Waverly
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Waverly clear sky chart from 2005-11-06 to 2024-10-25.

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	12% 7% 3 7% 4 4 4 3 5% 7% 44%	101098
	Night	12% 7% 3 6% 4 4 4 3 5% 6% 46%	97792
Transparency	Day	40% 5% 13% 26% 15% 2	100906
	Night	39% 4 12% 25% 17% 3	97655
Seeing	Day	14% 9% 26% 28% 18% 5%	15656
	Night	15% 8% 30% 33% 13% 1	25458

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	14% 11% 4 11% 4 4 4 3 4 7% 33%	2759
	11th to 20th	Day	11% 12% 4 9% 5% 7% 7% 3 3 4 35%	2850
	21st to end	Day	16% 16% 5% 11% 5% 4 4 3 3 5% 28%	3135
February	1st to 10th	Day	16% 12% 4 9% 5% 4 4 2 5% 7% 34%	1710
	11th to 20th	Day	13% 10% 4 7% 5% 3 3 3 6% 7% 39%	1664
	21st to end	Day	13% 8% 3 8% 5% 3 4 3 5% 6% 41%	1596
March	1st to 10th	Day	15% 11% 3 5% 4 3 3 2 3 5% 46%	3436
	11th to 20th	Day	11% 7% 2 5% 4 2 4 3 5% 7% 49%	3480
	21st to end	Day	18% 12% 4 9% 5% 4 4 3 5% 6% 31%	3814
April	1st to 10th	Day	15% 7% 2 7% 5% 3 4 3 5% 6% 43%	2253
	11th to 20th	Day	15% 9% 2 6% 4 3 4 4 5% 7% 40%	2254
	21st to end	Day	21% 8% 2 7% 4 5% 4 4 5% 6% 34%	2329
May	1st to 10th	Day	13% 8% 3 7% 5% 5% 5% 4 6% 7% 37%	4082
	11th to 20th	Day	16% 9% 3 7% 5% 4 3 3 5% 7% 38%	4104
	21st to end	Day	12% 6% 2 6% 5% 4 4 4 6% 7% 45%	4824
June	1st to 10th	Day	7% 4 2 5% 4 5% 5% 5% 7% 10% 47%	2660
	11th to 20th	Day	7% 6% 2 6% 4 5% 5% 4 6% 9% 46%	2660
	21st to end	Day	6% 5% 1 7% 5% 4 5% 4 7% 10% 47%	2660
July	1st to 10th	Day	12% 6% 2 7% 4 4 4 4 7% 8% 41%	4412
	11th to 20th	Day	6% 4 2 5% 3 3 4 4 6% 9% 54%	4120
	21st to end	Day	6% 4 2 6% 4 5% 5% 5% 7% 11% 45%	4465
August	1st to 10th	Day	4 4 1 5% 4 4 4 4 7% 11% 53%	4104
	11th to 20th	Day	12% 4 2 6% 4 3 4 3 6% 8% 46%	4024
	21st to end	Day	5% 4 2 5% 4 4 5% 4 6% 9% 54%	4180
September	1st to 10th	Day	11% 4 1 4 3 3 4 3 5% 7% 54%	2280
	11th to 20th	Day	9% 4 2 5% 4 4 4 3 6% 8% 52%	2209
	21st to end	Day	8% 5% 1 5% 4 3 4 3 5% 6% 55%	2021
October	1st to 10th	Day	12% 4 2 4 4 3 3 3 5% 7% 54%	1900
	11th to 20th	Day	13% 6% 2 4 3 3 2 2 4 6% 54%	1900
	21st to end	Day	17% 8% 3 6% 4 2 3 2 4 6% 45%	2026
November	1st to 10th	Day	11% 6% 2 5% 3 3 4 3 4 6% 54%	1854
	11th to 20th	Day	14% 7% 2 6% 3 3 3 2 5% 6% 49%	1592
	21st to end	Day	16% 9% 3 7% 4 3 2 3 4 5% 44%	1520
December	1st to 10th	Day	10% 9% 5% 8% 5% 4 4 3 4 6% 42%	1520
	11th to 20th	Day	13% 9% 4 8% 4 4 4 3 4 5% 41%	1918
	21st to end	Day	17% 14% 7% 12% 5% 4 4 3 4 4 24%	2783
January	1st to 10th	Night	10% 10% 5% 14% 5% 5% 4 3 4 4 37%	4192
	11th to 20th	Night	12% 10% 5% 9% 4 8% 4 5% 5% 4 33%	4120
	21st to end	Night	17% 13% 6% 10% 4 4 4 3 4 5% 31%	4532
February	1st to 10th	Night	14% 10% 4 7% 5% 5% 4 4 4 6% 36%	2470
	11th to 20th	Night	13% 8% 3 7% 5% 4 4 3 5% 6% 42%	2403
	21st to end	Night	14% 9% 3 7% 3 3 3 3 5% 6% 44%	1871
