Denali National Park & Preserve -- Headquarters
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Denali National Park & Preserve -- Headquarters clear sky chart from 2005-11-06 to 2024-04-10.

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	13% 12% 5% 10% 8% 5% 6% 6% 6% 7% 22%	81378
	Night	5% 10% 5% 11% 9% 5% 7% 6% 6% 7% 28%	87394
Transparency	Day	59% 8% 14% 12% 5% 1	81006
	Night	51% 8% 14% 16% 8% 4	87347
Seeing	Day	19% 13% 22% 23% 17% 5%	17443
	Night	12% 11% 21% 27% 22% 7%	21976

By Month

Percentage Cloud Cover NW (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	1 8% 4 12% 7% 6% 6% 7% 5% 9% 38%	1269
	11th to 20th	Day	1 5% 6% 10% 7% 4 6% 7% 11% 9% 36%	1258
	21st to end	Day	1 6% 3 10% 11% 7% 6% 7% 9% 9% 32%	1925
February	1st to 10th	Day	1 9% 4 9% 7% 4 6% 7% 7% 8% 39%	1187
	11th to 20th	Day	1 9% 5% 12% 10% 5% 8% 7% 7% 9% 27%	1425
	21st to end	Day	2 7% 6% 13% 12% 6% 7% 6% 6% 6% 29%	1294
March	1st to 10th	Day	1 7% 6% 15% 14% 6% 7% 6% 6% 6% 25%	3044
	11th to 20th	Day	1 9% 5% 12% 9% 6% 10% 10% 8% 7% 22%	3239
	21st to end	Day	2 12% 7% 14% 10% 6% 7% 6% 6% 7% 24%	4165
April	1st to 10th	Day	2 12% 7% 13% 10% 6% 8% 6% 7% 7% 22%	2390
	11th to 20th	Day	2 11% 6% 12% 10% 5% 6% 5% 6% 6% 29%	2486
	21st to end	Day	4 9% 6% 8% 8% 5% 7% 6% 7% 8% 33%	2673
May	1st to 10th	Day	6% 13% 5% 9% 7% 5% 8% 6% 8% 9% 25%	2880
	11th to 20th	Day	6% 13% 5% 7% 7% 4 5% 7% 7% 8% 30%	3015
	21st to end	Day	13% 12% 4 8% 5% 3 7% 7% 6% 7% 28%	3499
June	1st to 10th	Day	18% 13% 5% 10% 9% 5% 7% 6% 6% 6% 15%	3334
	11th to 20th	Day	19% 12% 5% 9% 8% 5% 6% 4 4 7% 20%	3580
	21st to end	Day	23% 9% 4 9% 8% 5% 7% 5% 5% 7% 17%	3600
July	1st to 10th	Day	25% 10% 4 8% 7% 4 6% 5% 6% 6% 20%	3349
	11th to 20th	Day	33% 11% 5% 7% 8% 4 6% 5% 5% 6% 11%	3240
	21st to end	Day	26% 11% 4 8% 7% 5% 6% 6% 6% 6% 16%	3397
August	1st to 10th	Day	29% 14% 4 9% 7% 4 5% 5% 4 5% 14%	2865
	11th to 20th	Day	28% 15% 4 9% 7% 4 6% 5% 5% 5% 13%	2679
	21st to end	Day	27% 17% 5% 10% 7% 4 5% 5% 4 4 11%	2772
September	1st to 10th	Day	20% 15% 5% 11% 7% 4 5% 6% 5% 6% 17%	2304
	11th to 20th	Day	19% 16% 4 9% 8% 4 5% 5% 4 6% 18%	2156
	21st to end	Day	15% 19% 7% 9% 7% 4 5% 5% 6% 6% 17%	1922
October	1st to 10th	Day	12% 20% 8% 9% 7% 3 5% 5% 5% 7% 20%	1745
	11th to 20th	Day	4 15% 7% 13% 8% 4 5% 5% 5% 7% 27%	1574
	21st to end	Day	6% 12% 6% 10% 10% 4 6% 7% 7% 8% 24%	1468
