Annapolis Royal
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Annapolis Royal clear sky chart from 2005-11-06 to 2025-09-19.

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	19% 12% 4 10% 6% 4 4 3 4 6% 29%	126597
	Night	19% 15% 5% 12% 6% 4 4 3 4 5% 24%	122529
Transparency	Day	57% 4 11% 18% 9% 1	130145
	Night	62% 5% 10% 16% 7% 1	127056
Seeing	Day	31% 19% 30% 15% 4 1	17948
	Night	31% 18% 28% 18% 5%	25583

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	14% 27% 8% 18% 10% 4 3 2 2 3 10%	3157
	11th to 20th	Day	15% 21% 11% 26% 6% 5% 3 2 2 2 6%	3772
	21st to end	Day	14% 17% 8% 19% 14% 7% 3 2 3 3 12%	4466
February	1st to 10th	Day	17% 19% 8% 16% 11% 5% 5% 2 3 4 10%	1800
	11th to 20th	Day	17% 16% 5% 17% 12% 5% 4 2 3 3 16%	1753
	21st to end	Day	11% 17% 6% 11% 9% 5% 4 2 4 6% 24%	1570
March	1st to 10th	Day	22% 18% 6% 14% 8% 5% 3 2 2 3 18%	4840
	11th to 20th	Day	17% 14% 5% 9% 5% 4 4 3 4 6% 29%	4980
	21st to end	Day	26% 17% 5% 9% 5% 4 3 3 3 4 21%	5466
April	1st to 10th	Day	22% 16% 3 7% 5% 3 4 3 4 5% 28%	2323
	11th to 20th	Day	20% 12% 2 5% 4 3 4 2 4 6% 37%	2542
	21st to end	Day	20% 12% 3 7% 4 4 3 3 5% 6% 35%	2600
May	1st to 10th	Day	23% 13% 4 9% 6% 5% 4 3 5% 5% 23%	5886
	11th to 20th	Day	18% 10% 2 7% 6% 5% 5% 3 5% 6% 31%	6221
	21st to end	Day	17% 11% 3 7% 4 4 4 3 5% 7% 34%	6948
June	1st to 10th	Day	23% 9% 2 6% 6% 4 4 4 5% 7% 32%	2904
	11th to 20th	Day	20% 7% 2 6% 4 4 4 4 5% 7% 38%	3000
	21st to end	Day	22% 9% 3 8% 5% 4 4 3 5% 6% 32%	3000
July	1st to 10th	Day	21% 8% 3 6% 5% 4 4 4 6% 7% 32%	6820
	11th to 20th	Day	21% 8% 2 6% 4 3 3 3 5% 7% 39%	6620
	21st to end	Day	13% 7% 2 6% 4 4 4 4 6% 9% 41%	6431
August	1st to 10th	Day	22% 10% 3 7% 4 4 4 3 5% 5% 33%	4235
	11th to 20th	Day	12% 6% 3 7% 4 4 5% 4 6% 7% 42%	4175
	21st to end	Day	11% 6% 2 4 3 3 4 3 4 6% 53%	4594
September	1st to 10th	Day	17% 6% 2 4 3 3 4 3 4 6% 48%	2400
	11th to 20th	Day	14% 7% 2 5% 3 4 4 3 3 6% 48%	2197
	21st to end	Day	18% 7% 2 7% 3 3 2 3 4 6% 45%	2090
October	1st to 10th	Day	19% 8% 2 5% 4 3 4 3 5% 7% 40%	1900
	11th to 20th	Day	20% 11% 3 7% 4 4 3 3 4 6% 35%	1900
	21st to end	Day	21% 13% 3 6% 5% 4 4 2 4 5% 31%	2049
November	1st to 10th	Day	20% 14% 3 8% 5% 4 4 3 4 7% 28%	1676
	11th to 20th	Day	20% 19% 7% 9% 5% 4 4 2 4 6% 20%	1600
	21st to end	Day	20% 21% 8% 12% 6% 5% 3 2 4 5% 16%	1600
December	1st to 10th	Day	20% 21% 9% 19% 4 4 3 2 3 3 12%	2610
	11th to 20th	Day	23% 19% 5% 17% 7% 5% 3 2 3 3 13%	2996
	21st to end	Day	18% 18% 9% 16% 7% 4 3 2 3 4 14%	3476
January	1st to 10th	Night	13% 24% 9% 24% 6% 3 3 2 2 2 10%	6808
	11th to 20th	Night	15% 23% 10% 23% 5% 4 2 2 3 3 9%	6095
	21st to end	Night	13% 15% 7% 22% 13% 6% 4 3 4 4 9%	6490
February	1st to 10th	Night	18% 19% 8% 18% 8% 5% 4 3 3 3 11%	2600
	11th to 20th	Night	17% 18% 6% 16% 10% 6% 4 2 3 4 14%	2533
