Grand Falls-Windsor
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Grand Falls-Windsor clear sky chart from 2005-11-06 to 2026-10-29.

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	21% 14% 4 9% 5% 5% 4 3 5% 6% 24%	150545
	Night	19% 13% 4 10% 5% 5% 5% 4 5% 6% 24%	141907
Transparency	Day	63% 3 10% 17% 6% 1	153986
	Night	62% 4 10% 16% 7% 1	146578
Seeing	Day	31% 12% 28% 19% 8% 2	20878
	Night	29% 11% 31% 22% 6% 1	27588

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	20% 18% 7% 12% 5% 5% 4 2 3 3 18%	4250
	11th to 20th	Day	19% 18% 7% 15% 6% 4 4 3 4 4 16%	4681
	21st to end	Day	7% 12% 5% 12% 8% 7% 6% 5% 6% 7% 24%	5157
February	1st to 10th	Day	18% 14% 4 10% 8% 6% 5% 4 5% 5% 19%	1680
	11th to 20th	Day	17% 22% 6% 11% 6% 4 4 4 5% 4 16%	1916
	21st to end	Day	12% 16% 6% 13% 7% 6% 5% 4 4 5% 23%	1730
March	1st to 10th	Day	19% 16% 4 11% 8% 5% 5% 3 4 5% 21%	4574
	11th to 20th	Day	20% 18% 7% 12% 6% 4 4 2 3 3 19%	4897
	21st to end	Day	24% 21% 7% 10% 5% 4 3 2 3 4 16%	5883
April	1st to 10th	Day	19% 21% 7% 12% 7% 5% 4 3 4 4 15%	2520
	11th to 20th	Day	22% 18% 5% 9% 4 4 3 3 4 6% 24%	2658
	21st to end	Day	23% 21% 6% 8% 4 4 3 2 4 4 20%	2730
May	1st to 10th	Day	26% 19% 5% 9% 5% 4 4 3 4 5% 16%	7986
	11th to 20th	Day	24% 15% 4 9% 5% 4 4 3 4 5% 24%	8328
	21st to end	Day	24% 18% 4 7% 4 4 4 3 4 5% 24%	9682
June	1st to 10th	Day	32% 16% 3 7% 5% 4 3 3 4 5% 18%	3150
	11th to 20th	Day	26% 12% 4 8% 5% 4 5% 4 5% 6% 23%	3150
	21st to end	Day	24% 11% 3 8% 6% 5% 4 4 5% 5% 24%	3150
July	1st to 10th	Day	21% 10% 3 8% 5% 5% 5% 3 5% 7% 26%	8850
	11th to 20th	Day	16% 8% 3 7% 5% 5% 6% 5% 7% 9% 29%	8569
	21st to end	Day	20% 8% 3 7% 4 4 4 4 5% 8% 33%	8995
August	1st to 10th	Day	22% 11% 4 9% 5% 5% 5% 4 5% 6% 23%	6484
	11th to 20th	Day	20% 10% 3 7% 5% 4 4 4 6% 7% 29%	6004
	21st to end	Day	19% 9% 3 7% 5% 4 4 4 5% 7% 33%	6508
September	1st to 10th	Day	19% 9% 3 8% 5% 3 4 4 5% 7% 32%	2520
	11th to 20th	Day	24% 10% 4 8% 5% 5% 4 3 5% 7% 27%	2324
	21st to end	Day	17% 10% 4 9% 5% 4 4 4 5% 6% 31%	2310
October	1st to 10th	Day	19% 12% 3 8% 5% 4 4 4 4 7% 31%	2289
	11th to 20th	Day	22% 14% 4 8% 6% 5% 4 3 5% 6% 24%	1890
	21st to end	Day	23% 15% 3 9% 6% 5% 4 3 4 4 21%	2052
November	1st to 10th	Day	23% 14% 4 9% 6% 5% 4 4 5% 5% 20%	1850
	11th to 20th	Day	22% 16% 6% 9% 5% 4 4 3 3 5% 23%	1675
	21st to end	Day	23% 17% 5% 8% 6% 5% 4 3 4 5% 21%	1470
December	1st to 10th	Day	13% 14% 4 9% 5% 5% 4 5% 5% 6% 30%	2360
	11th to 20th	Day	25% 12% 4 10% 4 5% 5% 4 5% 6% 21%	2698
	21st to end	Day	19% 16% 5% 11% 5% 4 4 5% 6% 6% 18%	3575
January	1st to 10th	Night	16% 19% 6% 12% 6% 5% 4 3 5% 5% 19%	8671
	11th to 20th	Night	15% 15% 7% 15% 7% 6% 5% 5% 5% 5% 14%	8234
	21st to end	Night	7% 12% 5% 10% 6% 7% 6% 5% 7% 9% 27%	9056
February	1st to 10th	Night	17% 13% 5% 13% 8% 5% 5% 4 4 6% 21%	2940
