Waldo Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Waldo Lake clear sky chart from 2005-11-06 to 2025-04-26.

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	7% 13% 4 8% 4 4 4 3 4 5% 43%	117792
	Night	7% 13% 5% 10% 5% 5% 4 3 5% 5% 37%	119645
Transparency	Day	40% 6% 9% 18% 17% 9%	117536
	Night	45% 8% 9% 15% 15% 8%	119490
Seeing	Day	19% 19% 27% 21% 11% 2	15261
	Night	16% 15% 20% 30% 17% 2	24451

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	8% 23% 10% 17% 8% 5% 4 3 4 4 15%	3639
	11th to 20th	Day	9% 15% 6% 10% 4 3 3 2 3 5% 41%	3640
	21st to end	Day	11% 18% 4 7% 4 4 4 3 4 5% 37%	4464
February	1st to 10th	Day	9% 20% 7% 11% 6% 6% 4 5% 6% 6% 22%	1800
	11th to 20th	Day	9% 20% 8% 12% 6% 5% 4 3 5% 5% 25%	1755
	21st to end	Day	6% 22% 9% 13% 6% 4 4 4 4 5% 22%	1625
March	1st to 10th	Day	6% 17% 8% 13% 5% 4 4 4 5% 7% 27%	4684
	11th to 20th	Day	6% 21% 7% 13% 6% 5% 4 2 3 4 30%	5000
	21st to end	Day	6% 22% 9% 14% 7% 6% 5% 4 5% 6% 16%	5653
April	1st to 10th	Day	10% 24% 8% 11% 6% 5% 4 4 4 4 20%	2400
	11th to 20th	Day	9% 20% 6% 9% 6% 4 4 3 4 4 30%	2369
	21st to end	Day	6% 21% 6% 8% 5% 4 4 3 5% 7% 31%	2433
May	1st to 10th	Day	10% 19% 7% 7% 4 3 3 3 4 4 35%	4324
	11th to 20th	Day	7% 9% 3 5% 3 2 3 3 5% 5% 55%	4377
	21st to end	Day	10% 13% 4 7% 5% 4 4 4 5% 8% 36%	4813
June	1st to 10th	Day	14% 13% 3 7% 5% 4 4 3 5% 6% 36%	2660
	11th to 20th	Day	8% 14% 2 7% 5% 4 5% 3 4 6% 41%	2660
	21st to end	Day	6% 5% 1 4 3 3 3 3 5% 6% 62%	2660
July	1st to 10th	Day	2 2 2 1 1 2 2 2 2 84%	4420
	11th to 20th	Day	3 2 1 3 2 2 2 2 3 4 78%	4420
	21st to end	Day	2 2 1 2 1 2 2 2 3 3 81%	4773
August	1st to 10th	Day	4 3 1 3 2 2 3 2 4 5% 71%	4091
	11th to 20th	Day	2 2 1 3 3 3 3 3 4 6% 69%	4026
	21st to end	Day	5% 4 1 3 2 2 2 3 4 5% 70%	4193
September	1st to 10th	Day	3 3 1 3 2 3 3 2 3 6% 71%	2280
	11th to 20th	Day	7% 7% 2 6% 4 4 3 3 5% 6% 53%	2280
	21st to end	Day	8% 7% 2 5% 3 3 4 3 5% 6% 54%	2015
October	1st to 10th	Day	6% 7% 1 5% 2 3 3 2 4 5% 62%	3180
	11th to 20th	Day	7% 10% 4 7% 5% 5% 5% 4 6% 8% 40%	3161
	21st to end	Day	8% 11% 5% 11% 6% 6% 6% 3 5% 6% 32%	3386
November	1st to 10th	Day	14% 19% 4 9% 6% 5% 4 3 4 6% 26%	1759
	11th to 20th	Day	11% 20% 5% 10% 5% 6% 5% 3 5% 7% 23%	1600
	21st to end	Day	8% 20% 6% 10% 6% 6% 4 2 5% 5% 29%	1600
December	1st to 10th	Day	6% 11% 4 8% 4 5% 4 4 6% 6% 43%	2620
	11th to 20th	Day	10% 20% 6% 14% 7% 7% 6% 4 5% 6% 15%	3028
	21st to end	Day	8% 20% 8% 15% 8% 8% 7% 4 5% 5% 13%	4004
January	1st to 10th	Night	7% 22% 8% 15% 7% 7% 6% 4 5% 4 13%	6306
	11th to 20th	Night	6% 15% 7% 12% 4 4 4 3 5% 6% 34%	6320
	21st to end	Night	11% 17% 5% 10% 4 4 3 2 3 3 37%	6498
February	1st to 10th	Night	6% 18% 8% 12% 8% 6% 6% 4 6% 5% 22%	2600
	11th to 20th	Night	7% 16% 8% 12% 6% 6% 6% 3 5% 5% 24%	2532
	21st to end	Night	6% 20% 7% 14% 6% 6% 4 4 4 5% 25%	2003
