Geraldton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Geraldton clear sky chart from 2005-11-06 to 2025-12-03.

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% 12% 4 9% 6% 5% 5% 4 5% 7% 30%	127417
	Night	13% 13% 5% 11% 7% 6% 5% 4 5% 6% 26%	123552
Transparency	Day	53% 6% 11% 20% 9% 1	130812
	Night	58% 6% 11% 18% 7% 1	128243
Seeing	Day	22% 15% 33% 20% 8% 2	17183
	Night	20% 12% 33% 25% 8% 1	26563

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	7% 16% 5% 16% 12% 12% 7% 3 6% 4 13%	3322
	11th to 20th	Day	6% 11% 6% 16% 9% 9% 7% 8% 9% 7% 13%	3589
	21st to end	Day	10% 16% 10% 16% 7% 6% 7% 5% 5% 7% 12%	3982
February	1st to 10th	Day	6% 14% 5% 10% 8% 8% 9% 6% 7% 7% 20%	1600
	11th to 20th	Day	6% 11% 6% 14% 10% 7% 5% 5% 7% 7% 22%	1789
	21st to end	Day	6% 13% 5% 15% 8% 6% 6% 5% 5% 6% 24%	1650
March	1st to 10th	Day	14% 16% 4 10% 6% 6% 5% 4 4 4 27%	4478
	11th to 20th	Day	9% 17% 6% 12% 8% 7% 5% 3 4 4 24%	4676
	21st to end	Day	15% 18% 5% 11% 5% 5% 4 3 3 5% 27%	5918
April	1st to 10th	Day	13% 14% 5% 9% 6% 5% 4 4 5% 5% 30%	2400
	11th to 20th	Day	18% 15% 4 8% 5% 4 3 3 5% 5% 29%	2492
	21st to end	Day	16% 13% 4 7% 4 4 3 3 5% 6% 34%	2600
May	1st to 10th	Day	17% 10% 3 7% 4 3 3 3 4 6% 39%	6343
	11th to 20th	Day	19% 9% 3 6% 4 4 3 3 5% 6% 38%	6319
	21st to end	Day	17% 11% 2 4 4 3 4 3 5% 7% 38%	7450
June	1st to 10th	Day	22% 9% 2 7% 6% 5% 4 4 6% 5% 31%	3000
	11th to 20th	Day	14% 8% 3 7% 5% 4 4 4 6% 7% 37%	3000
	21st to end	Day	18% 7% 3 7% 5% 4 4 4 6% 8% 35%	3000
July	1st to 10th	Day	14% 6% 2 6% 4 4 4 3 6% 8% 43%	6819
	11th to 20th	Day	12% 5% 2 6% 4 4 5% 4 7% 10% 42%	6504
	21st to end	Day	11% 6% 2 6% 5% 4 5% 4 8% 10% 38%	6926
August	1st to 10th	Day	18% 6% 2 6% 4 5% 5% 4 6% 8% 35%	4563
	11th to 20th	Day	12% 4 2 6% 3 4 5% 3 6% 9% 46%	4367
	21st to end	Day	14% 7% 2 6% 4 5% 5% 4 5% 8% 40%	4520
September	1st to 10th	Day	17% 7% 2 8% 5% 5% 4 3 4 7% 37%	2400
	11th to 20th	Day	23% 10% 3 5% 3 4 5% 4 5% 7% 32%	2265
	21st to end	Day	19% 12% 3 7% 5% 3 4 3 4 7% 32%	2200
October	1st to 10th	Day	19% 16% 3 8% 5% 3 4 4 4 7% 27%	2120
	11th to 20th	Day	21% 19% 4 9% 5% 5% 3 4 6% 6% 18%	1821
	21st to end	Day	20% 22% 6% 9% 5% 5% 5% 3 4 5% 16%	1980
November	1st to 10th	Day	17% 16% 7% 13% 6% 5% 5% 4 4 5% 17%	1852
	11th to 20th	Day	16% 21% 8% 15% 9% 6% 4 2 4 3 11%	1611
	21st to end	Day	16% 20% 8% 17% 9% 6% 4 2 4 4 11%	1470
December	1st to 10th	Day	8% 21% 8% 17% 16% 8% 5% 3 3 3 8%	2294
	11th to 20th	Day	8% 14% 6% 14% 10% 10% 7% 7% 7% 5% 11%	2621
	21st to end	Day	16% 23% 6% 15% 7% 6% 4 3 5% 4 11%	3476
January	1st to 10th	Night	7% 14% 5% 15% 10% 11% 8% 6% 6% 5% 14%	6642
	11th to 20th	Night	5% 13% 7% 18% 11% 10% 8% 6% 9% 4 10%	6316
	21st to end	Night	7% 13% 7% 15% 8% 7% 8% 6% 6% 6% 16%	6996
February	1st to 10th	Night	7% 12% 5% 10% 7% 6% 8% 6% 8% 6% 23%	2800
	11th to 20th	Night	7% 12% 5% 11% 9% 9% 7% 5% 6% 7% 22%	2495