	11th to 20th	Night	17% 17% 5% 11% 6% 5% 6% 4 5% 5% 19%	2588
	21st to end	Night	12% 13% 4 10% 7% 5% 5% 4 5% 6% 28%	2076
March	1st to 10th	Night	18% 14% 4 10% 6% 5% 5% 4 6% 6% 21%	5486
	11th to 20th	Night	17% 15% 7% 13% 7% 6% 5% 4 4 4 18%	5282
	21st to end	Night	22% 19% 6% 11% 6% 4 3 3 4 5% 18%	5288
April	1st to 10th	Night	23% 19% 6% 9% 4 3 3 2 4 4 22%	2100
	11th to 20th	Night	21% 15% 5% 9% 4 4 4 3 4 4 27%	1911
	21st to end	Night	23% 19% 5% 8% 3 4 3 3 4 6% 23%	1890
May	1st to 10th	Night	30% 18% 4 9% 4 4 4 3 4 5% 16%	4938
	11th to 20th	Night	23% 12% 4 10% 5% 6% 4 3 4 6% 23%	4562
	21st to end	Night	25% 16% 5% 6% 4 4 4 3 3 5% 26%	4524
June	1st to 10th	Night	32% 13% 4 7% 3 4 4 4 3 5% 20%	1470
	11th to 20th	Night	26% 10% 2 7% 4 4 4 3 7% 7% 26%	1470
	21st to end	Night	27% 11% 3 7% 5% 4 4 4 4 4 26%	1470
July	1st to 10th	Night	21% 11% 3 8% 4 4 4 3 5% 8% 30%	4139
	11th to 20th	Night	16% 9% 3 7% 5% 4 6% 4 7% 8% 31%	4418
	21st to end	Night	21% 9% 3 7% 4 4 4 3 5% 6% 34%	5116
August	1st to 10th	Night	15% 11% 4 8% 5% 5% 5% 4 6% 7% 30%	3686
	11th to 20th	Night	20% 9% 3 8% 4 4 4 4 4 6% 34%	4060
	21st to end	Night	18% 7% 3 7% 4 4 5% 4 6% 7% 35%	4620
September	1st to 10th	Night	20% 8% 2 8% 6% 4 3 3 4 6% 37%	2100
	11th to 20th	Night	22% 10% 3 6% 5% 4 4 4 5% 6% 32%	2295
	21st to end	Night	19% 9% 3 8% 5% 4 3 4 6% 7% 32%	2310
October	1st to 10th	Night	21% 10% 3 8% 4 5% 5% 3 5% 6% 31%	2330
	11th to 20th	Night	23% 12% 3 8% 4 5% 4 3 5% 6% 29%	2726
	21st to end	Night	25% 13% 3 7% 4 4 4 3 4 5% 27%	2965
November	1st to 10th	Night	22% 14% 4 8% 6% 5% 5% 4 6% 6% 20%	2668
	11th to 20th	Night	25% 14% 5% 8% 6% 4 4 4 5% 5% 20%	2942
	21st to end	Night	21% 16% 5% 10% 6% 5% 4 4 5% 5% 19%	3150
December	1st to 10th	Night	14% 12% 4 9% 5% 4 5% 3 6% 6% 31%	5050
	11th to 20th	Night	25% 13% 4 10% 6% 5% 5% 4 5% 5% 20%	5731
	21st to end	Night	17% 14% 6% 15% 6% 5% 5% 4 5% 6% 18%	7645

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	73% 2 6% 12% 6% 2	4251
	11th to 20th	Day	74% 2 6% 10% 8%	4710
	21st to end	Day	60% 5% 6% 17% 10% 2	5157
February	1st to 10th	Day	67% 3 9% 12% 7% 2	1680
	11th to 20th	Day	73% 3 5% 12% 7% 1	1923
	21st to end	Day	66% 2 5% 15% 11% 1	1730
March	1st to 10th	Day	67% 3 5% 12% 10% 2	4578
	11th to 20th	Day	73% 2 5% 11% 7% 3	4897
	21st to end	Day	75% 2 4 12% 7%	5883
April	1st to 10th	Day	75% 2 6% 10% 6% 1	2520
	11th to 20th	Day	65% 1 7% 16% 10% 1	2658
	21st to end	Day	70% 2 6% 13% 8% 1	2730
May	1st to 10th	Day	71% 3 10% 12% 3 1	7999
	11th to 20th	Day	65% 2 9% 17% 6%	8332
	21st to end	Day	65% 2 9% 18% 6%	9683
June	1st to 10th	Day	71% 2 7% 15% 6%	3150
	11th to 20th	Day	63% 3 10% 19% 5%	3150
	21st to end	Day	62% 3 10% 17% 7% 1	3150
July	1st to 10th	Day	59% 3 13% 20% 5%	8775
	11th to 20th	Day	51% 4 17% 23% 4	8487
	21st to end	Day	51% 3 15% 25% 4	8798
