Waltz Road
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Waltz Road clear sky chart from 2005-11-06 to 2026-03-18.

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	8% 3 1 3 2 2 3 2 4 5% 67%	140010
	Night	10% 4 1 4 3 3 3 2 4 5% 62%	138921
Transparency	Day	23% 3 7% 19% 25% 24%	134938
	Night	27% 3 8% 20% 23% 20%	134979
Seeing	Day	9% 5% 16% 26% 30% 15%	16878
	Night	11% 3 16% 38% 27% 4	26289

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	22% 7% 2 5% 4 4 4 4 6% 7% 36%	4722
	11th to 20th	Day	13% 6% 2 4 3 2 3 2 3 5% 56%	5255
	21st to end	Day	15% 6% 2 7% 4 4 4 4 5% 7% 42%	5843
February	1st to 10th	Day	18% 5% 2 5% 3 3 3 3 5% 6% 46%	1890
	11th to 20th	Day	15% 5% 2 5% 5% 4 3 4 4 7% 45%	1960
	21st to end	Day	15% 5% 1 5% 4 3 3 3 5% 6% 49%	1730
March	1st to 10th	Day	15% 9% 3 7% 4 4 4 4 5% 6% 39%	4798
	11th to 20th	Day	16% 5% 2 6% 3 4 4 2 5% 6% 48%	5078
	21st to end	Day	16% 6% 2 6% 4 4 4 4 5% 8% 41%	5661
April	1st to 10th	Day	13% 6% 2 4 4 3 4 4 5% 7% 50%	2400
	11th to 20th	Day	10% 3 1 4 3 3 3 3 6% 6% 58%	2369
	21st to end	Day	6% 3 1 3 3 2 3 3 5% 8% 64%	2400
May	1st to 10th	Day	4 2 1 2 1 2 1 2 2 4 79%	5602
	11th to 20th	Day	2 1 1 2 2 2 2 2 3 4 80%	6272
	21st to end	Day	2 1 1 1 1 1 2 3 5% 82%	6902
June	1st to 10th	Day	5% 2 1 3 2 3 2 2 4 6% 69%	2800
	11th to 20th	Day	1 1 1 1 1 1 2 2 4 4 82%	2800
	21st to end	Day	2 1 1 1 2 2 1 2 3 85%	2800
July	1st to 10th	Day	1 1 1 1 1 2 94%	6319
	11th to 20th	Day	1 1 1 1 1 1 1 1 3 90%	6290
	21st to end	Day	1 1 2 1 1 2 2 3 5% 83%	6402
August	1st to 10th	Day	1 1 1 1 1 1 1 2 4 85%	5777
	11th to 20th	Day	1 1 1 1 1 1 2 3 90%	5490
	21st to end	Day	1 1 1 1 1 1 1 1 2 4 86%	5984
September	1st to 10th	Day	1 1 1 1 1 1 1 2 4 87%	2400
	11th to 20th	Day	3 2 1 2 2 2 2 2 3 5% 77%	2400
	21st to end	Day	3 2 1 2 1 1 1 2 3 4 80%	2149
October	1st to 10th	Day	2 1 1 2 2 2 2 2 3 6% 76%	3280
	11th to 20th	Day	5% 2 1 3 2 2 3 2 4 5% 72%	3261
	21st to end	Day	5% 3 1 4 3 4 4 3 4 6% 65%	3558
November	1st to 10th	Day	10% 3 1 3 3 3 4 3 5% 7% 58%	1909
	11th to 20th	Day	14% 4 2 4 4 4 4 3 5% 7% 48%	1890
	21st to end	Day	11% 4 2 5% 4 3 3 2 5% 7% 53%	1719
December	1st to 10th	Day	8% 4 1 5% 3 4 4 3 6% 8% 55%	2700
	11th to 20th	Day	27% 7% 3 8% 5% 4 4 4 5% 6% 26%	3108
	21st to end	Day	26% 7% 3 7% 4 5% 5% 4 6% 8% 25%	4092
January	1st to 10th	Night	18% 6% 2 7% 4 4 4 3 5% 8% 40%	8172
	11th to 20th	Night	13% 4 1 4 2 2 3 2 4 5% 59%	7729
	21st to end	Night	16% 6% 2 6% 4 3 4 3 4 6% 45%	8371
February	1st to 10th	Night	18% 4 1 4 3 3 3 3 4 6% 50%	2730
	11th to 20th	Night	14% 5% 2 5% 3 4 3 3 5% 7% 48%	2547
	21st to end	Night	16% 5% 2 4 3 3 3 3 4 6% 52%	2076
March	1st to 10th	Night	17% 8% 3 6% 5% 4 4 3 4 6% 40%	5299
	11th to 20th	Night	18% 5% 1 4 3 3 3 2 4 6% 50%	5077