	21st to end	Night	7% 13% 6% 12% 7% 6% 7% 5% 7% 5% 25%	1980
March	1st to 10th	Night	11% 12% 4 13% 7% 6% 6% 4 5% 6% 27%	5362
	11th to 20th	Night	12% 15% 6% 12% 7% 5% 4 3 4 6% 26%	5269
	21st to end	Night	13% 15% 5% 10% 6% 6% 6% 3 4 5% 26%	5056
April	1st to 10th	Night	13% 14% 4 9% 6% 5% 5% 4 6% 5% 30%	2000
	11th to 20th	Night	18% 12% 3 8% 4 4 4 4 5% 7% 30%	1857
	21st to end	Night	18% 12% 3 6% 5% 3 4 3 5% 6% 36%	1800
May	1st to 10th	Night	18% 10% 3 6% 3 3 3 2 4 6% 41%	3615
	11th to 20th	Night	17% 8% 3 8% 4 4 4 3 5% 6% 36%	3596
	21st to end	Night	16% 12% 3 6% 4 4 3 3 5% 7% 38%	3447
June	1st to 10th	Night	16% 7% 2 7% 4 5% 5% 4 6% 8% 37%	1400
	11th to 20th	Night	16% 5% 2 5% 4 5% 5% 4 6% 7% 39%	1400
	21st to end	Night	16% 8% 3 6% 5% 4 4 4 5% 7% 38%	1400
July	1st to 10th	Night	10% 5% 2 7% 4 6% 6% 4 6% 9% 42%	3160
	11th to 20th	Night	13% 8% 2 6% 4 3 4 4 6% 9% 40%	3472
	21st to end	Night	13% 7% 3 6% 4 4 4 4 5% 9% 40%	3948
August	1st to 10th	Night	15% 6% 2 6% 4 4 3 4 5% 8% 42%	2597
	11th to 20th	Night	11% 6% 2 6% 3 3 3 3 4 7% 53%	2688
	21st to end	Night	12% 6% 2 6% 4 3 4 4 5% 7% 48%	3374
September	1st to 10th	Night	15% 7% 2 6% 4 4 4 3 6% 6% 43%	2000
	11th to 20th	Night	18% 9% 3 5% 4 3 4 3 5% 6% 40%	2115
	21st to end	Night	23% 9% 3 6% 3 3 4 3 6% 6% 34%	2200
October	1st to 10th	Night	19% 15% 3 6% 4 4 3 3 4 7% 32%	2277
	11th to 20th	Night	20% 19% 5% 9% 4 4 4 2 5% 6% 22%	2578
	21st to end	Night	20% 17% 5% 10% 5% 5% 5% 4 5% 5% 18%	2860
November	1st to 10th	Night	17% 19% 6% 12% 7% 4 4 3 5% 5% 18%	2666
	11th to 20th	Night	17% 18% 6% 14% 8% 5% 6% 4 5% 5% 14%	3007
	21st to end	Night	16% 19% 6% 17% 8% 6% 4 3 4 4 12%	3150
December	1st to 10th	Night	8% 22% 8% 22% 12% 7% 4 3 3 3 7%	4941
	11th to 20th	Night	10% 16% 6% 15% 9% 8% 7% 5% 4 4 16%	5586
	21st to end	Night	16% 24% 7% 13% 8% 5% 4 3 4 4 12%	7502

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	74% 4 6% 9% 4 3	3323
	11th to 20th	Day	65% 5% 8% 19% 3	3620
	21st to end	Day	72% 5% 6% 11% 5% 2	3982
February	1st to 10th	Day	60% 6% 9% 17% 6% 2	1600
	11th to 20th	Day	59% 5% 10% 19% 7%	1798
	21st to end	Day	59% 4 9% 16% 11% 2	1650
March	1st to 10th	Day	61% 4 6% 13% 14% 2	4480
	11th to 20th	Day	64% 5% 6% 15% 10% 1	4676
	21st to end	Day	61% 3 6% 19% 10% 1	5918
April	1st to 10th	Day	55% 5% 8% 20% 11% 2	2400
	11th to 20th	Day	56% 5% 7% 21% 10% 1	2492
	21st to end	Day	51% 5% 10% 17% 16% 2	2600
May	1st to 10th	Day	47% 4 8% 21% 18% 2	6352
	11th to 20th	Day	47% 6% 8% 20% 17% 3	6323
	21st to end	Day	44% 7% 12% 19% 16% 3	7450
June	1st to 10th	Day	52% 6% 10% 18% 12% 1	3000
	11th to 20th	Day	44% 7% 11% 25% 13% 1	3000
	21st to end	Day	46% 7% 13% 25% 9%	3000
July	1st to 10th	Day	38% 7% 13% 34% 9%	6746
	11th to 20th	Day	35% 8% 19% 28% 8%	6425
	21st to end	Day	38% 8% 17% 29% 8%	6728
August	1st to 10th	Day	44% 8% 15% 25% 7%	4548
