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 2024-10-20.

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%	102084
	Night	10% 14% 5% 9% 5% 5% 5% 4 5% 6% 33%	96669
Transparency	Day	48% 8% 13% 17% 10% 3	101846
	Night	49% 9% 14% 17% 9% 2	96553
Seeing	Day	17% 15% 26% 24% 14% 4	15334
	Night	17% 11% 23% 29% 17% 3	23735

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	11% 20% 9% 17% 9% 6% 4 3 4 5% 12%	2539
	11th to 20th	Day	9% 18% 6% 12% 6% 4 4 3 5% 8% 24%	2516
	21st to end	Day	10% 22% 8% 13% 7% 5% 5% 3 5% 5% 17%	2794
February	1st to 10th	Day	14% 20% 7% 13% 5% 4 4 4 5% 3 21%	1534
	11th to 20th	Day	9% 19% 9% 14% 6% 4 5% 3 4 5% 22%	1665
	21st to end	Day	9% 22% 8% 15% 7% 6% 4 2 5% 5% 17%	1570
March	1st to 10th	Day	7% 16% 9% 19% 7% 6% 5% 3 5% 5% 19%	3138
	11th to 20th	Day	7% 16% 5% 8% 5% 4 4 3 5% 6% 39%	3289
	21st to end	Day	8% 25% 7% 11% 6% 5% 5% 4 4 5% 20%	4155
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	13% 13% 3 8% 4 4 4 3 4 6% 37%	1907
	11th to 20th	Day	14% 14% 3 9% 4 6% 5% 3 5% 5% 31%	1815
	21st to end	Day	19% 15% 5% 8% 4 4 4 4 5% 6% 26%	1782
November	1st to 10th	Day	18% 18% 5% 10% 6% 5% 5% 4 5% 6% 18%	1605
	11th to 20th	Day	14% 19% 6% 11% 6% 5% 4 4 4 5% 21%	1520
	21st to end	Day	15% 18% 4 10% 4 4 5% 5% 6% 5% 22%	1358
December	1st to 10th	Day	10% 16% 5% 12% 7% 5% 6% 5% 6% 6% 22%	1330
	11th to 20th	Day	10% 19% 6% 13% 7% 7% 5% 4 5% 4 20%	1682
	21st to end	Day	10% 17% 6% 12% 6% 6% 7% 4 7% 6% 19%	2448
January	1st to 10th	Night	13% 22% 9% 16% 7% 5% 5% 3 5% 4 12%	4429
	11th to 20th	Night	8% 17% 6% 12% 6% 4 4 3 8% 7% 24%	4382
	21st to end	Night	11% 21% 8% 12% 7% 5% 5% 4 5% 6% 16%	4862
February	1st to 10th	Night	12% 20% 6% 12% 6% 5% 5% 3 5% 5% 21%	2642
	11th to 20th	Night	8% 19% 8% 12% 5% 5% 4 3 4 5% 27%	2402
	21st to end	Night	7% 21% 7% 13% 7% 5% 4 4 5% 5% 24%	1884
March	1st to 10th	Night	6% 13% 6% 13% 7% 6% 5% 5% 5% 7% 25%	3736
	11th to 20th	Night	7% 14% 3 8% 4 4 4 4 5% 7% 42%	3689
	21st to end	Night	8% 18% 5% 9% 6% 6% 6% 4 6% 5% 27%	3498
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	12% 10% 3 6% 4 4 6% 4 4 5% 41%	2270
	11th to 20th	Night	16% 11% 4 7% 5% 4 4 3 5% 5% 35%	2349
	21st to end	Night	16% 16% 4 8% 5% 4 4 4 5% 5% 31%	2574
November	1st to 10th	Night	18% 18% 5% 9% 5% 4 5% 4 5% 5% 23%	2471
	11th to 20th	Night	15% 18% 5% 10% 6% 4 4 3 4 5% 24%	2660
	21st to end	Night	12% 20% 5% 11% 6% 5% 4 5% 5% 6% 22%	2802
December	1st to 10th	Night	10% 15% 6% 13% 7% 6% 5% 4 5% 5% 25%	2850
	11th to 20th	Night	9% 22% 7% 12% 6% 5% 5% 4 5% 5% 19%	3510
	21st to end	Night	9% 18% 6% 14% 7% 6% 5% 4 6% 5% 20%	5214