	21st to end	Night	13% 16% 6% 12% 8% 5% 5% 3 4 5% 22%	2059
March	1st to 10th	Night	21% 19% 7% 14% 9% 4 3 2 2 3 16%	4999
	11th to 20th	Night	18% 15% 5% 10% 6% 5% 4 3 4 5% 24%	4979
	21st to end	Night	27% 14% 6% 8% 5% 3 3 2 3 4 24%	5466
April	1st to 10th	Night	24% 16% 4 7% 5% 3 4 3 4 5% 26%	2075
	11th to 20th	Night	22% 13% 3 6% 4 4 4 3 6% 8% 29%	1807
	21st to end	Night	21% 13% 4 7% 5% 4 4 3 4 6% 30%	1800
May	1st to 10th	Night	24% 17% 4 9% 5% 4 4 3 4 4 23%	4054
	11th to 20th	Night	22% 10% 2 7% 5% 4 5% 4 5% 7% 30%	3688
	21st to end	Night	18% 12% 3 8% 5% 4 4 3 5% 6% 31%	3948
June	1st to 10th	Night	25% 8% 3 6% 4 3 5% 4 7% 7% 28%	1511
	11th to 20th	Night	19% 8% 2 6% 4 5% 4 4 7% 8% 34%	1400
	21st to end	Night	20% 7% 2 10% 6% 6% 5% 5% 5% 8% 26%	1400
July	1st to 10th	Night	24% 9% 4 8% 5% 5% 5% 4 5% 7% 25%	3160
	11th to 20th	Night	21% 8% 3 6% 4 4 4 4 6% 6% 33%	3298
	21st to end	Night	15% 7% 2 6% 4 4 5% 4 6% 9% 39%	4418
August	1st to 10th	Night	23% 9% 3 7% 4 3 3 3 6% 7% 32%	2915
	11th to 20th	Night	16% 8% 3 7% 5% 5% 5% 4 6% 8% 32%	2872
	21st to end	Night	11% 7% 2 6% 4 4 4 4 5% 8% 46%	3303
September	1st to 10th	Night	15% 5% 2 6% 4 4 5% 4 6% 7% 43%	2000
	11th to 20th	Night	16% 7% 2 6% 3 4 3 3 5% 7% 43%	2157
	21st to end	Night	17% 7% 3 6% 4 4 4 4 5% 6% 39%	2090
October	1st to 10th	Night	19% 7% 3 6% 4 4 3 4 6% 6% 38%	2279
	11th to 20th	Night	17% 10% 3 7% 5% 4 3 3 6% 6% 36%	2280
	21st to end	Night	24% 14% 3 7% 4 4 3 3 4 4 29%	2546
November	1st to 10th	Night	21% 13% 3 7% 5% 4 4 3 5% 6% 29%	2622
	11th to 20th	Night	20% 23% 5% 9% 4 4 4 3 4 5% 20%	2800
	21st to end	Night	20% 20% 7% 10% 5% 4 4 3 4 5% 19%	2800
December	1st to 10th	Night	17% 22% 9% 20% 6% 4 4 2 3 4 9%	4580
	11th to 20th	Night	17% 18% 7% 18% 6% 4 4 2 3 3 17%	5213
	21st to end	Night	22% 20% 7% 15% 7% 3 2 2 2 3 18%	7484

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	84% 2 10% 4 1	3158
	11th to 20th	Day	85% 4 5% 5% 1	3805
	21st to end	Day	76% 7% 8% 6% 3 1	4466
February	1st to 10th	Day	79% 4 8% 6% 3	1800
	11th to 20th	Day	75% 4 8% 9% 3	1761
	21st to end	Day	62% 5% 11% 15% 6% 1	1570
March	1st to 10th	Day	74% 3 6% 11% 5% 1	4844
	11th to 20th	Day	57% 4 13% 19% 7% 1	4980
	21st to end	Day	70% 2 5% 14% 8% 1	5466
April	1st to 10th	Day	60% 3 8% 15% 12% 2	2323
	11th to 20th	Day	50% 3 9% 24% 13% 1	2542
	21st to end	Day	52% 2 10% 21% 13% 2	2600
May	1st to 10th	Day	63% 4 11% 16% 5% 1	5897
	11th to 20th	Day	53% 5% 14% 20% 7% 1	6225
	21st to end	Day	50% 4 15% 17% 13% 1	6948
June	1st to 10th	Day	53% 4 11% 22% 11%	2904
	11th to 20th	Day	46% 4 13% 22% 13% 2	3000
	21st to end	Day	55% 4 11% 18% 11% 1	3000
July	1st to 10th	Day	50% 5% 15% 19% 10% 1	6745
	11th to 20th	Day	45% 4 13% 26% 11% 1	6539
	21st to end	Day	39% 7% 17% 25% 12%	6247
