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Delta Junction
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Delta Junction clear sky chart from 2005-11-06 to 2025-09-19.

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	11% 11% 5% 11% 7% 6% 6% 5% 7% 8% 25%	131675
	Night	6% 12% 5% 13% 7% 6% 6% 5% 6% 8% 26%	126127
Transparency	Day	54% 9% 16% 16% 5%	131289
	Night	53% 8% 15% 16% 7% 1	126091
Seeing	Day	15% 7% 19% 25% 23% 11%	19700
	Night	13% 7% 20% 31% 24% 6%	23899

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	2 12% 6% 12% 6% 5% 5% 2 5% 6% 40%	1604
	11th to 20th	Day	1 11% 5% 12% 7% 7% 7% 6% 8% 10% 27%	1808
	21st to end	Day	2 7% 4 13% 11% 9% 10% 6% 7% 8% 23%	2699
February	1st to 10th	Day	2 10% 4 14% 6% 7% 6% 6% 6% 8% 31%	1210
	11th to 20th	Day	2 14% 6% 12% 7% 6% 6% 4 7% 11% 25%	1519
	21st to end	Day	2 14% 6% 13% 9% 9% 6% 4 6% 6% 26%	1341
March	1st to 10th	Day	2 8% 7% 14% 8% 7% 5% 4 7% 7% 31%	4380
	11th to 20th	Day	1 9% 6% 17% 10% 8% 8% 6% 6% 7% 23%	4703
	21st to end	Day	3 13% 5% 10% 6% 5% 5% 4 6% 7% 34%	5867
April	1st to 10th	Day	4 15% 5% 10% 7% 8% 7% 5% 7% 8% 25%	2560
	11th to 20th	Day	4 11% 4 10% 7% 6% 5% 4 6% 7% 36%	2746
	21st to end	Day	4 10% 4 9% 7% 6% 6% 5% 7% 7% 35%	3000
May	1st to 10th	Day	7% 16% 5% 12% 7% 7% 6% 5% 7% 8% 21%	7336
	11th to 20th	Day	9% 10% 3 8% 6% 6% 5% 5% 8% 9% 32%	7650
	21st to end	Day	12% 10% 4 10% 7% 7% 7% 6% 8% 8% 22%	9058
June	1st to 10th	Day	12% 8% 4 10% 8% 7% 8% 6% 9% 9% 21%	3800
	11th to 20th	Day	14% 9% 3 9% 7% 6% 7% 6% 7% 8% 26%	3860
	21st to end	Day	16% 7% 3 8% 6% 6% 7% 5% 8% 10% 24%	3940
July	1st to 10th	Day	20% 11% 4 10% 6% 6% 5% 4 6% 7% 22%	8620
	11th to 20th	Day	13% 9% 4 11% 7% 7% 6% 5% 7% 9% 22%	8207
	21st to end	Day	19% 11% 4 9% 5% 5% 6% 5% 7% 8% 22%	8606
August	1st to 10th	Day	19% 12% 4 8% 6% 6% 5% 4 6% 6% 24%	5219
	11th to 20th	Day	18% 10% 4 10% 7% 6% 6% 5% 6% 7% 19%	4879
	21st to end	Day	19% 14% 5% 12% 6% 6% 6% 4 5% 6% 17%	5016
September	1st to 10th	Day	15% 11% 5% 10% 8% 6% 6% 4 6% 7% 22%	2600
	11th to 20th	Day	20% 13% 4 10% 7% 5% 5% 4 6% 6% 22%	2305
	21st to end	Day	16% 15% 4 9% 6% 7% 6% 6% 5% 6% 21%	2090
October	1st to 10th	Day	11% 16% 5% 10% 4 4 5% 4 5% 7% 29%	2980
	11th to 20th	Day	6% 16% 6% 18% 8% 6% 5% 3 4 5% 22%	2834
	21st to end	Day	8% 17% 9% 17% 8% 6% 5% 4 4 6% 18%	2447
