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 2025-02-06.

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	21% 14% 5% 11% 6% 5% 4 3 5% 6% 22%	108117
	Night	21% 15% 6% 12% 6% 5% 4 3 4 5% 19%	110333
Transparency	Day	62% 7% 12% 14% 5%	111629
	Night	65% 6% 12% 12% 5%	115012
Seeing	Day	27% 13% 28% 23% 8% 1	18484
	Night	30% 13% 29% 21% 6% 1	25205

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	21% 23% 9% 18% 5% 3 3 3 4 3 9%	3176
	11th to 20th	Day	17% 23% 8% 17% 9% 5% 4 2 3 4 10%	3391
	21st to end	Day	11% 13% 5% 20% 12% 8% 4 3 4 5% 15%	3982
February	1st to 10th	Day	20% 13% 5% 15% 11% 7% 5% 4 5% 4 12%	1660
	11th to 20th	Day	20% 16% 5% 14% 8% 7% 4 3 5% 4 14%	1663
	21st to end	Day	15% 13% 5% 15% 8% 7% 6% 3 5% 6% 18%	1551
March	1st to 10th	Day	18% 13% 4 12% 7% 6% 5% 3 4 5% 22%	3140
	11th to 20th	Day	23% 15% 7% 13% 7% 5% 4 2 4 4 15%	3480
	21st to end	Day	27% 14% 4 9% 4 3 3 3 4 7% 22%	3817
April	1st to 10th	Day	18% 16% 4 11% 5% 5% 5% 3 5% 7% 22%	2316
	11th to 20th	Day	22% 14% 4 8% 4 4 4 3 5% 6% 25%	2441
	21st to end	Day	22% 16% 5% 9% 5% 4 4 3 4 6% 22%	2470
May	1st to 10th	Day	25% 20% 7% 10% 5% 3 3 3 4 5% 16%	4105
	11th to 20th	Day	28% 16% 6% 10% 5% 4 4 3 4 6% 15%	4597
	21st to end	Day	24% 16% 6% 8% 5% 4 3 3 4 6% 21%	5173
June	1st to 10th	Day	28% 18% 5% 10% 5% 4 4 4 4 4 14%	2850
	11th to 20th	Day	25% 14% 3 8% 4 4 4 4 5% 6% 26%	2850
	21st to end	Day	20% 12% 4 7% 6% 5% 5% 4 6% 7% 24%	2850
July	1st to 10th	Day	24% 11% 4 9% 5% 5% 5% 4 5% 6% 23%	4750
	11th to 20th	Day	15% 10% 3 8% 5% 5% 6% 5% 8% 8% 28%	4750
	21st to end	Day	13% 9% 3 6% 5% 4 5% 4 5% 8% 37%	4910
August	1st to 10th	Day	21% 11% 4 9% 5% 5% 6% 4 6% 7% 23%	4244
	11th to 20th	Day	14% 9% 3 6% 4 4 4 4 5% 7% 41%	4046
	21st to end	Day	17% 8% 3 7% 5% 4 4 4 5% 8% 35%	4532
September	1st to 10th	Day	19% 9% 3 7% 4 4 4 4 6% 8% 32%	2302
	11th to 20th	Day	26% 9% 3 5% 4 4 4 3 6% 6% 30%	2090
	21st to end	Day	19% 11% 3 7% 4 4 4 3 6% 7% 32%	2090
October	1st to 10th	Day	21% 13% 4 8% 5% 3 4 4 5% 6% 26%	1981
	11th to 20th	Day	26% 15% 4 9% 5% 4 3 3 5% 5% 19%	1843
	21st to end	Day	24% 19% 3 8% 4 5% 4 3 5% 6% 18%	1881
November	1st to 10th	Day	21% 18% 4 8% 5% 5% 4 4 5% 6% 20%	1680
	11th to 20th	Day	23% 18% 6% 9% 6% 5% 4 3 5% 5% 17%	1600
	21st to end	Day	24% 18% 7% 11% 4 5% 3 3 4 4 17%	1490
December	1st to 10th	Day	19% 15% 6% 9% 5% 5% 5% 4 5% 6% 21%	2290
	11th to 20th	Day	18% 15% 7% 16% 6% 4 4 3 4 5% 19%	2628
	21st to end	Day	21% 17% 8% 22% 7% 4 3 2 3 3 9%	3498
January	1st to 10th	Night	20% 23% 9% 18% 7% 4 4 3 3 3 7%	6789
	11th to 20th	Night	16% 20% 8% 16% 8% 5% 4 3 4 4 12%	6511
	21st to end	Night	10% 10% 4 17% 12% 8% 5% 3 4 5% 21%	6996
February	1st to 10th	Night	18% 16% 6% 16% 11% 6% 3 3 4 4 12%	2630
	11th to 20th	Night	22% 16% 6% 14% 8% 4 4 3 4 6% 13%	2403