August	1st to 10th	Day	61% 4 12% 20% 3	6470
	11th to 20th	Day	55% 3 17% 18% 7% 1	6044
	21st to end	Day	51% 3 14% 26% 6%	6508
September	1st to 10th	Day	53% 3 11% 24% 8% 2	2520
	11th to 20th	Day	58% 3 13% 19% 7% 1	2324
	21st to end	Day	54% 3 13% 20% 8%	2310
October	1st to 10th	Day	59% 4 11% 18% 8%	3667
	11th to 20th	Day	59% 6% 11% 19% 6%	3012
	21st to end	Day	62% 4 9% 16% 8% 1	3263
November	1st to 10th	Day	68% 4 11% 12% 5%	1850
	11th to 20th	Day	67% 2 9% 13% 8% 1	1675
	21st to end	Day	67% 3 10% 10% 8% 1	1470
December	1st to 10th	Day	56% 5% 8% 20% 11%	2360
	11th to 20th	Day	66% 4 15% 9% 6%	2697
	21st to end	Day	68% 3 7% 17% 4	3575
January	1st to 10th	Night	70% 3 7% 11% 7% 2	8671
	11th to 20th	Night	73% 5% 6% 10% 5%	8280
	21st to end	Night	55% 7% 8% 12% 16% 2	9056
February	1st to 10th	Night	67% 2 7% 13% 9% 1	2940
	11th to 20th	Night	70% 2 8% 12% 7% 1	2592
	21st to end	Night	57% 3 8% 18% 13% 2	2076
March	1st to 10th	Night	64% 4 7% 14% 9% 3	5495
	11th to 20th	Night	71% 3 7% 10% 8% 1	5283
	21st to end	Night	69% 2 8% 14% 6%	5288
April	1st to 10th	Night	69% 2 4 12% 12% 1	2100
	11th to 20th	Night	63% 2 7% 18% 10%	1911
	21st to end	Night	66% 3 7% 14% 10% 1	1890
May	1st to 10th	Night	72% 2 10% 13% 3	4943
	11th to 20th	Night	66% 3 11% 15% 6%	4563
	21st to end	Night	63% 2 8% 20% 6%	4525
June	1st to 10th	Night	68% 3 9% 14% 6%	1470
	11th to 20th	Night	59% 3 14% 18% 6%	1470
	21st to end	Night	61% 3 10% 18% 7% 1	1470
July	1st to 10th	Night	55% 3 17% 21% 3	4106
	11th to 20th	Night	51% 5% 16% 22% 6%	4376
	21st to end	Night	53% 4 15% 25% 3	4999
August	1st to 10th	Night	55% 5% 17% 19% 4	3675
	11th to 20th	Night	53% 3 18% 20% 5% 1	4086
	21st to end	Night	49% 4 16% 24% 6%	4619
September	1st to 10th	Night	50% 3 12% 25% 9%	2100
	11th to 20th	Night	55% 3 14% 19% 9% 1	2295
	21st to end	Night	53% 4 13% 21% 10% 1	2310
October	1st to 10th	Night	59% 4 15% 16% 6% 1	3733
	11th to 20th	Night	55% 6% 13% 18% 8%	4353
	21st to end	Night	58% 4 12% 17% 9% 1	4715
November	1st to 10th	Night	66% 4 9% 15% 5%	2668
	11th to 20th	Night	66% 3 9% 16% 6%	2942
	21st to end	Night	68% 4 8% 12% 7%	3150
December	1st to 10th	Night	55% 5% 7% 22% 12%	5050
	11th to 20th	Night	69% 4 11% 11% 5%	5733
	21st to end	Night	70% 3 8% 16% 3	7645

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	30% 17% 30% 16% 6% 2	430
	11th to 20th	Day	30% 17% 28% 20% 5%	430
	21st to end	Day	29% 15% 32% 19% 5%	473
February	1st to 10th	Day	31% 16% 29% 17% 7% 1	430
	11th to 20th	Day	31% 19% 31% 14% 3 1	426
	21st to end	Day	23% 18% 36% 15% 5% 2	355
March	1st to 10th	Day	29% 21% 31% 13% 5% 1	430
	11th to 20th	Day	31% 15% 24% 18% 9% 3	430
	21st to end	Day	37% 16% 26% 15% 5% 1	541
April	1st to 10th	Day	34% 18% 29% 14% 4	540
	11th to 20th	Day	34% 12% 28% 20% 5% 1	696
	21st to end	Day	37% 11% 28% 17% 6% 1	750
