Lewisporte
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lewisporte 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	20% 14% 4 9% 5% 5% 4 3 5% 6% 23%	150642
	Night	19% 14% 5% 10% 5% 5% 5% 3 5% 6% 23%	141792
Transparency	Day	60% 7% 12% 15% 5%	154071
	Night	61% 7% 12% 14% 6% 1	146477
Seeing	Day	29% 15% 29% 19% 7% 1	20921
	Night	29% 15% 31% 19% 5%	27573

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% 20% 7% 14% 6% 5% 4 3 4 4 15%	4122
	11th to 20th	Day	19% 18% 8% 14% 6% 5% 4 3 4 4 16%	4641
	21st to end	Day	8% 12% 6% 12% 9% 8% 7% 5% 7% 8% 20%	5157
February	1st to 10th	Day	16% 14% 5% 12% 8% 5% 5% 4 7% 5% 18%	1680
	11th to 20th	Day	19% 20% 6% 11% 7% 4 5% 4 4 4 16%	1899
	21st to end	Day	14% 13% 6% 12% 8% 6% 6% 3 4 5% 23%	1730
March	1st to 10th	Day	16% 13% 5% 14% 9% 6% 5% 3 5% 5% 18%	4574
	11th to 20th	Day	19% 16% 7% 13% 7% 5% 4 3 4 4 18%	4945
	21st to end	Day	24% 19% 7% 13% 5% 3 3 2 3 3 17%	5813
April	1st to 10th	Day	18% 19% 6% 12% 6% 4 5% 4 4 5% 17%	2520
	11th to 20th	Day	23% 17% 6% 7% 4 4 3 3 4 6% 24%	2687
	21st to end	Day	22% 19% 5% 8% 5% 4 4 3 4 4 21%	2730
May	1st to 10th	Day	24% 19% 6% 10% 5% 5% 4 3 4 5% 16%	7926
	11th to 20th	Day	24% 16% 5% 9% 5% 4 4 3 4 5% 21%	8493
	21st to end	Day	25% 19% 3 6% 4 3 3 3 4 5% 25%	9682
June	1st to 10th	Day	31% 15% 3 7% 5% 4 4 4 4 5% 19%	3150
	11th to 20th	Day	27% 12% 3 6% 4 4 4 3 5% 5% 24%	3150
	21st to end	Day	23% 11% 3 7% 5% 5% 5% 4 5% 7% 25%	3150
July	1st to 10th	Day	19% 11% 3 8% 5% 5% 5% 3 6% 7% 28%	8850
	11th to 20th	Day	14% 7% 3 8% 6% 6% 6% 6% 7% 9% 28%	8746
	21st to end	Day	20% 9% 3 7% 5% 4 4 4 5% 7% 32%	8995
August	1st to 10th	Day	21% 13% 4 10% 5% 5% 5% 4 5% 7% 21%	6484
	11th to 20th	Day	20% 9% 3 8% 5% 4 5% 4 6% 7% 30%	5960
	21st to end	Day	18% 8% 2 7% 4 4 4 4 6% 8% 35%	6594
September	1st to 10th	Day	22% 7% 3 6% 4 4 5% 3 5% 8% 33%	2520
	11th to 20th	Day	27% 9% 3 6% 5% 3 4 3 5% 6% 27%	2310
	21st to end	Day	19% 10% 3 7% 4 4 4 3 5% 8% 32%	2310
October	1st to 10th	Day	21% 11% 3 7% 4 5% 4 3 5% 6% 31%	2263
	11th to 20th	Day	24% 13% 3 8% 5% 4 4 4 6% 6% 23%	1918
	21st to end	Day	24% 19% 5% 7% 5% 5% 4 3 4 5% 19%	2052
November	1st to 10th	Day	22% 18% 5% 9% 5% 4 5% 4 5% 5% 18%	1850
	11th to 20th	Day	22% 18% 5% 8% 5% 3 4 3 4 6% 22%	1638
	21st to end	Day	24% 17% 5% 9% 5% 4 3 3 4 5% 20%	1470
December	1st to 10th	Day	13% 13% 5% 8% 5% 4 4 3 5% 7% 33%	2360
	11th to 20th	Day	21% 12% 4 13% 6% 5% 6% 4 5% 7% 18%	2698
	21st to end	Day	18% 15% 6% 16% 7% 5% 4 3 5% 5% 16%	3575
January	1st to 10th	Night	17% 20% 6% 13% 6% 6% 5% 3 4 5% 15%	8802
	11th to 20th	Night	14% 19% 7% 13% 7% 5% 5% 4 5% 5% 15%	8257
	21st to end	Night	7% 12% 5% 11% 8% 6% 7% 4 6% 9% 25%	9056
February	1st to 10th	Night	16% 13% 5% 13% 8% 5% 5% 4 5% 6% 20%	2940
	11th to 20th	Night	19% 19% 5% 11% 6% 5% 5% 4 4 4 18%	2605