	21st to end	Night	16% 16% 5% 13% 7% 7% 4 3 4 5% 20%	1899
March	1st to 10th	Night	22% 12% 5% 10% 5% 5% 4 4 6% 7% 19%	3700
	11th to 20th	Night	20% 14% 6% 14% 6% 5% 4 3 5% 5% 17%	3479
	21st to end	Night	31% 15% 4 9% 4 4 4 2 3 5% 17%	3815
April	1st to 10th	Night	22% 18% 5% 10% 5% 4 4 2 4 5% 20%	1862
	11th to 20th	Night	25% 15% 6% 9% 4 4 4 3 3 7% 22%	1688
	21st to end	Night	24% 18% 7% 7% 4 4 3 3 4 4 23%	1710
May	1st to 10th	Night	30% 19% 6% 7% 4 3 3 3 4 6% 16%	2845
	11th to 20th	Night	27% 19% 8% 9% 4 3 3 3 4 4 15%	2301
	21st to end	Night	27% 17% 6% 8% 4 4 4 3 4 5% 17%	2412
June	1st to 10th	Night	31% 17% 4 9% 5% 3 3 2 5% 5% 15%	1330
	11th to 20th	Night	30% 11% 4 8% 5% 4 4 4 5% 7% 20%	1330
	21st to end	Night	24% 13% 4 7% 5% 4 4 4 6% 7% 23%	1330
July	1st to 10th	Night	29% 12% 5% 8% 5% 4 4 4 4 6% 21%	2220
	11th to 20th	Night	18% 11% 3 9% 6% 7% 7% 5% 6% 7% 23%	2220
	21st to end	Night	14% 9% 3 7% 4 5% 5% 4 5% 7% 37%	2651
August	1st to 10th	Night	17% 10% 3 7% 5% 5% 7% 5% 8% 9% 25%	2695
	11th to 20th	Night	20% 8% 2 6% 4 4 4 3 5% 7% 37%	2791
	21st to end	Night	25% 9% 3 7% 3 3 4 3 5% 7% 31%	3135
September	1st to 10th	Night	21% 9% 3 7% 3 4 4 3 5% 6% 35%	1876
	11th to 20th	Night	23% 10% 3 8% 4 5% 4 3 5% 6% 29%	2090
	21st to end	Night	22% 13% 3 6% 4 4 5% 3 6% 7% 26%	2090
October	1st to 10th	Night	24% 13% 3 8% 4 4 5% 3 5% 6% 24%	2199
	11th to 20th	Night	25% 15% 4 9% 5% 5% 5% 3 4 6% 19%	2335
	21st to end	Night	28% 17% 4 8% 4 4 4 2 3 5% 20%	2717
November	1st to 10th	Night	22% 20% 5% 10% 5% 5% 4 3 5% 6% 16%	2618
	11th to 20th	Night	24% 18% 7% 9% 4 4 4 2 4 5% 17%	2800
	21st to end	Night	21% 19% 5% 12% 5% 4 4 3 4 5% 16%	2905
December	1st to 10th	Night	17% 15% 7% 13% 5% 5% 4 4 4 5% 20%	4900
	11th to 20th	Night	21% 17% 7% 15% 6% 4 4 3 4 4 14%	5581
	21st to end	Night	19% 18% 10% 22% 6% 4 3 3 3 3 9%	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	79% 5% 7% 6% 2	3177
	11th to 20th	Day	77% 5% 7% 7% 4	3419
	21st to end	Day	67% 6% 9% 10% 6% 1	3982
February	1st to 10th	Day	72% 7% 11% 7% 3	1660
	11th to 20th	Day	71% 6% 10% 9% 3	1670
	21st to end	Day	66% 6% 10% 10% 6% 1	1551
March	1st to 10th	Day	61% 7% 11% 13% 6% 2	3145
	11th to 20th	Day	71% 8% 7% 9% 5%	3480
	21st to end	Day	62% 8% 10% 15% 4 1	3817
April	1st to 10th	Day	62% 8% 9% 12% 8% 1	2316
	11th to 20th	Day	59% 8% 9% 14% 9% 1	2441
	21st to end	Day	63% 7% 10% 11% 8% 1	2470
May	1st to 10th	Day	69% 8% 9% 10% 3	4120
	11th to 20th	Day	69% 9% 9% 9% 4	4601
	21st to end	Day	64% 8% 9% 14% 5%	5173
June	1st to 10th	Day	74% 6% 7% 9% 3	2850
	11th to 20th	Day	60% 7% 13% 14% 5% 1	2850
	21st to end	Day	58% 9% 15% 13% 5%	2850
July	1st to 10th	Day	61% 6% 14% 15% 4	4675
	11th to 20th	Day	51% 10% 18% 17% 5%	4668
	21st to end	Day	44% 8% 17% 27% 5%	4753
August	1st to 10th	Day	59% 8% 15% 15% 2	4230
