Glacial Lakes State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Glacial Lakes State Park clear sky chart from 2005-11-06 to 2024-01-12.

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% 6% 7% 38%	74714
	Night	11% 8% 4 7% 6% 3 5% 5% 5% 7% 39%	75010
Transparency	Day	44% 6% 14% 24% 10% 1	74412
	Night	44% 6% 14% 24% 12% 1	74833
Seeing	Day	15% 9% 31% 28% 14% 3	14856
	Night	14% 9% 33% 33% 10% 1	24893

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	8% 11% 5% 11% 9% 5% 7% 6% 8% 7% 24%	1328
	11th to 20th	Day	9% 12% 7% 11% 9% 4 5% 6% 6% 8% 23%	1414
	21st to end	Day	9% 12% 7% 12% 11% 5% 7% 7% 7% 7% 16%	1782
February	1st to 10th	Day	8% 11% 6% 8% 7% 4 8% 6% 7% 8% 27%	1620
	11th to 20th	Day	7% 11% 5% 9% 8% 6% 6% 7% 8% 6% 28%	1574
	21st to end	Day	9% 13% 4 10% 10% 6% 6% 5% 7% 6% 23%	1394
March	1st to 10th	Day	13% 10% 5% 10% 8% 4 5% 5% 4 6% 30%	1934
	11th to 20th	Day	13% 10% 5% 8% 5% 2 5% 5% 5% 7% 33%	1980
	21st to end	Day	18% 12% 4 8% 8% 3 5% 5% 5% 7% 25%	2178
April	1st to 10th	Day	17% 9% 3 6% 5% 3 5% 4 6% 8% 35%	2097
	11th to 20th	Day	19% 11% 4 7% 5% 3 4 4 5% 6% 32%	2281
	21st to end	Day	24% 9% 4 5% 4 3 4 4 4 6% 33%	2340
May	1st to 10th	Day	18% 8% 3 8% 5% 4 4 4 5% 6% 35%	2340
	11th to 20th	Day	16% 7% 3 6% 5% 3 4 4 6% 8% 38%	2472
	21st to end	Day	15% 6% 3 6% 5% 3 4 5% 5% 9% 38%	2725
June	1st to 10th	Day	12% 5% 3 5% 5% 3 4 5% 7% 8% 43%	2664
	11th to 20th	Day	14% 6% 3 5% 5% 3 5% 5% 6% 8% 40%	2700
	21st to end	Day	8% 5% 2 4 5% 3 4 7% 7% 10% 46%	2700
July	1st to 10th	Day	6% 3 1 4 4 3 5% 5% 7% 10% 54%	2700
	11th to 20th	Day	7% 4 2 3 3 3 5% 5% 6% 8% 55%	2700
	21st to end	Day	5% 4 2 4 4 3 4 6% 6% 9% 54%	2594
August	1st to 10th	Day	9% 5% 3 5% 5% 3 5% 6% 7% 8% 44%	2328
	11th to 20th	Day	12% 5% 3 4 4 3 4 5% 5% 9% 46%	2301
	21st to end	Day	9% 4 1 3 4 3 4 4 5% 8% 55%	2564
September	1st to 10th	Day	11% 4 2 4 4 3 4 4 5% 8% 52%	2160
	11th to 20th	Day	11% 5% 2 5% 4 3 5% 5% 6% 7% 47%	2003
	21st to end	Day	16% 5% 2 4 4 2 4 3 5% 8% 47%	1976
October	1st to 10th	Day	16% 9% 2 5% 5% 3 2 5% 5% 8% 41%	1800
	11th to 20th	Day	16% 11% 3 5% 4 2 4 4 4 6% 41%	1800
	21st to end	Day	17% 9% 4 7% 5% 2 4 3 5% 6% 37%	1921
November	1st to 10th	Day	13% 12% 4 6% 7% 2 3 3 6% 7% 37%	1564
	11th to 20th	Day	11% 11% 5% 13% 9% 4 5% 4 3 6% 28%	1520
	21st to end	Day	13% 10% 5% 8% 8% 4 5% 5% 6% 6% 31%	1520
December	1st to 10th	Day	8% 11% 5% 11% 11% 6% 7% 6% 6% 5% 24%	1520
	11th to 20th	Day	9% 13% 7% 12% 8% 4 7% 3 5% 6% 26%	1778
	21st to end	Day	22% 13% 6% 12% 10% 3 3 3 4 6% 19%	2442
January	1st to 10th	Night	7% 8% 5% 9% 9% 5% 7% 6% 7% 8% 28%	2837
	11th to 20th	Night	8% 12% 5% 11% 9% 6% 8% 6% 6% 6% 23%	2572
	21st to end	Night	10% 12% 6% 11% 9% 4 6% 5% 6% 7% 24%	2574
February	1st to 10th	Night	6% 10% 4 9% 8% 4 7% 6% 7% 9% 31%	2340
	11th to 20th	Night	6% 9% 4 7% 7% 4 6% 6% 6% 7% 36%	2273