	21st to end	Night	15% 14% 5% 9% 7% 5% 6% 4 5% 6% 26%	2076
March	1st to 10th	Night	18% 13% 4 12% 5% 5% 5% 5% 5% 6% 21%	5486
	11th to 20th	Night	18% 16% 6% 13% 7% 6% 5% 4 5% 5% 15%	5233
	21st to end	Night	22% 16% 5% 11% 5% 4 4 3 5% 6% 19%	5358
April	1st to 10th	Night	24% 18% 5% 8% 4 4 3 3 5% 5% 21%	2100
	11th to 20th	Night	25% 17% 4 7% 4 3 4 3 3 5% 24%	1882
	21st to end	Night	26% 17% 4 7% 4 3 3 2 4 5% 24%	1890
May	1st to 10th	Night	31% 17% 5% 8% 4 4 3 3 4 5% 16%	4997
	11th to 20th	Night	22% 18% 7% 10% 4 4 3 2 4 5% 20%	4394
	21st to end	Night	27% 15% 5% 6% 3 3 3 3 4 5% 23%	4524
June	1st to 10th	Night	33% 13% 3 6% 4 3 4 3 5% 6% 19%	1470
	11th to 20th	Night	31% 10% 3 5% 4 3 4 4 6% 6% 24%	1470
	21st to end	Night	22% 12% 3 8% 6% 5% 5% 3 5% 6% 25%	1470
July	1st to 10th	Night	20% 11% 4 8% 4 4 5% 4 6% 7% 28%	4139
	11th to 20th	Night	12% 12% 4 8% 6% 4 5% 4 7% 9% 29%	4228
	21st to end	Night	20% 12% 3 8% 4 4 5% 3 5% 7% 30%	5116
August	1st to 10th	Night	18% 14% 4 8% 5% 4 4 4 6% 7% 26%	3686
	11th to 20th	Night	18% 10% 4 8% 4 5% 3 3 5% 6% 32%	4103
	21st to end	Night	17% 7% 3 7% 5% 5% 5% 4 6% 7% 35%	4553
September	1st to 10th	Night	23% 8% 3 7% 3 3 3 3 4 6% 37%	2096
	11th to 20th	Night	24% 10% 3 6% 5% 4 4 4 5% 5% 30%	2310
	21st to end	Night	22% 11% 3 7% 4 3 5% 3 4 7% 31%	2310
October	1st to 10th	Night	24% 11% 3 7% 4 4 3 3 5% 6% 30%	2357
	11th to 20th	Night	25% 13% 3 8% 4 4 4 3 5% 6% 26%	2698
	21st to end	Night	28% 17% 3 7% 4 3 4 3 3 5% 23%	2965
November	1st to 10th	Night	22% 17% 4 9% 6% 5% 5% 3 5% 6% 18%	2668
	11th to 20th	Night	25% 15% 5% 8% 4 3 4 4 5% 6% 20%	2977
	21st to end	Night	20% 17% 7% 9% 6% 4 4 3 6% 6% 19%	3150
December	1st to 10th	Night	14% 12% 4 9% 5% 5% 5% 3 5% 6% 30%	5050
	11th to 20th	Night	21% 15% 5% 13% 6% 5% 4 3 5% 5% 17%	5731
	21st to end	Night	17% 13% 6% 17% 7% 6% 4 3 5% 5% 17%	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	69% 8% 10% 10% 2	4123
	11th to 20th	Day	70% 7% 8% 9% 6%	4670
	21st to end	Day	57% 12% 10% 12% 6% 2	5157
February	1st to 10th	Day	64% 8% 12% 9% 6% 1	1680
	11th to 20th	Day	69% 7% 10% 10% 4	1906
	21st to end	Day	62% 7% 9% 13% 8% 1	1730
March	1st to 10th	Day	64% 7% 8% 12% 7% 1	4578
	11th to 20th	Day	69% 6% 8% 9% 6% 2	4945
	21st to end	Day	71% 4 7% 11% 6%	5813
April	1st to 10th	Day	69% 5% 9% 11% 5% 1	2520
	11th to 20th	Day	62% 5% 10% 15% 8% 1	2687
	21st to end	Day	66% 5% 8% 13% 8%	2730
May	1st to 10th	Day	68% 5% 12% 11% 3 1	7939
	11th to 20th	Day	64% 6% 10% 15% 6%	8497
	21st to end	Day	61% 5% 11% 17% 5%	9683
June	1st to 10th	Day	68% 6% 9% 12% 5%	3150
	11th to 20th	Day	60% 7% 12% 15% 4	3150
	21st to end	Day	57% 9% 12% 15% 7% 1	3150
July	1st to 10th	Day	53% 7% 13% 21% 6%	8775
	11th to 20th	Day	48% 9% 16% 22% 5%	8664
	21st to end	Day	50% 7% 13% 24% 5%	8798
August	1st to 10th	Day	61% 8% 14% 15% 3	6470
