Darwin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Darwin clear sky chart from 2005-11-06 to 2026-04-17.

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% 8% 3 8% 5% 5% 5% 4 6% 7% 39%	132600
	Night	11% 8% 3 8% 5% 4 4 4 5% 7% 39%	129724
Transparency	Day	44% 5% 14% 25% 11% 1	136186
	Night	44% 5% 13% 25% 12% 1	134216
Seeing	Day	16% 9% 31% 27% 13% 3	17932
	Night	15% 9% 33% 31% 10% 1	27981

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	8% 14% 5% 16% 11% 7% 6% 4 5% 7% 18%	4441
	11th to 20th	Day	5% 9% 5% 13% 7% 8% 8% 7% 9% 7% 21%	4948
	21st to end	Day	3 11% 6% 11% 6% 6% 6% 4 5% 8% 34%	5812
February	1st to 10th	Day	8% 12% 4 11% 7% 6% 5% 4 6% 8% 29%	1890
	11th to 20th	Day	8% 10% 4 10% 7% 5% 6% 4 6% 6% 34%	1844
	21st to end	Day	9% 11% 3 9% 7% 5% 6% 3 7% 8% 32%	1578
March	1st to 10th	Day	11% 9% 3 7% 4 4 4 3 5% 8% 43%	5046
	11th to 20th	Day	9% 9% 3 8% 4 4 5% 4 5% 8% 42%	5090
	21st to end	Day	21% 10% 4 10% 7% 5% 5% 3 5% 6% 25%	5583
April	1st to 10th	Day	17% 10% 3 8% 4 4 3 4 6% 6% 36%	2494
	11th to 20th	Day	18% 11% 4 8% 5% 4 4 3 6% 6% 32%	2533
	21st to end	Day	23% 10% 2 6% 5% 4 3 3 5% 6% 32%	2600
May	1st to 10th	Day	13% 5% 2 6% 3 4 4 3 5% 6% 49%	5972
	11th to 20th	Day	17% 8% 2 6% 4 3 3 3 4 6% 45%	6319
	21st to end	Day	17% 6% 2 6% 5% 4 5% 4 6% 8% 37%	6935
June	1st to 10th	Day	11% 5% 2 5% 4 5% 4 5% 6% 9% 45%	2800
	11th to 20th	Day	14% 7% 3 5% 5% 5% 5% 4 6% 8% 37%	2990
	21st to end	Day	10% 5% 2 5% 4 4 5% 5% 7% 10% 43%	3000
July	1st to 10th	Day	8% 4 2 5% 4 5% 5% 5% 7% 10% 46%	6800
	11th to 20th	Day	8% 4 2 4 3 3 3 3 5% 9% 57%	6450
	21st to end	Day	7% 4 2 6% 4 5% 5% 4 7% 10% 47%	6662
August	1st to 10th	Day	13% 6% 2 6% 4 4 4 4 6% 7% 44%	4234
	11th to 20th	Day	12% 6% 2 6% 5% 5% 5% 4 7% 9% 41%	4171
	21st to end	Day	9% 5% 2 5% 4 4 4 3 6% 7% 50%	4554
September	1st to 10th	Day	10% 5% 2 6% 3 4 4 4 5% 7% 50%	2400
	11th to 20th	Day	11% 5% 2 6% 4 4 6% 3 6% 7% 45%	2295
	21st to end	Day	15% 6% 2 4 3 3 3 3 5% 7% 48%	2150
October	1st to 10th	Day	16% 7% 3 6% 4 4 3 3 5% 7% 43%	2000
	11th to 20th	Day	15% 9% 2 6% 4 3 4 4 5% 7% 41%	2000
	21st to end	Day	18% 11% 4 7% 4 3 4 3 4 7% 37%	2200
November	1st to 10th	Day	13% 11% 3 8% 4 4 5% 3 6% 7% 36%	1691
	11th to 20th	Day	9% 12% 6% 12% 6% 5% 4 3 5% 6% 32%	1680
	21st to end	Day	13% 10% 4 8% 6% 5% 5% 4 5% 8% 32%	1680
December	1st to 10th	Day	6% 10% 4 12% 9% 9% 6% 6% 6% 6% 25%	2690
	11th to 20th	Day	9% 14% 6% 11% 6% 6% 6% 3 5% 6% 28%	3088
	21st to end	Day	19% 18% 6% 20% 5% 3 3 2 4 5% 16%	3980
January	1st to 10th	Night	8% 10% 5% 15% 7% 6% 5% 4 5% 6% 28%	8410
	11th to 20th	Night	5% 11% 4 11% 8% 7% 11% 7% 7% 5% 23%	8040
	21st to end	Night	4 12% 6% 8% 5% 5% 5% 4 6% 6% 38%	8402
February	1st to 10th	Night	7% 11% 5% 8% 6% 6% 5% 4 5% 6% 35%	2730
	11th to 20th	Night	6% 9% 3 8% 5% 5% 6% 4 6% 8% 40%	2663