	11th to 20th	Day	34% 7% 18% 33% 8%	4409
	21st to end	Day	41% 7% 12% 28% 11%	4519
September	1st to 10th	Day	47% 7% 13% 24% 9%	2400
	11th to 20th	Day	50% 8% 18% 19% 4	2265
	21st to end	Day	53% 6% 13% 21% 8%	2200
October	1st to 10th	Day	52% 7% 15% 16% 10%	3458
	11th to 20th	Day	57% 6% 13% 23% 2	2946
	21st to end	Day	64% 7% 15% 14% 1	3180
November	1st to 10th	Day	68% 6% 11% 12% 3	1852
	11th to 20th	Day	78% 5% 8% 7% 2	1611
	21st to end	Day	79% 4 8% 6% 3	1470
December	1st to 10th	Day	83% 4 7% 5% 2	2294
	11th to 20th	Day	70% 6% 8% 11% 4	2621
	21st to end	Day	76% 4 5% 13% 2	3476
January	1st to 10th	Night	71% 5% 8% 9% 4 3	6642
	11th to 20th	Night	71% 4 8% 14% 3	6360
	21st to end	Night	65% 6% 7% 15% 6%	6996
February	1st to 10th	Night	56% 6% 11% 18% 9%	2800
	11th to 20th	Night	59% 5% 10% 18% 7%	2496
	21st to end	Night	58% 5% 11% 16% 9% 1	1980
March	1st to 10th	Night	58% 5% 8% 14% 11% 3	5373
	11th to 20th	Night	59% 5% 8% 20% 6% 1	5270
	21st to end	Night	61% 4 7% 16% 11% 1	5056
April	1st to 10th	Night	54% 6% 8% 18% 12% 2	2000
	11th to 20th	Night	53% 5% 9% 20% 12% 2	1857
	21st to end	Night	48% 5% 10% 19% 14% 3	1800
May	1st to 10th	Night	44% 5% 9% 28% 11% 4	3622
	11th to 20th	Night	47% 7% 10% 19% 15% 1	3597
	21st to end	Night	46% 7% 11% 20% 15% 2	3448
June	1st to 10th	Night	43% 8% 11% 27% 11%	1400
	11th to 20th	Night	41% 7% 12% 24% 15% 1	1400
	21st to end	Night	44% 8% 14% 23% 10% 1	1400
July	1st to 10th	Night	37% 9% 17% 28% 9%	3125
	11th to 20th	Night	39% 8% 20% 26% 6% 1	3428
	21st to end	Night	40% 7% 14% 29% 9%	3832
August	1st to 10th	Night	38% 8% 16% 31% 7%	2588
	11th to 20th	Night	32% 6% 18% 35% 8%	2712
	21st to end	Night	35% 7% 18% 27% 13%	3374
September	1st to 10th	Night	42% 7% 14% 28% 8% 1	2000
	11th to 20th	Night	45% 7% 21% 23% 5%	2115
	21st to end	Night	50% 7% 14% 21% 9%	2200
October	1st to 10th	Night	42% 6% 17% 23% 12%	3719
	11th to 20th	Night	56% 6% 11% 21% 5%	4192
	21st to end	Night	64% 7% 16% 11% 2	4610
November	1st to 10th	Night	67% 7% 10% 12% 4	2666
	11th to 20th	Night	72% 6% 9% 10% 3	3007
	21st to end	Night	76% 5% 9% 7% 3	3150
December	1st to 10th	Night	83% 4 6% 5% 2	4941
	11th to 20th	Night	70% 6% 7% 13% 4	5585
	21st to end	Night	77% 4 5% 11% 3	7502

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	18% 13% 40% 23% 6%	237
	11th to 20th	Day	13% 14% 34% 26% 11% 2	300
	21st to end	Day	16% 19% 37% 20% 7% 1	330
February	1st to 10th	Day	17% 19% 39% 19% 5% 1	300
	11th to 20th	Day	11% 22% 44% 17% 3 2	300
	21st to end	Day	18% 27% 43% 12% 1	249
March	1st to 10th	Day	21% 17% 38% 19% 5%	300
	11th to 20th	Day	22% 19% 40% 13% 4 2	365
	21st to end	Day	20% 17% 36% 18% 5% 3	550
April	1st to 10th	Day	21% 18% 33% 21% 7% 1	500
	11th to 20th	Day	29% 19% 24% 19% 8% 1	492
	21st to end	Day	25% 14% 31% 20% 7% 2	500
May	1st to 10th	Day	26% 15% 33% 19% 6% 2	698
