Appleton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Appleton clear sky chart from 2005-11-06 to 2024-12-02.

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% 9% 3 8% 5% 5% 5% 4 5% 7% 38%	101705
	Night	13% 10% 3 8% 5% 4 4 4 5% 6% 38%	98027
Transparency	Day	44% 4 12% 26% 13% 1	105225
	Night	46% 4 12% 24% 13% 2	102635
Seeing	Day	17% 10% 30% 25% 13% 4	16045
	Night	18% 10% 32% 29% 11% 1	25943

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% 13% 6% 13% 6% 5% 4 4 5% 4 29%	2527
	11th to 20th	Day	11% 12% 5% 12% 7% 7% 8% 7% 7% 6% 19%	2530
	21st to end	Day	16% 17% 6% 14% 6% 5% 3 4 4 4 20%	2783
February	1st to 10th	Day	10% 11% 5% 10% 6% 5% 5% 4 6% 6% 31%	1694
	11th to 20th	Day	11% 11% 3 8% 4 6% 5% 4 5% 6% 36%	1805
	21st to end	Day	12% 12% 4 9% 5% 5% 5% 4 5% 6% 33%	1570
March	1st to 10th	Day	13% 8% 3 6% 4 3 4 3 4 7% 46%	3120
	11th to 20th	Day	10% 8% 3 8% 4 4 4 4 5% 7% 43%	3273
	21st to end	Day	21% 13% 3 11% 5% 4 4 3 3 5% 29%	4165
April	1st to 10th	Day	14% 14% 3 8% 4 5% 5% 4 5% 6% 30%	2280
	11th to 20th	Day	20% 9% 3 7% 5% 5% 4 3 5% 5% 34%	2254
	21st to end	Day	18% 9% 3 7% 5% 5% 5% 4 5% 7% 33%	2422
May	1st to 10th	Day	13% 7% 3 7% 5% 5% 4 4 5% 7% 40%	4199
	11th to 20th	Day	12% 6% 2 5% 4 4 4 3 6% 7% 46%	4399
	21st to end	Day	12% 7% 2 7% 5% 4 5% 4 6% 7% 40%	4824
June	1st to 10th	Day	10% 6% 2 7% 5% 4 4 4 6% 8% 45%	2660
	11th to 20th	Day	13% 7% 2 6% 4 4 5% 4 6% 9% 40%	2660
	21st to end	Day	10% 6% 3 6% 5% 5% 5% 4 7% 10% 42%	2660
July	1st to 10th	Day	12% 6% 2 7% 4 5% 5% 5% 7% 10% 36%	4440
	11th to 20th	Day	5% 3 1 4 4 4 5% 5% 8% 11% 50%	4440
	21st to end	Day	7% 6% 2 5% 5% 4 5% 5% 6% 8% 46%	4813
August	1st to 10th	Day	8% 5% 2 6% 5% 5% 6% 4 6% 9% 42%	4423
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 3 6% 9% 46%	3912
	21st to end	Day	10% 7% 2 7% 5% 5% 5% 4 6% 9% 41%	4180
September	1st to 10th	Day	11% 7% 2 6% 4 3 5% 3 6% 8% 44%	2280
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 5% 9% 48%	2181
	21st to end	Day	11% 7% 3 8% 4 4 5% 4 6% 9% 40%	2090
October	1st to 10th	Day	14% 7% 3 6% 4 3 4 3 4 6% 46%	1991
	11th to 20th	Day	18% 10% 3 8% 5% 5% 5% 4 5% 8% 32%	1863
	21st to end	Day	16% 10% 3 8% 5% 5% 4 3 4 6% 37%	1881
November	1st to 10th	Day	13% 9% 3 5% 5% 4 4 4 5% 7% 41%	1762
	11th to 20th	Day	11% 11% 4 9% 7% 5% 5% 4 6% 7% 30%	1795
	21st to end	Day	16% 11% 3 9% 4 4 5% 5% 5% 6% 34%	1600
December	1st to 10th	Day	12% 12% 4 9% 7% 5% 5% 5% 7% 7% 26%	1528
	11th to 20th	Day	12% 15% 5% 11% 7% 6% 5% 4 4 6% 25%	1918
	21st to end	Day	18% 17% 7% 15% 7% 6% 4 3 3 4 17%	2783
January	1st to 10th	Night	13% 15% 7% 10% 6% 4 3 3 3 4 32%	4428
	11th to 20th	Night	12% 13% 5% 13% 6% 6% 8% 5% 6% 5% 20%	4440
	21st to end	Night	14% 20% 6% 12% 5% 4 4 3 4 4 24%	4884
February	1st to 10th	Night	9% 14% 5% 11% 6% 5% 4 4 5% 5% 34%	2485
	11th to 20th	Night	10% 9% 4 9% 6% 5% 5% 4 5% 5% 39%	2261