March	1st to 10th	Night	15% 10% 2 7% 3 3 3 2 4 6% 45%	3419
	11th to 20th	Night	11% 6% 2 4 3 3 3 2 4 6% 54%	3480
	21st to end	Night	16% 10% 4 9% 5% 5% 4 4 5% 6% 32%	3817
April	1st to 10th	Night	11% 7% 2 6% 4 3 4 3 6% 6% 50%	1926
	11th to 20th	Night	14% 6% 3 7% 4 3 3 3 4 5% 48%	1875
	21st to end	Night	17% 8% 3 6% 4 4 4 3 5% 6% 41%	1848
May	1st to 10th	Night	15% 6% 3 7% 5% 4 4 4 6% 8% 38%	2823
	11th to 20th	Night	14% 8% 3 5% 4 4 3 4 5% 9% 41%	2796
	21st to end	Night	11% 5% 2 5% 4 3 5% 3 6% 7% 50%	2743
June	1st to 10th	Night	6% 4 1 4 3 4 3 4 7% 10% 54%	1520
	11th to 20th	Night	6% 3 2 5% 4 4 5% 4 7% 10% 51%	1520
	21st to end	Night	4 3 1 5% 2 4 5% 3 7% 9% 57%	1520
July	1st to 10th	Night	13% 6% 2 7% 3 4 4 3 5% 8% 47%	2552
	11th to 20th	Night	3 2 1 4 3 3 4 3 6% 9% 61%	2850
	21st to end	Night	5% 4 2 5% 4 5% 6% 5% 7% 10% 48%	3098
August	1st to 10th	Night	3 2 1 3 2 3 4 4 6% 10% 62%	2836
	11th to 20th	Night	11% 6% 1 4 3 3 3 3 5% 7% 52%	2812
	21st to end	Night	4 3 2 5% 4 4 5% 4 5% 8% 58%	3476
September	1st to 10th	Night	9% 4 2 5% 3 3 3 3 4 6% 58%	1900
	11th to 20th	Night	10% 4 2 3 3 3 4 4 5% 7% 55%	1967
	21st to end	Night	8% 5% 2 4 3 3 4 3 5% 6% 57%	2139
October	1st to 10th	Night	10% 5% 2 4 3 2 4 3 5% 5% 58%	2280
	11th to 20th	Night	13% 5% 1 5% 4 2 3 2 4 5% 56%	2280
	21st to end	Night	16% 8% 2 4 3 3 3 3 3 4 52%	2436
November	1st to 10th	Night	11% 5% 2 4 3 3 3 3 4 6% 58%	2222
	11th to 20th	Night	12% 6% 2 5% 3 3 3 3 4 6% 52%	2586
	21st to end	Night	17% 8% 2 4 3 3 3 3 4 5% 48%	2660
December	1st to 10th	Night	13% 8% 4 6% 4 3 4 4 5% 6% 43%	2660
	11th to 20th	Night	14% 8% 3 8% 4 4 4 3 5% 6% 42%	3279
	21st to end	Night	21% 16% 5% 10% 5% 3 3 3 3 4 27%	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	51% 4 11% 24% 10% 1	2760
	11th to 20th	Day	55% 3 12% 21% 9%	2850
	21st to end	Day	59% 3 11% 16% 10% 1	3135
February	1st to 10th	Day	51% 4 12% 21% 11% 1	1710
	11th to 20th	Day	45% 5% 12% 22% 13% 3	1673
	21st to end	Day	43% 5% 12% 22% 16% 3	1596
March	1st to 10th	Day	42% 4 9% 25% 18% 2	3436
	11th to 20th	Day	35% 4 12% 28% 17% 4	3480
	21st to end	Day	54% 5% 17% 19% 5% 1	3814
April	1st to 10th	Day	41% 5% 12% 26% 14% 1	2253
	11th to 20th	Day	44% 5% 12% 24% 14% 2	2254
	21st to end	Day	50% 5% 11% 22% 11%	2329
May	1st to 10th	Day	44% 7% 12% 23% 12% 1	4120
	11th to 20th	Day	46% 6% 13% 24% 11%	4108
	21st to end	Day	37% 6% 10% 31% 14% 1	4837
June	1st to 10th	Day	29% 8% 17% 31% 14% 1	2660
	11th to 20th	Day	33% 8% 13% 29% 16% 2	2660
	21st to end	Day	30% 6% 17% 30% 14% 4	2660
July	1st to 10th	Day	40% 5% 13% 24% 15% 3	4343
	11th to 20th	Day	28% 5% 13% 35% 17% 2	4051
	21st to end	Day	31% 5% 20% 30% 13% 1	4325
August	1st to 10th	Day	26% 6% 18% 31% 19% 1	4090
	11th to 20th	Day	36% 4 15% 29% 16% 1	4063
	21st to end	Day	27% 4 16% 35% 14% 5%	4179