November	1st to 10th	Day	3 14% 7% 12% 8% 7% 7% 5% 6% 5% 26%	1216
	11th to 20th	Day	4 12% 6% 11% 10% 7% 9% 5% 5% 5% 27%	994
	21st to end	Day	3 9% 5% 9% 11% 5% 10% 8% 7% 9% 25%	837
December	1st to 10th	Day	3 12% 5% 10% 9% 5% 8% 8% 8% 9% 23%	700
	11th to 20th	Day	2 9% 5% 13% 12% 3 5% 8% 6% 10% 26%	724
	21st to end	Day	1 5% 3 7% 8% 4 7% 7% 9% 7% 42%	1173
January	1st to 10th	Night	1 6% 4 11% 9% 5% 6% 5% 6% 8% 39%	5686
	11th to 20th	Night	1 8% 5% 9% 9% 5% 6% 5% 6% 9% 36%	5650
	21st to end	Night	1 6% 4 9% 10% 6% 8% 8% 8% 8% 32%	5745
February	1st to 10th	Night	1 7% 5% 11% 9% 5% 6% 5% 5% 7% 38%	2991
	11th to 20th	Night	2 7% 5% 11% 9% 5% 8% 6% 8% 10% 28%	2642
	21st to end	Night	2 9% 7% 15% 12% 6% 7% 6% 4 6% 26%	2159
March	1st to 10th	Night	1 9% 7% 16% 11% 5% 7% 5% 7% 6% 26%	3810
	11th to 20th	Night	1 6% 5% 12% 11% 7% 11% 10% 7% 7% 22%	3716
	21st to end	Night	2 8% 5% 10% 9% 6% 7% 7% 7% 8% 30%	3466
April	1st to 10th	Night	2 13% 6% 13% 9% 4 7% 6% 7% 8% 24%	1780
	11th to 20th	Night	2 10% 6% 9% 8% 4 8% 7% 7% 8% 30%	1423
	21st to end	Night	4 8% 4 7% 7% 4 6% 5% 8% 10% 37%	1284
May	1st to 10th	Night	6% 13% 4 8% 7% 5% 8% 7% 8% 9% 26%	1080
	11th to 20th	Night	8% 11% 3 5% 6% 4 5% 8% 8% 7% 35%	879
	21st to end	Night	13% 10% 5% 7% 5% 3 6% 7% 6% 7% 32%	776
June	1st to 10th	Night	17% 8% 6% 11% 8% 5% 8% 4 7% 7% 19%	625
	11th to 20th	Night	21% 10% 4 7% 8% 5% 4 4 6% 5% 27%	378
	21st to end	Night	20% 9% 6% 7% 9% 4 6% 8% 6% 7% 19%	360
July	1st to 10th	Night	20% 9% 5% 9% 4 3 6% 7% 5% 10% 22%	607
	11th to 20th	Night	29% 10% 6% 9% 8% 4 5% 5% 3 6% 15%	720
	21st to end	Night	25% 10% 4 7% 6% 3 4 5% 5% 9% 20%	919
August	1st to 10th	Night	26% 13% 5% 8% 7% 4 5% 6% 6% 6% 15%	1074
	11th to 20th	Night	24% 12% 4 8% 7% 4 6% 5% 4 7% 18%	1220
	21st to end	Night	27% 17% 4 9% 4 3 5% 5% 5% 5% 16%	1584
September	1st to 10th	Night	19% 13% 3 8% 8% 4 5% 5% 6% 7% 21%	1654
	11th to 20th	Night	20% 18% 5% 8% 8% 4 5% 4 4 6% 18%	1804
	21st to end	Night	15% 20% 7% 10% 7% 3 6% 5% 5% 4 17%	2036
October	1st to 10th	Night	11% 18% 7% 10% 8% 4 6% 5% 6% 7% 19%	2215
	11th to 20th	Night	7% 13% 6% 14% 8% 4 6% 5% 6% 7% 24%	2384
	21st to end	Night	5% 14% 7% 13% 9% 5% 4 5% 6% 7% 26%	2888
November	1st to 10th	Night	4 14% 7% 12% 9% 5% 6% 5% 5% 6% 28%	2862
	11th to 20th	Night	4 10% 7% 14% 12% 6% 8% 6% 5% 5% 22%	3186