	21st to end	Night	18% 6% 2 5% 4 3 4 3 6% 8% 41%	5301
April	1st to 10th	Night	10% 6% 2 4 4 3 4 3 5% 7% 53%	2000
	11th to 20th	Night	9% 4 1 3 3 3 2 3 4 7% 59%	1979
	21st to end	Night	6% 3 1 4 3 2 3 3 4 6% 67%	2000
May	1st to 10th	Night	3 2 2 2 2 2 2 3 5% 76%	4386
	11th to 20th	Night	2 1 1 2 2 2 2 2 4 5% 77%	3620
	21st to end	Night	2 1 1 1 1 1 2 1 2 4 85%	3972
June	1st to 10th	Night	4 2 1 2 3 2 3 3 4 7% 69%	1600
	11th to 20th	Night	1 1 2 2 1 1 1 3 5% 82%	1600
	21st to end	Night	2 1 1 1 1 1 2 2 2 3 84%	1600
July	1st to 10th	Night	1 1 1 1 1 2 93%	3640
	11th to 20th	Night	1 1 1 1 1 1 1 1 2 2 89%	3654
	21st to end	Night	1 1 1 1 1 1 2 2 3 4 81%	4472
August	1st to 10th	Night	2 1 2 1 1 2 1 3 4 83%	4035
	11th to 20th	Night	1 1 1 1 2 2 92%	4371
	21st to end	Night	2 1 1 2 1 1 2 2 3 3 84%	5015
September	1st to 10th	Night	1 1 1 1 1 1 1 1 3 89%	2000
	11th to 20th	Night	4 2 1 2 1 2 1 1 3 4 78%	2000
	21st to end	Night	2 2 1 1 2 1 2 2 5% 81%	2248
October	1st to 10th	Night	3 2 1 2 2 2 2 2 3 3 78%	3920
	11th to 20th	Night	3 1 1 2 1 2 2 2 3 5% 78%	3897
	21st to end	Night	6% 2 1 3 2 3 3 3 4 6% 66%	4253
November	1st to 10th	Night	11% 3 1 4 3 2 3 3 5% 8% 57%	2607
	11th to 20th	Night	11% 3 2 4 4 3 3 3 5% 7% 55%	2730
	21st to end	Night	12% 4 2 4 3 3 3 3 4 6% 57%	2898
December	1st to 10th	Night	10% 3 1 3 3 2 3 3 5% 7% 60%	4700
	11th to 20th	Night	25% 6% 2 6% 4 4 4 4 7% 8% 29%	5316
	21st to end	Night	25% 7% 2 7% 5% 5% 5% 4 5% 6% 29%	7106

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	47% 6% 13% 21% 9% 4	4723
	11th to 20th	Day	32% 3 5% 17% 26% 17%	5255
	21st to end	Day	43% 3 7% 20% 18% 9%	5843
February	1st to 10th	Day	41% 3 9% 20% 19% 8%	1890
	11th to 20th	Day	38% 6% 9% 22% 19% 6%	1969
	21st to end	Day	36% 4 11% 24% 19% 6%	1730
March	1st to 10th	Day	46% 5% 7% 21% 19% 2	4798
	11th to 20th	Day	38% 4 10% 27% 13% 8%	5078
	21st to end	Day	40% 6% 14% 26% 12% 2	5661
April	1st to 10th	Day	34% 5% 10% 25% 19% 7%	2400
	11th to 20th	Day	27% 6% 12% 25% 23% 8%	2372
	21st to end	Day	20% 5% 13% 29% 27% 6%	2400
May	1st to 10th	Day	13% 2 7% 25% 34% 21%	5602
	11th to 20th	Day	11% 2 5% 26% 40% 16%	6275
	21st to end	Day	8% 3 7% 31% 40% 12%	6904
June	1st to 10th	Day	17% 4 9% 28% 29% 14%	2800
	11th to 20th	Day	8% 2 8% 20% 35% 28%	2800
	21st to end	Day	7% 1 3 12% 37% 39%	2800
July	1st to 10th	Day	3 1 1 7% 19% 69%	6251
	11th to 20th	Day	5% 1 1 5% 14% 74%	6215
	21st to end	Day	8% 1 3 15% 27% 46%	6217
August	1st to 10th	Day	9% 1 2 8% 25% 55%	4206
	11th to 20th	Day	4 1 1 8% 39% 46%	3972
	21st to end	Day	6% 1 2 11% 40% 41%	4311
September	1st to 10th	Day	5% 1 3 9% 30% 52%	2400
	11th to 20th	Day	12% 3 6% 21% 38% 20%	2400
	21st to end	Day	12% 1 4 19% 33% 30%	2149
October	1st to 10th	Day	12% 2 4 12% 27% 43%	3280