	21st to end	Night	12% 9% 4 8% 7% 3 7% 5% 5% 7% 31%	1875
March	1st to 10th	Night	11% 10% 5% 8% 7% 4 5% 5% 5% 7% 34%	2025
	11th to 20th	Night	13% 9% 4 8% 5% 2 4 4 6% 6% 39%	1980
	21st to end	Night	15% 8% 5% 8% 5% 3 5% 5% 7% 7% 32%	2178
April	1st to 10th	Night	15% 9% 3 5% 4 3 5% 4 5% 6% 41%	1862
	11th to 20th	Night	18% 9% 4 7% 4 3 4 4 4 6% 37%	1627
	21st to end	Night	18% 10% 4 6% 4 3 4 4 4 5% 39%	1620
May	1st to 10th	Night	15% 8% 3 6% 6% 3 5% 4 4 7% 40%	1620
	11th to 20th	Night	13% 6% 2 6% 5% 4 4 5% 5% 7% 43%	1421
	21st to end	Night	12% 5% 3 4 6% 3 6% 5% 6% 9% 42%	1551
June	1st to 10th	Night	11% 5% 2 3 5% 2 4 5% 5% 9% 50%	1292
	11th to 20th	Night	10% 4 2 4 3 3 5% 5% 6% 8% 49%	1260
	21st to end	Night	8% 4 2 3 5% 2 4 4 6% 7% 57%	1260
July	1st to 10th	Night	4 3 2 3 4 2 4 5% 6% 9% 59%	1260
	11th to 20th	Night	5% 2 1 3 3 3 4 4 4 8% 63%	1260
	21st to end	Night	4 3 1 3 3 3 4 6% 6% 9% 58%	1719
August	1st to 10th	Night	7% 4 2 4 4 3 5% 6% 6% 9% 50%	1611
	11th to 20th	Night	9% 4 2 4 4 3 3 4 4 7% 57%	1600
	21st to end	Night	7% 3 2 3 3 2 3 4 4 6% 63%	1791
September	1st to 10th	Night	9% 5% 2 4 3 2 3 4 5% 7% 58%	1800
	11th to 20th	Night	10% 5% 2 4 5% 3 4 5% 4 6% 53%	1953
	21st to end	Night	11% 5% 2 5% 3 2 4 3 4 6% 53%	1980
October	1st to 10th	Night	13% 8% 3 6% 5% 3 4 4 4 7% 45%	2145
	11th to 20th	Night	15% 8% 2 5% 5% 2 3 5% 5% 5% 44%	2160
	21st to end	Night	16% 11% 3 7% 5% 2 3 4 4 6% 39%	2434
November	1st to 10th	Night	11% 8% 4 6% 5% 4 5% 5% 5% 6% 40%	2514
	11th to 20th	Night	11% 11% 5% 10% 7% 3 4 4 4 5% 36%	2660
	21st to end	Night	10% 10% 4 8% 7% 3 5% 4 5% 7% 37%	2660
December	1st to 10th	Night	8% 11% 6% 10% 8% 4 6% 4 5% 7% 30%	2660
	11th to 20th	Night	11% 11% 5% 10% 8% 5% 6% 6% 5% 7% 27%	3411
	21st to end	Night	19% 14% 6% 12% 9% 4 5% 5% 4 5% 18%	5225

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	55% 7% 14% 17% 6% 1	1329
	11th to 20th	Day	58% 5% 14% 17% 7%	1414
	21st to end	Day	64% 6% 12% 12% 5%	1782
February	1st to 10th	Day	53% 6% 12% 20% 8%	1620
	11th to 20th	Day	54% 7% 13% 20% 6% 1	1583
	21st to end	Day	58% 7% 10% 17% 8%	1394
March	1st to 10th	Day	55% 6% 15% 17% 6% 1	1934
	11th to 20th	Day	52% 6% 13% 22% 8%	1980
	21st to end	Day	58% 6% 12% 19% 4	2178
April	1st to 10th	Day	47% 6% 12% 23% 11% 1	2097
	11th to 20th	Day	53% 5% 11% 17% 13% 1	2281
	21st to end	Day	52% 5% 11% 22% 8% 1	2340
May	1st to 10th	Day	50% 5% 13% 21% 10% 1	2340
	11th to 20th	Day	44% 6% 13% 25% 11% 1	2476
	21st to end	Day	43% 7% 13% 24% 11% 1	2725
June	1st to 10th	Day	37% 6% 17% 28% 11% 1	2664
	11th to 20th	Day	41% 8% 14% 21% 14% 1	2700
	21st to end	Day	31% 8% 20% 28% 11% 2	2700
July	1st to 10th	Day	24% 7% 18% 33% 17% 1	2626
	11th to 20th	Day	27% 7% 16% 29% 18% 3	2619
	21st to end	Day	25% 8% 17% 31% 17% 2	2450
August	1st to 10th	Day	35% 6% 16% 29% 10% 3	2314