	11th to 20th	Day	52% 7% 17% 15% 8% 1	5999
	21st to end	Day	46% 6% 16% 25% 6%	6594
September	1st to 10th	Day	49% 7% 12% 24% 8% 1	2520
	11th to 20th	Day	57% 7% 13% 16% 5%	2310
	21st to end	Day	51% 6% 17% 19% 7%	2310
October	1st to 10th	Day	57% 7% 12% 17% 6%	3617
	11th to 20th	Day	60% 8% 12% 15% 6%	3053
	21st to end	Day	66% 6% 10% 10% 8% 1	3263
November	1st to 10th	Day	67% 7% 12% 10% 4	1850
	11th to 20th	Day	64% 7% 11% 12% 6% 1	1638
	21st to end	Day	66% 8% 12% 9% 5% 1	1470
December	1st to 10th	Day	49% 7% 11% 23% 10%	2360
	11th to 20th	Day	65% 9% 18% 6% 3	2697
	21st to end	Day	69% 8% 9% 11% 3	3575
January	1st to 10th	Night	68% 8% 10% 9% 4	8802
	11th to 20th	Night	68% 8% 10% 9% 4	8303
	21st to end	Night	53% 9% 15% 11% 11% 2	9056
February	1st to 10th	Night	63% 8% 12% 11% 6% 1	2940
	11th to 20th	Night	68% 7% 10% 11% 4	2609
	21st to end	Night	57% 8% 10% 17% 7% 1	2076
March	1st to 10th	Night	61% 7% 10% 12% 7% 2	5495
	11th to 20th	Night	69% 8% 9% 8% 5% 1	5234
	21st to end	Night	65% 6% 11% 13% 5%	5358
April	1st to 10th	Night	64% 5% 8% 13% 9% 1	2100
	11th to 20th	Night	63% 4 10% 17% 6%	1882
	21st to end	Night	63% 5% 8% 13% 9%	1890
May	1st to 10th	Night	69% 5% 12% 12% 2	5002
	11th to 20th	Night	67% 4 12% 11% 5%	4395
	21st to end	Night	63% 5% 10% 16% 6%	4525
June	1st to 10th	Night	66% 6% 12% 11% 5%	1470
	11th to 20th	Night	58% 8% 14% 14% 5%	1470
	21st to end	Night	59% 8% 11% 15% 6% 1	1470
July	1st to 10th	Night	56% 6% 16% 20% 3	4106
	11th to 20th	Night	51% 7% 15% 20% 7%	4186
	21st to end	Night	54% 7% 14% 23% 3	4999
August	1st to 10th	Night	56% 8% 15% 17% 4	3675
	11th to 20th	Night	51% 7% 19% 16% 6% 1	4130
	21st to end	Night	46% 7% 18% 23% 6%	4552
September	1st to 10th	Night	49% 6% 13% 24% 8%	2096
	11th to 20th	Night	56% 6% 13% 17% 8%	2310
	21st to end	Night	53% 7% 14% 18% 8%	2310
October	1st to 10th	Night	59% 6% 15% 14% 5% 1	3786
	11th to 20th	Night	58% 8% 15% 13% 6%	4312
	21st to end	Night	58% 5% 13% 16% 8% 1	4715
November	1st to 10th	Night	67% 8% 10% 11% 4	2668
	11th to 20th	Night	65% 7% 12% 13% 3	2977
	21st to end	Night	66% 7% 12% 10% 5%	3150
December	1st to 10th	Night	53% 7% 10% 19% 11%	5050
	11th to 20th	Night	69% 7% 14% 6% 4	5733
	21st to end	Night	67% 9% 10% 11% 2	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	26% 22% 33% 15% 5%	430
	11th to 20th	Day	24% 23% 33% 17% 3	430
	21st to end	Day	27% 21% 32% 16% 3	473
February	1st to 10th	Day	25% 24% 30% 15% 4	430
	11th to 20th	Day	29% 22% 34% 12% 2 1	426
	21st to end	Day	21% 23% 36% 15% 4 1	355
March	1st to 10th	Day	23% 23% 37% 13% 3	430
	11th to 20th	Day	27% 18% 29% 17% 7% 1	430
	21st to end	Day	34% 21% 25% 15% 3 2	526
April	1st to 10th	Day	28% 23% 31% 15% 3	540
	11th to 20th	Day	32% 14% 30% 20% 4 1	725
	21st to end	Day	33% 16% 28% 18% 5% 1	750