	11th to 20th	Day	16% 2 5% 26% 33% 19%	3261
	21st to end	Day	21% 3 8% 21% 32% 15%	3558
November	1st to 10th	Day	26% 5% 9% 27% 23% 10%	1909
	11th to 20th	Day	36% 4 12% 24% 18% 6%	1890
	21st to end	Day	33% 4 11% 22% 21% 10%	1719
December	1st to 10th	Day	28% 4 11% 28% 21% 8%	2700
	11th to 20th	Day	59% 4 9% 15% 12% 2	3108
	21st to end	Day	56% 6% 13% 16% 7% 2	4092
January	1st to 10th	Night	44% 4 16% 23% 9% 4	8172
	11th to 20th	Night	29% 3 7% 18% 29% 14%	7729
	21st to end	Night	42% 3 8% 17% 20% 10%	8371
February	1st to 10th	Night	37% 3 8% 22% 20% 9%	2730
	11th to 20th	Night	35% 4 9% 24% 21% 7%	2549
	21st to end	Night	34% 4 9% 24% 21% 8%	2076
March	1st to 10th	Night	45% 5% 8% 19% 18% 4	5299
	11th to 20th	Night	37% 3 12% 23% 16% 10%	5077
	21st to end	Night	42% 5% 13% 24% 13% 3	5301
April	1st to 10th	Night	31% 5% 12% 21% 23% 7%	2000
	11th to 20th	Night	26% 4 12% 27% 18% 12%	1979
	21st to end	Night	20% 4 13% 30% 26% 7%	2000
May	1st to 10th	Night	13% 3 11% 25% 28% 21%	4383
	11th to 20th	Night	11% 2 7% 30% 39% 12%	3620
	21st to end	Night	7% 2 9% 33% 38% 12%	3972
June	1st to 10th	Night	17% 3 12% 27% 29% 12%	1600
	11th to 20th	Night	8% 2 7% 20% 35% 29%	1600
	21st to end	Night	9% 1 3 12% 34% 42%	1600
July	1st to 10th	Night	3 1 1 7% 23% 65%	3600
	11th to 20th	Night	6% 1 1 4 13% 75%	3606
	21st to end	Night	9% 1 2 17% 27% 44%	4345
August	1st to 10th	Night	12% 1 2 8% 28% 49%	2929
	11th to 20th	Night	4 1 2 8% 39% 47%	3158
	21st to end	Night	7% 1 2 9% 36% 45%	3608
September	1st to 10th	Night	6% 1 2 8% 30% 53%	2000
	11th to 20th	Night	13% 1 6% 19% 37% 24%	2000
	21st to end	Night	9% 2 5% 17% 31% 36%	2248
October	1st to 10th	Night	14% 2 4 10% 20% 51%	3920
	11th to 20th	Night	12% 2 6% 28% 29% 23%	3897
	21st to end	Night	20% 2 5% 21% 31% 20%	4253
November	1st to 10th	Night	27% 3 10% 24% 21% 15%	2607
	11th to 20th	Night	29% 4 12% 26% 20% 8%	2730
	21st to end	Night	30% 4 7% 24% 23% 11%	2898
December	1st to 10th	Night	25% 3 10% 29% 23% 10%	4700
	11th to 20th	Night	52% 4 9% 19% 13% 3	5316
	21st to end	Night	56% 5% 13% 15% 8% 2	7106

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% 5% 14% 23% 17% 3	220
	11th to 20th	Day	18% 5% 17% 22% 25% 12%	397
	21st to end	Day	17% 6% 15% 25% 25% 12%	473
February	1st to 10th	Day	22% 7% 15% 22% 26% 10%	430
	11th to 20th	Day	19% 9% 26% 21% 16% 9%	486
	21st to end	Day	16% 8% 20% 28% 23% 5%	446
March	1st to 10th	Day	21% 11% 22% 25% 16% 6%	540
	11th to 20th	Day	20% 8% 22% 20% 19% 10%	529
	21st to end	Day	19% 9% 23% 24% 19% 6%	550
April	1st to 10th	Day	16% 7% 21% 26% 20% 10%	500
	11th to 20th	Day	11% 8% 25% 25% 19% 12%	492
	21st to end	Day	5% 8% 19% 28% 24% 16%	500
May	1st to 10th	Day	6% 8% 24% 25% 24% 12%	503
	11th to 20th	Day	6% 4 22% 25% 26% 16%	528