November	1st to 10th	Day	5% 18% 7% 11% 8% 8% 5% 4 6% 8% 19%	1291
	11th to 20th	Day	5% 18% 7% 15% 10% 7% 4 3 5% 6% 20%	1000
	21st to end	Day	9% 10% 6% 13% 9% 6% 5% 6% 7% 8% 22%	890
December	1st to 10th	Day	4 9% 4 9% 7% 7% 7% 4 7% 9% 31%	980
	11th to 20th	Day	4 14% 5% 12% 7% 7% 5% 5% 6% 8% 28%	1134
	21st to end	Day	1 6% 4 12% 6% 7% 6% 5% 9% 10% 32%	1496
January	1st to 10th	Night	1 7% 5% 14% 6% 6% 4 4 5% 6% 41%	8404
	11th to 20th	Night	2 11% 5% 13% 8% 6% 7% 5% 7% 9% 28%	8110
	21st to end	Night	2 9% 4 14% 9% 9% 7% 6% 8% 9% 23%	8256
February	1st to 10th	Night	2 10% 5% 10% 6% 6% 5% 6% 7% 9% 33%	3190
	11th to 20th	Night	2 11% 5% 13% 7% 6% 5% 5% 7% 8% 30%	2766
	21st to end	Night	2 13% 5% 15% 10% 8% 7% 4 5% 5% 25%	2289
March	1st to 10th	Night	2 9% 7% 15% 9% 7% 6% 4 6% 8% 28%	5477
	11th to 20th	Night	2 9% 6% 21% 10% 7% 6% 4 5% 6% 24%	5255
	21st to end	Night	2 14% 6% 11% 5% 6% 6% 5% 7% 8% 29%	5064
April	1st to 10th	Night	4 12% 5% 11% 7% 5% 5% 6% 8% 9% 28%	1840
	11th to 20th	Night	5% 13% 4 9% 5% 5% 6% 5% 7% 7% 32%	1603
	21st to end	Night	5% 9% 4 8% 7% 4 5% 5% 6% 8% 38%	1400
May	1st to 10th	Night	9% 15% 5% 11% 7% 8% 8% 6% 7% 7% 18%	2635
	11th to 20th	Night	8% 12% 4 8% 6% 4 5% 5% 8% 8% 31%	2245
	21st to end	Night	11% 11% 4 10% 7% 6% 7% 4 8% 10% 22%	1823
June	1st to 10th	Night	11% 9% 4 11% 7% 7% 8% 6% 9% 10% 19%	600
	11th to 20th	Night	14% 6% 4 7% 9% 6% 6% 7% 8% 8% 25%	535
	21st to end	Night	12% 9% 4 11% 4 6% 7% 5% 10% 11% 20%	457
July	1st to 10th	Night	21% 8% 3 11% 8% 5% 7% 5% 7% 7% 18%	1360
	11th to 20th	Night	18% 11% 5% 10% 6% 6% 6% 5% 7% 8% 18%	1771
	21st to end	Night	22% 12% 4 11% 6% 6% 5% 5% 7% 6% 16%	2247
August	1st to 10th	Night	23% 11% 4 8% 5% 4 4 3 6% 7% 24%	1939
	11th to 20th	Night	24% 13% 5% 10% 7% 6% 6% 3 5% 5% 18%	2179
	21st to end	Night	21% 15% 4 11% 6% 6% 5% 3 5% 6% 19%	2892
September	1st to 10th	Night	14% 11% 3 10% 7% 7% 6% 5% 7% 7% 24%	1800
	11th to 20th	Night	19% 13% 3 11% 6% 5% 5% 4 6% 5% 22%	2052
	21st to end	Night	18% 16% 6% 11% 5% 6% 5% 3 5% 5% 20%	2090
October	1st to 10th	Night	12% 17% 5% 11% 6% 5% 6% 5% 6% 7% 21%	3987
	11th to 20th	Night	7% 17% 7% 15% 8% 6% 4 4 5% 6% 21%	4094
	21st to end	Night	7% 18% 8% 13% 6% 6% 6% 4 5% 6% 20%	5111
November	1st to 10th	Night	6% 17% 6% 13% 7% 5% 5% 4 6% 8% 22%	3006
	11th to 20th	Night	4 17% 8% 18% 9% 6% 5% 4 5% 6% 18%	3400
