2549
	21st to end	Night	12% 12% 7% 11% 7% 4 5% 5% 5% 6% 27%	2772
February	1st to 10th	Night	11% 13% 5% 9% 7% 4 5% 5% 5% 6% 33%	2355
	11th to 20th	Night	11% 8% 5% 8% 6% 4 6% 5% 4 4 38%	2130
	21st to end	Night	17% 12% 4 7% 5% 3 4 4 5% 4 36%	1776
March	1st to 10th	Night	15% 8% 3 6% 5% 3 4 5% 6% 6% 39%	2160
	11th to 20th	Night	12% 7% 4 5% 6% 3 5% 4 5% 6% 42%	2119
	21st to end	Night	18% 8% 4 6% 5% 3 5% 4 5% 6% 36%	1980
April	1st to 10th	Night	18% 9% 5% 7% 5% 3 5% 3 5% 6% 34%	1800
	11th to 20th	Night	20% 7% 2 6% 6% 2 4 4 5% 7% 37%	1775
	21st to end	Night	17% 8% 3 7% 6% 3 5% 4 5% 7% 37%	1663
May	1st to 10th	Night	17% 8% 3 6% 6% 3 4 5% 6% 8% 34%	1567
	11th to 20th	Night	17% 7% 3 6% 6% 3 5% 5% 5% 6% 39%	1416
	21st to end	Night	12% 5% 3 5% 5% 3 5% 5% 7% 9% 41%	1551
June	1st to 10th	Night	9% 6% 2 4 6% 3 5% 4 6% 8% 47%	1440
	11th to 20th	Night	12% 6% 2 6% 5% 2 4 4 7% 8% 44%	1440
	21st to end	Night	8% 4 2 4 5% 3 5% 6% 6% 9% 49%	1440
July	1st to 10th	Night	7% 4 1 3 3 3 4 5% 7% 8% 54%	1440
	11th to 20th	Night	6% 5% 3 5% 5% 3 4 5% 6% 8% 51%	1440
	21st to end	Night	6% 3 2 5% 4 2 4 5% 6% 8% 54%	1575
August	1st to 10th	Night	8% 4 2 4 5% 3 4 5% 6% 11% 48%	1432
	11th to 20th	Night	8% 5% 2 4 4 3 5% 4 5% 8% 52%	1669
	21st to end	Night	9% 5% 2 4 4 3 4 4 5% 8% 52%	1980
September	1st to 10th	Night	10% 5% 2 4 4 2 4 4 4 8% 52%	1800
	11th to 20th	Night	13% 4 1 4 4 3 3 4 4 6% 54%	1879
	21st to end	Night	12% 6% 2 5% 4 3 4 4 6% 8% 45%	1980
October	1st to 10th	Night	13% 6% 3 5% 4 3 3 4 5% 7% 47%	2060
	11th to 20th	Night	16% 8% 4 6% 5% 3 5% 5% 5% 7% 36%	2196
	21st to end	Night	18% 10% 3 6% 5% 3 4 4 5% 7% 34%	2574
November	1st to 10th	Night	12% 8% 3 5% 5% 3 4 4 4 7% 45%	2406
	11th to 20th	Night	14% 11% 6% 8% 7% 4 4 5% 5% 5% 33%	2470
	21st to end	Night	15% 10% 4 7% 6% 3 4 4 4 6% 37%	2650
December	1st to 10th	Night	13% 12% 5% 9% 7% 3 5% 5% 5% 7% 29%	2660
	11th to 20th	Night	13% 15% 5% 10% 6% 3 5% 4 4 6% 29%	3279
	21st to end	Night	19% 17% 6% 10% 7% 4 4 4 4 4 21%	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	53% 6% 13% 19% 8% 1	1518
	11th to 20th	Day	63% 7% 10% 12% 8%	1456
	21st to end	Day	60% 6% 12% 15% 8%	1584
February	1st to 10th	Day	53% 5% 11% 20% 9% 1	1602
	11th to 20th	Day	47% 5% 11% 23% 12% 2	1725
	21st to end	Day	54% 6% 10% 18% 11% 2	1480
March	1st to 10th	Day	47% 7% 15% 21% 9% 2	1800
	11th to 20th	Day	45% 7% 14% 19% 13% 2	1855
	21st to end	Day	53% 6% 12% 20% 7% 1	2376
April	1st to 10th	Day	53% 7% 12% 18% 10%	2160
	11th to 20th	Day	50% 6% 9% 21% 12% 2	2134
	21st to end	Day	50% 7% 12% 19% 11% 2	2295
May	1st to 10th	Day	47% 7% 14% 21% 10% 1	2389
	11th to 20th	Day	42% 7% 13% 23% 13% 2	2483
	21st to end	Day	40% 8% 13% 23% 13% 2	2725
June	1st to 10th	Day	36% 7% 13% 28% 14% 2	2520
	11th to 20th	Day	37% 7% 14% 26% 15% 1	2520
	21st to end	Day	34% 10% 15% 25% 15% 1	2520
July	1st to 10th	Day	27% 10% 14% 31% 16% 2	2451