	21st to end	Night	15% 13% 3 7% 4 4 4 4 4 5% 36%	1884
March	1st to 10th	Night	14% 9% 2 6% 3 4 4 3 6% 6% 44%	3733
	11th to 20th	Night	9% 9% 3 8% 6% 5% 5% 3 5% 6% 40%	3715
	21st to end	Night	19% 10% 4 10% 4 4 5% 3 5% 5% 30%	3466
April	1st to 10th	Night	18% 11% 3 7% 4 5% 4 3 5% 6% 35%	1900
	11th to 20th	Night	20% 8% 2 6% 4 3 4 3 6% 7% 37%	1875
	21st to end	Night	17% 8% 3 7% 4 5% 4 4 5% 5% 38%	1758
May	1st to 10th	Night	15% 7% 3 8% 5% 5% 4 4 6% 7% 37%	2698
	11th to 20th	Night	12% 6% 2 7% 5% 4 4 4 6% 8% 42%	2506
	21st to end	Night	16% 8% 3 8% 4 4 4 4 5% 6% 39%	2743
June	1st to 10th	Night	9% 5% 1 7% 5% 4 4 4 6% 7% 48%	1520
	11th to 20th	Night	11% 8% 2 5% 4 4 4 4 6% 9% 43%	1520
	21st to end	Night	7% 5% 2 4 5% 4 5% 4 8% 9% 47%	1520
July	1st to 10th	Night	15% 7% 2 5% 3 4 5% 4 6% 7% 43%	2530
	11th to 20th	Night	4 3 2 5% 4 3 4 4 6% 9% 56%	2530
	21st to end	Night	6% 5% 3 7% 3 4 5% 4 7% 8% 49%	2750
August	1st to 10th	Night	11% 5% 2 6% 3 3 4 4 6% 7% 48%	2517
	11th to 20th	Night	11% 6% 3 6% 4 4 4 3 6% 7% 47%	2913
	21st to end	Night	8% 6% 2 6% 4 4 5% 4 6% 8% 48%	3476
September	1st to 10th	Night	10% 5% 2 5% 3 3 4 3 5% 6% 53%	1900
	11th to 20th	Night	12% 4 2 5% 3 3 4 3 4 7% 54%	1979
	21st to end	Night	11% 7% 2 6% 4 4 4 3 5% 7% 46%	2090
October	1st to 10th	Night	13% 7% 2 5% 3 3 3 4 5% 6% 48%	2185
	11th to 20th	Night	15% 8% 3 7% 5% 4 5% 3 6% 7% 38%	2315
	21st to end	Night	17% 10% 3 7% 5% 4 4 3 5% 8% 33%	2717
November	1st to 10th	Night	13% 8% 2 6% 5% 3 4 4 4 7% 44%	2536
	11th to 20th	Night	13% 12% 4 9% 6% 5% 5% 4 5% 6% 33%	2603
	21st to end	Night	14% 11% 3 7% 6% 4 4 3 5% 6% 36%	2800
December	1st to 10th	Night	13% 13% 4 9% 5% 5% 4 4 5% 7% 30%	2687
	11th to 20th	Night	12% 17% 5% 9% 6% 5% 4 3 4 5% 30%	3279
	21st to end	Night	20% 18% 5% 11% 6% 4 4 3 3 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	58% 3 16% 17% 6% 1	2528
	11th to 20th	Day	62% 4 13% 17% 5%	2530
	21st to end	Day	67% 3 11% 15% 5%	2783
February	1st to 10th	Day	51% 4 11% 23% 11% 1	1694
	11th to 20th	Day	47% 4 11% 25% 12% 1	1815
	21st to end	Day	50% 4 12% 21% 11% 2	1570
March	1st to 10th	Day	39% 3 13% 27% 16% 3	3120
	11th to 20th	Day	40% 4 12% 26% 16% 2	3273
	21st to end	Day	59% 3 9% 22% 7% 1	4165
April	1st to 10th	Day	53% 5% 11% 20% 11%	2280
	11th to 20th	Day	51% 4 7% 22% 13% 2	2254
	21st to end	Day	51% 5% 10% 21% 11% 2	2422
May	1st to 10th	Day	43% 4 11% 25% 16% 1	4237
	11th to 20th	Day	36% 5% 10% 34% 14% 1	4403
	21st to end	Day	42% 5% 11% 24% 17% 2	4837
June	1st to 10th	Day	38% 4 12% 29% 15% 2	2660
	11th to 20th	Day	39% 5% 13% 27% 15% 1	2660
	21st to end	Day	37% 6% 14% 27% 15% 1	2660
July	1st to 10th	Day	42% 5% 14% 27% 10% 2	4371
	11th to 20th	Day	25% 6% 17% 34% 16% 2	4365
	21st to end	Day	34% 5% 13% 24% 21% 3	4662
August	1st to 10th	Day	37% 5% 16% 29% 12% 1	4408
	11th to 20th	Day	34% 5% 13% 35% 12% 1	3952