August	1st to 10th	Day	54% 4 10% 20% 11%	4222
	11th to 20th	Day	41% 6% 17% 25% 11%	4214
	21st to end	Day	32% 4 15% 29% 20% 1	4594
September	1st to 10th	Day	39% 3 12% 29% 16% 2	2400
	11th to 20th	Day	39% 4 12% 27% 18% 2	2197
	21st to end	Day	43% 3 9% 27% 15% 2	2090
October	1st to 10th	Day	45% 5% 11% 28% 11%	3160
	11th to 20th	Day	47% 4 9% 28% 13%	3140
	21st to end	Day	46% 3 13% 23% 14% 1	3351
November	1st to 10th	Day	58% 4 11% 19% 7% 1	1676
	11th to 20th	Day	67% 4 10% 15% 4 1	1600
	21st to end	Day	73% 4 10% 11% 2	1600
December	1st to 10th	Day	78% 4 6% 10% 1	2610
	11th to 20th	Day	76% 5% 6% 9% 3 1	2995
	21st to end	Day	75% 4 10% 6% 6%	3476
January	1st to 10th	Night	81% 4 7% 7% 1	6808
	11th to 20th	Night	82% 4 6% 6% 2	6137
	21st to end	Night	77% 5% 8% 8% 2	6490
February	1st to 10th	Night	80% 4 6% 7% 4	2600
	11th to 20th	Night	77% 3 7% 9% 4	2536
	21st to end	Night	64% 5% 10% 15% 6% 1	2059
March	1st to 10th	Night	74% 5% 5% 9% 7% 1	5008
	11th to 20th	Night	60% 5% 13% 16% 6%	4980
	21st to end	Night	66% 3 6% 17% 8% 1	5466
April	1st to 10th	Night	61% 4 9% 14% 11% 2	2075
	11th to 20th	Night	54% 5% 8% 21% 12% 1	1807
	21st to end	Night	56% 3 9% 17% 12% 1	1800
May	1st to 10th	Night	66% 3 9% 15% 7%	4060
	11th to 20th	Night	54% 4 13% 21% 6% 2	3689
	21st to end	Night	52% 5% 15% 19% 7% 1	3949
June	1st to 10th	Night	52% 5% 12% 22% 8% 1	1511
	11th to 20th	Night	45% 5% 14% 24% 10% 1	1400
	21st to end	Night	54% 8% 11% 16% 9% 3	1400
July	1st to 10th	Night	57% 6% 12% 16% 9%	3125
	11th to 20th	Night	48% 7% 15% 18% 11% 1	3256
	21st to end	Night	42% 6% 15% 24% 13%	4288
August	1st to 10th	Night	53% 4 12% 23% 8%	2903
	11th to 20th	Night	46% 7% 18% 22% 7%	2899
	21st to end	Night	35% 7% 15% 26% 16% 1	3302
September	1st to 10th	Night	39% 5% 11% 29% 15% 1	2000
	11th to 20th	Night	41% 3 10% 28% 16% 1	2157
	21st to end	Night	45% 4 9% 25% 15% 2	2090
October	1st to 10th	Night	47% 4 13% 24% 11% 1	3799
	11th to 20th	Night	43% 4 12% 25% 15%	3779
	21st to end	Night	49% 3 9% 25% 13%	4182
November	1st to 10th	Night	55% 6% 12% 18% 8%	2622
	11th to 20th	Night	67% 5% 9% 13% 5%	2800
	21st to end	Night	68% 5% 13% 11% 3	2800
December	1st to 10th	Night	78% 5% 8% 8% 1	4580
	11th to 20th	Night	72% 5% 9% 13% 2	5215
	21st to end	Night	74% 3 7% 11% 4	7484

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	46% 25% 21% 9%	200
	11th to 20th	Day	41% 25% 23% 9% 2	320
	21st to end	Day	30% 27% 33% 9% 1	440
February	1st to 10th	Day	37% 26% 27% 9% 1	400
	11th to 20th	Day	41% 28% 21% 7% 2	396
	21st to end	Day	33% 26% 27% 12% 1	374
March	1st to 10th	Day	38% 23% 30% 7% 1	500
	11th to 20th	Day	35% 27% 26% 9% 2	500
	21st to end	Day	38% 27% 23% 9% 3 1	550
April	1st to 10th	Day	45% 25% 21% 7% 1 1	500
	11th to 20th	Day	36% 26% 24% 10% 2	492
	21st to end	Day	35% 20% 28% 12% 5%	500
