Natural Tunnel State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Natural Tunnel State Park clear sky chart from 2005-11-06 to 2024-11-12.

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% 8% 3 7% 5% 5% 5% 4 6% 8% 37%	101206
	Night	15% 8% 3 7% 5% 4 4 4 5% 7% 39%	97938
Transparency	Day	45% 4 11% 23% 15% 3	104961
	Night	44% 4 10% 23% 16% 3	102322
Seeing	Day	20% 9% 20% 25% 19% 8%	15004
	Night	18% 7% 19% 34% 19% 2	25053

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	18% 13% 4 9% 5% 3 4 3 5% 7% 29%	2836
	11th to 20th	Day	18% 14% 8% 10% 7% 4 4 2 3 4 26%	2840
	21st to end	Day	19% 14% 3 8% 5% 4 3 3 4 4 32%	3124
February	1st to 10th	Day	19% 11% 3 7% 5% 4 4 3 4 6% 33%	1771
	11th to 20th	Day	21% 9% 4 8% 5% 4 4 4 4 6% 31%	1848
	21st to end	Day	24% 8% 3 7% 4 4 3 3 4 6% 32%	1570
March	1st to 10th	Day	24% 10% 3 7% 4 3 3 2 4 6% 34%	3330
	11th to 20th	Day	14% 7% 2 6% 4 4 4 3 4 7% 46%	3480
	21st to end	Day	15% 9% 3 7% 5% 4 4 3 5% 6% 39%	3815
April	1st to 10th	Day	13% 7% 2 7% 4 4 4 4 7% 8% 39%	2090
	11th to 20th	Day	15% 7% 3 6% 4 4 3 3 5% 8% 42%	2322
	21st to end	Day	15% 6% 2 7% 5% 5% 4 3 6% 7% 40%	2470
May	1st to 10th	Day	20% 9% 3 8% 5% 5% 5% 4 6% 7% 29%	4082
	11th to 20th	Day	17% 8% 3 9% 5% 6% 5% 4 5% 7% 31%	4081
	21st to end	Day	11% 6% 2 7% 5% 5% 5% 5% 7% 9% 37%	4476
June	1st to 10th	Day	11% 7% 2 7% 5% 5% 5% 5% 7% 9% 36%	2470
	11th to 20th	Day	7% 6% 2 7% 6% 5% 6% 6% 7% 10% 37%	2470
	21st to end	Day	9% 6% 3 7% 6% 5% 6% 6% 8% 10% 36%	2470
July	1st to 10th	Day	7% 5% 2 6% 6% 6% 7% 5% 9% 11% 37%	4120
	11th to 20th	Day	11% 6% 2 7% 5% 5% 6% 5% 7% 10% 36%	4120
	21st to end	Day	19% 11% 4 9% 7% 6% 6% 4 6% 8% 20%	4466
August	1st to 10th	Day	10% 6% 2 7% 6% 6% 6% 6% 8% 11% 31%	4104
	11th to 20th	Day	8% 5% 2 7% 5% 5% 6% 5% 8% 11% 36%	4044
	21st to end	Day	5% 3 1 4 4 4 4 4 6% 10% 55%	4260
September	1st to 10th	Day	10% 6% 2 6% 5% 5% 5% 4 5% 8% 43%	2090
	11th to 20th	Day	12% 7% 3 5% 5% 5% 5% 4 6% 7% 42%	2090
	21st to end	Day	16% 6% 2 6% 5% 4 4 4 6% 5% 42%	2090
October	1st to 10th	Day	13% 5% 2 5% 4 4 4 3 4 6% 50%	2057
	11th to 20th	Day	14% 6% 1 6% 3 3 4 3 4 6% 50%	1900
	21st to end	Day	16% 8% 2 6% 3 3 4 2 3 7% 45%	2090
November	1st to 10th	Day	10% 6% 2 6% 4 3 4 3 6% 6% 51%	1814
	11th to 20th	Day	13% 9% 2 5% 3 4 4 3 4 7% 45%	1719
	21st to end	Day	15% 8% 3 6% 4 3 3 3 5% 5% 44%	1710
December	1st to 10th	Day	23% 11% 4 7% 4 3 4 3 4 5% 32%	1710
	11th to 20th	Day	17% 13% 3 6% 4 3 3 3 5% 7% 35%	2153
	21st to end	Day	19% 15% 5% 7% 5% 4 5% 4 6% 6% 25%	3124
January	1st to 10th	Night	17% 13% 6% 8% 6% 4 5% 3 4 5% 28%	4109
	11th to 20th	Night	22% 10% 3 9% 6% 3 3 3 3 4 35%	4120
	21st to end	Night	20% 12% 3 7% 5% 4 4 3 4 5% 33%	4532
February	1st to 10th	Night	17% 9% 2 7% 5% 5% 4 3 5% 6% 35%	2406
	11th to 20th	Night	23% 8% 3 7% 4 4 4 4 5% 5% 32%	2218
	21st to end	Night	22% 10% 3 8% 5% 4 4 3 5% 6% 30%	1884
