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 2025-07-06.

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% 5% 9% 6% 5% 4 3 5% 6% 23%	120000
	Night	20% 14% 5% 10% 5% 5% 4 3 5% 6% 23%	119013
Transparency	Day	61% 7% 11% 14% 6% 1	123471
	Night	61% 7% 12% 13% 6% 1	123727
Seeing	Day	29% 15% 29% 19% 7% 1	19048
	Night	29% 15% 31% 19% 5%	25812

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	19% 21% 7% 14% 7% 6% 4 3 4 4 13%	3176
	11th to 20th	Day	14% 20% 9% 16% 6% 5% 4 3 4 4 15%	3564
	21st to end	Day	8% 10% 5% 11% 9% 9% 7% 5% 8% 7% 22%	3982
February	1st to 10th	Day	16% 14% 5% 11% 9% 5% 6% 4 7% 5% 19%	1600
	11th to 20th	Day	19% 19% 5% 11% 7% 4 5% 4 5% 4 17%	1806
	21st to end	Day	13% 13% 5% 12% 8% 6% 6% 3 4 5% 23%	1650
March	1st to 10th	Day	16% 13% 5% 15% 9% 6% 5% 3 5% 5% 17%	4474
	11th to 20th	Day	19% 17% 7% 13% 7% 5% 4 3 4 4 18%	4838
	21st to end	Day	24% 19% 7% 13% 5% 3 3 2 2 3 17%	5687
April	1st to 10th	Day	18% 19% 6% 12% 7% 5% 5% 4 4 5% 17%	2400
	11th to 20th	Day	23% 17% 6% 7% 4 4 3 3 4 6% 23%	2558
	21st to end	Day	22% 20% 4 8% 5% 4 4 4 4 4 21%	2600
May	1st to 10th	Day	27% 21% 7% 8% 4 4 3 3 3 4 16%	6105
	11th to 20th	Day	19% 18% 5% 10% 5% 5% 4 3 4 5% 23%	6526
	21st to end	Day	26% 17% 3 6% 4 3 3 3 4 6% 24%	7428
June	1st to 10th	Day	32% 15% 3 7% 5% 4 4 4 4 5% 18%	3000
	11th to 20th	Day	27% 12% 3 6% 4 4 4 4 5% 5% 25%	3000
	21st to end	Day	23% 11% 3 7% 5% 5% 5% 4 5% 7% 25%	3000
July	1st to 10th	Day	20% 12% 3 8% 5% 5% 5% 4 6% 7% 25%	4825
	11th to 20th	Day	14% 8% 3 8% 6% 5% 6% 5% 7% 9% 28%	4698
	21st to end	Day	15% 7% 2 6% 5% 5% 5% 4 7% 8% 36%	4815
August	1st to 10th	Day	21% 10% 3 9% 5% 5% 6% 4 6% 8% 23%	4424
	11th to 20th	Day	19% 8% 3 6% 4 4 4 3 5% 6% 38%	4051
	21st to end	Day	20% 8% 2 6% 4 4 4 4 6% 8% 34%	4532
September	1st to 10th	Day	22% 7% 3 6% 4 4 5% 3 5% 8% 33%	2281
	11th to 20th	Day	28% 9% 3 6% 5% 3 4 3 5% 6% 28%	2090
	21st to end	Day	20% 10% 3 7% 4 4 4 3 5% 8% 30%	2090
October	1st to 10th	Day	22% 11% 3 7% 4 4 4 3 5% 6% 31%	2047
	11th to 20th	Day	23% 13% 3 9% 5% 4 4 4 6% 6% 22%	1736
	21st to end	Day	25% 19% 4 7% 5% 5% 4 3 4 4 19%	1881
November	1st to 10th	Day	22% 18% 5% 9% 5% 4 5% 4 5% 5% 18%	1760
	11th to 20th	Day	22% 18% 5% 8% 5% 3 4 3 4 6% 22%	1560
	21st to end	Day	24% 18% 5% 10% 5% 4 4 2 4 5% 19%	1400
December	1st to 10th	Day	13% 12% 5% 8% 5% 4 4 3 5% 7% 33%	2290
	11th to 20th	Day	21% 12% 4 13% 7% 5% 5% 4 5% 7% 18%	2628
	21st to end	Day	18% 15% 6% 15% 7% 5% 4 3 5% 5% 16%	3498
January	1st to 10th	Night	18% 22% 6% 13% 7% 7% 5% 3 3 4 13%	6789
	11th to 20th	Night	12% 19% 8% 13% 7% 5% 5% 4 5% 6% 17%	6337
	21st to end	Night	7% 10% 4 10% 8% 7% 7% 4 6% 9% 28%	6996
February	1st to 10th	Night	16% 12% 5% 12% 8% 5% 5% 4 5% 7% 20%	2800
	11th to 20th	Night	19% 17% 5% 10% 6% 5% 5% 4 4 5% 19%	2478