	21st to end	Night	10% 9% 3 8% 5% 5% 5% 4 6% 8% 37%	2243
March	1st to 10th	Night	10% 6% 2 6% 4 4 4 3 5% 7% 49%	5031
	11th to 20th	Night	10% 7% 2 7% 4 4 4 4 7% 9% 42%	5090
	21st to end	Night	24% 11% 3 9% 5% 4 3 3 4 5% 29%	5588
April	1st to 10th	Night	15% 9% 3 7% 5% 4 4 4 5% 6% 40%	2125
	11th to 20th	Night	18% 11% 3 7% 4 3 3 3 6% 5% 37%	1947
	21st to end	Night	20% 10% 3 6% 4 4 3 3 4 6% 37%	1800
May	1st to 10th	Night	11% 5% 2 5% 3 3 3 3 4 5% 55%	3943
	11th to 20th	Night	15% 7% 2 4 3 3 4 3 5% 7% 48%	3596
	21st to end	Night	17% 8% 3 7% 3 4 4 3 5% 7% 39%	3942
June	1st to 10th	Night	11% 4 2 4 4 4 4 4 6% 9% 50%	1600
	11th to 20th	Night	10% 4 2 6% 4 4 4 4 7% 8% 47%	1405
	21st to end	Night	10% 3 1 4 3 3 4 4 7% 6% 55%	1400
July	1st to 10th	Night	8% 3 2 4 4 4 5% 4 6% 10% 50%	3178
	11th to 20th	Night	5% 3 1 5% 4 4 3 4 6% 8% 57%	3524
	21st to end	Night	9% 5% 2 5% 4 4 4 4 6% 7% 50%	4192
August	1st to 10th	Night	12% 6% 2 5% 4 4 4 3 5% 6% 49%	2926
	11th to 20th	Night	13% 5% 2 5% 3 4 4 3 5% 7% 50%	2888
	21st to end	Night	8% 4 2 6% 4 3 4 3 6% 7% 53%	3350
September	1st to 10th	Night	7% 4 2 5% 3 3 4 3 6% 8% 56%	2000
	11th to 20th	Night	9% 5% 1 4 3 4 3 3 6% 7% 54%	2102
	21st to end	Night	10% 5% 2 5% 3 2 3 3 5% 6% 56%	2229
October	1st to 10th	Night	14% 6% 2 5% 3 3 3 3 4 7% 51%	2400
	11th to 20th	Night	15% 9% 3 5% 3 4 4 3 4 7% 43%	2400
	21st to end	Night	17% 11% 3 6% 4 3 3 3 5% 6% 40%	2640
November	1st to 10th	Night	12% 7% 3 6% 5% 4 4 4 6% 7% 42%	2823
	11th to 20th	Night	12% 11% 5% 10% 5% 4 3 3 4 5% 37%	2940
	21st to end	Night	12% 10% 3 9% 5% 4 4 3 5% 6% 38%	2940
December	1st to 10th	Night	6% 7% 4 12% 8% 6% 5% 5% 6% 8% 32%	4720
	11th to 20th	Night	10% 13% 6% 13% 7% 6% 5% 4 5% 6% 26%	5339
	21st to end	Night	19% 16% 5% 17% 6% 4 4 3 4 4 18%	7178

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	66% 4 10% 12% 7%	4442
	11th to 20th	Day	56% 4 11% 20% 8%	4948
	21st to end	Day	48% 5% 12% 23% 10%	5812
February	1st to 10th	Day	52% 6% 13% 20% 8% 1	1890
	11th to 20th	Day	49% 6% 14% 22% 8% 1	1853
	21st to end	Day	48% 7% 13% 21% 11%	1578
March	1st to 10th	Day	40% 5% 16% 26% 10% 2	5046
	11th to 20th	Day	41% 4 14% 29% 10% 1	5090
	21st to end	Day	60% 5% 11% 19% 6%	5585
April	1st to 10th	Day	48% 5% 11% 23% 11% 1	2494
	11th to 20th	Day	52% 5% 13% 18% 11% 2	2533
	21st to end	Day	52% 6% 12% 20% 10% 1	2600
May	1st to 10th	Day	34% 6% 13% 29% 17% 1	6010
	11th to 20th	Day	41% 5% 8% 23% 16% 7%	6323
	21st to end	Day	43% 6% 11% 30% 9% 1	6949
June	1st to 10th	Day	34% 8% 16% 29% 12% 1	2800
	11th to 20th	Day	43% 8% 14% 20% 14% 1	2990
	21st to end	Day	34% 9% 18% 27% 11% 1	3000
July	1st to 10th	Day	33% 4 20% 32% 10%	6726
	11th to 20th	Day	27% 3 16% 37% 15% 1	6372
	21st to end	Day	34% 4 17% 31% 14% 1	6473
August	1st to 10th	Day	39% 5% 13% 29% 12% 2	4220
	11th to 20th	Day	40% 5% 14% 32% 8%	4210
