Guysborough
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Guysborough clear sky chart from 2005-11-06 to 2024-01-16.

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% 10% 4 7% 6% 3 5% 5% 5% 7% 27%	74760
	Night	21% 10% 4 7% 6% 3 5% 4 5% 6% 27%	75060
Transparency	Day	57% 7% 11% 17% 8% 1	74463
	Night	57% 6% 11% 17% 8% 1	74892
Seeing	Day	28% 21% 31% 15% 4 1	16407
	Night	27% 19% 31% 18% 5%	24030

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	18% 13% 7% 11% 6% 4 6% 4 6% 6% 19%	1516
	11th to 20th	Day	21% 15% 6% 10% 6% 4 5% 4 6% 6% 18%	1481
	21st to end	Day	15% 11% 6% 10% 8% 4 5% 4 6% 7% 25%	1686
February	1st to 10th	Day	19% 11% 4 10% 9% 4 5% 5% 5% 6% 23%	1620
	11th to 20th	Day	18% 12% 4 8% 8% 4 6% 5% 5% 7% 22%	1573
	21st to end	Day	12% 12% 7% 8% 8% 4 5% 5% 5% 7% 28%	1453
March	1st to 10th	Day	15% 15% 6% 9% 6% 4 5% 4 6% 6% 25%	1830
	11th to 20th	Day	16% 10% 7% 9% 9% 5% 5% 4 4 6% 26%	1980
	21st to end	Day	18% 16% 7% 8% 7% 4 4 3 3 4 25%	2268
April	1st to 10th	Day	24% 13% 5% 7% 6% 3 4 4 4 5% 25%	2160
	11th to 20th	Day	23% 11% 3 6% 5% 3 4 4 4 6% 31%	2134
	21st to end	Day	23% 13% 3 7% 6% 3 4 4 4 6% 27%	2291
May	1st to 10th	Day	27% 12% 4 6% 5% 2 3 4 4 6% 26%	2520
	11th to 20th	Day	20% 11% 4 7% 6% 4 4 4 5% 6% 29%	2478
	21st to end	Day	20% 9% 3 7% 6% 3 5% 4 5% 8% 30%	2724
June	1st to 10th	Day	28% 9% 3 5% 5% 3 5% 6% 5% 7% 23%	2520
	11th to 20th	Day	22% 9% 4 7% 6% 3 4 5% 5% 6% 29%	2520
	21st to end	Day	27% 11% 4 8% 5% 3 5% 3 5% 6% 23%	2520
July	1st to 10th	Day	18% 7% 3 6% 6% 3 5% 6% 5% 8% 32%	2520
	11th to 20th	Day	18% 7% 4 7% 7% 4 6% 5% 6% 8% 28%	2520
	21st to end	Day	22% 10% 3 7% 5% 4 5% 5% 6% 8% 25%	2745
August	1st to 10th	Day	18% 7% 3 6% 5% 3 5% 6% 6% 8% 33%	2431
	11th to 20th	Day	19% 7% 3 6% 6% 4 5% 4 6% 8% 31%	2304
	21st to end	Day	17% 6% 3 6% 6% 3 5% 5% 6% 8% 35%	2381
September	1st to 10th	Day	18% 6% 3 6% 6% 3 6% 4 6% 6% 36%	2160
	11th to 20th	Day	20% 8% 3 6% 5% 3 4 5% 5% 7% 33%	2160
	21st to end	Day	20% 7% 3 5% 6% 3 4 4 4 8% 35%	1910
October	1st to 10th	Day	19% 8% 3 6% 6% 4 5% 5% 5% 7% 32%	1800
	11th to 20th	Day	22% 8% 4 7% 6% 4 5% 5% 6% 8% 26%	1800
	21st to end	Day	22% 11% 4 7% 7% 3 5% 6% 5% 6% 23%	1867
November	1st to 10th	Day	24% 12% 3 5% 6% 3 4 5% 4 7% 26%	1639
	11th to 20th	Day	23% 13% 4 9% 6% 4 4 4 4 7% 22%	1520
	21st to end	Day	15% 14% 5% 7% 6% 4 6% 5% 7% 7% 24%	1520
December	1st to 10th	Day	21% 16% 6% 9% 6% 4 5% 5% 6% 6% 16%	1520
	11th to 20th	Day	32% 11% 5% 8% 6% 4 5% 5% 5% 5% 15%	1906
	21st to end	Day	23% 11% 9% 11% 6% 3 4 3 5% 6% 19%	2783
January	1st to 10th	Night	19% 13% 6% 10% 7% 3 5% 5% 5% 6% 22%	2649
	11th to 20th	Night	19% 12% 6% 10% 8% 4 6% 4 5% 6% 21%	2601
	21st to end	Night	16% 11% 5% 10% 7% 3 6% 5% 5% 7% 24%	2668
February	1st to 10th	Night	19% 11% 4 9% 7% 4 6% 5% 4 6% 24%	2340