	11th to 20th	Day	26% 14% 34% 16% 8% 1	725
	21st to end	Day	26% 17% 30% 18% 7% 2	789
June	1st to 10th	Day	27% 12% 34% 19% 6% 2	730
	11th to 20th	Day	19% 15% 36% 20% 8% 2	730
	21st to end	Day	21% 14% 34% 20% 8% 3	730
July	1st to 10th	Day	16% 12% 34% 23% 12% 3	721
	11th to 20th	Day	13% 15% 33% 25% 11% 2	718
	21st to end	Day	14% 10% 34% 26% 12% 4	794
August	1st to 10th	Day	17% 13% 33% 25% 10% 2	726
	11th to 20th	Day	16% 11% 27% 27% 13% 6%	638
	21st to end	Day	21% 12% 30% 22% 12% 3	583
September	1st to 10th	Day	23% 12% 30% 22% 10% 3	530
	11th to 20th	Day	27% 13% 28% 18% 13% 2	530
	21st to end	Day	27% 12% 26% 23% 11% 1	530
October	1st to 10th	Day	29% 17% 31% 15% 7% 2	450
	11th to 20th	Day	29% 19% 34% 14% 4	330
	21st to end	Day	31% 18% 35% 12% 4 1	363
November	1st to 10th	Day	27% 19% 34% 16% 4	330
	11th to 20th	Day	27% 20% 34% 14% 4 1	271
	21st to end	Day	28% 21% 35% 13% 2	220
December	1st to 10th	Day	20% 19% 31% 20% 6% 4	204
	11th to 20th	Day	24% 12% 41% 18% 5% 1	200
	21st to end	Day	20% 18% 32% 20% 6% 3	220
January	1st to 10th	Night	18% 14% 40% 22% 6%	1000
	11th to 20th	Night	17% 14% 34% 27% 7% 1	1000
	21st to end	Night	16% 12% 37% 26% 8% 1	1100
February	1st to 10th	Night	13% 14% 38% 27% 7% 1	1000
	11th to 20th	Night	14% 14% 38% 24% 9% 1	887
	21st to end	Night	12% 13% 40% 25% 8% 1	660
March	1st to 10th	Night	12% 15% 36% 26% 9% 1	800
	11th to 20th	Night	18% 16% 37% 21% 7% 1	800
	21st to end	Night	18% 15% 31% 25% 10% 2	702
April	1st to 10th	Night	22% 11% 34% 24% 7% 2	600
	11th to 20th	Night	23% 13% 30% 26% 8% 1	593
	21st to end	Night	21% 11% 31% 28% 9% 1	600
May	1st to 10th	Night	26% 9% 29% 28% 8%	600
	11th to 20th	Night	23% 11% 30% 28% 6% 1	591
	21st to end	Night	25% 10% 32% 28% 5%	433
June	1st to 10th	Night	19% 7% 38% 27% 10%	400
	11th to 20th	Night	20% 10% 32% 31% 7% 1	400
	21st to end	Night	19% 9% 34% 29% 9% 1	400
July	1st to 10th	Night	14% 9% 32% 33% 11%	390
	11th to 20th	Night	14% 7% 36% 32% 9% 1	516
	21st to end	Night	15% 6% 30% 32% 15% 1	657
August	1st to 10th	Night	14% 7% 30% 37% 11% 1	597
	11th to 20th	Night	13% 7% 29% 30% 21% 1	594
	21st to end	Night	15% 7% 37% 26% 14% 1	660
September	1st to 10th	Night	19% 7% 30% 31% 11% 1	600
	11th to 20th	Night	24% 8% 35% 25% 8%	715
	21st to end	Night	29% 11% 23% 24% 12% 1	800
October	1st to 10th	Night	27% 15% 27% 22% 7% 1	800
	11th to 20th	Night	30% 13% 29% 21% 5% 1	800
	21st to end	Night	27% 11% 30% 21% 10%	880
November	1st to 10th	Night	27% 15% 30% 21% 6%	820
	11th to 20th	Night	27% 16% 32% 19% 5% 1	1007
	21st to end	Night	27% 16% 33% 20% 5%	1050
December	1st to 10th	Night	18% 18% 34% 19% 9% 1	1011
	11th to 20th	Night	19% 13% 35% 23% 8% 2	1000
	21st to end	Night	25% 13% 31% 20% 9% 2	1100

Page generated at 2025-11-30 01:00:57. Version ac07

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