	21st to end	Night	5% 14% 5% 12% 8% 6% 7% 5% 7% 9% 19%	3488
December	1st to 10th	Night	6% 10% 5% 11% 7% 6% 6% 4 7% 8% 31%	6210
	11th to 20th	Night	3 12% 7% 14% 8% 6% 6% 5% 7% 9% 24%	7070
	21st to end	Night	1 9% 6% 14% 7% 6% 6% 5% 7% 10% 28%	9482

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	45% 6% 13% 16% 18% 2	1604
	11th to 20th	Day	47% 9% 19% 18% 7%	1820
	21st to end	Day	54% 7% 12% 16% 7% 5%	2699
February	1st to 10th	Day	46% 6% 10% 17% 17% 3	1210
	11th to 20th	Day	49% 9% 18% 14% 10%	1526
	21st to end	Day	55% 7% 11% 15% 11% 1	1341
March	1st to 10th	Day	49% 7% 9% 21% 14%	4380
	11th to 20th	Day	53% 8% 12% 13% 13%	4703
	21st to end	Day	44% 10% 13% 17% 15% 1	5867
April	1st to 10th	Day	52% 8% 18% 16% 6%	2560
	11th to 20th	Day	45% 9% 15% 23% 7% 2	2746
	21st to end	Day	43% 9% 15% 22% 11% 1	3000
May	1st to 10th	Day	55% 10% 10% 18% 7%	7336
	11th to 20th	Day	43% 9% 12% 24% 11% 1	7653
	21st to end	Day	52% 10% 14% 19% 5%	9059
June	1st to 10th	Day	53% 12% 18% 16% 2	3800
	11th to 20th	Day	52% 12% 17% 16% 4	3860
	21st to end	Day	52% 12% 20% 15% 2	3940
July	1st to 10th	Day	60% 6% 20% 13% 1	8526
	11th to 20th	Day	56% 7% 20% 16% 1	8106
	21st to end	Day	57% 7% 23% 11% 1	8365
August	1st to 10th	Day	59% 8% 19% 11% 3	5199
	11th to 20th	Day	60% 10% 16% 13% 1	4925
	21st to end	Day	67% 7% 19% 6%	5015
September	1st to 10th	Day	58% 12% 19% 10% 1	2600
	11th to 20th	Day	61% 9% 17% 12% 1	2305
	21st to end	Day	60% 10% 14% 14% 2	2090
October	1st to 10th	Day	54% 7% 13% 21% 5%	2980
	11th to 20th	Day	62% 9% 12% 16% 1	2834
	21st to end	Day	67% 6% 17% 10% 1	2447
November	1st to 10th	Day	58% 9% 16% 13% 4	1291
	11th to 20th	Day	63% 8% 12% 14% 3	1000
	21st to end	Day	57% 8% 17% 14% 5%	890
December	1st to 10th	Day	47% 9% 19% 22% 3	980
	11th to 20th	Day	51% 7% 19% 15% 6% 1	1136
	21st to end	Day	41% 8% 23% 17% 11% 1	1496
January	1st to 10th	Night	43% 8% 13% 18% 16% 2	8404
	11th to 20th	Night	48% 9% 20% 16% 7%	8160
	21st to end	Night	52% 6% 12% 16% 10% 4	8256
February	1st to 10th	Night	43% 8% 11% 17% 19% 2	3190
	11th to 20th	Night	47% 9% 16% 18% 10%	2770
	21st to end	Night	58% 7% 11% 15% 8% 1	2289
March	1st to 10th	Night	52% 6% 9% 22% 10% 1	5477
	11th to 20th	Night	58% 8% 10% 14% 10%	5257
	21st to end	Night	46% 12% 14% 14% 12% 1	5064
April	1st to 10th	Night	47% 10% 19% 17% 6% 1	1840