March	1st to 10th	Night	5% 14% 7% 15% 6% 6% 7% 5% 6% 7% 22%	5205
	11th to 20th	Night	4 15% 7% 14% 7% 6% 6% 3 4 4 30%	5000
	21st to end	Night	5% 18% 8% 15% 9% 9% 7% 3 5% 5% 16%	5321
April	1st to 10th	Night	9% 21% 8% 13% 6% 4 4 3 4 5% 22%	2000
	11th to 20th	Night	7% 17% 8% 12% 6% 5% 5% 3 6% 5% 28%	1979
	21st to end	Night	8% 20% 7% 11% 5% 5% 4 4 6% 6% 27%	1858
May	1st to 10th	Night	10% 16% 11% 10% 4 4 4 3 4 3 32%	2637
	11th to 20th	Night	5% 9% 4 7% 5% 5% 4 4 5% 6% 46%	2516
	21st to end	Night	7% 19% 5% 8% 4 4 4 3 6% 7% 33%	2762
June	1st to 10th	Night	12% 15% 3 7% 4 5% 4 4 5% 6% 35%	1520
	11th to 20th	Night	7% 13% 4 7% 4 4 4 4 5% 7% 42%	1520
	21st to end	Night	6% 4 1 5% 3 3 4 3 4 6% 60%	1520
July	1st to 10th	Night	2 2 1 2 2 2 1 1 3 4 80%	2540
	11th to 20th	Night	1 2 1 3 2 2 2 2 3 4 79%	2540
	21st to end	Night	1 1 1 2 1 2 2 2 3 4 81%	2777
August	1st to 10th	Night	1 3 1 5% 3 2 3 2 4 5% 71%	2848
	11th to 20th	Night	2 3 1 4 3 3 4 3 5% 6% 66%	2812
	21st to end	Night	6% 2 1 4 4 3 3 2 4 4 69%	3484
September	1st to 10th	Night	3 3 1 3 2 2 2 1 4 5% 72%	1900
	11th to 20th	Night	5% 6% 2 6% 3 4 4 4 5% 6% 54%	1900
	21st to end	Night	7% 7% 2 6% 4 4 4 3 5% 6% 53%	2161
October	1st to 10th	Night	4 6% 2 6% 3 3 3 2 3 5% 64%	3800
	11th to 20th	Night	7% 9% 3 6% 5% 4 5% 4 6% 7% 44%	3777
	21st to end	Night	6% 12% 4 13% 7% 7% 7% 4 4 6% 31%	4181
November	1st to 10th	Night	11% 19% 5% 11% 6% 5% 4 4 5% 6% 25%	2540
	11th to 20th	Night	11% 19% 6% 9% 7% 6% 5% 4 5% 5% 23%	2800
	21st to end	Night	6% 17% 5% 11% 6% 5% 5% 4 5% 6% 30%	2800
December	1st to 10th	Night	6% 9% 3 8% 4 4 4 3 5% 7% 45%	4560
	11th to 20th	Night	8% 22% 7% 15% 7% 7% 5% 4 5% 6% 15%	5176
	21st to end	Night	12% 18% 7% 15% 7% 6% 5% 4 4 4 18%	6952

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	67% 10% 8% 8% 6% 2	3639
	11th to 20th	Day	46% 6% 8% 16% 20% 6%	3640
	21st to end	Day	48% 7% 6% 10% 20% 9%	4464
February	1st to 10th	Day	60% 8% 10% 14% 8% 1	1800
	11th to 20th	Day	59% 8% 9% 13% 8% 4	1764
	21st to end	Day	62% 8% 10% 11% 7% 3	1625
March	1st to 10th	Day	51% 8% 9% 19% 11% 2	4684
	11th to 20th	Day	57% 6% 8% 18% 11% 1	5000
	21st to end	Day	62% 12% 12% 10% 4	5653
April	1st to 10th	Day	63% 8% 10% 11% 6% 1	2400
	11th to 20th	Day	53% 8% 11% 14% 10% 3	2372
	21st to end	Day	50% 9% 13% 17% 10% 1	2433
May	1st to 10th	Day	43% 12% 10% 19% 16%	4324
	11th to 20th	Day	28% 5% 11% 29% 24% 2	4380
	21st to end	Day	38% 12% 24% 22% 5%	4814
June	1st to 10th	Day	46% 7% 14% 22% 10%	2660
	11th to 20th	Day	39% 7% 14% 26% 12% 3	2660
	21st to end	Day	23% 4 11% 32% 22% 7%	2660
July	1st to 10th	Day	9% 3 6% 13% 21% 49%	4351
	11th to 20th	Day	13% 2 4 11% 22% 48%	4345
	21st to end	Day	9% 2 4 18% 39% 27%	4622
August	1st to 10th	Day	17% 3 6% 19% 34% 21%	4076
	11th to 20th	Day	16% 3 6% 31% 33% 11%	4065
	21st to end	Day	18% 3 7% 28% 25% 19%	4192