March	1st to 10th	Night	22% 9% 3 6% 6% 4 4 3 4 7% 32%	3522
	11th to 20th	Night	12% 6% 3 5% 4 4 4 3 4 7% 48%	3480
	21st to end	Night	13% 7% 2 6% 4 5% 5% 4 5% 7% 42%	3817
April	1st to 10th	Night	12% 7% 3 6% 4 3 4 4 6% 7% 42%	2090
	11th to 20th	Night	13% 8% 2 7% 4 5% 4 3 6% 7% 43%	1821
	21st to end	Night	13% 6% 2 6% 4 4 5% 4 5% 7% 43%	1710
May	1st to 10th	Night	20% 8% 3 8% 5% 4 5% 4 5% 7% 32%	2813
	11th to 20th	Night	18% 8% 3 6% 4 4 4 4 5% 7% 36%	2812
	21st to end	Night	10% 7% 3 8% 5% 5% 5% 5% 7% 8% 39%	3079
June	1st to 10th	Night	10% 6% 2 6% 5% 4 5% 4 8% 11% 39%	1710
	11th to 20th	Night	7% 5% 3 5% 5% 5% 5% 5% 8% 10% 43%	1710
	21st to end	Night	10% 6% 2 7% 6% 5% 5% 4 7% 10% 37%	1710
July	1st to 10th	Night	8% 5% 2 6% 6% 5% 7% 6% 10% 12% 35%	2840
	11th to 20th	Night	10% 6% 2 5% 4 4 4 4 7% 9% 43%	2840
	21st to end	Night	18% 11% 3 8% 5% 5% 6% 4 6% 8% 23%	3087
August	1st to 10th	Night	9% 7% 3 8% 5% 5% 5% 5% 7% 9% 36%	2825
	11th to 20th	Night	11% 6% 2 7% 4 5% 5% 4 7% 10% 40%	2785
	21st to end	Night	6% 3 1 4 3 4 4 4 6% 9% 56%	3358
September	1st to 10th	Night	12% 6% 3 7% 5% 4 4 4 4 7% 45%	2090
	11th to 20th	Night	13% 6% 2 7% 4 4 4 3 6% 8% 44%	2090
	21st to end	Night	14% 5% 2 5% 4 4 4 3 4 6% 48%	2090
October	1st to 10th	Night	12% 6% 2 5% 3 3 4 3 4 6% 52%	2123
	11th to 20th	Night	15% 6% 2 5% 3 3 3 2 4 7% 51%	2280
	21st to end	Night	14% 6% 2 6% 4 3 3 3 5% 7% 49%	2508
November	1st to 10th	Night	12% 6% 2 5% 4 3 3 3 5% 6% 51%	2481
	11th to 20th	Night	13% 7% 2 6% 4 4 3 3 4 6% 46%	2484
	21st to end	Night	16% 7% 3 6% 3 3 4 3 5% 6% 44%	2470
December	1st to 10th	Night	21% 10% 4 8% 5% 4 4 4 5% 6% 30%	2470
	11th to 20th	Night	15% 11% 4 10% 4 4 4 3 4 5% 35%	3042
	21st to end	Night	18% 13% 4 7% 5% 5% 5% 4 6% 8% 24%	4532

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	56% 2 5% 20% 15% 2	2837
	11th to 20th	Day	65% 1 5% 16% 12% 1	2840
	21st to end	Day	58% 2 6% 20% 14% 1	3124
February	1st to 10th	Day	53% 3 7% 19% 16% 2	1771
	11th to 20th	Day	56% 2 7% 20% 13% 2	1858
	21st to end	Day	55% 2 8% 15% 16% 4	1570
March	1st to 10th	Day	54% 1 7% 20% 14% 5%	3330
	11th to 20th	Day	41% 2 6% 27% 19% 5%	3480
	21st to end	Day	47% 2 7% 27% 14% 2	3815
April	1st to 10th	Day	42% 4 10% 24% 17% 3	2090
	11th to 20th	Day	42% 3 8% 21% 21% 5%	2322
	21st to end	Day	45% 2 11% 26% 13% 2	2470
May	1st to 10th	Day	55% 3 11% 19% 11% 1	4120
	11th to 20th	Day	54% 2 9% 24% 9% 1	4085
	21st to end	Day	43% 4 13% 23% 14% 3	4489
June	1st to 10th	Day	42% 5% 15% 24% 13% 1	2470
	11th to 20th	Day	39% 7% 17% 21% 14% 2	2470
	21st to end	Day	41% 7% 14% 20% 16% 2	2470
July	1st to 10th	Day	36% 11% 21% 19% 12% 1	4055
	11th to 20th	Day	41% 6% 16% 27% 8% 2	4051
	21st to end	Day	61% 6% 11% 15% 7% 1	4324
August	1st to 10th	Day	43% 8% 16% 24% 9%	4091
	11th to 20th	Day	37% 8% 18% 24% 11% 2	4083
