Woodland Trails
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Woodland Trails clear sky chart from 2005-11-06 to 2024-11-04.

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	14% 10% 4 9% 5% 5% 5% 4 6% 7% 32%	101654
	Night	14% 10% 4 8% 5% 5% 5% 4 5% 6% 33%	97324
Transparency	Day	48% 7% 13% 20% 11% 1	105257
	Night	47% 7% 13% 21% 11% 1	101809
Seeing	Day	20% 16% 31% 21% 10% 3	14594
	Night	20% 13% 32% 25% 10% 1	23776

By Month

Percentage Cloud Cover NE (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	16% 15% 5% 9% 6% 4 5% 3 4 5% 27%	2517
	11th to 20th	Day	10% 19% 7% 16% 9% 6% 5% 4 4 4 16%	2718
	21st to end	Day	20% 19% 8% 12% 6% 5% 5% 3 4 4 15%	3124
February	1st to 10th	Day	14% 17% 5% 13% 7% 6% 5% 3 6% 5% 19%	1710
	11th to 20th	Day	12% 16% 6% 13% 6% 5% 4 3 5% 6% 24%	1663
	21st to end	Day	16% 16% 5% 10% 6% 5% 5% 3 5% 4 25%	1458
March	1st to 10th	Day	17% 12% 5% 9% 5% 5% 4 3 4 5% 31%	3432
	11th to 20th	Day	10% 14% 6% 11% 6% 6% 5% 4 5% 5% 27%	3480
	21st to end	Day	16% 10% 3 8% 5% 5% 4 4 5% 5% 35%	3815
April	1st to 10th	Day	18% 14% 4 8% 5% 5% 4 4 5% 6% 27%	2251
	11th to 20th	Day	20% 10% 3 7% 4 3 4 3 5% 6% 34%	2323
	21st to end	Day	20% 10% 3 9% 5% 4 4 3 5% 6% 33%	2470
May	1st to 10th	Day	17% 9% 3 7% 5% 4 4 4 6% 8% 33%	4122
	11th to 20th	Day	16% 10% 4 7% 5% 5% 5% 4 6% 7% 32%	4398
	21st to end	Day	12% 6% 2 6% 4 4 4 4 5% 7% 46%	4837
June	1st to 10th	Day	15% 8% 2 7% 5% 5% 5% 4 6% 7% 35%	2660
	11th to 20th	Day	13% 6% 3 6% 5% 4 5% 5% 7% 9% 38%	2660
	21st to end	Day	15% 7% 2 7% 5% 5% 6% 3 6% 8% 37%	2804
July	1st to 10th	Day	11% 5% 2 7% 5% 5% 6% 5% 7% 10% 37%	4477
	11th to 20th	Day	10% 5% 2 6% 4 5% 6% 5% 7% 10% 40%	4440
	21st to end	Day	8% 5% 2 8% 5% 5% 6% 5% 8% 9% 40%	4543
August	1st to 10th	Day	15% 8% 3 6% 4 4 5% 4 7% 8% 35%	4104
	11th to 20th	Day	11% 8% 3 8% 5% 5% 6% 4 7% 9% 35%	4044
	21st to end	Day	9% 7% 3 6% 5% 5% 5% 4 6% 9% 42%	4351
September	1st to 10th	Day	13% 6% 2 7% 5% 4 5% 3 6% 6% 42%	2280
	11th to 20th	Day	11% 6% 2 5% 4 5% 5% 4 6% 8% 44%	2178
	21st to end	Day	14% 7% 3 8% 5% 5% 4 4 5% 6% 37%	2045
October	1st to 10th	Day	18% 9% 3 8% 5% 4 5% 3 5% 7% 34%	1900
	11th to 20th	Day	19% 10% 4 9% 5% 4 5% 4 5% 6% 28%	1900
	21st to end	Day	23% 14% 4 9% 5% 4 4 4 5% 6% 22%	2090
November	1st to 10th	Day	14% 12% 3 9% 5% 5% 5% 4 5% 7% 30%	1622
	11th to 20th	Day	15% 13% 4 10% 7% 6% 6% 5% 5% 6% 23%	1520
	21st to end	Day	19% 15% 5% 11% 7% 6% 5% 4 5% 5% 20%	1520
December	1st to 10th	Day	15% 18% 6% 15% 8% 5% 6% 5% 5% 5% 13%	1520
	11th to 20th	Day	17% 15% 4 10% 7% 5% 5% 5% 6% 7% 19%	1906
	21st to end	Day	25% 18% 5% 15% 6% 6% 4 3 3 4 11%	2772
January	1st to 10th	Night	16% 14% 6% 12% 7% 5% 5% 4 6% 6% 20%	4429
	11th to 20th	Night	13% 13% 6% 16% 8% 7% 5% 4 5% 6% 16%	4239
	21st to end	Night	18% 14% 6% 11% 7% 6% 5% 4 5% 5% 18%	4532
February	1st to 10th	Night	12% 16% 5% 10% 8% 6% 7% 4 5% 6% 22%	2470