	21st to end	Night	14% 13% 5% 9% 7% 5% 6% 4 5% 6% 26%	1980
March	1st to 10th	Night	18% 13% 4 12% 5% 5% 5% 5% 5% 6% 21%	5366
	11th to 20th	Night	18% 16% 6% 13% 7% 6% 5% 4 5% 5% 15%	5120
	21st to end	Night	22% 16% 5% 11% 5% 4 4 3 5% 6% 19%	5242
April	1st to 10th	Night	24% 18% 6% 7% 4 4 3 3 5% 5% 21%	2000
	11th to 20th	Night	25% 17% 4 6% 4 3 4 3 4 5% 25%	1791
	21st to end	Night	25% 18% 4 8% 4 3 3 3 4 5% 24%	1800
May	1st to 10th	Night	33% 19% 6% 8% 4 3 3 2 3 4 15%	3850
	11th to 20th	Night	23% 19% 8% 11% 4 3 2 2 3 4 20%	3385
	21st to end	Night	29% 14% 4 6% 3 3 4 4 5% 6% 22%	3468
June	1st to 10th	Night	33% 13% 3 7% 5% 3 4 3 6% 6% 18%	1400
	11th to 20th	Night	31% 9% 3 5% 4 3 4 4 6% 7% 24%	1400
	21st to end	Night	22% 12% 3 9% 6% 5% 5% 3 5% 6% 25%	1400
July	1st to 10th	Night	23% 11% 4 7% 4 5% 5% 4 6% 6% 26%	2256
	11th to 20th	Night	14% 12% 3 9% 7% 5% 4 4 7% 7% 29%	2269
	21st to end	Night	16% 9% 3 7% 4 4 5% 3 5% 8% 38%	2750
August	1st to 10th	Night	15% 9% 3 8% 5% 5% 5% 5% 6% 8% 32%	2516
	11th to 20th	Night	16% 9% 4 7% 4 4 3 3 5% 7% 38%	2784
	21st to end	Night	21% 7% 3 6% 4 4 4 3 5% 6% 37%	3135
September	1st to 10th	Night	24% 8% 3 6% 3 3 3 3 4 6% 36%	1896
	11th to 20th	Night	24% 10% 3 6% 5% 4 4 3 5% 5% 31%	2090
	21st to end	Night	22% 11% 3 7% 4 3 5% 3 5% 7% 29%	2090
October	1st to 10th	Night	24% 11% 3 7% 4 4 3 3 5% 6% 29%	2133
	11th to 20th	Night	25% 12% 3 8% 4 4 4 3 5% 6% 26%	2441
	21st to end	Night	29% 17% 3 7% 4 3 4 3 3 5% 22%	2717
November	1st to 10th	Night	22% 16% 4 9% 6% 5% 5% 4 5% 6% 18%	2538
	11th to 20th	Night	25% 15% 5% 8% 4 3 4 3 5% 6% 20%	2835
	21st to end	Night	21% 17% 7% 9% 6% 4 4 3 6% 6% 19%	3000
December	1st to 10th	Night	15% 12% 4 9% 5% 5% 5% 4 5% 6% 30%	4900
	11th to 20th	Night	21% 15% 5% 13% 6% 5% 4 3 4 5% 17%	5581
	21st to end	Night	16% 13% 6% 17% 7% 6% 4 3 5% 5% 17%	7480

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% 10% 9% 8% 2	3177
	11th to 20th	Day	71% 8% 9% 7% 4	3593
	21st to end	Day	56% 12% 10% 13% 7% 3	3982
February	1st to 10th	Day	63% 8% 12% 10% 6% 1	1600
	11th to 20th	Day	68% 7% 10% 11% 4	1813
	21st to end	Day	62% 7% 9% 13% 8% 1	1650
March	1st to 10th	Day	65% 7% 8% 12% 7% 1	4478
	11th to 20th	Day	69% 7% 8% 9% 6% 2	4838
	21st to end	Day	72% 4 7% 11% 6%	5687
April	1st to 10th	Day	69% 5% 8% 11% 5% 1	2400
	11th to 20th	Day	62% 5% 10% 15% 8% 1	2558
	21st to end	Day	66% 6% 8% 13% 8%	2600
May	1st to 10th	Day	72% 5% 9% 10% 4 1	6117
	11th to 20th	Day	63% 6% 9% 15% 6%	6530
	21st to end	Day	61% 6% 11% 18% 5%	7428
June	1st to 10th	Day	69% 6% 9% 12% 4	3000
	11th to 20th	Day	60% 7% 12% 16% 5% 1	3000
	21st to end	Day	58% 9% 12% 14% 7% 1	3000
July	1st to 10th	Day	57% 7% 12% 17% 6%	4750
	11th to 20th	Day	50% 9% 17% 19% 5%	4616
	21st to end	Day	42% 10% 17% 26% 6%	4662
August	1st to 10th	Day	57% 8% 16% 16% 3	4410
