Goudie Road
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Goudie Road clear sky chart from 2005-11-06 to 2025-03-27.

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	10% 13% 4 9% 5% 5% 5% 4 5% 6% 34%	113067
	Night	9% 13% 5% 10% 5% 5% 5% 4 6% 6% 33%	114925
Transparency	Day	48% 8% 14% 18% 10% 3	112829
	Night	48% 9% 15% 18% 9% 2	114809
Seeing	Day	17% 15% 26% 24% 14% 4	15748
	Night	17% 11% 23% 29% 17% 3	24406

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	8% 19% 9% 16% 9% 6% 5% 3 5% 5% 15%	3639
	11th to 20th	Day	6% 14% 6% 14% 6% 4 4 3 6% 8% 29%	3616
	21st to end	Day	8% 20% 6% 10% 6% 5% 6% 3 5% 4 26%	4004
February	1st to 10th	Day	13% 19% 6% 13% 6% 4 4 4 5% 4 22%	1615
	11th to 20th	Day	8% 18% 9% 15% 6% 5% 5% 3 4 5% 22%	1755
	21st to end	Day	8% 22% 8% 15% 7% 7% 5% 3 5% 5% 17%	1650
March	1st to 10th	Day	7% 16% 9% 19% 7% 6% 5% 3 5% 5% 19%	3238
	11th to 20th	Day	7% 16% 5% 8% 5% 4 4 3 5% 6% 38%	3392
	21st to end	Day	8% 25% 7% 11% 6% 5% 5% 4 4 5% 20%	4229
April	1st to 10th	Day	11% 20% 6% 12% 7% 6% 5% 4 5% 5% 18%	2280
	11th to 20th	Day	11% 17% 6% 11% 7% 6% 5% 3 6% 4 25%	2290
	21st to end	Day	12% 18% 5% 11% 6% 5% 5% 3 5% 6% 24%	2579
May	1st to 10th	Day	8% 16% 4 8% 5% 5% 5% 4 5% 7% 33%	4420
	11th to 20th	Day	12% 15% 3 8% 6% 5% 5% 4 7% 8% 27%	4377
	21st to end	Day	18% 14% 5% 10% 7% 6% 6% 4 5% 6% 20%	4931
June	1st to 10th	Day	21% 11% 4 8% 6% 6% 4 3 4 6% 26%	2850
	11th to 20th	Day	22% 11% 4 9% 6% 5% 5% 4 5% 5% 23%	3013
	21st to end	Day	13% 7% 3 7% 7% 6% 5% 4 6% 6% 36%	3040
July	1st to 10th	Day	6% 4 1 5% 3 4 3 4 5% 6% 59%	4879
	11th to 20th	Day	4 3 1 3 3 2 3 3 3 5% 69%	4420
	21st to end	Day	5% 3 1 4 3 3 4 3 6% 8% 60%	4790
August	1st to 10th	Day	3 3 1 4 3 3 5% 5% 7% 8% 59%	4401
	11th to 20th	Day	4 3 2 5% 5% 5% 5% 4 7% 8% 51%	4330
	21st to end	Day	11% 6% 2 5% 4 4 5% 4 7% 7% 45%	4225
September	1st to 10th	Day	11% 6% 2 5% 3 4 4 3 6% 6% 51%	2280
	11th to 20th	Day	12% 8% 2 7% 5% 5% 5% 3 5% 6% 43%	2242
	21st to end	Day	16% 10% 2 6% 4 4 3 4 5% 7% 38%	2090
October	1st to 10th	Day	12% 10% 3 9% 5% 5% 4 3 4 7% 38%	3187
	11th to 20th	Day	16% 14% 4 9% 4 5% 4 3 5% 6% 31%	3034
	21st to end	Day	14% 13% 5% 10% 6% 5% 4 3 4 5% 30%	3101
November	1st to 10th	Day	18% 19% 5% 11% 6% 5% 5% 4 4 6% 18%	1691
	11th to 20th	Day	14% 20% 6% 11% 6% 5% 4 4 5% 5% 20%	1600
	21st to end	Day	14% 18% 4 10% 4 5% 5% 5% 7% 5% 22%	1429
December	1st to 10th	Day	7% 12% 4 11% 6% 5% 5% 4 7% 7% 32%	2290
	11th to 20th	Day	7% 19% 8% 15% 7% 6% 5% 4 6% 5% 19%	2642
	21st to end	Day	7% 17% 7% 14% 7% 6% 6% 4 6% 7% 18%	3518
January	1st to 10th	Night	10% 18% 8% 18% 7% 6% 6% 3 5% 4 15%	6329
	11th to 20th	Night	6% 12% 5% 12% 5% 5% 5% 4 9% 8% 31%	6282
	21st to end	Night	8% 17% 6% 11% 6% 5% 5% 4 5% 6% 27%	6952
February	1st to 10th	Night	12% 19% 6% 12% 6% 5% 5% 3 5% 5% 22%	2781
	11th to 20th	Night	8% 19% 7% 12% 5% 5% 4 3 4 5% 28%	2532