September	1st to 10th	Day	30% 5% 12% 27% 20% 7%	2280
	11th to 20th	Day	30% 5% 13% 25% 24% 3	2209
	21st to end	Day	30% 5% 10% 29% 23% 3	2021
October	1st to 10th	Day	32% 4 10% 26% 24% 4	1900
	11th to 20th	Day	34% 3 7% 28% 24% 5%	1900
	21st to end	Day	42% 3 10% 22% 19% 4	2026
November	1st to 10th	Day	33% 3 14% 27% 19% 4	1854
	11th to 20th	Day	38% 3 10% 26% 20% 3	1592
	21st to end	Day	44% 3 9% 27% 16% 1	1520
December	1st to 10th	Day	43% 4 13% 26% 13% 1	1520
	11th to 20th	Day	46% 4 14% 26% 9% 1	1915
	21st to end	Day	63% 4 9% 15% 7% 1	2783
January	1st to 10th	Night	52% 3 12% 22% 11% 1	4192
	11th to 20th	Night	53% 4 12% 20% 11% 1	4120
	21st to end	Night	56% 4 11% 19% 9% 1	4532
February	1st to 10th	Night	48% 5% 12% 20% 13% 3	2470
	11th to 20th	Night	44% 4 11% 21% 17% 3	2404
	21st to end	Night	41% 4 10% 21% 19% 5%	1871
March	1st to 10th	Night	43% 4 9% 23% 18% 3	3419
	11th to 20th	Night	33% 3 9% 27% 24% 4	3480
	21st to end	Night	52% 4 15% 23% 5% 1	3817
April	1st to 10th	Night	35% 6% 10% 27% 19% 4	1926
	11th to 20th	Night	38% 4 9% 28% 16% 4	1875
	21st to end	Night	43% 4 10% 24% 17% 1	1848
May	1st to 10th	Night	42% 8% 14% 20% 15% 1	2850
	11th to 20th	Night	40% 6% 13% 28% 12% 1	2797
	21st to end	Night	33% 6% 11% 25% 24% 2	2751
June	1st to 10th	Night	25% 6% 16% 31% 18% 4	1520
	11th to 20th	Night	26% 8% 12% 29% 20% 5%	1520
	21st to end	Night	23% 5% 15% 32% 19% 5%	1520
July	1st to 10th	Night	37% 4 11% 25% 19% 3	2512
	11th to 20th	Night	21% 5% 15% 37% 21% 2	2796
	21st to end	Night	29% 4 22% 32% 12% 1	2999
August	1st to 10th	Night	18% 4 23% 28% 25% 2	2826
	11th to 20th	Night	34% 3 11% 29% 22% 1	2839
	21st to end	Night	25% 4 14% 36% 17% 4	3476
September	1st to 10th	Night	28% 5% 10% 24% 25% 7%	1900
	11th to 20th	Night	28% 5% 10% 27% 25% 5%	1967
	21st to end	Night	28% 5% 9% 28% 27% 4	2139
October	1st to 10th	Night	27% 5% 10% 25% 28% 6%	2280
	11th to 20th	Night	33% 3 6% 28% 22% 8%	2280
	21st to end	Night	38% 3 9% 22% 23% 4	2436
November	1st to 10th	Night	29% 4 12% 26% 22% 6%	2222
	11th to 20th	Night	34% 3 8% 27% 24% 4	2586
	21st to end	Night	41% 3 10% 27% 17% 2	2660
December	1st to 10th	Night	42% 4 13% 26% 14% 1	2660
	11th to 20th	Night	43% 3 12% 29% 12% 1	3281
	21st to end	Night	62% 4 9% 16% 8% 2	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	19% 15% 33% 25% 7%	270
	11th to 20th	Day	30% 15% 34% 19% 3	270
	21st to end	Day	16% 15% 41% 22% 6%	297
February	1st to 10th	Day	25% 12% 41% 18% 3	270
	11th to 20th	Day	18% 18% 37% 20% 7%	270
	21st to end	Day	15% 20% 42% 18% 4	225
March	1st to 10th	Day	17% 16% 43% 20% 4	270
	11th to 20th	Day	27% 11% 32% 24% 5%	270
	21st to end	Day	33% 21% 29% 13% 4	297
April	1st to 10th	Day	20% 16% 32% 24% 7% 1	433
	11th to 20th	Day	19% 15% 34% 23% 8% 1	452
	21st to end	Day	22% 12% 33% 23% 10% 1	509
