Bonavista
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bonavista clear sky chart from 2005-11-06 to 2026-06-01.

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% 11% 6% 5% 4 3 5% 6% 22%	132056
	Night	21% 15% 6% 12% 6% 5% 4 3 4 5% 18%	131388
Transparency	Day	62% 6% 12% 14% 5%	135521
	Night	66% 6% 11% 12% 5%	136038
Seeing	Day	27% 12% 27% 23% 9% 1	20346
	Night	30% 13% 29% 22% 6% 1	26975

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	22% 22% 8% 15% 5% 3 3 3 3 3 12%	4122
	11th to 20th	Day	20% 20% 7% 16% 7% 4 4 2 3 4 12%	4429
	21st to end	Day	11% 13% 6% 19% 14% 8% 4 3 4 4 14%	5157
February	1st to 10th	Day	20% 13% 5% 15% 11% 7% 5% 3 5% 4 12%	1791
	11th to 20th	Day	21% 16% 6% 14% 9% 7% 4 3 5% 4 13%	1843
	21st to end	Day	16% 12% 5% 15% 8% 7% 6% 3 5% 6% 18%	1709
March	1st to 10th	Day	16% 13% 5% 15% 10% 6% 5% 3 4 5% 19%	4615
	11th to 20th	Day	22% 14% 6% 13% 7% 5% 4 3 4 4 19%	5090
	21st to end	Day	24% 17% 6% 11% 4 3 3 2 4 6% 20%	5588
April	1st to 10th	Day	18% 15% 4 11% 5% 5% 5% 3 5% 7% 22%	2560
	11th to 20th	Day	22% 14% 4 9% 4 4 4 3 5% 6% 26%	2701
	21st to end	Day	23% 16% 5% 9% 5% 4 4 3 4 6% 22%	2730
May	1st to 10th	Day	22% 19% 7% 10% 5% 4 3 3 4 5% 19%	6015
	11th to 20th	Day	23% 16% 6% 10% 5% 4 4 3 5% 5% 20%	6753
	21st to end	Day	23% 17% 6% 9% 5% 4 4 3 4 6% 21%	7593
June	1st to 10th	Day	28% 17% 4 10% 5% 4 4 4 4 5% 16%	3000
	11th to 20th	Day	24% 14% 3 8% 4 4 4 4 5% 6% 26%	3000
	21st to end	Day	20% 12% 4 8% 6% 5% 5% 4 6% 8% 24%	3000
July	1st to 10th	Day	22% 10% 4 9% 6% 5% 5% 4 5% 7% 23%	6800
	11th to 20th	Day	12% 8% 3 8% 5% 5% 6% 5% 8% 10% 30%	6800
	21st to end	Day	18% 9% 3 7% 5% 5% 5% 4 5% 8% 31%	7061
August	1st to 10th	Day	20% 10% 4 9% 5% 5% 6% 4 6% 7% 25%	4378
	11th to 20th	Day	14% 9% 3 6% 4 4 4 4 5% 7% 41%	4176
	21st to end	Day	17% 9% 3 7% 5% 4 4 4 5% 8% 34%	4675
September	1st to 10th	Day	19% 9% 3 7% 5% 4 4 4 5% 8% 33%	2422
	11th to 20th	Day	26% 10% 3 6% 4 4 4 3 6% 6% 29%	2200
	21st to end	Day	18% 11% 3 7% 4 4 4 3 6% 7% 32%	2200
October	1st to 10th	Day	21% 13% 4 8% 5% 3 4 4 5% 6% 27%	2085
	11th to 20th	Day	26% 16% 4 9% 5% 4 3 3 5% 5% 19%	1940
	21st to end	Day	24% 18% 3 9% 4 4 4 3 5% 6% 18%	1980
November	1st to 10th	Day	22% 18% 4 8% 5% 5% 4 4 5% 6% 20%	1766
	11th to 20th	Day	23% 17% 6% 9% 6% 4 5% 3 5% 5% 17%	1680
	21st to end	Day	24% 18% 7% 10% 4 5% 3 3 4 4 18%	1564
December	1st to 10th	Day	19% 15% 6% 10% 5% 5% 5% 4 5% 6% 21%	2360
	11th to 20th	Day	18% 15% 7% 16% 6% 4 4 3 4 5% 19%	2698
	21st to end	Day	21% 17% 8% 22% 6% 4 3 2 3 3 9%	3575
January	1st to 10th	Night	20% 21% 9% 18% 7% 4 4 3 3 3 8%	8802
	11th to 20th	Night	19% 20% 8% 16% 7% 5% 4 3 4 4 11%	8483
	21st to end	Night	10% 12% 5% 16% 12% 10% 4 3 4 5% 19%	9056
February	1st to 10th	Night	18% 16% 6% 16% 11% 5% 3 3 4 4 12%	2828