	11th to 20th	Day	44% 7% 18% 24% 7%	4085
	21st to end	Day	48% 7% 18% 24% 4	4532
September	1st to 10th	Day	49% 7% 12% 23% 8% 1	2302
	11th to 20th	Day	53% 8% 14% 17% 8%	2090
	21st to end	Day	51% 8% 18% 16% 6% 1	2090
October	1st to 10th	Day	63% 6% 11% 15% 4	3299
	11th to 20th	Day	61% 7% 12% 14% 6%	3056
	21st to end	Day	65% 6% 8% 15% 6% 1	3092
November	1st to 10th	Day	64% 7% 14% 11% 5%	1680
	11th to 20th	Day	69% 6% 9% 11% 5%	1600
	21st to end	Day	70% 5% 11% 8% 5% 1	1490
December	1st to 10th	Day	61% 6% 13% 16% 6%	2290
	11th to 20th	Day	68% 5% 14% 8% 5%	2627
	21st to end	Day	80% 6% 6% 6% 3	3498
January	1st to 10th	Night	81% 4 8% 5% 2	6789
	11th to 20th	Night	71% 6% 12% 8% 3	6558
	21st to end	Night	61% 7% 13% 12% 6% 1	6996
February	1st to 10th	Night	74% 4 9% 8% 4 1	2630
	11th to 20th	Night	72% 5% 10% 10% 3	2407
	21st to end	Night	65% 4 10% 14% 6% 1	1899
March	1st to 10th	Night	59% 10% 14% 12% 4	3708
	11th to 20th	Night	65% 7% 12% 10% 5% 1	3480
	21st to end	Night	67% 5% 11% 13% 3	3815
April	1st to 10th	Night	68% 4 7% 14% 7% 1	1862
	11th to 20th	Night	63% 6% 10% 14% 7% 1	1688
	21st to end	Night	65% 5% 7% 14% 8% 1	1710
May	1st to 10th	Night	69% 5% 13% 9% 3	2850
	11th to 20th	Night	72% 6% 8% 10% 5%	2302
	21st to end	Night	68% 6% 10% 8% 7%	2413
June	1st to 10th	Night	71% 7% 9% 10% 4	1330
	11th to 20th	Night	64% 8% 11% 12% 6%	1330
	21st to end	Night	60% 8% 13% 13% 5% 1	1330
July	1st to 10th	Night	65% 6% 12% 15% 3	2186
	11th to 20th	Night	60% 9% 13% 12% 5%	2178
	21st to end	Night	46% 6% 24% 20% 3	2568
August	1st to 10th	Night	53% 9% 17% 18% 2	2684
	11th to 20th	Night	48% 5% 16% 22% 9%	2818
	21st to end	Night	52% 6% 14% 23% 5%	3134
September	1st to 10th	Night	49% 6% 16% 19% 9% 1	1876
	11th to 20th	Night	55% 7% 13% 16% 8% 1	2090
	21st to end	Night	56% 7% 15% 16% 6%	2090
October	1st to 10th	Night	66% 5% 14% 11% 3	3667
	11th to 20th	Night	60% 7% 14% 14% 5%	3871
	21st to end	Night	61% 4 11% 16% 7% 1	4467
November	1st to 10th	Night	67% 8% 11% 9% 4	2618
	11th to 20th	Night	68% 6% 11% 11% 4	2800
	21st to end	Night	68% 6% 13% 10% 4 1	2905
December	1st to 10th	Night	63% 6% 8% 14% 8%	4900
	11th to 20th	Night	73% 5% 14% 7% 1	5583
	21st to end	Night	76% 7% 9% 7% 1	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	35% 18% 28% 13% 5% 1	400
	11th to 20th	Day	24% 22% 34% 16% 4	400
	21st to end	Day	23% 22% 35% 16% 4	440
February	1st to 10th	Day	24% 24% 32% 15% 4 1	385
	11th to 20th	Day	25% 25% 37% 11% 2	366
	21st to end	Day	19% 20% 37% 17% 7%	307
March	1st to 10th	Day	22% 23% 35% 15% 5%	370
	11th to 20th	Day	27% 14% 30% 20% 8% 2	370
	21st to end	Day	31% 17% 30% 16% 6% 1	407
April	1st to 10th	Day	26% 18% 28% 23% 5% 1	506
	11th to 20th	Day	29% 12% 29% 22% 7% 1	639
	21st to end	Day	28% 13% 29% 24% 5% 1	650
May	1st to 10th	Day	30% 14% 26% 20% 7% 2	653