September	1st to 10th	Day	17% 3 6% 23% 33% 19%	2280
	11th to 20th	Day	30% 4 11% 24% 22% 10%	2280
	21st to end	Day	30% 5% 10% 24% 22% 9%	2015
October	1st to 10th	Day	25% 4 8% 17% 32% 14%	3180
	11th to 20th	Day	39% 6% 14% 24% 15% 3	3161
	21st to end	Day	49% 6% 9% 17% 17% 3	3386
November	1st to 10th	Day	57% 7% 9% 13% 12% 2	1759
	11th to 20th	Day	59% 8% 10% 11% 9% 3	1600
	21st to end	Day	55% 6% 8% 11% 14% 5%	1600
December	1st to 10th	Day	39% 6% 8% 17% 20% 11%	2620
	11th to 20th	Day	67% 8% 9% 10% 6%	3028
	21st to end	Day	68% 8% 9% 9% 4 1	4004
January	1st to 10th	Night	64% 12% 8% 8% 7% 1	6306
	11th to 20th	Night	46% 7% 7% 17% 17% 7%	6320
	21st to end	Night	51% 6% 5% 7% 17% 13%	6498
February	1st to 10th	Night	57% 11% 10% 12% 9% 1	2600
	11th to 20th	Night	58% 9% 9% 12% 8% 4	2534
	21st to end	Night	59% 9% 8% 12% 10% 2	2003
March	1st to 10th	Night	51% 10% 12% 16% 7% 4	5205
	11th to 20th	Night	54% 7% 9% 18% 12%	5000
	21st to end	Night	63% 13% 9% 13% 3	5321
April	1st to 10th	Night	60% 10% 11% 11% 7%	2000
	11th to 20th	Night	54% 9% 10% 14% 9% 3	1979
	21st to end	Night	52% 11% 12% 14% 9% 1	1858
May	1st to 10th	Night	47% 11% 11% 19% 11% 1	2637
	11th to 20th	Night	28% 11% 11% 24% 24% 1	2516
	21st to end	Night	40% 14% 21% 21% 4	2762
June	1st to 10th	Night	46% 9% 12% 23% 9% 1	1520
	11th to 20th	Night	38% 8% 14% 27% 10% 3	1520
	21st to end	Night	24% 6% 11% 30% 22% 7%	1520
July	1st to 10th	Night	9% 3 6% 12% 21% 48%	2500
	11th to 20th	Night	11% 3 4 12% 23% 47%	2492
	21st to end	Night	8% 3 4 16% 45% 24%	2690
August	1st to 10th	Night	17% 2 5% 18% 39% 19%	2839
	11th to 20th	Night	17% 3 7% 29% 33% 10%	2839
	21st to end	Night	18% 4 8% 26% 25% 19%	3484
September	1st to 10th	Night	15% 3 8% 23% 34% 18%	1900
	11th to 20th	Night	28% 6% 9% 20% 26% 11%	1900
	21st to end	Night	31% 5% 10% 20% 21% 13%	2161
October	1st to 10th	Night	25% 4 7% 18% 32% 15%	3800
	11th to 20th	Night	37% 6% 15% 23% 14% 5%	3777
	21st to end	Night	53% 6% 8% 13% 16% 4	4181
November	1st to 10th	Night	57% 8% 10% 10% 12% 3	2540
	11th to 20th	Night	60% 8% 9% 11% 9% 3	2800
	21st to end	Night	52% 7% 9% 11% 13% 8%	2800
December	1st to 10th	Night	36% 6% 7% 14% 25% 12%	4560
	11th to 20th	Night	66% 9% 9% 9% 6% 1	5176
	21st to end	Night	64% 8% 9% 11% 6% 1	6952

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	38% 21% 23% 13% 6% 1	200
	11th to 20th	Day	33% 16% 24% 18% 5% 5%	200
	21st to end	Day	27% 19% 20% 21% 10% 2	420
February	1st to 10th	Day	26% 24% 26% 14% 10%	400
	11th to 20th	Day	28% 29% 22% 16% 4 1	395
	21st to end	Day	31% 20% 26% 19% 4	401
March	1st to 10th	Day	28% 25% 26% 17% 4	500
	11th to 20th	Day	25% 22% 24% 21% 7%	500
	21st to end	Day	33% 25% 24% 13% 4	550
April	1st to 10th	Day	30% 23% 23% 17% 5% 2	500
	11th to 20th	Day	29% 23% 27% 14% 6% 1	492
	21st to end	Day	24% 26% 26% 16% 8% 1	481
May	1st to 10th	Day	24% 22% 28% 18% 7% 1	463