	11th to 20th	Day	29% 9% 16% 28% 16% 3	2445
	21st to end	Day	30% 9% 15% 27% 16% 3	2591
August	1st to 10th	Day	31% 9% 18% 29% 11% 2	2492
	11th to 20th	Day	34% 9% 16% 28% 13% 1	2226
	21st to end	Day	37% 6% 14% 25% 16% 1	2376
September	1st to 10th	Day	39% 7% 13% 26% 15% 1	2160
	11th to 20th	Day	34% 6% 15% 32% 11% 1	2062
	21st to end	Day	42% 7% 13% 29% 9%	1980
October	1st to 10th	Day	42% 6% 13% 28% 12%	1895
	11th to 20th	Day	52% 7% 12% 20% 8% 1	1762
	21st to end	Day	51% 6% 13% 19% 10%	1782
November	1st to 10th	Day	42% 6% 13% 24% 14% 1	1672
	11th to 20th	Day	54% 6% 15% 18% 7%	1710
	21st to end	Day	52% 5% 15% 21% 6% 1	1526
December	1st to 10th	Day	58% 7% 13% 18% 4 1	1520
	11th to 20th	Day	59% 5% 14% 14% 6% 2	1915
	21st to end	Day	72% 6% 8% 10% 5%	2783
January	1st to 10th	Night	54% 4 12% 17% 11% 1	2648
	11th to 20th	Night	59% 6% 12% 16% 7% 1	2549
	21st to end	Night	58% 5% 11% 16% 10%	2772
February	1st to 10th	Night	53% 5% 9% 22% 10% 2	2355
	11th to 20th	Night	49% 5% 10% 22% 12% 2	2131
	21st to end	Night	52% 4 13% 19% 11% 2	1776
March	1st to 10th	Night	45% 6% 15% 22% 11% 2	2160
	11th to 20th	Night	43% 5% 12% 23% 15% 2	2119
	21st to end	Night	49% 5% 10% 22% 12% 2	1980
April	1st to 10th	Night	51% 6% 7% 17% 17% 1	1800
	11th to 20th	Night	47% 4 9% 21% 14% 4	1775
	21st to end	Night	47% 6% 11% 19% 14% 2	1663
May	1st to 10th	Night	47% 6% 15% 19% 11% 1	1567
	11th to 20th	Night	45% 6% 11% 24% 13% 2	1417
	21st to end	Night	37% 7% 15% 23% 15% 2	1552
June	1st to 10th	Night	35% 7% 12% 29% 16% 1	1440
	11th to 20th	Night	36% 7% 11% 27% 17% 2	1440
	21st to end	Night	29% 10% 18% 26% 14% 4	1440
July	1st to 10th	Night	26% 6% 15% 32% 18% 4	1400
	11th to 20th	Night	28% 8% 14% 28% 18% 3	1392
	21st to end	Night	25% 7% 16% 30% 18% 3	1487
August	1st to 10th	Night	29% 7% 17% 29% 15% 2	1423
	11th to 20th	Night	30% 6% 16% 32% 16% 1	1669
	21st to end	Night	30% 5% 14% 27% 21% 3	1980
September	1st to 10th	Night	32% 6% 11% 26% 23% 2	1800
	11th to 20th	Night	32% 5% 12% 35% 15% 1	1879
	21st to end	Night	38% 6% 13% 29% 14% 1	1980
October	1st to 10th	Night	37% 6% 10% 29% 16% 2	2060
	11th to 20th	Night	47% 6% 15% 19% 12% 1	2196
	21st to end	Night	49% 6% 13% 20% 11%	2574
November	1st to 10th	Night	40% 5% 13% 26% 16% 2	2406
	11th to 20th	Night	53% 5% 13% 18% 10% 1	2470
	21st to end	Night	49% 5% 16% 24% 6% 1	2650
December	1st to 10th	Night	55% 6% 14% 19% 6% 1	2660
	11th to 20th	Night	58% 6% 11% 17% 8% 1	3281
	21st to end	Night	66% 7% 9% 14% 5%	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	16% 14% 35% 26% 8% 1	270
	11th to 20th	Day	20% 12% 34% 28% 5% 1	246
	21st to end	Day	19% 13% 33% 27% 8% 1	264
February	1st to 10th	Day	13% 17% 43% 21% 6%	240
	11th to 20th	Day	15% 20% 40% 17% 8%	240
	21st to end	Day	20% 17% 44% 16% 2 1	198
March	1st to 10th	Day	16% 15% 44% 18% 7%	240
	11th to 20th	Day	23% 12% 32% 22% 8% 2	254
	21st to end	Day	25% 12% 30% 23% 8% 1	462