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	70% 12% 13% 4 2	2539
	11th to 20th	Day	57% 7% 15% 13% 3 5%	2540
	21st to end	Day	67% 14% 9% 8% 2	2794
February	1st to 10th	Day	65% 9% 11% 10% 4 1	1534
	11th to 20th	Day	64% 8% 11% 10% 6% 1	1674
	21st to end	Day	70% 8% 9% 11% 3	1570
March	1st to 10th	Day	61% 9% 11% 10% 7%	3138
	11th to 20th	Day	42% 9% 18% 28% 4	3289
	21st to end	Day	62% 9% 12% 9% 8%	4155
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	48% 7% 16% 23% 6%	1907
	11th to 20th	Day	53% 7% 14% 20% 5%	1815
	21st to end	Day	58% 9% 14% 14% 5%	1782
November	1st to 10th	Day	67% 8% 12% 9% 4	1605
	11th to 20th	Day	65% 9% 12% 10% 3 1	1520
	21st to end	Day	59% 12% 15% 8% 5%	1358
December	1st to 10th	Day	60% 11% 12% 14% 4	1330
	11th to 20th	Day	64% 15% 10% 7% 4	1684
	21st to end	Day	61% 15% 12% 9% 3	2448
January	1st to 10th	Night	72% 12% 9% 5% 2	4429
	11th to 20th	Night	54% 8% 14% 13% 4 6%	4420
	21st to end	Night	68% 13% 9% 6% 3	4862
February	1st to 10th	Night	64% 7% 12% 11% 4 1	2642
	11th to 20th	Night	59% 7% 12% 13% 7% 1	2404
	21st to end	Night	61% 7% 13% 12% 7%	1884
March	1st to 10th	Night	50% 11% 16% 15% 7%	3736
	11th to 20th	Night	37% 9% 20% 27% 6%	3690
	21st to end	Night	51% 12% 16% 14% 7%	3498
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% 8% 15% 25% 7% 1	2270
	11th to 20th	Night	50% 7% 13% 21% 9%	2349
	21st to end	Night	54% 8% 15% 17% 6%	2574
November	1st to 10th	Night	62% 9% 12% 12% 5%	2471
	11th to 20th	Night	64% 8% 12% 10% 5% 1	2660
	21st to end	Night	63% 10% 13% 8% 5%	2802
December	1st to 10th	Night	60% 9% 13% 14% 3	2850
	11th to 20th	Night	67% 13% 11% 7% 2	3507
	21st to end	Night	64% 13% 11% 9% 3	5214

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% 31% 16% 9% 6%	180
	11th to 20th	Day	15% 21% 28% 21% 12% 3	180
	21st to end	Day	17% 19% 32% 22% 7% 3	198
February	1st to 10th	Day	24% 21% 31% 16% 7% 1	194
	11th to 20th	Day	20% 21% 27% 22% 7% 2	365
	21st to end	Day	17% 16% 35% 20% 11% 2	382
March	1st to 10th	Day	21% 22% 29% 18% 9% 1	460
	11th to 20th	Day	18% 23% 23% 19% 13% 3	460
	21st to end	Day	22% 21% 24% 18% 12% 3	506
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% 17% 14% 3	411
	21st to end	Day	27% 14% 28% 21% 8% 2	297
November	1st to 10th	Day	27% 20% 25% 18% 9% 1	237
	11th to 20th	Day	24% 17% 28% 17% 11% 2	180
	21st to end	Day	23% 17% 23% 20% 11% 6%	180
December	1st to 10th	Day	16% 18% 21% 21% 20% 4	180
	11th to 20th	Day	21% 18% 29% 19% 11% 2	180
	21st to end	Day	15% 14% 28% 34% 6% 3	198
January	1st to 10th	Night	26% 17% 23% 24% 9% 1	770
	11th to 20th	Night	16% 14% 29% 27% 13% 2	760
	21st to end	Night	16% 14% 27% 28% 13% 2	836
February	1st to 10th	Night	20% 14% 28% 25% 11% 2	760
	11th to 20th	Night	16% 13% 26% 31% 13% 1	744
	21st to end	Night	15% 15% 22% 25% 19% 4	628
March	1st to 10th	Night	17% 14% 25% 26% 16% 2	760
	11th to 20th	Night	16% 16% 26% 24% 17% 2	760
	21st to end	Night	17% 13% 24% 28% 14% 4	836
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% 10% 21% 27% 19% 3	758
	21st to end	Night	21% 12% 24% 28% 12% 4	792
November	1st to 10th	Night	27% 13% 25% 26% 8% 1	740
	11th to 20th	Night	24% 17% 24% 23% 10% 2	760
	21st to end	Night	21% 15% 26% 25% 11% 3	902
December	1st to 10th	Night	16% 14% 26% 30% 13% 2	950
	11th to 20th	Night	20% 14% 31% 25% 9% 1	950
	21st to end	Night	20% 15% 31% 26% 7% 1	1045

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