	21st to end	Day	34% 4 19% 29% 12% 1	4553
September	1st to 10th	Day	33% 6% 14% 35% 12%	2400
	11th to 20th	Day	37% 7% 17% 29% 9% 1	2295
	21st to end	Day	36% 5% 11% 34% 13% 1	2150
October	1st to 10th	Day	32% 3 9% 33% 23% 1	3260
	11th to 20th	Day	38% 4 12% 23% 21% 1	3240
	21st to end	Day	45% 2 15% 28% 9%	3538
November	1st to 10th	Day	46% 6% 14% 19% 12% 2	1691
	11th to 20th	Day	52% 6% 12% 18% 10% 1	1680
	21st to end	Day	49% 6% 15% 22% 7% 1	1680
December	1st to 10th	Day	58% 6% 14% 17% 5%	2690
	11th to 20th	Day	58% 3 15% 17% 6%	3085
	21st to end	Day	73% 3 9% 10% 5%	3980
January	1st to 10th	Night	57% 3 14% 18% 7%	8411
	11th to 20th	Night	59% 5% 9% 17% 10%	8040
	21st to end	Night	46% 3 11% 29% 10%	8402
February	1st to 10th	Night	49% 5% 14% 20% 11% 1	2730
	11th to 20th	Night	42% 6% 15% 25% 11% 2	2664
	21st to end	Night	45% 6% 14% 21% 13% 2	2243
March	1st to 10th	Night	35% 4 13% 31% 15% 2	5031
	11th to 20th	Night	36% 5% 16% 30% 13%	5090
	21st to end	Night	59% 3 9% 19% 9% 1	5588
April	1st to 10th	Night	45% 5% 12% 26% 11% 1	2125
	11th to 20th	Night	47% 5% 9% 22% 15% 2	1947
	21st to end	Night	49% 6% 10% 20% 14% 2	1800
May	1st to 10th	Night	32% 5% 12% 30% 19% 2	3970
	11th to 20th	Night	36% 5% 10% 21% 20% 8%	3597
	21st to end	Night	44% 5% 11% 27% 12% 1	3950
June	1st to 10th	Night	30% 7% 16% 30% 15% 2	1600
	11th to 20th	Night	33% 7% 16% 25% 17% 3	1405
	21st to end	Night	27% 8% 15% 30% 17% 3	1400
July	1st to 10th	Night	31% 4 20% 28% 16% 1	3145
	11th to 20th	Night	26% 2 16% 39% 15% 2	3482
	21st to end	Night	34% 4 16% 31% 12% 2	4071
August	1st to 10th	Night	37% 4 14% 26% 14% 5%	2916
	11th to 20th	Night	35% 5% 15% 33% 12% 1	2915
	21st to end	Night	31% 5% 18% 31% 14% 2	3350
September	1st to 10th	Night	27% 7% 15% 33% 18% 1	2000
	11th to 20th	Night	30% 6% 17% 30% 17%	2102
	21st to end	Night	30% 5% 12% 34% 17% 2	2229
October	1st to 10th	Night	23% 3 6% 37% 26% 5%	3920
	11th to 20th	Night	33% 3 11% 28% 22% 3	3899
	21st to end	Night	43% 4 12% 29% 12% 1	4252
November	1st to 10th	Night	40% 6% 15% 25% 13% 2	2823
	11th to 20th	Night	50% 5% 12% 19% 13% 1	2940
	21st to end	Night	47% 6% 17% 23% 7% 1	2940
December	1st to 10th	Night	50% 4 19% 21% 6%	4720
	11th to 20th	Night	59% 6% 10% 19% 5% 1	5341
	21st to end	Night	70% 5% 8% 14% 4	7178

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	14% 9% 35% 26% 12% 2	330
	11th to 20th	Day	15% 9% 40% 32% 4 1	330
	21st to end	Day	13% 11% 41% 24% 9% 2	363
February	1st to 10th	Day	15% 13% 40% 28% 3 1	330
	11th to 20th	Day	14% 15% 35% 27% 8% 1	330
	21st to end	Day	16% 10% 44% 25% 5%	273
March	1st to 10th	Day	18% 11% 41% 25% 4 1	330
	11th to 20th	Day	18% 11% 40% 23% 7% 1	330
	21st to end	Day	27% 12% 29% 22% 9% 2	363
April	1st to 10th	Day	25% 14% 34% 23% 5%	514
	11th to 20th	Day	25% 14% 29% 21% 9% 1	603
	21st to end	Day	26% 11% 34% 19% 10% 1	700