	21st to end	Night	3 9% 6% 10% 9% 5% 7% 7% 7% 8% 30%	3340
December	1st to 10th	Night	3 11% 5% 10% 9% 4 8% 7% 7% 9% 28%	3458
	11th to 20th	Night	1 9% 7% 14% 9% 6% 7% 7% 7% 7% 26%	4470
	21st to end	Night	1 6% 4 11% 10% 6% 7% 7% 7% 8% 34%	6523

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	42% 7% 14% 23% 9% 5%	1269
	11th to 20th	Day	38% 7% 17% 23% 9% 6%	1270
	21st to end	Day	43% 6% 10% 12% 18% 13%	1925
February	1st to 10th	Day	40% 7% 9% 20% 16% 9%	1187
	11th to 20th	Day	48% 10% 16% 15% 8% 3	1432
	21st to end	Day	50% 7% 11% 17% 12% 2	1294
March	1st to 10th	Day	57% 6% 9% 11% 13% 3	3044
	11th to 20th	Day	46% 13% 12% 15% 11% 2	3239
	21st to end	Day	53% 10% 15% 12% 7% 3	4165
April	1st to 10th	Day	58% 8% 12% 15% 7%	2390
	11th to 20th	Day	53% 8% 14% 15% 8% 2	2486
	21st to end	Day	48% 7% 15% 21% 10%	2673
May	1st to 10th	Day	53% 9% 19% 17% 3	2880
	11th to 20th	Day	49% 8% 16% 22% 5%	3018
	21st to end	Day	52% 9% 16% 19% 4	3500
June	1st to 10th	Day	67% 9% 13% 10% 1	3334
	11th to 20th	Day	64% 7% 15% 11% 2	3580
	21st to end	Day	66% 9% 17% 8%	3600
July	1st to 10th	Day	63% 9% 17% 11% 1	3260
	11th to 20th	Day	74% 9% 15% 3	3141
	21st to end	Day	67% 11% 18% 5%	3207
August	1st to 10th	Day	73% 8% 14% 5% 1	2846
	11th to 20th	Day	73% 8% 12% 7%	2679
	21st to end	Day	77% 7% 10% 5% 1	2772
September	1st to 10th	Day	69% 8% 13% 9% 1	2304
	11th to 20th	Day	68% 7% 15% 9% 1	2156
	21st to end	Day	67% 7% 11% 13% 2	1922
October	1st to 10th	Day	64% 8% 15% 8% 4 1	1745
	11th to 20th	Day	56% 8% 19% 11% 4 1	1574
	21st to end	Day	55% 9% 14% 16% 4 1	1468
November	1st to 10th	Day	58% 7% 13% 12% 6% 3	1216
	11th to 20th	Day	57% 6% 12% 16% 7% 1	994
	21st to end	Day	50% 10% 16% 13% 11% 1	837
December	1st to 10th	Day	52% 10% 11% 15% 10% 2	700
	11th to 20th	Day	50% 10% 16% 17% 6% 2	726
	21st to end	Day	34% 8% 13% 18% 16% 10%	1173
January	1st to 10th	Night	39% 8% 13% 28% 6% 5%	5686
	11th to 20th	Night	39% 10% 17% 23% 8% 3	5700
	21st to end	Night	42% 8% 9% 11% 15% 15%	5745
February	1st to 10th	Night	44% 6% 8% 17% 15% 10%	2991
	11th to 20th	Night	47% 8% 14% 17% 10% 3	2646
	21st to end	Night	57% 6% 9% 15% 11% 2	2159
March	1st to 10th	Night	55% 5% 9% 10% 16% 6%	3810
	11th to 20th	Night	47% 12% 12% 17% 10% 3	3718
	21st to end	Night	45% 10% 17% 18% 7% 3	3466
April	1st to 10th	Night	54% 7% 12% 18% 7% 1	1780