	11th to 20th	Day	34% 7% 18% 29% 10% 1	2301
	21st to end	Day	28% 5% 14% 35% 16% 3	2564
September	1st to 10th	Day	30% 6% 16% 35% 13% 1	2160
	11th to 20th	Day	34% 6% 19% 31% 10%	2003
	21st to end	Day	36% 6% 14% 32% 12% 1	1976
October	1st to 10th	Day	42% 5% 13% 27% 12% 1	1800
	11th to 20th	Day	44% 5% 12% 24% 13% 2	1800
	21st to end	Day	48% 5% 12% 26% 8% 1	1921
November	1st to 10th	Day	46% 5% 13% 22% 12% 3	1564
	11th to 20th	Day	58% 5% 12% 17% 8%	1520
	21st to end	Day	50% 5% 18% 19% 6% 2	1520
December	1st to 10th	Day	57% 6% 16% 15% 6%	1520
	11th to 20th	Day	59% 5% 16% 17% 4	1775
	21st to end	Day	68% 4 10% 13% 5%	2442
January	1st to 10th	Night	50% 6% 15% 22% 7%	2837
	11th to 20th	Night	59% 7% 12% 14% 8%	2572
	21st to end	Night	56% 6% 13% 16% 8% 1	2574
February	1st to 10th	Night	49% 6% 14% 20% 11% 1	2340
	11th to 20th	Night	45% 6% 14% 22% 12% 1	2274
	21st to end	Night	50% 7% 12% 19% 11% 2	1875
March	1st to 10th	Night	48% 6% 16% 22% 7%	2025
	11th to 20th	Night	46% 4 13% 25% 12%	1980
	21st to end	Night	49% 7% 13% 22% 7% 1	2178
April	1st to 10th	Night	43% 5% 13% 26% 11% 1	1862
	11th to 20th	Night	50% 3 6% 24% 14% 2	1627
	21st to end	Night	48% 4 11% 23% 12% 2	1620
May	1st to 10th	Night	44% 5% 12% 26% 13% 1	1620
	11th to 20th	Night	39% 7% 13% 24% 14% 3	1422
	21st to end	Night	38% 7% 14% 24% 14% 3	1552
June	1st to 10th	Night	32% 5% 15% 31% 14% 2	1292
	11th to 20th	Night	30% 7% 17% 26% 16% 3	1260
	21st to end	Night	26% 4 18% 30% 18% 3	1260
July	1st to 10th	Night	20% 6% 17% 36% 19% 1	1225
	11th to 20th	Night	21% 4 15% 36% 19% 5%	1218
	21st to end	Night	21% 6% 16% 37% 16% 4	1624
August	1st to 10th	Night	29% 7% 17% 30% 14% 4	1601
	11th to 20th	Night	27% 5% 19% 34% 13% 2	1600
	21st to end	Night	21% 6% 14% 33% 22% 4	1791
September	1st to 10th	Night	25% 5% 18% 33% 18% 1	1800
	11th to 20th	Night	32% 6% 15% 31% 17%	1953
	21st to end	Night	33% 4 13% 33% 17% 1	1980
October	1st to 10th	Night	38% 5% 11% 28% 15% 2	2145
	11th to 20th	Night	40% 5% 13% 27% 13% 2	2160
	21st to end	Night	46% 5% 14% 23% 12% 1	2434
November	1st to 10th	Night	42% 5% 14% 24% 13% 2	2514
	11th to 20th	Night	50% 5% 14% 20% 11% 1	2660
	21st to end	Night	45% 6% 18% 22% 8% 2	2660
December	1st to 10th	Night	53% 5% 16% 19% 7%	2660
	11th to 20th	Night	55% 6% 17% 17% 5% 1	3413
	21st to end	Night	67% 6% 10% 13% 4	5225

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% 7% 35% 29% 9% 3	270
	11th to 20th	Day	14% 12% 30% 33% 10% 1	243
	21st to end	Day	14% 13% 38% 23% 10% 2	264
February	1st to 10th	Day	12% 16% 43% 27% 3	240
	11th to 20th	Day	13% 17% 37% 27% 7%	240
	21st to end	Day	14% 16% 36% 27% 8%	198
March	1st to 10th	Day	16% 15% 37% 25% 8%	240
	11th to 20th	Day	20% 6% 35% 25% 11% 3	240
	21st to end	Day	23% 12% 24% 26% 11% 4	264
April	1st to 10th	Day	26% 14% 32% 20% 7%	357
	11th to 20th	Day	28% 14% 24% 24% 10% 1	559