	11th to 20th	Day	29% 8% 26% 23% 11% 2	674
	21st to end	Day	28% 9% 29% 27% 6% 1	735
June	1st to 10th	Day	42% 7% 24% 19% 7% 1	680
	11th to 20th	Day	31% 6% 25% 27% 10% 1	680
	21st to end	Day	24% 6% 24% 30% 12% 4	680
July	1st to 10th	Day	26% 7% 25% 30% 11% 2	670
	11th to 20th	Day	21% 5% 23% 33% 17% 1	668
	21st to end	Day	25% 5% 21% 36% 12% 1	740
August	1st to 10th	Day	27% 4 23% 31% 13% 1	675
	11th to 20th	Day	22% 6% 22% 31% 16% 2	667
	21st to end	Day	24% 7% 21% 31% 15% 1	748
September	1st to 10th	Day	22% 5% 25% 32% 14% 2	550
	11th to 20th	Day	32% 14% 21% 26% 7% 1	390
	21st to end	Day	25% 13% 32% 21% 7% 1	390
October	1st to 10th	Day	25% 12% 33% 21% 8% 1	390
	11th to 20th	Day	34% 12% 26% 18% 9% 2	390
	21st to end	Day	29% 19% 28% 16% 7%	429
November	1st to 10th	Day	32% 18% 30% 17% 3	395
	11th to 20th	Day	35% 16% 27% 17% 6% 1	400
	21st to end	Day	34% 17% 33% 14% 2	400
December	1st to 10th	Day	30% 15% 33% 17% 5% 1	400
	11th to 20th	Day	31% 26% 29% 11% 4	400
	21st to end	Day	24% 22% 30% 16% 7% 1	440
January	1st to 10th	Night	30% 21% 28% 16% 5%	900
	11th to 20th	Night	28% 21% 31% 14% 5% 1	900
	21st to end	Night	26% 20% 37% 14% 2	990
February	1st to 10th	Night	26% 22% 35% 14% 3	876
	11th to 20th	Night	30% 22% 35% 10% 3	833
	21st to end	Night	24% 17% 37% 16% 5% 1	635
March	1st to 10th	Night	26% 19% 36% 15% 4	746
	11th to 20th	Night	22% 15% 29% 24% 10% 1	570
	21st to end	Night	35% 14% 26% 20% 4	627
April	1st to 10th	Night	31% 14% 29% 18% 7% 2	570
	11th to 20th	Night	31% 12% 29% 22% 6% 1	564
	21st to end	Night	31% 8% 32% 24% 5% 1	570
May	1st to 10th	Night	35% 6% 26% 26% 6% 2	570
	11th to 20th	Night	31% 5% 27% 26% 10% 1	562
	21st to end	Night	31% 8% 27% 25% 8%	616
June	1st to 10th	Night	39% 6% 25% 23% 6% 1	570
	11th to 20th	Night	36% 4 21% 29% 10% 1	570
	21st to end	Night	31% 5% 25% 26% 12% 2	570
July	1st to 10th	Night	26% 5% 27% 33% 7% 2	556
	11th to 20th	Night	23% 4 28% 36% 10%	552
	21st to end	Night	25% 5% 24% 34% 11%	623
August	1st to 10th	Night	27% 5% 23% 34% 10% 1	568
	11th to 20th	Night	24% 4 26% 33% 12% 1	562
	21st to end	Night	26% 5% 21% 34% 13% 1	627
September	1st to 10th	Night	22% 7% 28% 31% 11% 1	570
	11th to 20th	Night	29% 7% 28% 30% 5%	570
	21st to end	Night	32% 9% 27% 24% 6% 1	570
October	1st to 10th	Night	29% 13% 27% 23% 7% 1	627
	11th to 20th	Night	35% 11% 22% 23% 7%	725
	21st to end	Night	38% 12% 25% 19% 6%	946
November	1st to 10th	Night	33% 17% 29% 17% 4	880
	11th to 20th	Night	34% 15% 28% 18% 5%	900
	21st to end	Night	30% 21% 30% 15% 3	900
December	1st to 10th	Night	29% 18% 32% 17% 4	900
	11th to 20th	Night	33% 24% 27% 12% 3	900
	21st to end	Night	25% 20% 29% 18% 6% 1	990

Page generated at 2025-02-03 04:05:54. Version ac07

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