	11th to 20th	Night	21% 17% 7% 14% 9% 4 4 3 4 5% 12%	2663
	21st to end	Night	16% 15% 5% 13% 7% 7% 4 3 4 5% 20%	2092
March	1st to 10th	Night	20% 12% 5% 13% 6% 5% 5% 4 5% 6% 18%	5445
	11th to 20th	Night	20% 14% 6% 14% 6% 5% 4 3 5% 5% 17%	5089
	21st to end	Night	26% 17% 5% 13% 5% 4 4 2 3 5% 15%	5586
April	1st to 10th	Night	22% 18% 5% 10% 4 4 4 3 4 5% 21%	2058
	11th to 20th	Night	23% 14% 5% 9% 4 4 4 3 3 7% 22%	1868
	21st to end	Night	25% 18% 7% 7% 4 4 3 3 3 4 24%	1890
May	1st to 10th	Night	28% 18% 5% 7% 4 3 3 3 4 5% 19%	4165
	11th to 20th	Night	25% 18% 7% 9% 5% 3 4 3 4 4 17%	3375
	21st to end	Night	26% 18% 6% 8% 4 4 4 3 4 6% 17%	3545
June	1st to 10th	Night	30% 16% 4 9% 5% 3 3 3 5% 5% 16%	1401
	11th to 20th	Night	29% 11% 4 8% 5% 4 4 4 5% 7% 20%	1400
	21st to end	Night	23% 13% 4 7% 5% 4 4 4 6% 7% 23%	1400
July	1st to 10th	Night	25% 11% 4 10% 6% 4 4 3 4 7% 22%	3179
	11th to 20th	Night	14% 9% 3 8% 5% 7% 7% 5% 6% 9% 28%	3180
	21st to end	Night	17% 11% 4 8% 5% 5% 5% 4 5% 7% 31%	3810
August	1st to 10th	Night	16% 9% 3 7% 5% 5% 7% 5% 8% 8% 27%	2781
	11th to 20th	Night	20% 8% 2 6% 4 4 4 3 5% 7% 37%	2881
	21st to end	Night	25% 9% 3 6% 3 3 4 3 5% 8% 30%	3234
September	1st to 10th	Night	20% 9% 3 7% 4 4 4 3 5% 6% 36%	1976
	11th to 20th	Night	24% 11% 2 8% 4 5% 5% 3 5% 6% 28%	2200
	21st to end	Night	22% 13% 3 6% 4 4 5% 3 6% 7% 27%	2200
October	1st to 10th	Night	23% 13% 3 9% 4 4 5% 3 5% 6% 25%	2315
	11th to 20th	Night	26% 16% 4 9% 5% 5% 4 3 4 6% 18%	2458
	21st to end	Night	27% 17% 4 8% 4 4 4 2 4 5% 20%	2860
November	1st to 10th	Night	23% 20% 5% 10% 5% 4 4 3 4 6% 16%	2752
	11th to 20th	Night	24% 18% 6% 9% 4 4 4 2 4 6% 18%	2940
	21st to end	Night	21% 19% 5% 12% 5% 4 4 3 4 5% 16%	3050
December	1st to 10th	Night	17% 15% 7% 13% 6% 5% 4 4 4 5% 20%	5050
	11th to 20th	Night	21% 17% 7% 15% 6% 4 4 3 4 4 14%	5731
	21st to end	Night	19% 18% 10% 22% 6% 4 3 3 3 3 9%	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	77% 4 7% 9% 3	4123
	11th to 20th	Day	76% 4 7% 6% 6% 1	4457
	21st to end	Day	71% 6% 9% 8% 6% 1	5157
February	1st to 10th	Day	73% 6% 10% 7% 3	1791
	11th to 20th	Day	73% 5% 9% 9% 4	1850
	21st to end	Day	67% 6% 10% 10% 6% 1	1709
March	1st to 10th	Day	65% 6% 9% 12% 6% 1	4620
	11th to 20th	Day	68% 7% 9% 10% 6% 1	5090
	21st to end	Day	66% 6% 8% 13% 6% 1	5588
April	1st to 10th	Day	63% 7% 9% 13% 8% 1	2560
	11th to 20th	Day	59% 7% 9% 15% 9% 1	2701
	21st to end	Day	63% 6% 10% 12% 8% 1	2730
May	1st to 10th	Day	68% 6% 9% 12% 4 1	6027
	11th to 20th	Day	65% 7% 10% 14% 4	6757
	21st to end	Day	65% 6% 11% 15% 4	7593
June	1st to 10th	Day	72% 5% 7% 11% 4	3000
	11th to 20th	Day	60% 7% 12% 16% 5% 1	3000
	21st to end	Day	57% 9% 14% 14% 5%	3000
July	1st to 10th	Day	60% 6% 14% 16% 4	6725
	11th to 20th	Day	47% 8% 19% 20% 6%	6718
	21st to end	Day	52% 6% 17% 22% 3	6860