	21st to end	Day	25% 11% 32% 20% 11% 2	600
May	1st to 10th	Day	18% 12% 34% 24% 10% 1	603
	11th to 20th	Day	20% 12% 29% 25% 12% 2	625
	21st to end	Day	17% 8% 32% 28% 13% 2	679
June	1st to 10th	Day	10% 7% 24% 35% 21% 3	630
	11th to 20th	Day	13% 8% 37% 29% 12% 2	630
	21st to end	Day	11% 6% 34% 30% 16% 3	630
July	1st to 10th	Day	5% 4 25% 35% 26% 6%	621
	11th to 20th	Day	7% 7% 28% 35% 18% 5%	618
	21st to end	Day	5% 3 25% 37% 24% 6%	684
August	1st to 10th	Day	9% 2 23% 33% 27% 5%	626
	11th to 20th	Day	12% 4 22% 33% 23% 7%	615
	21st to end	Day	9% 6% 26% 32% 22% 5%	683
September	1st to 10th	Day	12% 8% 28% 31% 16% 4	450
	11th to 20th	Day	11% 3 35% 31% 16% 4	293
	21st to end	Day	19% 14% 30% 24% 12% 1	270
October	1st to 10th	Day	18% 13% 30% 24% 11% 4	270
	11th to 20th	Day	16% 18% 36% 20% 8% 2	270
	21st to end	Day	23% 16% 36% 19% 6% 1	297
November	1st to 10th	Day	24% 12% 26% 30% 7% 1	270
	11th to 20th	Day	17% 17% 41% 21% 4	270
	21st to end	Day	19% 19% 34% 23% 4	270
December	1st to 10th	Day	10% 10% 44% 26% 10%	270
	11th to 20th	Day	16% 13% 43% 23% 5%	270
	21st to end	Day	28% 11% 34% 23% 5%	297
January	1st to 10th	Night	11% 9% 40% 30% 8% 2	950
	11th to 20th	Night	13% 11% 35% 31% 8% 1	908
	21st to end	Night	15% 11% 38% 29% 7%	990
February	1st to 10th	Night	10% 10% 38% 32% 9% 1	900
	11th to 20th	Night	12% 11% 40% 28% 9% 1	879
	21st to end	Night	16% 11% 31% 30% 10% 1	691
March	1st to 10th	Night	15% 11% 36% 29% 8% 1	585
	11th to 20th	Night	17% 8% 37% 31% 6% 1	540
	21st to end	Night	17% 10% 30% 29% 13% 1	594
April	1st to 10th	Night	18% 11% 38% 28% 4	540
	11th to 20th	Night	22% 11% 30% 27% 8% 1	533
	21st to end	Night	21% 10% 32% 28% 8% 1	540
May	1st to 10th	Night	18% 10% 32% 30% 9% 1	540
	11th to 20th	Night	15% 8% 34% 32% 11%	531
	21st to end	Night	13% 9% 29% 39% 10%	584
June	1st to 10th	Night	12% 7% 25% 38% 16% 1	540
	11th to 20th	Night	10% 4 34% 44% 8%	540
	21st to end	Night	8% 4 26% 47% 15% 1	540
July	1st to 10th	Night	4 3 21% 46% 25% 1	525
	11th to 20th	Night	5% 4 25% 48% 16% 2	522
	21st to end	Night	6% 2 23% 46% 21% 2	591
August	1st to 10th	Night	7% 1 21% 47% 22% 1	537
	11th to 20th	Night	10% 3 22% 39% 23% 3	534
	21st to end	Night	7% 4 26% 38% 23% 2	594
September	1st to 10th	Night	11% 4 26% 41% 16% 2	540
	11th to 20th	Night	12% 5% 28% 37% 16% 1	540
	21st to end	Night	13% 7% 36% 33% 11% 1	540
October	1st to 10th	Night	17% 9% 35% 28% 10%	705
	11th to 20th	Night	19% 11% 32% 30% 8% 1	720
	21st to end	Night	21% 12% 34% 28% 5%	850
November	1st to 10th	Night	15% 11% 32% 33% 9%	925
	11th to 20th	Night	16% 12% 37% 25% 9% 1	950
	21st to end	Night	14% 13% 39% 27% 7%	950
December	1st to 10th	Night	13% 11% 37% 31% 8% 1	950
	11th to 20th	Night	17% 10% 35% 31% 6% 1	950
	21st to end	Night	23% 11% 35% 25% 5% 1	1045

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