	21st to end	Day	4 4 16% 26% 28% 22%	573
June	1st to 10th	Day	3 3 18% 25% 34% 16%	530
	11th to 20th	Day	2 4 18% 28% 36% 12%	530
	21st to end	Day	1 2 11% 27% 40% 19%	530
July	1st to 10th	Day	1 1 10% 32% 41% 16%	526
	11th to 20th	Day	1 6% 28% 45% 21%	524
	21st to end	Day	1 1 8% 27% 43% 20%	575
August	1st to 10th	Day	2 1 8% 31% 37% 21%	527
	11th to 20th	Day	1 1 7% 30% 38% 22%	517
	21st to end	Day	1 1 7% 25% 41% 26%	583
September	1st to 10th	Day	2 1 7% 28% 41% 22%	530
	11th to 20th	Day	4 2 15% 26% 32% 21%	530
	21st to end	Day	3 2 15% 27% 31% 22%	530
October	1st to 10th	Day	4 5% 15% 22% 32% 21%	530
	11th to 20th	Day	6% 4 14% 21% 31% 23%	530
	21st to end	Day	9% 6% 13% 24% 29% 19%	583
November	1st to 10th	Day	12% 4 15% 24% 28% 18%	385
	11th to 20th	Day	16% 2 13% 28% 30% 10%	330
	21st to end	Day	13% 1 17% 23% 36% 10%	239
December	1st to 10th	Day	18% 6% 14% 24% 25% 13%	220
	11th to 20th	Day	22% 4 14% 24% 23% 13%	220
	21st to end	Day	24% 10% 19% 24% 21% 3	242
January	1st to 10th	Night	23% 3 15% 32% 22% 5%	840
	11th to 20th	Night	16% 3 12% 38% 26% 5%	840
	21st to end	Night	18% 2 11% 39% 25% 5%	924
February	1st to 10th	Night	20% 4 14% 36% 23% 3	840
	11th to 20th	Night	17% 4 20% 35% 21% 3	824
	21st to end	Night	17% 5% 18% 40% 16% 3	692
March	1st to 10th	Night	19% 5% 20% 33% 21% 3	840
	11th to 20th	Night	19% 4 17% 31% 25% 3	828
	21st to end	Night	17% 5% 22% 33% 21% 1	880
April	1st to 10th	Night	12% 3 23% 37% 23% 2	800
	11th to 20th	Night	11% 5% 22% 35% 24% 4	791
	21st to end	Night	8% 5% 19% 38% 28% 3	800
May	1st to 10th	Night	6% 4 26% 38% 23% 3	730
	11th to 20th	Night	5% 3 24% 43% 23% 2	398
	21st to end	Night	4 5% 19% 45% 26% 1	433
June	1st to 10th	Night	5% 2 24% 43% 25% 1	400
	11th to 20th	Night	2 2 25% 49% 23% 1	400
	21st to end	Night	2 2 22% 43% 30% 1	400
July	1st to 10th	Night	1 1 20% 54% 24% 1	390
	11th to 20th	Night	1 1 18% 57% 23%	389
	21st to end	Night	1 1 16% 50% 31% 2	657
August	1st to 10th	Night	3 1 20% 47% 27% 2	597
	11th to 20th	Night	1 1 12% 51% 33% 2	732
	21st to end	Night	2 10% 46% 40% 2	880
September	1st to 10th	Night	2 1 10% 39% 45% 4	800
	11th to 20th	Night	4 2 15% 36% 39% 5%	800
	21st to end	Night	3 1 16% 36% 37% 7%	800
October	1st to 10th	Night	6% 4 11% 39% 33% 8%	800
	11th to 20th	Night	6% 2 13% 36% 38% 5%	800
	21st to end	Night	6% 3 13% 37% 31% 10%	880
November	1st to 10th	Night	12% 3 13% 31% 33% 9%	820
	11th to 20th	Night	12% 2 13% 42% 28% 4	840
	21st to end	Night	13% 3 14% 38% 28% 5%	840
December	1st to 10th	Night	18% 4 12% 33% 25% 8%	840
	11th to 20th	Night	27% 2 12% 31% 24% 4	840
	21st to end	Night	25% 5% 15% 34% 19% 3	924

Page generated at 2026-03-14 23:23:54. Version ac07

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