August	1st to 10th	Day	57% 8% 15% 17% 3	4364
	11th to 20th	Day	44% 7% 18% 24% 7%	4215
	21st to end	Day	48% 7% 18% 23% 4	4675
September	1st to 10th	Day	49% 7% 13% 23% 8%	2422
	11th to 20th	Day	54% 7% 14% 16% 8%	2200
	21st to end	Day	51% 8% 18% 17% 6% 1	2200
October	1st to 10th	Day	62% 6% 11% 16% 4	3403
	11th to 20th	Day	61% 7% 12% 14% 6%	3153
	21st to end	Day	65% 5% 9% 15% 6% 1	3191
November	1st to 10th	Day	64% 7% 14% 11% 5%	1766
	11th to 20th	Day	68% 6% 10% 12% 4	1680
	21st to end	Day	70% 5% 11% 9% 5% 1	1564
December	1st to 10th	Day	61% 5% 13% 16% 6%	2360
	11th to 20th	Day	68% 5% 14% 8% 5%	2697
	21st to end	Day	80% 5% 6% 6% 3	3575
January	1st to 10th	Night	79% 4 8% 6% 3	8802
	11th to 20th	Night	73% 5% 10% 8% 3	8530
	21st to end	Night	65% 7% 11% 11% 7% 1	9056
February	1st to 10th	Night	74% 4 8% 8% 4 1	2828
	11th to 20th	Night	73% 5% 9% 10% 3	2667
	21st to end	Night	65% 4 9% 14% 6% 1	2092
March	1st to 10th	Night	62% 8% 12% 11% 6% 1	5453
	11th to 20th	Night	67% 5% 12% 10% 5% 2	5090
	21st to end	Night	71% 4 9% 11% 4	5586
April	1st to 10th	Night	67% 4 6% 13% 8% 1	2058
	11th to 20th	Night	63% 5% 11% 15% 6% 1	1868
	21st to end	Night	66% 4 7% 14% 8% 1	1890
May	1st to 10th	Night	68% 5% 11% 13% 3	4170
	11th to 20th	Night	71% 4 9% 10% 5%	3376
	21st to end	Night	68% 5% 11% 10% 5%	3546
June	1st to 10th	Night	69% 7% 9% 11% 4	1401
	11th to 20th	Night	64% 7% 10% 13% 6%	1400
	21st to end	Night	59% 8% 13% 14% 5% 1	1400
July	1st to 10th	Night	64% 6% 12% 16% 2	3146
	11th to 20th	Night	53% 8% 16% 18% 5%	3138
	21st to end	Night	53% 5% 20% 19% 3	3697
August	1st to 10th	Night	52% 9% 17% 19% 3	2770
	11th to 20th	Night	47% 5% 16% 23% 9%	2908
	21st to end	Night	53% 5% 14% 23% 5%	3233
September	1st to 10th	Night	48% 6% 15% 21% 9% 1	1976
	11th to 20th	Night	56% 7% 13% 16% 8% 1	2200
	21st to end	Night	56% 7% 14% 17% 6%	2200
October	1st to 10th	Night	66% 5% 14% 12% 3	3783
	11th to 20th	Night	60% 7% 14% 14% 5%	3994
	21st to end	Night	62% 4 11% 16% 7%	4610
November	1st to 10th	Night	68% 8% 11% 9% 4	2752
	11th to 20th	Night	67% 6% 11% 12% 4	2940
	21st to end	Night	68% 6% 12% 10% 4 1	3050
December	1st to 10th	Night	64% 6% 8% 14% 8%	5050
	11th to 20th	Night	73% 5% 14% 7% 2	5733
	21st to end	Night	76% 7% 8% 7% 1	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	35% 17% 29% 13% 5% 1	430
	11th to 20th	Day	26% 21% 34% 15% 4	430
	21st to end	Day	24% 22% 35% 16% 3	473
February	1st to 10th	Day	24% 22% 33% 15% 4 1	430
	11th to 20th	Day	26% 24% 35% 13% 2 1	426
	21st to end	Day	19% 19% 38% 17% 7%	355
March	1st to 10th	Day	21% 23% 36% 15% 5%	430
	11th to 20th	Day	28% 13% 31% 20% 7% 1	430
	21st to end	Day	30% 16% 31% 16% 5% 1	473
April	1st to 10th	Day	26% 17% 30% 22% 5% 1	590
	11th to 20th	Day	27% 12% 28% 24% 8% 1	739
	21st to end	Day	29% 12% 27% 23% 6% 2	750