	11th to 20th	Night	13% 14% 4 11% 5% 6% 5% 4 7% 6% 24%	2403
	21st to end	Night	14% 13% 4 11% 5% 5% 5% 4 6% 6% 27%	1991
March	1st to 10th	Night	16% 10% 4 9% 6% 5% 4 3 5% 6% 32%	3408
	11th to 20th	Night	12% 11% 4 9% 6% 4 5% 3 6% 6% 34%	3479
	21st to end	Night	15% 7% 3 8% 5% 5% 4 4 5% 6% 38%	3817
April	1st to 10th	Night	18% 13% 3 6% 4 5% 4 3 6% 5% 31%	1929
	11th to 20th	Night	16% 9% 3 7% 5% 4 4 3 5% 5% 38%	1820
	21st to end	Night	14% 10% 3 8% 5% 4 5% 4 6% 7% 34%	1710
May	1st to 10th	Night	17% 7% 3 6% 4 4 4 3 5% 7% 39%	2816
	11th to 20th	Night	15% 8% 3 6% 4 5% 4 4 6% 7% 38%	2495
	21st to end	Night	10% 5% 2 5% 4 4 4 4 5% 8% 50%	2738
June	1st to 10th	Night	13% 7% 2 7% 5% 3 6% 4 6% 7% 40%	1520
	11th to 20th	Night	9% 6% 2 6% 5% 5% 5% 4 7% 8% 42%	1520
	21st to end	Night	13% 6% 3 6% 5% 4 4 3 5% 8% 43%	1359
July	1st to 10th	Night	6% 5% 2 5% 4 4 5% 4 6% 8% 50%	2458
	11th to 20th	Night	11% 5% 2 4 3 4 4 3 5% 8% 51%	2520
	21st to end	Night	7% 5% 2 5% 4 4 4 4 7% 8% 50%	3007
August	1st to 10th	Night	9% 6% 3 6% 4 3 5% 4 6% 7% 47%	2825
	11th to 20th	Night	11% 6% 3 6% 3 3 3 3 5% 8% 49%	2785
	21st to end	Night	9% 7% 2 6% 4 4 4 3 6% 7% 48%	3272
September	1st to 10th	Night	9% 6% 2 6% 4 5% 3 4 6% 8% 46%	1900
	11th to 20th	Night	11% 5% 2 5% 4 3 3 3 6% 6% 53%	2000
	21st to end	Night	15% 7% 4 6% 4 4 4 3 5% 7% 41%	2134
October	1st to 10th	Night	15% 7% 3 9% 5% 4 5% 4 5% 6% 38%	2280
	11th to 20th	Night	18% 9% 3 9% 6% 4 4 4 5% 6% 32%	2280
	21st to end	Night	21% 10% 3 7% 6% 5% 5% 4 6% 6% 28%	2508
November	1st to 10th	Night	17% 10% 3 6% 4 4 4 4 5% 7% 35%	2528
	11th to 20th	Night	16% 12% 4 9% 6% 5% 5% 4 5% 7% 27%	2660
	21st to end	Night	18% 14% 3 9% 6% 5% 6% 4 6% 7% 22%	2660
December	1st to 10th	Night	18% 15% 6% 11% 7% 6% 5% 4 5% 6% 17%	2660
	11th to 20th	Night	15% 19% 5% 11% 7% 5% 5% 4 5% 5% 20%	3288
	21st to end	Night	26% 16% 5% 13% 6% 5% 5% 3 4 5% 11%	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	55% 10% 16% 12% 7% 1	2518
	11th to 20th	Day	69% 7% 10% 9% 4	2718
	21st to end	Day	70% 7% 9% 8% 5% 1	3124
February	1st to 10th	Day	65% 7% 9% 15% 4 1	1710
	11th to 20th	Day	59% 6% 10% 16% 8% 1	1672
	21st to end	Day	61% 6% 10% 15% 7% 1	1458
March	1st to 10th	Day	55% 6% 13% 17% 9% 1	3435
	11th to 20th	Day	54% 6% 12% 18% 8% 1	3480
	21st to end	Day	47% 6% 13% 18% 14% 2	3815
April	1st to 10th	Day	56% 5% 12% 15% 10% 1	2251
	11th to 20th	Day	50% 6% 10% 20% 14% 1	2323
	21st to end	Day	51% 7% 11% 17% 12% 3	2470
May	1st to 10th	Day	47% 7% 12% 18% 14% 2	4134
	11th to 20th	Day	48% 9% 12% 20% 9% 1	4402
	21st to end	Day	37% 6% 14% 23% 17% 4	4837
June	1st to 10th	Day	44% 8% 12% 19% 15% 1	2660
	11th to 20th	Day	40% 8% 12% 23% 16% 1	2660
	21st to end	Day	43% 7% 13% 23% 13% 1	2804
July	1st to 10th	Day	40% 8% 14% 23% 14% 1	4407
	11th to 20th	Day	35% 8% 14% 33% 11% 1	4365
	21st to end	Day	37% 9% 14% 23% 17% 1	4398