May	1st to 10th	Day	34% 21% 31% 10% 3	503
	11th to 20th	Day	27% 20% 29% 18% 5%	679
	21st to end	Day	30% 19% 29% 17% 3 1	790
June	1st to 10th	Day	35% 16% 25% 19% 4	730
	11th to 20th	Day	24% 17% 34% 18% 6% 1	730
	21st to end	Day	31% 15% 33% 16% 5% 1	730
July	1st to 10th	Day	23% 12% 38% 20% 7% 1	720
	11th to 20th	Day	22% 10% 37% 21% 8% 1	718
	21st to end	Day	21% 11% 43% 22% 4	582
August	1st to 10th	Day	17% 12% 42% 23% 4 1	526
	11th to 20th	Day	20% 11% 35% 23% 10% 1	519
	21st to end	Day	18% 15% 32% 26% 7% 2	583
September	1st to 10th	Day	19% 14% 39% 21% 6% 1	530
	11th to 20th	Day	22% 16% 31% 21% 7% 3	522
	21st to end	Day	24% 17% 30% 20% 8% 2	490
October	1st to 10th	Day	27% 16% 25% 20% 9% 3	390
	11th to 20th	Day	31% 18% 29% 15% 5% 2	390
	21st to end	Day	34% 21% 28% 12% 4 1	429
November	1st to 10th	Day	33% 23% 28% 11% 4 1	395
	11th to 20th	Day	44% 22% 20% 11% 4	400
	21st to end	Day	41% 25% 25% 7% 3 1	400
December	1st to 10th	Day	39% 27% 23% 10% 1	400
	11th to 20th	Day	49% 26% 18% 6% 1	400
	21st to end	Day	40% 26% 25% 6% 1	220
January	1st to 10th	Night	38% 25% 23% 13% 1	900
	11th to 20th	Night	38% 23% 23% 12% 3	815
	21st to end	Night	31% 28% 28% 11% 3	880
February	1st to 10th	Night	37% 24% 26% 11% 2	800
	11th to 20th	Night	40% 23% 25% 10% 2	783
	21st to end	Night	27% 27% 27% 17% 3	660
March	1st to 10th	Night	34% 24% 28% 13% 1	800
	11th to 20th	Night	32% 21% 26% 17% 3	800
	21st to end	Night	32% 21% 27% 16% 4	880
April	1st to 10th	Night	40% 18% 25% 15% 2	675
	11th to 20th	Night	31% 21% 29% 17% 3	594
	21st to end	Night	34% 16% 27% 18% 5%	600
May	1st to 10th	Night	29% 15% 33% 18% 4 1	600
	11th to 20th	Night	29% 14% 29% 24% 4	592
	21st to end	Night	22% 14% 39% 20% 4 1	649
June	1st to 10th	Night	30% 12% 30% 23% 5%	511
	11th to 20th	Night	23% 13% 33% 25% 6% 1	400
	21st to end	Night	24% 9% 38% 20% 8% 1	400
July	1st to 10th	Night	19% 9% 40% 25% 6%	390
	11th to 20th	Night	23% 7% 35% 24% 11%	448
	21st to end	Night	19% 9% 35% 32% 5%	656
August	1st to 10th	Night	19% 8% 34% 31% 8% 1	598
	11th to 20th	Night	20% 9% 29% 30% 11% 1	592
	21st to end	Night	18% 8% 33% 30% 10%	660
September	1st to 10th	Night	18% 10% 34% 28% 10% 1	600
	11th to 20th	Night	21% 10% 27% 29% 12% 2	771
	21st to end	Night	23% 12% 30% 23% 10% 1	760
October	1st to 10th	Night	23% 10% 27% 29% 10% 1	760
	11th to 20th	Night	24% 19% 28% 19% 8% 1	760
	21st to end	Night	37% 20% 22% 16% 4	836
November	1st to 10th	Night	33% 18% 26% 17% 5% 1	823
	11th to 20th	Night	36% 23% 21% 15% 5%	900
	21st to end	Night	38% 21% 23% 15% 3	900
December	1st to 10th	Night	40% 21% 24% 12% 2	900
	11th to 20th	Night	39% 27% 23% 9% 2	900
	21st to end	Night	41% 23% 21% 12% 2	990

Page generated at 2025-09-16 02:49:10. Version ac07

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