	21st to end	Night	7% 21% 7% 12% 7% 5% 4 4 4 5% 23%	1980
March	1st to 10th	Night	6% 13% 6% 13% 7% 6% 5% 5% 6% 7% 26%	3856
	11th to 20th	Night	6% 14% 3 8% 4 4 4 4 5% 7% 41%	3806
	21st to end	Night	9% 18% 5% 10% 6% 6% 6% 4 6% 5% 26%	3562
April	1st to 10th	Night	8% 15% 5% 9% 6% 5% 5% 4 6% 7% 30%	1900
	11th to 20th	Night	10% 14% 4 8% 7% 7% 5% 4 5% 6% 31%	1840
	21st to end	Night	10% 15% 4 8% 6% 5% 5% 4 5% 7% 33%	1599
May	1st to 10th	Night	8% 12% 3 7% 6% 5% 5% 4 6% 7% 39%	2540
	11th to 20th	Night	7% 12% 2 6% 5% 4 6% 5% 8% 10% 34%	2516
	21st to end	Night	12% 11% 3 8% 5% 6% 6% 5% 6% 6% 30%	2639
June	1st to 10th	Night	17% 10% 3 7% 4 5% 5% 4 7% 7% 31%	1330
	11th to 20th	Night	17% 8% 3 7% 6% 5% 4 4 7% 6% 33%	1161
	21st to end	Night	7% 5% 3 6% 4 6% 6% 4 6% 8% 44%	1140
July	1st to 10th	Night	4 4 1 4 3 3 3 3 5% 7% 63%	2075
	11th to 20th	Night	3 3 1 4 3 3 3 3 4 5% 68%	2540
	21st to end	Night	3 3 1 4 3 3 4 3 5% 7% 65%	2762
August	1st to 10th	Night	3 2 1 4 3 4 5% 5% 6% 8% 60%	2529
	11th to 20th	Night	4 3 1 5% 4 4 5% 3 7% 10% 55%	2497
	21st to end	Night	9% 8% 2 6% 5% 4 5% 4 6% 7% 46%	3449
September	1st to 10th	Night	7% 5% 2 6% 4 4 4 3 4 6% 55%	1900
	11th to 20th	Night	11% 8% 2 5% 5% 4 4 3 5% 5% 48%	1938
	21st to end	Night	13% 8% 3 7% 3 4 4 3 5% 8% 41%	2090
October	1st to 10th	Night	9% 10% 3 9% 6% 4 5% 4 5% 5% 41%	3790
	11th to 20th	Night	20% 10% 4 6% 4 3 3 3 6% 7% 35%	3900
	21st to end	Night	12% 15% 5% 11% 5% 4 4 3 4 4 32%	4457
November	1st to 10th	Night	17% 18% 5% 9% 5% 4 4 4 5% 6% 23%	2605
	11th to 20th	Night	15% 18% 6% 11% 6% 5% 4 4 4 5% 24%	2800
	21st to end	Night	12% 20% 5% 11% 6% 5% 4 5% 5% 6% 21%	2950
December	1st to 10th	Night	8% 10% 4 10% 6% 5% 5% 4 6% 7% 36%	4890
	11th to 20th	Night	9% 20% 7% 13% 7% 6% 5% 4 5% 5% 19%	5550
	21st to end	Night	8% 18% 7% 15% 7% 6% 5% 4 5% 5% 21%	7458

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% 10% 13% 8% 2	3639
	11th to 20th	Day	52% 7% 21% 13% 3 3	3640
	21st to end	Day	58% 11% 13% 11% 6%	4004
February	1st to 10th	Day	63% 9% 11% 10% 6% 2	1615
	11th to 20th	Day	63% 8% 11% 11% 6% 1	1764
	21st to end	Day	69% 8% 10% 10% 3	1650
March	1st to 10th	Day	61% 9% 11% 11% 7%	3238
	11th to 20th	Day	42% 8% 18% 27% 4	3392
	21st to end	Day	62% 9% 12% 9% 7%	4229
April	1st to 10th	Day	65% 10% 11% 10% 3	2280
	11th to 20th	Day	60% 7% 11% 14% 7% 1	2290
	21st to end	Day	58% 8% 13% 15% 5% 1	2579
May	1st to 10th	Day	44% 9% 15% 22% 11%	4420
	11th to 20th	Day	47% 10% 18% 20% 5%	4380
	21st to end	Day	59% 11% 14% 14% 2	4932
June	1st to 10th	Day	59% 7% 10% 14% 8% 3	2850
	11th to 20th	Day	61% 8% 10% 15% 6% 1	3013
	21st to end	Day	46% 9% 14% 19% 11% 2	3040
July	1st to 10th	Day	26% 6% 9% 18% 24% 17%	4804
	11th to 20th	Day	19% 4 8% 18% 34% 17%	4345
	21st to end	Day	22% 5% 14% 26% 23% 9%	4639
August	1st to 10th	Day	21% 7% 12% 29% 27% 4	4384
	11th to 20th	Day	28% 8% 19% 33% 11% 2	4372