May	1st to 10th	Day	30% 13% 26% 22% 7% 2	753
	11th to 20th	Day	29% 7% 28% 23% 11% 2	774
	21st to end	Day	29% 8% 29% 27% 7% 1	845
June	1st to 10th	Day	40% 7% 23% 21% 8% 1	730
	11th to 20th	Day	30% 6% 25% 28% 10% 2	730
	21st to end	Day	23% 6% 24% 31% 12% 3	730
July	1st to 10th	Day	25% 6% 24% 31% 11% 2	720
	11th to 20th	Day	20% 5% 23% 33% 18% 1	718
	21st to end	Day	26% 5% 21% 37% 11% 1	795
August	1st to 10th	Day	25% 4 23% 31% 14% 2	725
	11th to 20th	Day	22% 6% 22% 30% 17% 3	717
	21st to end	Day	25% 7% 22% 31% 14% 1	803
September	1st to 10th	Day	21% 5% 24% 32% 16% 3	590
	11th to 20th	Day	32% 14% 20% 25% 8% 1	420
	21st to end	Day	25% 13% 32% 21% 8% 1	420
October	1st to 10th	Day	25% 11% 31% 23% 9% 1	420
	11th to 20th	Day	35% 12% 25% 18% 8% 1	420
	21st to end	Day	29% 18% 27% 18% 7% 1	462
November	1st to 10th	Day	32% 18% 30% 17% 3	425
	11th to 20th	Day	34% 16% 27% 17% 6%	430
	21st to end	Day	34% 17% 33% 14% 2	430
December	1st to 10th	Day	29% 16% 34% 16% 5%	430
	11th to 20th	Day	30% 26% 30% 10% 4	430
	21st to end	Day	25% 21% 30% 16% 6% 1	473
January	1st to 10th	Night	30% 21% 28% 16% 4	950
	11th to 20th	Night	30% 21% 30% 13% 5% 1	950
	21st to end	Night	26% 21% 37% 14% 2	1045
February	1st to 10th	Night	27% 21% 34% 15% 3	950
	11th to 20th	Night	30% 21% 35% 11% 3	933
	21st to end	Night	23% 17% 36% 17% 5% 1	700
March	1st to 10th	Night	25% 19% 37% 15% 4	824
	11th to 20th	Night	23% 15% 30% 22% 9% 1	630
	21st to end	Night	34% 14% 27% 20% 5%	693
April	1st to 10th	Night	32% 15% 29% 17% 6% 1	630
	11th to 20th	Night	29% 11% 29% 24% 6%	624
	21st to end	Night	31% 8% 30% 23% 6% 1	630
May	1st to 10th	Night	35% 5% 26% 27% 6% 1	630
	11th to 20th	Night	31% 5% 28% 26% 10% 1	622
	21st to end	Night	32% 8% 26% 26% 9%	682
June	1st to 10th	Night	37% 6% 26% 24% 6% 1	601
	11th to 20th	Night	35% 4 21% 29% 10% 1	600
	21st to end	Night	31% 5% 24% 27% 12% 2	600
July	1st to 10th	Night	27% 5% 27% 33% 7% 2	586
	11th to 20th	Night	23% 3 27% 36% 11%	582
	21st to end	Night	25% 5% 24% 34% 11%	656
August	1st to 10th	Night	26% 5% 23% 34% 11% 2	598
	11th to 20th	Night	24% 4 24% 33% 13% 1	592
	21st to end	Night	27% 5% 22% 34% 12% 1	660
September	1st to 10th	Night	22% 7% 28% 32% 12% 1	600
	11th to 20th	Night	30% 7% 28% 30% 5%	600
	21st to end	Night	32% 10% 28% 24% 6% 1	600
October	1st to 10th	Night	29% 12% 27% 24% 8% 1	663
	11th to 20th	Night	37% 11% 23% 22% 7%	768
	21st to end	Night	36% 12% 24% 20% 7%	1001
November	1st to 10th	Night	35% 16% 28% 17% 3	930
	11th to 20th	Night	34% 15% 28% 18% 5%	950
	21st to end	Night	31% 20% 30% 16% 3	950
December	1st to 10th	Night	29% 18% 32% 17% 4	950
	11th to 20th	Night	33% 24% 28% 12% 3	950
	21st to end	Night	26% 19% 30% 18% 6% 1	1045

Page generated at 2026-05-29 02:53:30. Version ac07

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