	11th to 20th	Night	47% 9% 16% 19% 7% 2	1423
	21st to end	Night	39% 7% 17% 27% 10%	1284
May	1st to 10th	Night	51% 8% 20% 19% 3	1080
	11th to 20th	Night	43% 8% 18% 23% 8%	879
	21st to end	Night	47% 10% 17% 20% 5%	776
June	1st to 10th	Night	62% 8% 16% 12% 2	625
	11th to 20th	Night	57% 10% 17% 14% 2	378
	21st to end	Night	63% 9% 20% 9%	360
July	1st to 10th	Night	57% 9% 22% 11% 1	587
	11th to 20th	Night	69% 11% 18% 3	696
	21st to end	Night	58% 12% 25% 5%	869
August	1st to 10th	Night	68% 11% 16% 5% 1	1068
	11th to 20th	Night	65% 9% 17% 8%	1220
	21st to end	Night	69% 10% 14% 6%	1584
September	1st to 10th	Night	62% 10% 17% 9% 1	1654
	11th to 20th	Night	68% 6% 14% 10% 1	1804
	21st to end	Night	70% 7% 10% 11% 3	2036
October	1st to 10th	Night	64% 7% 17% 7% 3 1	2215
	11th to 20th	Night	56% 8% 18% 12% 5% 1	2384
	21st to end	Night	56% 6% 17% 14% 6% 1	2888
November	1st to 10th	Night	55% 7% 13% 17% 6% 2	2862
	11th to 20th	Night	60% 8% 11% 14% 6%	3186
	21st to end	Night	49% 7% 15% 17% 10% 2	3340
December	1st to 10th	Night	50% 10% 12% 16% 10% 2	3458
	11th to 20th	Night	53% 7% 13% 17% 8% 2	4467
	21st to end	Night	42% 9% 12% 17% 12% 8%	6523

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	4 10% 24% 30% 20% 11%	90
	11th to 20th	Day	4 8% 32% 33% 18% 4	90
	21st to end	Day	5% 11% 23% 34% 22% 5%	302
February	1st to 10th	Day	5% 10% 22% 28% 22% 13%	280
	11th to 20th	Day	11% 19% 26% 22% 15% 7%	340
	21st to end	Day	8% 17% 32% 22% 15% 5%	307
March	1st to 10th	Day	6% 12% 32% 29% 15% 6%	370
	11th to 20th	Day	6% 12% 30% 28% 20% 5%	405
	21st to end	Day	9% 17% 25% 27% 17% 5%	616
April	1st to 10th	Day	7% 17% 31% 26% 16% 4	593
	11th to 20th	Day	8% 12% 24% 29% 22% 6%	590
	21st to end	Day	9% 10% 22% 30% 24% 6%	600
May	1st to 10th	Day	11% 13% 24% 28% 19% 5%	603
	11th to 20th	Day	12% 12% 24% 27% 18% 7%	667
	21st to end	Day	17% 15% 23% 23% 17% 5%	874
June	1st to 10th	Day	21% 9% 21% 22% 20% 7%	904
	11th to 20th	Day	19% 13% 19% 22% 21% 6%	990
	21st to end	Day	23% 9% 18% 21% 23% 7%	990
July	1st to 10th	Day	25% 11% 23% 19% 18% 4	847
	11th to 20th	Day	34% 10% 18% 20% 14% 4	792
	21st to end	Day	28% 12% 21% 20% 14% 5%	831
August	1st to 10th	Day	34% 13% 23% 16% 10% 4	626
	11th to 20th	Day	38% 14% 18% 19% 10% 2	615
	21st to end	Day	38% 13% 20% 19% 9% 1	693
September	1st to 10th	Day	31% 15% 24% 17% 9% 4	588