	21st to end	Day	35% 8% 21% 23% 13% 1	4224
September	1st to 10th	Day	33% 6% 17% 27% 14% 4	2280
	11th to 20th	Day	41% 8% 12% 22% 15% 2	2242
	21st to end	Day	45% 8% 19% 18% 9% 1	2090
October	1st to 10th	Day	45% 6% 19% 24% 6%	3187
	11th to 20th	Day	55% 6% 10% 25% 5%	3034
	21st to end	Day	54% 7% 16% 18% 5%	3101
November	1st to 10th	Day	67% 8% 12% 9% 4	1691
	11th to 20th	Day	65% 9% 12% 10% 3 1	1600
	21st to end	Day	59% 12% 16% 9% 4	1429
December	1st to 10th	Day	49% 10% 24% 14% 4	2290
	11th to 20th	Day	64% 12% 11% 10% 3	2644
	21st to end	Day	61% 12% 14% 10% 2	3518
January	1st to 10th	Night	68% 11% 10% 9% 2	6329
	11th to 20th	Night	46% 8% 20% 15% 6% 4	6320
	21st to end	Night	57% 10% 12% 13% 8%	6952
February	1st to 10th	Night	62% 7% 12% 11% 6% 1	2781
	11th to 20th	Night	58% 8% 12% 14% 7% 1	2534
	21st to end	Night	60% 7% 13% 12% 7%	1980
March	1st to 10th	Night	50% 11% 16% 15% 8%	3856
	11th to 20th	Night	38% 9% 19% 27% 6%	3807
	21st to end	Night	52% 12% 16% 14% 7%	3562
April	1st to 10th	Night	49% 11% 20% 15% 5%	1900
	11th to 20th	Night	53% 9% 14% 15% 8% 1	1840
	21st to end	Night	49% 9% 14% 20% 9%	1599
May	1st to 10th	Night	40% 8% 15% 25% 12%	2540
	11th to 20th	Night	34% 12% 21% 26% 7%	2516
	21st to end	Night	43% 15% 17% 21% 3	2639
June	1st to 10th	Night	48% 9% 13% 17% 11% 2	1330
	11th to 20th	Night	47% 11% 14% 20% 8%	1161
	21st to end	Night	36% 10% 17% 26% 10% 2	1140
July	1st to 10th	Night	20% 5% 12% 26% 22% 16%	2041
	11th to 20th	Night	18% 5% 9% 18% 35% 15%	2492
	21st to end	Night	19% 4 13% 31% 22% 11%	2674
August	1st to 10th	Night	20% 5% 11% 33% 28% 4	2521
	11th to 20th	Night	22% 8% 23% 30% 14% 2	2521
	21st to end	Night	35% 6% 19% 26% 13% 1	3449
September	1st to 10th	Night	29% 7% 14% 29% 17% 4	1900
	11th to 20th	Night	36% 7% 14% 22% 18% 3	1938
	21st to end	Night	41% 9% 17% 22% 11% 1	2090
October	1st to 10th	Night	43% 7% 17% 26% 7%	3790
	11th to 20th	Night	48% 6% 11% 24% 11%	3900
	21st to end	Night	53% 7% 16% 19% 5%	4457
November	1st to 10th	Night	61% 9% 12% 12% 5%	2605
	11th to 20th	Night	64% 8% 12% 11% 5% 1	2800
	21st to end	Night	63% 10% 13% 8% 5%	2950
December	1st to 10th	Night	46% 11% 20% 19% 4	4890
	11th to 20th	Night	66% 11% 13% 9% 2	5547
	21st to end	Night	63% 11% 11% 12% 3	7458

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	19% 19% 32% 17% 9% 5%	200
	11th to 20th	Day	14% 23% 27% 22% 12% 3	200
	21st to end	Day	17% 17% 33% 22% 8% 3	220
February	1st to 10th	Day	21% 20% 31% 17% 9% 1	215
	11th to 20th	Day	19% 21% 29% 23% 6% 2	395
	21st to end	Day	18% 17% 34% 19% 10% 1	414
March	1st to 10th	Day	21% 22% 29% 19% 9% 1	500
	11th to 20th	Day	19% 23% 24% 19% 12% 3	500
	21st to end	Day	23% 22% 24% 17% 11% 2	531
April	1st to 10th	Day	20% 24% 28% 19% 8% 1	460
	11th to 20th	Day	21% 21% 24% 19% 11% 4	452
	21st to end	Day	17% 18% 32% 19% 10% 4	460
May	1st to 10th	Day	14% 18% 27% 26% 11% 4	463