	11th to 20th	Day	46% 7% 15% 19% 12% 1	4090
	21st to end	Day	47% 7% 16% 24% 6%	4532
September	1st to 10th	Day	48% 7% 12% 23% 8% 1	2281
	11th to 20th	Day	57% 7% 13% 17% 6%	2090
	21st to end	Day	52% 6% 18% 17% 6%	2090
October	1st to 10th	Day	58% 7% 12% 16% 6%	3401
	11th to 20th	Day	60% 8% 11% 15% 6%	2871
	21st to end	Day	66% 6% 9% 10% 8% 1	3092
November	1st to 10th	Day	67% 7% 12% 10% 4	1760
	11th to 20th	Day	64% 7% 11% 11% 6% 1	1560
	21st to end	Day	67% 8% 12% 8% 5% 1	1400
December	1st to 10th	Day	49% 7% 11% 22% 10%	2290
	11th to 20th	Day	65% 9% 18% 6% 3	2627
	21st to end	Day	69% 8% 9% 11% 3	3498
January	1st to 10th	Night	71% 10% 9% 7% 3	6789
	11th to 20th	Night	66% 8% 11% 10% 5%	6383
	21st to end	Night	49% 9% 18% 11% 10% 2	6996
February	1st to 10th	Night	62% 8% 12% 11% 6% 1	2800
	11th to 20th	Night	67% 7% 10% 11% 4	2482
	21st to end	Night	56% 8% 10% 17% 8% 1	1980
March	1st to 10th	Night	61% 7% 10% 12% 8% 3	5375
	11th to 20th	Night	68% 8% 9% 8% 5% 1	5121
	21st to end	Night	65% 6% 11% 13% 5%	5242
April	1st to 10th	Night	65% 5% 8% 12% 9% 1	2000
	11th to 20th	Night	62% 4 10% 17% 6% 1	1791
	21st to end	Night	63% 6% 8% 13% 9% 1	1800
May	1st to 10th	Night	74% 4 8% 12% 3	3855
	11th to 20th	Night	69% 4 9% 12% 7%	3386
	21st to end	Night	62% 6% 11% 15% 5%	3469
June	1st to 10th	Night	67% 6% 12% 10% 5%	1400
	11th to 20th	Night	58% 8% 14% 15% 5%	1400
	21st to end	Night	60% 8% 11% 14% 7% 1	1400
July	1st to 10th	Night	57% 7% 14% 18% 3	2222
	11th to 20th	Night	52% 9% 15% 16% 7%	2227
	21st to end	Night	45% 7% 17% 26% 5%	2663
August	1st to 10th	Night	47% 10% 18% 22% 4	2505
	11th to 20th	Night	45% 7% 17% 21% 9% 1	2811
	21st to end	Night	47% 6% 16% 26% 5%	3134
September	1st to 10th	Night	49% 6% 13% 22% 9% 1	1896
	11th to 20th	Night	55% 6% 13% 17% 9% 1	2090
	21st to end	Night	54% 7% 13% 17% 7%	2090
October	1st to 10th	Night	60% 6% 15% 13% 5% 1	3562
	11th to 20th	Night	58% 8% 15% 13% 6%	4055
	21st to end	Night	58% 5% 12% 15% 8% 1	4467
November	1st to 10th	Night	66% 8% 11% 11% 4	2538
	11th to 20th	Night	65% 7% 12% 13% 3	2835
	21st to end	Night	66% 7% 12% 10% 5%	3000
December	1st to 10th	Night	53% 7% 10% 19% 11%	4900
	11th to 20th	Night	69% 7% 14% 6% 4	5583
	21st to end	Night	67% 9% 11% 11% 2	7480

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	25% 21% 34% 14% 6%	400
	11th to 20th	Day	22% 23% 34% 18% 3	400
	21st to end	Day	28% 20% 32% 17% 3	440
February	1st to 10th	Day	25% 26% 31% 15% 4	400
	11th to 20th	Day	28% 23% 34% 11% 2 1	396
	21st to end	Day	20% 23% 36% 15% 4 1	331
March	1st to 10th	Day	23% 22% 37% 14% 4 1	400
	11th to 20th	Day	28% 17% 29% 17% 8% 2	400
	21st to end	Day	36% 21% 23% 15% 3 2	488
April	1st to 10th	Day	28% 23% 29% 16% 3	500
	11th to 20th	Day	33% 13% 29% 19% 5% 1	676
	21st to end	Day	32% 16% 29% 18% 4 1	700