	11th to 20th	Night	17% 10% 6% 9% 7% 4 5% 5% 5% 7% 23%	2273
	21st to end	Night	12% 11% 8% 9% 6% 4 6% 4 6% 5% 29%	1802
March	1st to 10th	Night	16% 13% 5% 10% 8% 5% 5% 5% 5% 4 23%	2115
	11th to 20th	Night	18% 9% 5% 7% 7% 3 4 5% 5% 6% 30%	1979
	21st to end	Night	20% 12% 6% 7% 6% 3 3 3 4 5% 29%	2088
April	1st to 10th	Night	25% 12% 4 6% 5% 4 5% 4 4 6% 27%	1800
	11th to 20th	Night	22% 10% 2 5% 5% 3 5% 6% 5% 7% 30%	1776
	21st to end	Night	26% 11% 3 6% 5% 3 4 4 4 5% 28%	1664
May	1st to 10th	Night	30% 9% 3 6% 5% 2 4 4 4 5% 28%	1440
	11th to 20th	Night	23% 9% 3 6% 4 3 4 3 5% 7% 33%	1416
	21st to end	Night	17% 9% 4 6% 7% 4 5% 5% 6% 9% 28%	1550
June	1st to 10th	Night	28% 10% 3 7% 5% 3 4 5% 4 5% 26%	1440
	11th to 20th	Night	24% 9% 3 5% 4 3 4 4 5% 7% 31%	1440
	21st to end	Night	27% 10% 3 7% 6% 3 4 4 5% 8% 23%	1440
July	1st to 10th	Night	19% 9% 3 8% 5% 4 5% 4 7% 8% 29%	1440
	11th to 20th	Night	17% 9% 5% 7% 5% 5% 6% 6% 7% 8% 25%	1440
	21st to end	Night	19% 10% 4 6% 6% 4 6% 5% 5% 9% 26%	1573
August	1st to 10th	Night	16% 7% 4 6% 7% 4 5% 5% 5% 8% 33%	1506
	11th to 20th	Night	18% 8% 3 7% 7% 3 5% 5% 6% 7% 31%	1596
	21st to end	Night	16% 5% 2 5% 5% 3 5% 5% 6% 8% 38%	1975
September	1st to 10th	Night	17% 6% 3 5% 5% 3 5% 5% 6% 8% 37%	1800
	11th to 20th	Night	18% 7% 2 5% 4 4 4 4 4 7% 40%	1800
	21st to end	Night	20% 8% 4 7% 5% 3 4 3 4 6% 37%	2048
October	1st to 10th	Night	19% 7% 3 5% 5% 2 4 5% 5% 8% 37%	2160
	11th to 20th	Night	21% 7% 3 6% 6% 3 5% 5% 5% 6% 34%	2160
	21st to end	Night	25% 10% 3 6% 6% 4 4 4 5% 6% 26%	2488
November	1st to 10th	Night	21% 11% 4 7% 5% 3 5% 4 6% 7% 27%	2436
	11th to 20th	Night	21% 12% 4 6% 6% 3 5% 6% 5% 6% 26%	2660
	21st to end	Night	20% 13% 4 7% 6% 4 5% 5% 5% 6% 25%	2660
December	1st to 10th	Night	25% 14% 4 8% 6% 3 3 4 5% 6% 21%	2660
	11th to 20th	Night	31% 12% 5% 7% 6% 3 4 4 5% 6% 19%	3293
	21st to end	Night	29% 11% 6% 10% 5% 3 4 4 3 5% 21%	4884

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	64% 7% 8% 13% 7% 1	1517
	11th to 20th	Day	66% 7% 11% 10% 6%	1481
	21st to end	Day	58% 7% 8% 15% 10% 1	1686
February	1st to 10th	Day	63% 5% 10% 12% 10% 1	1620
	11th to 20th	Day	61% 6% 10% 15% 7%	1581
	21st to end	Day	56% 5% 9% 17% 10% 3	1453
March	1st to 10th	Day	60% 5% 7% 17% 11% 1	1834
	11th to 20th	Day	59% 6% 9% 17% 8% 2	1980
	21st to end	Day	64% 5% 7% 15% 8% 2	2268
April	1st to 10th	Day	61% 5% 8% 13% 11% 3	2160
	11th to 20th	Day	55% 4 9% 17% 13% 1	2134
	21st to end	Day	59% 5% 12% 15% 8% 1	2291
May	1st to 10th	Day	61% 4 11% 14% 8% 1	2520
	11th to 20th	Day	55% 6% 9% 21% 9%	2482
	21st to end	Day	54% 7% 13% 19% 8%	2724
June	1st to 10th	Day	59% 7% 12% 16% 4	2520
	11th to 20th	Day	55% 6% 10% 20% 9% 1	2520
	21st to end	Day	63% 7% 11% 12% 7% 1	2520
July	1st to 10th	Day	48% 9% 16% 19% 7%	2450
	11th to 20th	Day	52% 7% 15% 19% 7%	2444