	21st to end	Day	39% 4 15% 25% 16% 1	4179
September	1st to 10th	Day	38% 5% 13% 28% 16% 1	2280
	11th to 20th	Day	34% 4 16% 33% 12% 1	2181
	21st to end	Day	41% 4 13% 31% 11%	2090
October	1st to 10th	Day	25% 3 9% 37% 24% 1	3303
	11th to 20th	Day	44% 4 9% 27% 15% 1	3079
	21st to end	Day	43% 4 14% 28% 11%	3081
November	1st to 10th	Day	43% 4 13% 24% 14% 1	1762
	11th to 20th	Day	52% 4 14% 20% 9% 1	1795
	21st to end	Day	51% 3 17% 21% 7% 1	1600
December	1st to 10th	Day	53% 5% 15% 22% 4 1	1528
	11th to 20th	Day	59% 3 14% 15% 7% 2	1915
	21st to end	Day	73% 2 8% 12% 5%	2783
January	1st to 10th	Night	57% 3 10% 21% 9% 1	4428
	11th to 20th	Night	64% 3 10% 16% 7%	4440
	21st to end	Night	64% 3 11% 16% 5%	4884
February	1st to 10th	Night	52% 3 9% 22% 11% 2	2485
	11th to 20th	Night	47% 4 10% 25% 12% 2	2262
	21st to end	Night	51% 3 11% 22% 11% 2	1884
March	1st to 10th	Night	41% 3 14% 29% 11% 2	3733
	11th to 20th	Night	44% 3 9% 26% 16% 1	3715
	21st to end	Night	56% 3 8% 21% 10% 2	3466
April	1st to 10th	Night	51% 4 7% 18% 18% 1	1900
	11th to 20th	Night	47% 3 9% 22% 15% 4	1875
	21st to end	Night	48% 3 11% 22% 14% 2	1758
May	1st to 10th	Night	45% 5% 14% 18% 18% 1	2725
	11th to 20th	Night	39% 5% 11% 30% 14% 1	2507
	21st to end	Night	45% 4 12% 19% 16% 4	2751
June	1st to 10th	Night	34% 5% 13% 31% 16% 1	1520
	11th to 20th	Night	37% 6% 11% 27% 18% 2	1520
	21st to end	Night	32% 6% 17% 27% 14% 3	1520
July	1st to 10th	Night	40% 4 16% 22% 12% 5%	2490
	11th to 20th	Night	23% 5% 17% 36% 17% 3	2482
	21st to end	Night	32% 6% 13% 25% 23% 2	2662
August	1st to 10th	Night	34% 4 14% 28% 18% 2	2508
	11th to 20th	Night	36% 4 13% 31% 16% 1	2939
	21st to end	Night	35% 4 14% 24% 20% 3	3476
September	1st to 10th	Night	31% 5% 11% 29% 23% 1	1900
	11th to 20th	Night	33% 3 13% 35% 16% 1	1979
	21st to end	Night	37% 3 13% 31% 15% 1	2090
October	1st to 10th	Night	28% 3 8% 38% 21% 2	3640
	11th to 20th	Night	35% 4 12% 31% 16% 2	3838
	21st to end	Night	46% 4 11% 24% 16%	4467
November	1st to 10th	Night	41% 4 13% 26% 15% 2	2536
	11th to 20th	Night	51% 4 12% 20% 12% 1	2603
	21st to end	Night	49% 4 15% 24% 7% 1	2800
December	1st to 10th	Night	53% 4 15% 21% 7% 1	2687
	11th to 20th	Night	57% 3 12% 18% 8% 1	3281
	21st to end	Night	68% 3 9% 15% 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	19% 12% 32% 26% 9% 2	270
	11th to 20th	Day	20% 15% 34% 24% 7%	270
	21st to end	Day	23% 9% 33% 27% 7% 1	297
February	1st to 10th	Day	14% 16% 38% 24% 6% 1	270
	11th to 20th	Day	16% 19% 39% 17% 9%	270
	21st to end	Day	19% 16% 46% 16% 2	225
March	1st to 10th	Day	20% 15% 39% 19% 7%	270
	11th to 20th	Day	24% 16% 31% 20% 8% 2	279
	21st to end	Day	29% 11% 27% 25% 8% 1	506
April	1st to 10th	Day	27% 13% 34% 21% 5% 1	460
	11th to 20th	Day	28% 15% 27% 20% 8% 2	452
	21st to end	Day	23% 12% 28% 25% 11% 2	460