	11th to 20th	Day	28% 17% 24% 19% 10% 3	488
	21st to end	Day	22% 18% 27% 19% 12% 2	529
June	1st to 10th	Day	18% 19% 28% 20% 12% 3	490
	11th to 20th	Day	19% 24% 27% 22% 7% 2	490
	21st to end	Day	8% 16% 29% 30% 16% 2	490
July	1st to 10th	Day	5% 11% 40% 26% 15% 3	486
	11th to 20th	Day	2 16% 36% 27% 16% 4	484
	21st to end	Day	3 11% 37% 25% 18% 5%	531
August	1st to 10th	Day	4 11% 35% 27% 18% 5%	487
	11th to 20th	Day	4 11% 27% 30% 20% 7%	477
	21st to end	Day	9% 12% 32% 27% 17% 5%	539
September	1st to 10th	Day	4 13% 31% 28% 21% 3	490
	11th to 20th	Day	12% 14% 29% 28% 15% 2	490
	21st to end	Day	12% 18% 26% 27% 15% 2	490
October	1st to 10th	Day	17% 16% 27% 22% 16% 2	490
	11th to 20th	Day	21% 14% 23% 22% 19% 1	490
	21st to end	Day	24% 22% 23% 17% 12% 3	501
November	1st to 10th	Day	26% 17% 23% 24% 9% 2	297
	11th to 20th	Day	26% 19% 24% 21% 11% 2	200
	21st to end	Day	24% 20% 20% 25% 10% 2	200
December	1st to 10th	Day	21% 20% 24% 20% 13% 4	200
	11th to 20th	Day	29% 25% 23% 17% 7% 1	200
	21st to end	Day	32% 22% 20% 17% 8%	220
January	1st to 10th	Night	25% 20% 26% 21% 8% 1	800
	11th to 20th	Night	23% 18% 21% 25% 12% 2	800
	21st to end	Night	19% 17% 21% 29% 12% 2	880
February	1st to 10th	Night	18% 19% 27% 27% 8% 1	800
	11th to 20th	Night	18% 20% 26% 27% 9% 1	784
	21st to end	Night	19% 19% 28% 27% 6%	660
March	1st to 10th	Night	19% 24% 23% 25% 9% 1	800
	11th to 20th	Night	20% 17% 23% 29% 11% 1	800
	21st to end	Night	22% 22% 24% 23% 8%	880
April	1st to 10th	Night	21% 20% 22% 26% 11% 1	800
	11th to 20th	Night	14% 25% 24% 23% 13% 1	791
	21st to end	Night	16% 21% 23% 26% 13% 1	686
May	1st to 10th	Night	18% 15% 21% 29% 16% 2	438
	11th to 20th	Night	17% 10% 20% 31% 22% 1	374
	21st to end	Night	16% 13% 18% 31% 21% 1	411
June	1st to 10th	Night	18% 11% 16% 32% 23% 1	380
	11th to 20th	Night	11% 13% 20% 33% 22% 1	380
	21st to end	Night	10% 3 17% 43% 26% 1	380
July	1st to 10th	Night	3 4 12% 47% 31% 2	370
	11th to 20th	Night	2 2 16% 52% 27% 1	368
	21st to end	Night	1 1 11% 47% 39% 1	420
August	1st to 10th	Night	2 1 9% 38% 45% 4	567
	11th to 20th	Night	4 2 8% 41% 41% 5%	564
	21st to end	Night	4 4 19% 42% 29% 2	822
September	1st to 10th	Night	5% 4 18% 42% 29% 3	760
	11th to 20th	Night	8% 6% 15% 37% 30% 3	760
	21st to end	Night	10% 8% 16% 38% 25% 3	760
October	1st to 10th	Night	11% 9% 24% 33% 21% 3	760
	11th to 20th	Night	15% 11% 15% 35% 22% 1	760
	21st to end	Night	19% 15% 19% 27% 17% 3	836
November	1st to 10th	Night	21% 17% 22% 28% 11% 1	780
	11th to 20th	Night	23% 21% 20% 25% 11%	800
	21st to end	Night	15% 19% 24% 28% 12% 1	800
December	1st to 10th	Night	20% 16% 22% 28% 13% 1	800
	11th to 20th	Night	23% 21% 21% 25% 9% 1	800
	21st to end	Night	25% 25% 24% 20% 6% 1	880

Page generated at 2025-04-23 06:25:03. Version ac07

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