August	1st to 10th	Day	45% 7% 13% 22% 12% 1	4091
	11th to 20th	Day	41% 8% 14% 26% 10%	4083
	21st to end	Day	37% 7% 13% 33% 10% 1	4351
September	1st to 10th	Day	38% 9% 13% 27% 11% 1	2280
	11th to 20th	Day	36% 7% 13% 28% 14%	2178
	21st to end	Day	46% 7% 12% 25% 9%	2045
October	1st to 10th	Day	41% 5% 13% 26% 14% 1	3160
	11th to 20th	Day	42% 6% 15% 23% 14% 1	3140
	21st to end	Day	54% 7% 14% 19% 6%	3428
November	1st to 10th	Day	50% 8% 14% 19% 8% 1	1622
	11th to 20th	Day	56% 10% 13% 12% 8% 1	1520
	21st to end	Day	61% 9% 13% 14% 3	1520
December	1st to 10th	Day	67% 10% 11% 10% 3	1520
	11th to 20th	Day	60% 10% 14% 10% 6%	1906
	21st to end	Day	74% 7% 8% 8% 2	2772
January	1st to 10th	Night	60% 8% 15% 12% 4	4429
	11th to 20th	Night	64% 10% 12% 10% 3 1	4239
	21st to end	Night	64% 9% 12% 10% 5% 1	4532
February	1st to 10th	Night	60% 8% 10% 17% 5% 1	2470
	11th to 20th	Night	56% 7% 13% 16% 8% 1	2405
	21st to end	Night	54% 7% 13% 18% 8%	1991
March	1st to 10th	Night	53% 6% 11% 22% 7% 1	3418
	11th to 20th	Night	46% 7% 15% 19% 11% 2	3480
	21st to end	Night	41% 6% 15% 20% 17% 2	3817
April	1st to 10th	Night	53% 5% 10% 18% 13% 1	1929
	11th to 20th	Night	48% 5% 9% 20% 16% 2	1820
	21st to end	Night	46% 7% 12% 18% 16% 2	1710
May	1st to 10th	Night	43% 7% 12% 18% 16% 4	2823
	11th to 20th	Night	43% 9% 13% 22% 11% 2	2496
	21st to end	Night	31% 7% 13% 25% 21% 2	2739
June	1st to 10th	Night	40% 8% 10% 24% 17% 2	1520
	11th to 20th	Night	37% 6% 12% 22% 21% 2	1520
	21st to end	Night	38% 7% 13% 24% 16% 1	1359
July	1st to 10th	Night	30% 6% 15% 27% 20% 3	2418
	11th to 20th	Night	31% 6% 13% 35% 15% 1	2472
	21st to end	Night	29% 8% 15% 31% 16% 1	2911
August	1st to 10th	Night	36% 5% 13% 29% 15% 2	2814
	11th to 20th	Night	33% 6% 16% 31% 13% 1	2812
	21st to end	Night	34% 7% 12% 33% 14% 1	3272
September	1st to 10th	Night	35% 7% 16% 27% 15% 1	1900
	11th to 20th	Night	29% 6% 12% 33% 19% 1	2000
	21st to end	Night	41% 8% 12% 27% 12%	2134
October	1st to 10th	Night	33% 6% 8% 28% 24% 1	3800
	11th to 20th	Night	42% 6% 15% 25% 12%	3779
	21st to end	Night	41% 7% 15% 26% 10%	4120
November	1st to 10th	Night	47% 6% 13% 21% 12% 1	2528
	11th to 20th	Night	54% 9% 13% 15% 9% 1	2660
	21st to end	Night	57% 10% 17% 13% 3	2660
December	1st to 10th	Night	63% 10% 12% 11% 4	2660
	11th to 20th	Night	63% 9% 11% 13% 4	3288
	21st to end	Night	72% 9% 11% 7% 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	21% 24% 30% 19% 6% 1	180
	11th to 20th	Day	25% 29% 26% 16% 4 1	238
	21st to end	Day	24% 25% 35% 13% 3	297
February	1st to 10th	Day	26% 25% 33% 12% 3	270
	11th to 20th	Day	25% 26% 40% 8% 1	270
	21st to end	Day	37% 22% 30% 10%	245
March	1st to 10th	Day	24% 21% 35% 15% 4	460
	11th to 20th	Day	22% 23% 35% 16% 3 1	460
	21st to end	Day	30% 20% 30% 15% 4 1	506
April	1st to 10th	Day	26% 20% 35% 13% 6%	460
	11th to 20th	Day	31% 19% 25% 16% 6% 3	452