April	1st to 10th	Day	25% 13% 33% 23% 6%	420
	11th to 20th	Day	26% 15% 29% 18% 10% 2	412
	21st to end	Day	20% 13% 27% 25% 11% 3	420
May	1st to 10th	Day	19% 11% 33% 25% 9% 2	472
	11th to 20th	Day	17% 12% 32% 27% 9% 4	625
	21st to end	Day	15% 9% 29% 26% 15% 5%	679
June	1st to 10th	Day	10% 9% 31% 31% 14% 4	630
	11th to 20th	Day	16% 6% 33% 28% 13% 3	630
	21st to end	Day	12% 8% 28% 32% 16% 4	630
July	1st to 10th	Day	9% 4 21% 33% 25% 9%	621
	11th to 20th	Day	10% 6% 26% 33% 18% 7%	618
	21st to end	Day	8% 4 28% 32% 21% 8%	684
August	1st to 10th	Day	8% 3 26% 33% 22% 8%	626
	11th to 20th	Day	11% 4 18% 28% 26% 12%	465
	21st to end	Day	17% 5% 20% 30% 20% 9%	495
September	1st to 10th	Day	16% 8% 20% 28% 20% 8%	450
	11th to 20th	Day	12% 5% 22% 37% 17% 8%	450
	21st to end	Day	15% 10% 27% 26% 16% 5%	450
October	1st to 10th	Day	19% 12% 22% 26% 17% 3	365
	11th to 20th	Day	21% 19% 30% 22% 8%	270
	21st to end	Day	26% 12% 39% 16% 5% 1	297
November	1st to 10th	Day	15% 16% 35% 23% 10% 1	270
	11th to 20th	Day	17% 16% 41% 18% 9%	270
	21st to end	Day	21% 16% 42% 14% 7%	270
December	1st to 10th	Day	19% 15% 43% 19% 5%	270
	11th to 20th	Day	22% 14% 41% 16% 5% 2	270
	21st to end	Day	26% 13% 39% 16% 5%	297
January	1st to 10th	Night	16% 14% 38% 26% 6%	950
	11th to 20th	Night	20% 11% 37% 25% 7% 1	911
	21st to end	Night	20% 8% 37% 27% 7%	990
February	1st to 10th	Night	18% 13% 37% 27% 5%	900
	11th to 20th	Night	15% 14% 39% 25% 7%	735
	21st to end	Night	23% 12% 34% 26% 4 1	592
March	1st to 10th	Night	19% 10% 33% 28% 9% 1	720
	11th to 20th	Night	17% 11% 36% 30% 6% 1	694
	21st to end	Night	20% 6% 31% 32% 10% 1	594
April	1st to 10th	Night	22% 9% 38% 26% 5%	540
	11th to 20th	Night	23% 10% 30% 29% 7% 1	533
	21st to end	Night	20% 7% 33% 31% 8% 1	540
May	1st to 10th	Night	21% 7% 33% 30% 8%	540
	11th to 20th	Night	20% 6% 36% 29% 9%	531
	21st to end	Night	13% 5% 28% 38% 15% 1	584
June	1st to 10th	Night	10% 5% 30% 41% 14% 1	540
	11th to 20th	Night	15% 5% 30% 37% 12% 1	540
	21st to end	Night	9% 3 27% 44% 16% 1	540
July	1st to 10th	Night	8% 1 20% 46% 23% 2	525
	11th to 20th	Night	9% 3 23% 40% 23% 2	522
	21st to end	Night	6% 2 23% 46% 23% 1	591
August	1st to 10th	Night	9% 2 16% 46% 26% 2	537
	11th to 20th	Night	10% 2 18% 40% 26% 4	534
	21st to end	Night	10% 3 22% 40% 23% 2	594
September	1st to 10th	Night	12% 4 24% 36% 20% 5%	540
	11th to 20th	Night	15% 5% 22% 33% 21% 4	619
	21st to end	Night	14% 9% 27% 29% 19% 2	720
October	1st to 10th	Night	16% 8% 28% 31% 16% 1	720
	11th to 20th	Night	20% 12% 34% 26% 8%	720
	21st to end	Night	24% 10% 31% 25% 9% 1	792
November	1st to 10th	Night	16% 9% 40% 26% 8% 1	740
	11th to 20th	Night	20% 16% 36% 23% 5%	760
	21st to end	Night	20% 14% 36% 22% 7%	940
December	1st to 10th	Night	21% 14% 39% 20% 6%	950
	11th to 20th	Night	22% 13% 37% 22% 5% 1	950
	21st to end	Night	25% 14% 36% 22% 3	1045

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