May	1st to 10th	Day	20% 12% 33% 25% 9% 2	528
	11th to 20th	Day	19% 8% 34% 27% 8% 4	675
	21st to end	Day	16% 10% 30% 25% 14% 5%	734
June	1st to 10th	Day	12% 9% 33% 29% 13% 4	680
	11th to 20th	Day	16% 8% 33% 27% 13% 3	680
	21st to end	Day	14% 8% 31% 30% 15% 3	680
July	1st to 10th	Day	10% 5% 22% 32% 24% 8%	671
	11th to 20th	Day	9% 7% 26% 30% 20% 7%	668
	21st to end	Day	8% 5% 26% 32% 21% 7%	739
August	1st to 10th	Day	9% 5% 26% 31% 22% 8%	676
	11th to 20th	Day	13% 4 19% 30% 24% 11%	515
	21st to end	Day	16% 6% 24% 27% 19% 8%	539
September	1st to 10th	Day	16% 6% 23% 29% 19% 7%	490
	11th to 20th	Day	12% 4 23% 33% 20% 7%	490
	21st to end	Day	17% 11% 28% 23% 17% 5%	490
October	1st to 10th	Day	19% 12% 25% 26% 17% 2	391
	11th to 20th	Day	19% 20% 33% 20% 7%	300
	21st to end	Day	23% 16% 38% 18% 5% 1	330
November	1st to 10th	Day	17% 15% 38% 21% 7% 1	300
	11th to 20th	Day	16% 21% 39% 15% 9% 1	300
	21st to end	Day	25% 14% 41% 14% 5%	300
December	1st to 10th	Day	20% 16% 40% 19% 5%	273
	11th to 20th	Day	24% 14% 36% 19% 5% 1	270
	21st to end	Day	25% 19% 35% 16% 4	297
January	1st to 10th	Night	17% 13% 37% 25% 7% 1	950
	11th to 20th	Night	20% 13% 37% 23% 6% 1	950
	21st to end	Night	20% 11% 36% 26% 7%	1045
February	1st to 10th	Night	16% 13% 37% 27% 6% 1	950
	11th to 20th	Night	16% 16% 37% 23% 8%	786
	21st to end	Night	22% 14% 34% 25% 4	628
March	1st to 10th	Night	19% 11% 32% 28% 8% 1	760
	11th to 20th	Night	17% 11% 37% 27% 6% 1	724
	21st to end	Night	22% 8% 31% 29% 9% 1	627
April	1st to 10th	Night	24% 9% 38% 24% 5%	570
	11th to 20th	Night	24% 12% 29% 28% 7% 1	563
	21st to end	Night	20% 8% 35% 29% 8% 1	570
May	1st to 10th	Night	21% 9% 32% 30% 7%	570
	11th to 20th	Night	18% 9% 33% 32% 7% 1	561
	21st to end	Night	14% 7% 26% 36% 16% 1	617
June	1st to 10th	Night	11% 6% 31% 38% 14% 1	570
	11th to 20th	Night	16% 5% 29% 36% 12% 1	570
	21st to end	Night	10% 4 28% 43% 14% 1	570
July	1st to 10th	Night	10% 2 20% 45% 22% 1	555
	11th to 20th	Night	10% 4 24% 40% 21% 1	552
	21st to end	Night	6% 3 23% 44% 23% 1	624
August	1st to 10th	Night	10% 2 18% 45% 24% 1	567
	11th to 20th	Night	10% 2 20% 36% 27% 3	564
	21st to end	Night	11% 3 23% 38% 22% 1	627
September	1st to 10th	Night	11% 5% 25% 37% 17% 4	570
	11th to 20th	Night	13% 4 24% 33% 22% 3	649
	21st to end	Night	14% 9% 26% 33% 18% 1	760
October	1st to 10th	Night	18% 9% 27% 28% 17% 1	760
	11th to 20th	Night	20% 13% 34% 25% 8%	760
	21st to end	Night	24% 13% 29% 26% 8% 1	836
November	1st to 10th	Night	17% 10% 39% 25% 7% 1	780
	11th to 20th	Night	21% 17% 35% 22% 5%	803
	21st to end	Night	20% 14% 36% 22% 6%	1000
December	1st to 10th	Night	22% 13% 39% 20% 6%	960
	11th to 20th	Night	22% 13% 35% 23% 6% 1	950
	21st to end	Night	29% 12% 33% 22% 4	1045

Page generated at 2024-11-29 09:43:11. Version ac07

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