	21st to end	Day	56% 9% 14% 15% 6% 1	2592
August	1st to 10th	Day	47% 8% 16% 22% 6%	2417
	11th to 20th	Day	50% 8% 15% 20% 6%	2304
	21st to end	Day	46% 7% 15% 22% 10%	2381
September	1st to 10th	Day	47% 7% 14% 22% 10% 1	2160
	11th to 20th	Day	49% 6% 10% 22% 11% 1	2160
	21st to end	Day	48% 5% 10% 25% 11%	1910
October	1st to 10th	Day	51% 6% 10% 22% 9% 1	1800
	11th to 20th	Day	54% 7% 14% 19% 7%	1800
	21st to end	Day	60% 7% 12% 14% 6% 1	1867
November	1st to 10th	Day	58% 6% 11% 18% 7%	1639
	11th to 20th	Day	61% 6% 12% 13% 7% 1	1520
	21st to end	Day	58% 9% 13% 14% 6%	1520
December	1st to 10th	Day	66% 8% 10% 13% 3	1520
	11th to 20th	Day	71% 8% 7% 10% 4 1	1905
	21st to end	Day	66% 8% 15% 7% 4 1	2783
January	1st to 10th	Night	61% 8% 11% 14% 5%	2649
	11th to 20th	Night	63% 8% 9% 14% 5% 1	2601
	21st to end	Night	58% 6% 12% 16% 8%	2668
February	1st to 10th	Night	61% 5% 10% 14% 9% 1	2340
	11th to 20th	Night	59% 8% 10% 14% 7% 1	2276
	21st to end	Night	55% 7% 9% 18% 10% 1	1802
March	1st to 10th	Night	63% 5% 7% 15% 9%	2124
	11th to 20th	Night	54% 6% 11% 19% 9% 2	1980
	21st to end	Night	58% 4 8% 17% 10% 2	2088
April	1st to 10th	Night	61% 4 10% 13% 10% 2	1800
	11th to 20th	Night	52% 6% 9% 18% 12% 2	1776
	21st to end	Night	58% 4 10% 17% 11%	1664
May	1st to 10th	Night	59% 3 9% 18% 9% 1	1440
	11th to 20th	Night	52% 5% 8% 25% 10%	1417
	21st to end	Night	52% 8% 13% 19% 8% 1	1551
June	1st to 10th	Night	60% 6% 10% 18% 5%	1440
	11th to 20th	Night	53% 5% 13% 17% 12% 1	1440
	21st to end	Night	60% 6% 11% 15% 7%	1440
July	1st to 10th	Night	52% 7% 17% 17% 7%	1401
	11th to 20th	Night	53% 7% 14% 17% 8% 1	1392
	21st to end	Night	55% 7% 17% 15% 5% 1	1486
August	1st to 10th	Night	50% 6% 17% 22% 5%	1495
	11th to 20th	Night	51% 7% 15% 20% 6%	1596
	21st to end	Night	42% 7% 17% 25% 9%	1975
September	1st to 10th	Night	44% 7% 13% 24% 11%	1800
	11th to 20th	Night	44% 5% 11% 27% 13% 1	1800
	21st to end	Night	50% 6% 9% 24% 11% 1	2048
October	1st to 10th	Night	44% 6% 14% 24% 12%	2160
	11th to 20th	Night	49% 7% 13% 26% 5%	2160
	21st to end	Night	59% 6% 10% 16% 9%	2488
November	1st to 10th	Night	55% 8% 13% 17% 7%	2436
	11th to 20th	Night	56% 9% 12% 15% 8% 1	2660
	21st to end	Night	59% 8% 12% 14% 6%	2660
December	1st to 10th	Night	64% 6% 10% 14% 5%	2660
	11th to 20th	Night	68% 6% 9% 12% 5% 1	3295
	21st to end	Night	67% 6% 12% 11% 3	4884

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% 28% 30% 10% 1	370
	11th to 20th	Day	27% 32% 27% 11% 2	356
	21st to end	Day	24% 31% 32% 10% 3	374
February	1st to 10th	Day	29% 33% 28% 9% 1	340
	11th to 20th	Day	33% 34% 22% 10% 1	336
	21st to end	Day	23% 29% 32% 13% 3	280
March	1st to 10th	Day	26% 29% 35% 9% 1	356
	11th to 20th	Day	26% 28% 30% 11% 4	420
	21st to end	Day	31% 31% 24% 10% 3	462
April	1st to 10th	Day	35% 33% 24% 7% 1	420