May	1st to 10th	Day	36% 13% 25% 17% 6% 2	753
	11th to 20th	Day	31% 13% 28% 18% 8% 1	774
	21st to end	Day	35% 12% 29% 19% 4 1	845
June	1st to 10th	Day	39% 11% 24% 16% 9% 1	780
	11th to 20th	Day	33% 12% 25% 20% 9% 1	780
	21st to end	Day	27% 10% 25% 22% 12% 3	780
July	1st to 10th	Day	28% 10% 26% 24% 9% 2	770
	11th to 20th	Day	20% 11% 28% 29% 11% 1	768
	21st to end	Day	25% 10% 26% 28% 9% 1	850
August	1st to 10th	Day	24% 9% 27% 25% 12% 3	775
	11th to 20th	Day	23% 7% 27% 25% 16% 2	767
	21st to end	Day	23% 8% 30% 24% 12% 3	858
September	1st to 10th	Day	25% 11% 30% 22% 10% 2	572
	11th to 20th	Day	35% 12% 28% 20% 4	450
	21st to end	Day	21% 20% 34% 18% 5% 2	450
October	1st to 10th	Day	24% 19% 34% 17% 4 2	450
	11th to 20th	Day	36% 12% 26% 16% 8% 2	450
	21st to end	Day	32% 19% 26% 16% 6% 2	486
November	1st to 10th	Day	37% 18% 30% 13% 2	425
	11th to 20th	Day	35% 21% 24% 15% 4 1	430
	21st to end	Day	37% 20% 30% 11% 1	430
December	1st to 10th	Day	25% 18% 34% 17% 5% 1	430
	11th to 20th	Day	29% 26% 30% 12% 3	430
	21st to end	Day	24% 21% 30% 18% 6% 1	473
January	1st to 10th	Night	27% 18% 32% 17% 4 1	950
	11th to 20th	Night	24% 24% 33% 15% 4	950
	21st to end	Night	23% 22% 37% 15% 3	1045
February	1st to 10th	Night	26% 20% 35% 16% 4	950
	11th to 20th	Night	30% 22% 33% 12% 3	897
	21st to end	Night	22% 15% 39% 17% 7% 1	692
March	1st to 10th	Night	27% 20% 34% 14% 4 1	840
	11th to 20th	Night	25% 17% 30% 22% 6%	696
	21st to end	Night	32% 16% 30% 17% 4	693
April	1st to 10th	Night	32% 20% 29% 15% 4 1	630
	11th to 20th	Night	32% 11% 33% 18% 5% 1	624
	21st to end	Night	33% 11% 32% 20% 4	630
May	1st to 10th	Night	36% 10% 25% 21% 7% 1	630
	11th to 20th	Night	33% 12% 28% 19% 8%	622
	21st to end	Night	35% 10% 31% 19% 5%	682
June	1st to 10th	Night	39% 10% 23% 25% 3	630
	11th to 20th	Night	36% 9% 23% 24% 7%	630
	21st to end	Night	29% 9% 30% 22% 10%	630
July	1st to 10th	Night	25% 7% 33% 28% 7%	616
	11th to 20th	Night	21% 9% 31% 33% 6%	612
	21st to end	Night	24% 8% 30% 30% 7%	689
August	1st to 10th	Night	23% 6% 29% 30% 11% 1	628
	11th to 20th	Night	23% 5% 29% 32% 11%	622
	21st to end	Night	23% 8% 28% 31% 9% 1	693
September	1st to 10th	Night	27% 7% 33% 25% 7%	630
	11th to 20th	Night	29% 13% 31% 24% 3	630
	21st to end	Night	30% 13% 32% 21% 4	630
October	1st to 10th	Night	32% 11% 32% 21% 4	657
	11th to 20th	Night	34% 12% 29% 19% 6%	928
	21st to end	Night	36% 14% 26% 18% 5% 1	1042
November	1st to 10th	Night	33% 20% 29% 14% 3	930
	11th to 20th	Night	35% 16% 30% 14% 5% 1	950
	21st to end	Night	33% 20% 31% 14% 2	950
December	1st to 10th	Night	28% 18% 34% 15% 4 1	950
	11th to 20th	Night	32% 23% 32% 12% 2	950
	21st to end	Night	24% 20% 31% 18% 5% 1	1045

Page generated at 2026-10-26 05:37:46. Version ac07

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