	21st to end	Day	26% 4 18% 37% 12% 2	4260
September	1st to 10th	Day	38% 5% 13% 23% 16% 6%	2090
	11th to 20th	Day	41% 4 9% 25% 18% 2	2090
	21st to end	Day	42% 4 10% 22% 18% 4	2090
October	1st to 10th	Day	28% 4 8% 20% 33% 7%	3421
	11th to 20th	Day	27% 3 9% 24% 23% 14%	3140
	21st to end	Day	31% 3 9% 29% 18% 11%	3428
November	1st to 10th	Day	34% 3 8% 23% 28% 5%	1814
	11th to 20th	Day	40% 2 6% 25% 22% 5%	1719
	21st to end	Day	43% 2 8% 22% 22% 3	1710
December	1st to 10th	Day	56% 3 8% 21% 10% 2	1710
	11th to 20th	Day	50% 2 10% 17% 19% 2	2150
	21st to end	Day	61% 2 6% 22% 9%	3124
January	1st to 10th	Night	60% 1 5% 18% 14% 2	4109
	11th to 20th	Night	55% 1 5% 19% 16% 4	4120
	21st to end	Night	55% 2 7% 20% 15% 1	4532
February	1st to 10th	Night	50% 2 9% 22% 15% 2	2406
	11th to 20th	Night	54% 2 7% 21% 12% 4	2219
	21st to end	Night	55% 3 7% 19% 12% 4	1884
March	1st to 10th	Night	56% 1 7% 20% 15% 2	3522
	11th to 20th	Night	38% 1 7% 31% 15% 8%	3480
	21st to end	Night	43% 2 9% 26% 18% 2	3817
April	1st to 10th	Night	41% 3 10% 25% 18% 3	2090
	11th to 20th	Night	41% 3 9% 20% 20% 7%	1821
	21st to end	Night	42% 3 12% 26% 14% 2	1710
May	1st to 10th	Night	53% 4 13% 22% 8% 1	2840
	11th to 20th	Night	48% 4 13% 27% 7% 1	2813
	21st to end	Night	42% 4 13% 25% 14% 2	3087
June	1st to 10th	Night	39% 6% 17% 21% 15% 2	1710
	11th to 20th	Night	35% 8% 18% 24% 13% 2	1710
	21st to end	Night	40% 7% 14% 21% 14% 4	1710
July	1st to 10th	Night	37% 10% 22% 20% 9% 1	2795
	11th to 20th	Night	35% 6% 19% 29% 8% 3	2786
	21st to end	Night	56% 9% 12% 16% 7%	2988
August	1st to 10th	Night	41% 7% 18% 26% 7% 1	2814
	11th to 20th	Night	38% 6% 17% 26% 12%	2812
	21st to end	Night	23% 6% 17% 38% 14% 1	3358
September	1st to 10th	Night	40% 5% 12% 20% 18% 5%	2090
	11th to 20th	Night	40% 5% 10% 23% 20% 2	2090
	21st to end	Night	38% 4 10% 25% 20% 3	2090
October	1st to 10th	Night	29% 6% 7% 23% 29% 7%	3539
	11th to 20th	Night	25% 3 8% 25% 26% 13%	3779
	21st to end	Night	26% 2 6% 30% 26% 11%	4120
November	1st to 10th	Night	36% 3 8% 23% 24% 6%	2481
	11th to 20th	Night	40% 2 6% 22% 23% 7%	2484
	21st to end	Night	42% 2 7% 25% 21% 2	2470
December	1st to 10th	Night	56% 3 7% 21% 11% 2	2470
	11th to 20th	Night	52% 1 7% 21% 16% 2	3044
	21st to end	Night	59% 1 8% 18% 13% 1	4532

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	29% 19% 29% 19% 3 1	270
	11th to 20th	Day	36% 19% 24% 16% 6%	270
	21st to end	Day	29% 20% 31% 15% 4	297
February	1st to 10th	Day	29% 17% 30% 17% 7%	270
	11th to 20th	Day	39% 21% 28% 9% 3	270
	21st to end	Day	39% 16% 32% 11% 2	225
March	1st to 10th	Day	29% 11% 28% 23% 7% 1	389
	11th to 20th	Day	27% 14% 29% 25% 3 1	460
	21st to end	Day	25% 15% 27% 23% 10%	506
April	1st to 10th	Day	27% 10% 23% 27% 10% 3	460
	11th to 20th	Day	22% 14% 25% 22% 14% 2	452
	21st to end	Day	22% 8% 27% 25% 15% 2	460