May	1st to 10th	Day	38% 13% 24% 17% 6% 2	703
	11th to 20th	Day	30% 13% 28% 18% 9% 2	724
	21st to end	Day	34% 12% 29% 19% 4 1	790
June	1st to 10th	Day	39% 11% 24% 15% 9% 1	730
	11th to 20th	Day	32% 12% 26% 20% 9% 1	730
	21st to end	Day	27% 11% 27% 22% 10% 3	730
July	1st to 10th	Day	29% 10% 27% 23% 9% 2	695
	11th to 20th	Day	21% 11% 28% 28% 10% 1	668
	21st to end	Day	23% 10% 25% 31% 10% 1	740
August	1st to 10th	Day	25% 9% 28% 25% 10% 2	675
	11th to 20th	Day	22% 7% 28% 24% 16% 2	667
	21st to end	Day	24% 8% 27% 25% 12% 3	748
September	1st to 10th	Day	25% 12% 31% 23% 9% 1	493
	11th to 20th	Day	36% 12% 28% 20% 4 1	390
	21st to end	Day	23% 20% 34% 16% 5% 2	390
October	1st to 10th	Day	25% 19% 33% 17% 5% 2	390
	11th to 20th	Day	35% 11% 26% 18% 7% 3	390
	21st to end	Day	33% 21% 25% 14% 6% 1	429
November	1st to 10th	Day	37% 18% 30% 13% 2	395
	11th to 20th	Day	35% 22% 23% 15% 5% 1	400
	21st to end	Day	39% 20% 29% 12% 1	400
December	1st to 10th	Day	26% 17% 34% 18% 6% 1	400
	11th to 20th	Day	30% 25% 30% 13% 3	400
	21st to end	Day	23% 20% 30% 20% 7% 1	440
January	1st to 10th	Night	27% 19% 31% 17% 5% 1	900
	11th to 20th	Night	23% 23% 33% 16% 4	900
	21st to end	Night	23% 21% 38% 15% 3	990
February	1st to 10th	Night	25% 21% 36% 15% 3	900
	11th to 20th	Night	29% 23% 34% 12% 2	850
	21st to end	Night	21% 15% 39% 17% 7% 1	660
March	1st to 10th	Night	27% 19% 34% 15% 5% 1	800
	11th to 20th	Night	24% 16% 30% 23% 7%	663
	21st to end	Night	32% 17% 30% 17% 4	660
April	1st to 10th	Night	32% 19% 28% 16% 4 1	600
	11th to 20th	Night	32% 11% 34% 18% 5% 1	594
	21st to end	Night	33% 11% 33% 19% 3	600
May	1st to 10th	Night	36% 10% 25% 22% 7% 1	600
	11th to 20th	Night	34% 11% 28% 19% 8%	592
	21st to end	Night	35% 10% 31% 18% 5%	649
June	1st to 10th	Night	40% 10% 23% 24% 3	600
	11th to 20th	Night	37% 8% 24% 24% 7% 1	600
	21st to end	Night	28% 9% 32% 23% 8%	600
July	1st to 10th	Night	24% 8% 34% 27% 7% 1	572
	11th to 20th	Night	22% 9% 31% 33% 5%	552
	21st to end	Night	24% 7% 30% 32% 7%	623
August	1st to 10th	Night	23% 6% 30% 30% 10%	568
	11th to 20th	Night	23% 6% 30% 31% 10%	562
	21st to end	Night	24% 8% 28% 31% 9% 1	627
September	1st to 10th	Night	27% 7% 34% 25% 6%	570
	11th to 20th	Night	29% 13% 31% 24% 3	570
	21st to end	Night	31% 12% 32% 21% 4	570
October	1st to 10th	Night	32% 11% 32% 21% 4 1	593
	11th to 20th	Night	33% 11% 29% 20% 7%	831
	21st to end	Night	38% 15% 25% 16% 5% 1	946
November	1st to 10th	Night	32% 20% 30% 14% 3	880
	11th to 20th	Night	35% 15% 30% 14% 5% 1	900
	21st to end	Night	34% 20% 30% 14% 2	900
December	1st to 10th	Night	28% 18% 34% 16% 4 1	900
	11th to 20th	Night	32% 22% 32% 12% 2	900
	21st to end	Night	24% 19% 32% 18% 6% 1	990

Page generated at 2025-07-03 02:30:18. Version ac07

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