	11th to 20th	Night	46% 10% 14% 21% 7% 1	1603
	21st to end	Night	39% 9% 16% 23% 12%	1400
May	1st to 10th	Night	59% 10% 9% 18% 4	2632
	11th to 20th	Night	45% 10% 11% 22% 11% 1	2245
	21st to end	Night	51% 11% 14% 19% 6%	1823
June	1st to 10th	Night	50% 15% 17% 17% 1	600
	11th to 20th	Night	54% 9% 18% 17% 2	535
	21st to end	Night	51% 14% 20% 14%	457
July	1st to 10th	Night	63% 6% 21% 9% 1	1345
	11th to 20th	Night	62% 8% 19% 11%	1749
	21st to end	Night	66% 7% 18% 8% 1	2183
August	1st to 10th	Night	58% 7% 20% 12% 3	1934
	11th to 20th	Night	68% 8% 11% 13%	2199
	21st to end	Night	67% 6% 18% 10%	2892
September	1st to 10th	Night	55% 12% 21% 11% 1	1800
	11th to 20th	Night	60% 10% 16% 13% 1	2052
	21st to end	Night	65% 8% 13% 12% 1	2090
October	1st to 10th	Night	60% 7% 12% 19% 2	3987
	11th to 20th	Night	63% 7% 12% 14% 3	4094
	21st to end	Night	63% 7% 17% 12% 2	5111
November	1st to 10th	Night	58% 9% 15% 14% 4	3006
	11th to 20th	Night	65% 8% 13% 12% 2	3400
	21st to end	Night	56% 10% 13% 17% 5%	3488
December	1st to 10th	Night	49% 7% 17% 22% 5%	6210
	11th to 20th	Night	53% 8% 21% 13% 4 2	7067
	21st to end	Night	48% 8% 19% 15% 10% 1	9482

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	9% 9% 23% 29% 22% 8%	100
	11th to 20th	Day	9% 7% 21% 44% 15% 4	100
	21st to end	Day	10% 7% 16% 31% 24% 13%	225
February	1st to 10th	Day	7% 9% 18% 29% 20% 17%	305
	11th to 20th	Day	8% 10% 29% 32% 16% 5%	395
	21st to end	Day	8% 12% 25% 31% 17% 7%	331
March	1st to 10th	Day	7% 7% 25% 31% 24% 8%	400
	11th to 20th	Day	6% 8% 23% 28% 24% 12%	400
	21st to end	Day	8% 8% 24% 29% 20% 11%	610
April	1st to 10th	Day	8% 11% 26% 31% 19% 6%	680
	11th to 20th	Day	10% 9% 24% 27% 21% 8%	690
	21st to end	Day	8% 6% 19% 31% 29% 7%	700
May	1st to 10th	Day	12% 11% 23% 24% 24% 6%	703
	11th to 20th	Day	13% 7% 23% 23% 22% 13%	725
	21st to end	Day	16% 8% 20% 24% 23% 9%	1062
June	1st to 10th	Day	13% 6% 17% 26% 25% 13%	1130
	11th to 20th	Day	15% 5% 14% 22% 27% 17%	1130
	21st to end	Day	15% 4 12% 23% 30% 17%	1130
July	1st to 10th	Day	17% 5% 14% 24% 27% 13%	1111
	11th to 20th	Day	20% 5% 16% 20% 25% 15%	931
	21st to end	Day	18% 4 14% 23% 25% 16%	893
August	1st to 10th	Day	23% 7% 15% 21% 21% 12%	726
	11th to 20th	Day	23% 7% 16% 24% 21% 8%	715
	21st to end	Day	25% 8% 16% 21% 21% 9%	803
September	1st to 10th	Day	18% 11% 17% 22% 19% 13%	730