	11th to 20th	Day	19% 11% 24% 23% 18% 4	488
	21st to end	Day	19% 12% 23% 23% 18% 5%	595
June	1st to 10th	Day	22% 12% 28% 24% 14% 2	680
	11th to 20th	Day	24% 15% 23% 22% 13% 3	843
	21st to end	Day	15% 11% 24% 26% 19% 5%	870
July	1st to 10th	Day	12% 12% 22% 32% 18% 4	757
	11th to 20th	Day	7% 11% 33% 31% 15% 3	484
	21st to end	Day	6% 8% 27% 36% 19% 5%	531
August	1st to 10th	Day	7% 10% 25% 31% 20% 7%	487
	11th to 20th	Day	8% 8% 27% 30% 20% 7%	477
	21st to end	Day	14% 13% 26% 28% 14% 5%	539
September	1st to 10th	Day	15% 11% 27% 26% 16% 5%	490
	11th to 20th	Day	17% 11% 27% 26% 16% 3	490
	21st to end	Day	21% 16% 27% 22% 11% 3	490
October	1st to 10th	Day	20% 15% 26% 23% 13% 3	490
	11th to 20th	Day	22% 20% 24% 16% 14% 3	414
	21st to end	Day	25% 15% 30% 21% 8% 2	330
November	1st to 10th	Day	27% 21% 26% 17% 9% 1	263
	11th to 20th	Day	28% 18% 26% 17% 10% 2	200
	21st to end	Day	21% 18% 25% 21% 11% 6%	200
December	1st to 10th	Day	15% 18% 20% 22% 22% 4	200
	11th to 20th	Day	21% 21% 27% 20% 10% 2	200
	21st to end	Day	15% 16% 27% 33% 6% 2	220
January	1st to 10th	Night	25% 17% 23% 25% 9% 1	810
	11th to 20th	Night	15% 14% 30% 27% 12% 2	800
	21st to end	Night	15% 14% 28% 28% 12% 2	880
February	1st to 10th	Night	20% 14% 27% 26% 11% 2	800
	11th to 20th	Night	15% 13% 27% 31% 12% 1	784
	21st to end	Night	15% 16% 23% 24% 18% 3	660
March	1st to 10th	Night	17% 13% 25% 27% 16% 2	800
	11th to 20th	Night	16% 17% 26% 24% 16% 2	800
	21st to end	Night	17% 13% 25% 27% 14% 4	862
April	1st to 10th	Night	14% 11% 23% 31% 16% 4	760
	11th to 20th	Night	15% 11% 24% 30% 17% 3	712
	21st to end	Night	14% 13% 26% 31% 14% 3	459
May	1st to 10th	Night	14% 8% 21% 32% 22% 3	380
	11th to 20th	Night	13% 7% 18% 36% 22% 5%	374
	21st to end	Night	17% 7% 18% 27% 27% 6%	411
June	1st to 10th	Night	18% 8% 23% 31% 18% 2	380
	11th to 20th	Night	19% 9% 19% 34% 17% 3	380
	21st to end	Night	9% 6% 19% 37% 25% 3	380
July	1st to 10th	Night	8% 3 16% 32% 37% 3	370
	11th to 20th	Night	5% 5% 19% 35% 32% 4	368
	21st to end	Night	6% 3 14% 36% 36% 5%	416
August	1st to 10th	Night	6% 3 12% 34% 35% 10%	378
	11th to 20th	Night	6% 2 14% 33% 38% 7%	376
	21st to end	Night	11% 5% 16% 36% 29% 4	800
September	1st to 10th	Night	10% 6% 16% 35% 26% 7%	760
	11th to 20th	Night	15% 5% 16% 27% 27% 10%	760
	21st to end	Night	19% 8% 19% 31% 19% 5%	760
October	1st to 10th	Night	17% 8% 20% 28% 23% 4	760
	11th to 20th	Night	21% 11% 21% 27% 19% 3	760
	21st to end	Night	21% 12% 25% 27% 11% 4	836
November	1st to 10th	Night	27% 13% 26% 26% 8% 1	780
	11th to 20th	Night	25% 17% 24% 22% 10% 2	800
	21st to end	Night	20% 15% 27% 24% 11% 3	950
December	1st to 10th	Night	15% 14% 27% 30% 12% 2	1000
	11th to 20th	Night	21% 14% 30% 25% 9% 1	1000
	21st to end	Night	20% 16% 31% 25% 7% 1	1100

Page generated at 2025-03-24 06:04:26. Version ac07

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