May	1st to 10th	Day	16% 13% 34% 26% 9% 1	653
	11th to 20th	Day	19% 8% 27% 28% 15% 3	675
	21st to end	Day	14% 8% 25% 29% 18% 5%	734
June	1st to 10th	Day	7% 5% 19% 33% 28% 10%	680
	11th to 20th	Day	9% 2 25% 34% 26% 5%	680
	21st to end	Day	5% 6% 29% 38% 18% 4	680
July	1st to 10th	Day	12% 3 12% 28% 30% 15%	671
	11th to 20th	Day	6% 2 18% 33% 32% 10%	668
	21st to end	Day	8% 2 13% 32% 34% 11%	739
August	1st to 10th	Day	5% 2 16% 38% 32% 7%	676
	11th to 20th	Day	10% 3 16% 35% 29% 8%	661
	21st to end	Day	9% 1 12% 29% 35% 14%	539
September	1st to 10th	Day	12% 2 13% 33% 31% 9%	490
	11th to 20th	Day	9% 2 15% 33% 31% 11%	419
	21st to end	Day	11% 5% 23% 31% 23% 7%	300
October	1st to 10th	Day	13% 5% 27% 28% 17% 9%	300
	11th to 20th	Day	10% 15% 38% 25% 12% 1	300
	21st to end	Day	25% 15% 32% 21% 7%	311
November	1st to 10th	Day	18% 6% 35% 26% 10% 6%	270
	11th to 20th	Day	15% 18% 30% 24% 11% 2	270
	21st to end	Day	24% 13% 29% 27% 7%	270
December	1st to 10th	Day	12% 16% 36% 25% 8% 3	270
	11th to 20th	Day	21% 12% 36% 21% 9% 1	270
	21st to end	Day	22% 19% 38% 20% 1	297
January	1st to 10th	Night	14% 11% 40% 27% 8%	950
	11th to 20th	Night	18% 13% 39% 25% 6% 1	950
	21st to end	Night	16% 12% 39% 29% 4	1045
February	1st to 10th	Night	17% 11% 43% 25% 4	950
	11th to 20th	Night	16% 12% 37% 31% 4	929
	21st to end	Night	19% 13% 46% 19% 3	615
March	1st to 10th	Night	17% 12% 42% 26% 4	570
	11th to 20th	Night	18% 10% 35% 30% 6% 1	570
	21st to end	Night	27% 12% 34% 22% 5%	627
April	1st to 10th	Night	15% 14% 36% 31% 5%	570
	11th to 20th	Night	17% 12% 34% 29% 8%	563
	21st to end	Night	19% 8% 37% 28% 8%	570
May	1st to 10th	Night	17% 8% 31% 36% 7% 1	570
	11th to 20th	Night	15% 6% 27% 36% 15% 1	561
	21st to end	Night	12% 6% 26% 34% 19% 2	617
June	1st to 10th	Night	7% 3 19% 45% 22% 4	570
	11th to 20th	Night	6% 3 23% 46% 20% 2	570
	21st to end	Night	5% 3 26% 47% 19% 1	570
July	1st to 10th	Night	10% 3 10% 40% 34% 4	555
	11th to 20th	Night	5% 2 14% 43% 34% 2	552
	21st to end	Night	7% 1 12% 43% 36% 2	624
August	1st to 10th	Night	5% 2 11% 46% 34% 2	567
	11th to 20th	Night	8% 2 12% 42% 32% 3	564
	21st to end	Night	7% 1 10% 42% 37% 3	627
September	1st to 10th	Night	11% 2 14% 41% 29% 4	570
	11th to 20th	Night	12% 1 16% 38% 27% 5%	570
	21st to end	Night	8% 4 23% 40% 22% 3	619
October	1st to 10th	Night	12% 4 28% 34% 19% 3	760
	11th to 20th	Night	16% 9% 35% 32% 9%	760
	21st to end	Night	19% 11% 33% 27% 9%	812
November	1st to 10th	Night	13% 8% 33% 36% 10%	740
	11th to 20th	Night	15% 11% 36% 30% 9%	876
	21st to end	Night	21% 10% 35% 29% 5%	950
December	1st to 10th	Night	17% 10% 39% 29% 6% 1	950
	11th to 20th	Night	20% 9% 34% 33% 5%	950
	21st to end	Night	22% 13% 36% 26% 4	1045

Page generated at 2024-10-22 19:21:06. Version ac07

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