	11th to 20th	Day	26% 7% 22% 22% 15% 7%	539
	21st to end	Day	24% 7% 16% 23% 17% 13%	390
October	1st to 10th	Day	21% 13% 21% 20% 16% 9%	390
	11th to 20th	Day	15% 8% 18% 26% 21% 11%	390
	21st to end	Day	16% 6% 18% 24% 27% 9%	429
November	1st to 10th	Day	15% 10% 15% 30% 21% 9%	327
	11th to 20th	Day	11% 11% 20% 25% 23% 10%	100
	21st to end	Day	10% 10% 27% 29% 16% 8%	100
December	1st to 10th	Day	13% 12% 19% 32% 18% 6%	100
	11th to 20th	Day	13% 10% 23% 38% 12% 4	100
	21st to end	Day	6% 11% 26% 30% 21% 5%	110
January	1st to 10th	Night	6% 6% 23% 32% 25% 8%	1115
	11th to 20th	Night	9% 9% 22% 39% 17% 5%	1000
	21st to end	Night	10% 7% 21% 33% 24% 5%	1000
February	1st to 10th	Night	5% 6% 25% 33% 24% 7%	900
	11th to 20th	Night	6% 9% 30% 36% 17% 3	884
	21st to end	Night	9% 6% 25% 35% 21% 3	743
March	1st to 10th	Night	6% 7% 20% 39% 25% 3	749
	11th to 20th	Night	5% 5% 18% 38% 28% 5%	660
	21st to end	Night	7% 6% 22% 33% 25% 7%	660
April	1st to 10th	Night	8% 6% 21% 38% 22% 4	600
	11th to 20th	Night	12% 8% 17% 34% 23% 6%	593
	21st to end	Night	8% 3 16% 31% 36% 6%	600
May	1st to 10th	Night	14% 6% 18% 28% 31% 3	367
	11th to 20th	Night	8% 9% 22% 33% 26% 3	197
	21st to end	Night	11% 8% 15% 34% 29% 4	217
June	1st to 10th	Night	12% 5% 17% 31% 31% 5%	200
	11th to 20th	Night	17% 4 10% 29% 31% 10%	200
	21st to end	Night	16% 2 11% 30% 33% 10%	200
July	1st to 10th	Night	21% 4 13% 25% 30% 8%	195
	11th to 20th	Night	24% 6% 7% 25% 33% 6%	194
	21st to end	Night	20% 6% 10% 26% 29% 10%	219
August	1st to 10th	Night	25% 4 15% 24% 27% 5%	383
	11th to 20th	Night	26% 6% 17% 22% 23% 6%	543
	21st to end	Night	25% 6% 12% 22% 26% 9%	660
September	1st to 10th	Night	19% 6% 18% 25% 25% 8%	600
	11th to 20th	Night	25% 7% 17% 26% 21% 5%	594
	21st to end	Night	26% 5% 15% 22% 22% 9%	570
October	1st to 10th	Night	24% 8% 21% 25% 19% 4	790
	11th to 20th	Night	20% 6% 18% 27% 22% 7%	860
	21st to end	Night	15% 7% 18% 29% 25% 7%	946
November	1st to 10th	Night	16% 7% 18% 30% 25% 5%	880
	11th to 20th	Night	11% 6% 16% 31% 29% 7%	900
	21st to end	Night	11% 8% 22% 31% 22% 6%	960
December	1st to 10th	Night	12% 10% 22% 30% 20% 7%	1200
	11th to 20th	Night	10% 7% 23% 31% 23% 6%	1200
	21st to end	Night	8% 9% 21% 34% 22% 7%	1320

Page generated at 2025-09-15 21:49:14. Version ac07

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