May	1st to 10th	Day	41% 12% 21% 17% 7% 2	753
	11th to 20th	Day	32% 10% 25% 22% 8% 3	774
	21st to end	Day	38% 10% 28% 18% 6% 1	845
June	1st to 10th	Day	41% 9% 23% 17% 8% 2	780
	11th to 20th	Day	34% 9% 26% 18% 11% 2	780
	21st to end	Day	29% 10% 27% 19% 9% 6%	780
July	1st to 10th	Day	31% 8% 26% 21% 12% 2	770
	11th to 20th	Day	24% 9% 26% 27% 12% 1	768
	21st to end	Day	28% 7% 26% 27% 11% 1	850
August	1st to 10th	Day	23% 8% 28% 24% 14% 3	775
	11th to 20th	Day	26% 6% 25% 27% 14% 3	767
	21st to end	Day	25% 8% 27% 25% 13% 3	824
September	1st to 10th	Day	21% 12% 31% 23% 9% 4	570
	11th to 20th	Day	35% 11% 29% 19% 5% 1	457
	21st to end	Day	20% 14% 37% 20% 7% 2	450
October	1st to 10th	Day	25% 14% 34% 21% 5% 2	450
	11th to 20th	Day	34% 10% 27% 18% 8% 3	450
	21st to end	Day	31% 13% 28% 17% 9% 2	486
November	1st to 10th	Day	39% 14% 27% 15% 5%	425
	11th to 20th	Day	35% 16% 26% 18% 5% 1	430
	21st to end	Day	38% 18% 28% 12% 4	430
December	1st to 10th	Day	28% 13% 33% 17% 9%	430
	11th to 20th	Day	29% 20% 30% 16% 4	430
	21st to end	Day	26% 17% 29% 19% 6% 2	473
January	1st to 10th	Night	28% 14% 31% 20% 6% 1	950
	11th to 20th	Night	27% 17% 32% 19% 4 1	950
	21st to end	Night	23% 17% 36% 20% 4	1045
February	1st to 10th	Night	26% 15% 36% 17% 4 1	950
	11th to 20th	Night	30% 17% 32% 17% 3 1	876
	21st to end	Night	22% 11% 37% 21% 6% 2	692
March	1st to 10th	Night	26% 19% 33% 17% 4	840
	11th to 20th	Night	25% 13% 30% 25% 7%	719
	21st to end	Night	33% 13% 30% 18% 5%	693
April	1st to 10th	Night	33% 16% 29% 17% 4 1	630
	11th to 20th	Night	31% 10% 34% 20% 5%	624
	21st to end	Night	34% 11% 29% 21% 4	630
May	1st to 10th	Night	37% 6% 29% 20% 7% 1	630
	11th to 20th	Night	32% 7% 31% 22% 8%	622
	21st to end	Night	36% 9% 29% 21% 5%	682
June	1st to 10th	Night	41% 8% 25% 23% 4	630
	11th to 20th	Night	35% 6% 26% 24% 8%	630
	21st to end	Night	33% 7% 29% 22% 8% 1	630
July	1st to 10th	Night	27% 8% 31% 25% 8% 1	616
	11th to 20th	Night	22% 8% 34% 32% 5%	612
	21st to end	Night	26% 6% 32% 29% 6%	689
August	1st to 10th	Night	22% 5% 27% 34% 11% 1	628
	11th to 20th	Night	25% 6% 28% 30% 12%	622
	21st to end	Night	22% 6% 29% 33% 10% 1	693
September	1st to 10th	Night	26% 5% 32% 30% 8%	630
	11th to 20th	Night	30% 9% 30% 27% 4	630
	21st to end	Night	27% 8% 33% 27% 5%	630
October	1st to 10th	Night	30% 8% 32% 25% 5%	642
	11th to 20th	Night	33% 8% 28% 23% 8% 1	956
	21st to end	Night	33% 11% 27% 21% 7%	1042
November	1st to 10th	Night	35% 13% 28% 19% 4 1	930
	11th to 20th	Night	34% 11% 30% 19% 5% 1	950
	21st to end	Night	31% 18% 30% 20% 2	950
December	1st to 10th	Night	29% 15% 29% 20% 7% 1	950
	11th to 20th	Night	34% 17% 29% 17% 4	950
	21st to end	Night	25% 13% 32% 22% 7% 1	1045

Page generated at 2026-10-26 05:37:48. Version ac07

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