May	1st to 10th	Day	22% 11% 27% 22% 12% 6%	463
	11th to 20th	Day	18% 8% 20% 28% 19% 7%	487
	21st to end	Day	15% 5% 18% 23% 23% 16%	529
June	1st to 10th	Day	15% 4 18% 27% 26% 11%	490
	11th to 20th	Day	10% 4 17% 28% 27% 14%	490
	21st to end	Day	13% 6% 20% 24% 26% 12%	490
July	1st to 10th	Day	13% 2 14% 27% 24% 19%	485
	11th to 20th	Day	13% 2 10% 26% 30% 19%	484
	21st to end	Day	15% 3 11% 27% 30% 15%	532
August	1st to 10th	Day	15% 3 14% 26% 25% 17%	486
	11th to 20th	Day	14% 2 11% 30% 27% 15%	479
	21st to end	Day	12% 2 9% 24% 30% 22%	539
September	1st to 10th	Day	12% 2 12% 28% 31% 15%	490
	11th to 20th	Day	12% 4 12% 24% 33% 15%	490
	21st to end	Day	21% 7% 13% 29% 23% 7%	490
October	1st to 10th	Day	16% 5% 16% 29% 26% 9%	490
	11th to 20th	Day	14% 11% 20% 29% 21% 5%	490
	21st to end	Day	21% 8% 21% 27% 19% 4	539
November	1st to 10th	Day	16% 10% 25% 30% 15% 4	352
	11th to 20th	Day	22% 10% 27% 27% 12% 2	273
	21st to end	Day	18% 11% 31% 22% 16% 1	270
December	1st to 10th	Day	31% 13% 28% 23% 4	270
	11th to 20th	Day	27% 14% 24% 26% 7% 2	270
	21st to end	Day	27% 15% 27% 23% 7% 1	297
January	1st to 10th	Night	24% 13% 26% 34% 3	760
	11th to 20th	Night	29% 11% 25% 31% 4	760
	21st to end	Night	20% 12% 34% 31% 3	836
February	1st to 10th	Night	23% 10% 27% 37% 3	760
	11th to 20th	Night	30% 12% 30% 27% 1	743
	21st to end	Night	30% 12% 31% 25% 3	628
March	1st to 10th	Night	21% 10% 28% 35% 6%	760
	11th to 20th	Night	22% 11% 27% 32% 7% 1	760
	21st to end	Night	19% 9% 29% 33% 10%	836
April	1st to 10th	Night	18% 13% 24% 35% 10%	760
	11th to 20th	Night	18% 8% 24% 36% 13% 1	612
	21st to end	Night	17% 4 23% 44% 11% 1	570
May	1st to 10th	Night	17% 7% 20% 36% 18% 2	570
	11th to 20th	Night	19% 6% 12% 39% 23% 2	561
	21st to end	Night	12% 2 10% 35% 36% 5%	617
June	1st to 10th	Night	12% 3 9% 40% 31% 5%	570
	11th to 20th	Night	7% 3 9% 36% 38% 6%	570
	21st to end	Night	11% 4 8% 38% 35% 4	570
July	1st to 10th	Night	13% 2 5% 29% 45% 6%	555
	11th to 20th	Night	11% 3 4 27% 47% 8%	552
	21st to end	Night	11% 4 4 33% 39% 8%	624
August	1st to 10th	Night	12% 2 5% 30% 46% 4	567
	11th to 20th	Night	15% 1 3 35% 40% 6%	564
	21st to end	Night	10% 2 6% 29% 43% 11%	651
September	1st to 10th	Night	14% 3 8% 29% 41% 5%	760
	11th to 20th	Night	16% 3 9% 31% 36% 6%	760
	21st to end	Night	18% 3 14% 36% 27% 2	760
October	1st to 10th	Night	15% 4 13% 34% 29% 5%	760
	11th to 20th	Night	17% 6% 19% 38% 19% 1	760
	21st to end	Night	18% 6% 19% 39% 17% 1	836
November	1st to 10th	Night	15% 5% 20% 41% 17% 2	780
	11th to 20th	Night	18% 9% 21% 40% 11% 1	765
	21st to end	Night	19% 9% 20% 41% 10% 1	760
December	1st to 10th	Night	27% 8% 24% 34% 7%	760
	11th to 20th	Night	22% 8% 26% 37% 7% 1	760
	21st to end	Night	26% 10% 24% 34% 6%	836

Page generated at 2024-11-08 22:45:39. Version ac07

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