	11th to 20th	Day	34% 28% 24% 11% 2	412
	21st to end	Day	31% 21% 30% 14% 3	435
May	1st to 10th	Day	36% 23% 27% 9% 3 2	603
	11th to 20th	Day	26% 20% 31% 17% 4 1	624
	21st to end	Day	29% 19% 33% 15% 3 1	680
June	1st to 10th	Day	37% 15% 29% 13% 4 1	630
	11th to 20th	Day	24% 18% 35% 17% 4	630
	21st to end	Day	33% 12% 32% 19% 5%	630
July	1st to 10th	Day	23% 12% 37% 22% 5% 1	620
	11th to 20th	Day	23% 11% 37% 23% 6%	618
	21st to end	Day	27% 11% 32% 22% 7% 1	685
August	1st to 10th	Day	18% 10% 37% 28% 7% 1	550
	11th to 20th	Day	25% 10% 34% 21% 9% 1	439
	21st to end	Day	19% 15% 32% 26% 8% 1	495
September	1st to 10th	Day	20% 15% 41% 17% 6% 2	450
	11th to 20th	Day	28% 18% 31% 17% 4 1	450
	21st to end	Day	25% 18% 29% 20% 6% 2	374
October	1st to 10th	Day	23% 16% 35% 18% 6% 2	360
	11th to 20th	Day	24% 22% 33% 13% 6% 2	360
	21st to end	Day	27% 27% 30% 10% 6% 1	396
November	1st to 10th	Day	28% 22% 31% 13% 4 1	365
	11th to 20th	Day	33% 28% 24% 11% 3 1	370
	21st to end	Day	29% 30% 28% 9% 3 1	370
December	1st to 10th	Day	36% 23% 28% 11% 2	370
	11th to 20th	Day	36% 29% 27% 7% 1	370
	21st to end	Day	25% 31% 30% 10% 3 1	407
January	1st to 10th	Night	28% 27% 31% 12% 2	850
	11th to 20th	Night	29% 26% 32% 11% 3	829
	21st to end	Night	24% 28% 32% 12% 3	834
February	1st to 10th	Night	28% 22% 34% 13% 2	720
	11th to 20th	Night	27% 34% 27% 10% 2	703
	21st to end	Night	20% 27% 34% 16% 4	592
March	1st to 10th	Night	26% 26% 32% 14% 2	720
	11th to 20th	Night	25% 21% 31% 18% 6%	720
	21st to end	Night	28% 22% 31% 16% 4	702
April	1st to 10th	Night	32% 20% 32% 14% 3	540
	11th to 20th	Night	28% 20% 32% 17% 3	534
	21st to end	Night	34% 16% 27% 19% 4	540
May	1st to 10th	Night	36% 14% 29% 15% 5% 1	540
	11th to 20th	Night	29% 13% 33% 18% 7% 1	532
	21st to end	Night	23% 16% 39% 18% 3 1	583
June	1st to 10th	Night	35% 12% 27% 23% 3	540
	11th to 20th	Night	29% 11% 35% 23% 3	540
	21st to end	Night	32% 7% 35% 21% 5%	540
July	1st to 10th	Night	25% 6% 36% 28% 5% 1	526
	11th to 20th	Night	20% 7% 37% 28% 7%	522
	21st to end	Night	23% 7% 35% 27% 7%	590
August	1st to 10th	Night	21% 5% 33% 30% 10% 1	538
	11th to 20th	Night	23% 8% 32% 29% 9%	532
	21st to end	Night	19% 8% 30% 31% 11% 1	594
September	1st to 10th	Night	20% 9% 35% 27% 8% 1	540
	11th to 20th	Night	23% 12% 31% 23% 11%	540
	21st to end	Night	25% 12% 33% 23% 6%	636
October	1st to 10th	Night	23% 13% 32% 22% 9% 1	720
	11th to 20th	Night	25% 16% 33% 19% 7% 1	720
	21st to end	Night	30% 21% 30% 15% 4	848
November	1st to 10th	Night	29% 19% 32% 14% 5% 1	830
	11th to 20th	Night	30% 24% 27% 14% 4	850
	21st to end	Night	31% 25% 28% 12% 4	850
December	1st to 10th	Night	34% 24% 27% 11% 4	850
	11th to 20th	Night	32% 29% 27% 10% 2	850
	21st to end	Night	30% 28% 28% 11% 3 1	935

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