	21st to end	Day	26% 17% 35% 13% 7% 2	460
May	1st to 10th	Day	23% 16% 29% 20% 8% 4	463
	11th to 20th	Day	17% 15% 31% 23% 9% 4	487
	21st to end	Day	16% 12% 27% 28% 12% 3	529
June	1st to 10th	Day	16% 16% 30% 28% 9% 1	490
	11th to 20th	Day	17% 12% 30% 28% 12% 2	490
	21st to end	Day	18% 10% 34% 26% 9% 3	634
July	1st to 10th	Day	11% 8% 29% 30% 19% 4	509
	11th to 20th	Day	14% 8% 26% 30% 16% 6%	484
	21st to end	Day	9% 8% 33% 32% 12% 6%	532
August	1st to 10th	Day	13% 9% 27% 28% 14% 8%	486
	11th to 20th	Day	12% 8% 24% 27% 22% 8%	479
	21st to end	Day	13% 8% 31% 26% 15% 7%	539
September	1st to 10th	Day	13% 9% 29% 25% 17% 8%	490
	11th to 20th	Day	9% 9% 25% 24% 21% 13%	490
	21st to end	Day	16% 12% 29% 24% 12% 7%	490
October	1st to 10th	Day	23% 11% 30% 18% 14% 4	490
	11th to 20th	Day	22% 20% 33% 17% 7% 2	490
	21st to end	Day	30% 18% 31% 17% 4	539
November	1st to 10th	Day	25% 22% 29% 16% 7%	267
	11th to 20th	Day	22% 27% 31% 15% 3 1	180
	21st to end	Day	27% 23% 38% 10% 2	180
December	1st to 10th	Day	26% 21% 36% 13% 4	180
	11th to 20th	Day	29% 21% 32% 14% 3 1	180
	21st to end	Day	28% 22% 37% 12% 1	198
January	1st to 10th	Night	24% 20% 37% 14% 4 1	760
	11th to 20th	Night	28% 16% 32% 19% 4 1	760
	21st to end	Night	20% 14% 38% 21% 6%	836
February	1st to 10th	Night	22% 18% 39% 19% 2	760
	11th to 20th	Night	24% 17% 37% 19% 3	743
	21st to end	Night	22% 20% 38% 17% 4	628
March	1st to 10th	Night	21% 19% 36% 20% 4	760
	11th to 20th	Night	23% 19% 34% 18% 4 1	760
	21st to end	Night	21% 16% 33% 23% 6%	836
April	1st to 10th	Night	26% 15% 35% 21% 3	760
	11th to 20th	Night	19% 17% 35% 21% 8% 1	696
	21st to end	Night	20% 14% 32% 25% 9%	570
May	1st to 10th	Night	19% 8% 30% 31% 10% 1	566
	11th to 20th	Night	17% 7% 34% 29% 13% 1	374
	21st to end	Night	11% 8% 28% 35% 17% 1	411
June	1st to 10th	Night	15% 6% 33% 34% 11%	380
	11th to 20th	Night	11% 9% 30% 36% 13% 1	380
	21st to end	Night	16% 6% 30% 36% 12%	380
July	1st to 10th	Night	8% 5% 27% 41% 18% 1	370
	11th to 20th	Night	11% 5% 26% 38% 20% 1	368
	21st to end	Night	8% 4 27% 41% 19% 2	570
August	1st to 10th	Night	10% 2 21% 37% 27% 1	567
	11th to 20th	Night	8% 5% 19% 41% 24% 3	564
	21st to end	Night	13% 4 27% 34% 20% 3	710
September	1st to 10th	Night	12% 8% 26% 32% 19% 4	760
	11th to 20th	Night	14% 6% 23% 29% 24% 5%	760
	21st to end	Night	18% 8% 22% 32% 16% 4	760
October	1st to 10th	Night	20% 9% 28% 26% 15% 2	760
	11th to 20th	Night	22% 14% 33% 22% 9% 1	760
	21st to end	Night	26% 13% 33% 24% 4	836
November	1st to 10th	Night	24% 12% 32% 23% 8% 1	755
	11th to 20th	Night	23% 17% 32% 20% 6% 1	760
	21st to end	Night	25% 17% 30% 23% 5%	760
December	1st to 10th	Night	29% 15% 36% 16% 4	760
	11th to 20th	Night	22% 19% 38% 18% 3 1	760
	21st to end	Night	31% 15% 36% 16% 2	836

Page generated at 2024-11-01 22:47:39. Version ac07

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