May	1st to 10th	Day	20% 10% 34% 25% 10% 2	703
	11th to 20th	Day	20% 10% 28% 26% 14% 3	725
	21st to end	Day	19% 7% 30% 29% 12% 3	789
June	1st to 10th	Day	11% 8% 27% 30% 21% 4	730
	11th to 20th	Day	18% 7% 33% 30% 10% 2	730
	21st to end	Day	13% 7% 33% 28% 15% 4	730
July	1st to 10th	Day	8% 4 22% 35% 22% 8%	721
	11th to 20th	Day	9% 6% 27% 30% 22% 6%	718
	21st to end	Day	7% 4 24% 38% 23% 5%	794
August	1st to 10th	Day	13% 3 23% 33% 24% 4	726
	11th to 20th	Day	14% 5% 22% 31% 23% 5%	715
	21st to end	Day	8% 5% 28% 33% 21% 5%	734
September	1st to 10th	Day	11% 9% 28% 33% 13% 5%	530
	11th to 20th	Day	12% 5% 28% 33% 18% 5%	425
	21st to end	Day	18% 10% 27% 23% 15% 6%	330
October	1st to 10th	Day	17% 11% 31% 23% 14% 4	330
	11th to 20th	Day	16% 18% 38% 20% 7% 1	330
	21st to end	Day	26% 12% 36% 18% 7% 1	363
November	1st to 10th	Day	18% 15% 34% 24% 8% 2	330
	11th to 20th	Day	15% 16% 42% 23% 4	330
	21st to end	Day	20% 15% 39% 21% 5%	330
December	1st to 10th	Day	15% 9% 43% 23% 9%	330
	11th to 20th	Day	17% 15% 37% 27% 4	330
	21st to end	Day	28% 11% 38% 19% 4	363
January	1st to 10th	Night	11% 11% 39% 30% 8% 1	1050
	11th to 20th	Night	14% 12% 38% 30% 6% 1	1050
	21st to end	Night	15% 12% 37% 30% 6%	1155
February	1st to 10th	Night	13% 11% 40% 28% 8% 1	1050
	11th to 20th	Night	10% 11% 43% 29% 5% 1	1029
	21st to end	Night	15% 11% 37% 28% 8% 1	859
March	1st to 10th	Night	16% 10% 38% 26% 9% 1	632
	11th to 20th	Night	18% 11% 37% 29% 4 1	630
	21st to end	Night	22% 10% 32% 25% 9% 2	693
April	1st to 10th	Night	20% 8% 38% 26% 7%	630
	11th to 20th	Night	21% 14% 29% 28% 8% 1	611
	21st to end	Night	25% 10% 31% 27% 7% 1	600
May	1st to 10th	Night	18% 10% 33% 30% 9% 1	600
	11th to 20th	Night	17% 8% 34% 30% 9% 1	591
	21st to end	Night	18% 7% 26% 38% 11% 1	650
June	1st to 10th	Night	13% 5% 29% 37% 16%	600
	11th to 20th	Night	12% 3 35% 41% 9%	600
	21st to end	Night	10% 4 27% 43% 16%	600
July	1st to 10th	Night	6% 2 23% 42% 25% 2	585
	11th to 20th	Night	6% 2 26% 49% 17% 1	582
	21st to end	Night	6% 2 22% 47% 21% 2	657
August	1st to 10th	Night	9% 4 17% 46% 22% 2	597
	11th to 20th	Night	11% 3 19% 40% 24% 3	594
	21st to end	Night	7% 3 25% 39% 23% 2	660
September	1st to 10th	Night	9% 5% 26% 39% 18% 2	600
	11th to 20th	Night	11% 6% 30% 33% 18% 2	600
	21st to end	Night	11% 9% 32% 31% 14% 2	629
October	1st to 10th	Night	18% 7% 32% 30% 12% 1	800
	11th to 20th	Night	20% 11% 35% 26% 8% 1	800
	21st to end	Night	23% 12% 31% 28% 6%	880
November	1st to 10th	Night	16% 10% 36% 30% 8%	1012
	11th to 20th	Night	16% 14% 37% 25% 7% 1	1050
	21st to end	Night	17% 13% 38% 25% 7%	1050
December	1st to 10th	Night	14% 10% 38% 29% 8%	1050
	11th to 20th	Night	19% 11% 37% 26% 6%	1050
	21st to end	Night	24% 11% 34% 26% 5% 1	1155

Page generated at 2026-04-14 01:44:29. Version ac07

Copyright © 2026 Attilla Danko.