	11th to 20th	Day	32% 20% 22% 15% 9% 2	536
	21st to end	Day	29% 11% 20% 21% 12% 7%	360
October	1st to 10th	Day	26% 19% 23% 18% 10% 4	360
	11th to 20th	Day	12% 11% 21% 24% 21% 11%	360
	21st to end	Day	13% 13% 18% 24% 24% 8%	396
November	1st to 10th	Day	9% 9% 22% 31% 18% 10%	325
	11th to 20th	Day	9% 13% 22% 21% 28% 7%	134
	21st to end	Day	9% 16% 21% 24% 22% 8%	90
December	1st to 10th	Day	9% 18% 17% 33% 19% 4	90
	11th to 20th	Day	13% 11% 20% 32% 19% 4	90
	21st to end	Day	8% 18% 24% 30% 12% 7%	99
January	1st to 10th	Night	5% 9% 21% 30% 25% 10%	940
	11th to 20th	Night	6% 9% 28% 32% 19% 6%	940
	21st to end	Night	5% 11% 25% 33% 22% 5%	976
February	1st to 10th	Night	4 9% 24% 31% 22% 10%	850
	11th to 20th	Night	8% 16% 28% 30% 15% 4	834
	21st to end	Night	8% 15% 25% 27% 21% 4	664
March	1st to 10th	Night	5% 11% 23% 38% 19% 4	660
	11th to 20th	Night	3 6% 19% 33% 30% 8%	657
	21st to end	Night	8% 13% 18% 21% 27% 13%	627
April	1st to 10th	Night	5% 11% 25% 28% 22% 8%	570
	11th to 20th	Night	6% 9% 18% 25% 31% 11%	533
	21st to end	Night	8% 5% 15% 30% 32% 9%	500
May	1st to 10th	Night	12% 7% 18% 26% 27% 10%	360
	11th to 20th	Night	12% 12% 14% 28% 29% 7%	214
	21st to end	Night	14% 12% 17% 27% 26% 5%	195
June	1st to 10th	Night	18% 10% 19% 24% 25% 4	180
	11th to 20th	Night	22% 6% 13% 27% 28% 4	180
	21st to end	Night	22% 8% 11% 19% 32% 9%	180
July	1st to 10th	Night	28% 5% 16% 19% 27% 5%	175
	11th to 20th	Night	30% 8% 14% 18% 26% 3	174
	21st to end	Night	23% 9% 17% 23% 21% 6%	278
August	1st to 10th	Night	30% 11% 15% 23% 15% 5%	358
	11th to 20th	Night	31% 9% 17% 20% 17% 4	429
	21st to end	Night	33% 12% 11% 19% 19% 6%	594
September	1st to 10th	Night	28% 14% 19% 18% 17% 6%	540
	11th to 20th	Night	31% 15% 16% 18% 14% 6%	540
	21st to end	Night	24% 9% 17% 21% 22% 6%	569
October	1st to 10th	Night	23% 17% 18% 19% 17% 6%	685
	11th to 20th	Night	13% 10% 18% 26% 25% 9%	810
	21st to end	Night	12% 10% 19% 30% 23% 7%	891
November	1st to 10th	Night	9% 10% 22% 31% 22% 7%	830
	11th to 20th	Night	9% 9% 22% 29% 22% 9%	850
	21st to end	Night	9% 12% 22% 26% 24% 8%	902
December	1st to 10th	Night	11% 14% 22% 25% 20% 8%	978
	11th to 20th	Night	7% 10% 24% 30% 20% 9%	1130
	21st to end	Night	8% 11% 22% 30% 20% 8%	1183

Page generated at 2024-04-07 05:28:14. Version ac07

Copyright © 2024 Attilla Danko.