Port Carling
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port Carling clear sky chart from 2005-11-06 to 2024-02-05.

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	17% 11% 4 7% 6% 3 5% 4 5% 6% 32%	78368
	Night	18% 13% 5% 8% 6% 3 4 4 5% 6% 28%	80456
Transparency	Day	53% 7% 12% 18% 9% 1	78071
	Night	57% 7% 11% 16% 9% 1	80288
Seeing	Day	23% 16% 31% 19% 8% 3	13864
	Night	23% 13% 29% 24% 9% 1	22993

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	16% 22% 13% 10% 5% 3 3 3 2 3 19%	2269
	11th to 20th	Day	12% 16% 8% 16% 13% 4 5% 4 4 4 13%	2652
	21st to end	Day	16% 21% 9% 11% 7% 3 4 3 3 4 17%	3124
February	1st to 10th	Day	13% 19% 7% 14% 9% 4 4 4 3 4 19%	1656
	11th to 20th	Day	14% 14% 7% 12% 7% 3 4 4 4 5% 26%	1573
	21st to end	Day	18% 16% 7% 10% 7% 3 6% 4 3 3 22%	1353
March	1st to 10th	Day	15% 12% 5% 9% 7% 3 5% 5% 5% 5% 30%	1974
	11th to 20th	Day	12% 13% 6% 8% 7% 4 5% 4 4 5% 32%	1980
	21st to end	Day	18% 9% 4 6% 5% 4 5% 4 4 5% 35%	2178
April	1st to 10th	Day	21% 13% 4 6% 6% 4 4 3 4 6% 29%	2131
	11th to 20th	Day	21% 10% 3 5% 6% 3 5% 4 4 5% 36%	2238
	21st to end	Day	22% 11% 3 6% 5% 3 4 4 4 5% 34%	2340
May	1st to 10th	Day	20% 7% 3 5% 5% 3 5% 5% 6% 7% 34%	2371
	11th to 20th	Day	16% 8% 3 5% 5% 4 4 4 5% 7% 41%	2478
	21st to end	Day	14% 6% 2 4 5% 3 5% 5% 6% 7% 42%	2725
June	1st to 10th	Day	19% 6% 3 5% 5% 4 5% 5% 4 7% 38%	2531
	11th to 20th	Day	15% 5% 2 5% 5% 3 5% 5% 6% 9% 39%	2700
	21st to end	Day	18% 7% 3 5% 5% 3 3 4 5% 8% 37%	2700
July	1st to 10th	Day	11% 5% 2 4 4 3 5% 6% 6% 8% 46%	2700
	11th to 20th	Day	13% 6% 3 5% 6% 3 4 4 5% 9% 43%	2579
	21st to end	Day	13% 5% 2 6% 5% 4 5% 5% 7% 7% 40%	2637
August	1st to 10th	Day	12% 6% 3 5% 4 3 5% 5% 5% 9% 43%	2327
	11th to 20th	Day	13% 5% 2 5% 4 4 5% 5% 6% 9% 40%	2303
	21st to end	Day	13% 6% 3 6% 6% 3 5% 5% 6% 9% 38%	2502
September	1st to 10th	Day	15% 6% 2 5% 5% 3 5% 5% 6% 8% 40%	2160
	11th to 20th	Day	16% 5% 3 5% 4 3 4 5% 5% 6% 43%	2057
	21st to end	Day	19% 8% 3 6% 5% 3 5% 4 4 6% 36%	1944
October	1st to 10th	Day	22% 9% 3 6% 5% 3 5% 5% 4 6% 34%	1800
	11th to 20th	Day	29% 10% 4 7% 6% 3 5% 4 4 6% 22%	1800
	21st to end	Day	32% 11% 3 7% 6% 3 4 4 4 5% 20%	1980
November	1st to 10th	Day	20% 14% 4 7% 5% 4 4 4 5% 8% 26%	1527
	11th to 20th	Day	19% 16% 5% 8% 7% 4 5% 5% 5% 6% 21%	1520
	21st to end	Day	22% 19% 5% 8% 7% 3 5% 4 5% 5% 16%	1520
December	1st to 10th	Day	18% 25% 8% 9% 5% 3 3 3 3 4 17%	1520
	11th to 20th	Day	19% 21% 7% 10% 6% 3 3 3 3 4 20%	1906
	21st to end	Day	26% 19% 7% 11% 6% 3 4 4 3 4 14%	2613
January	1st to 10th	Night	17% 21% 11% 13% 7% 4 4 4 3 3 13%	4676
	11th to 20th	Night	14% 16% 6% 14% 10% 6% 6% 5% 5% 4 14%	4303
	21st to end	Night	17% 19% 8% 11% 7% 4 4 4 4 4 17%	4532
February	1st to 10th	Night	13% 19% 7% 11% 8% 4 5% 4 4 6% 19%	2399
	11th to 20th	Night	13% 15% 8% 10% 8% 4 5% 4 4 5% 25%	2273
	21st to end	Night	17% 17% 5% 9% 8% 4 4 5% 3 4 24%	1902
March	1st to 10th	Night	15% 11% 5% 8% 7% 3 4 3 4 6% 34%	1972
	11th to 20th	Night	13% 13% 5% 9% 6% 3 4 4 5% 4 35%	1979
	21st to end	Night	16% 10% 4 7% 5% 3 3 3 5% 6% 37%	2178
April	1st to 10th	Night	22% 11% 5% 6% 5% 2 4 4 4 5% 31%	1828
	11th to 20th	Night	18% 10% 4 7% 5% 2 3 4 4 5% 37%	1687
	21st to end	Night	19% 9% 4 7% 6% 4 5% 4 5% 7% 31%	1620
May	1st to 10th	Night	19% 6% 2 5% 5% 3 4 4 6% 7% 38%	1589
	11th to 20th	Night	16% 6% 3 4 5% 3 4 4 5% 8% 43%	1415
	21st to end	Night	12% 5% 2 5% 5% 3 4 5% 5% 10% 46%	1550
June	1st to 10th	Night	15% 8% 3 6% 6% 3 5% 4 7% 8% 36%	1423
	11th to 20th	Night	12% 7% 3 4 4 3 4 4 5% 10% 44%	1260
	21st to end	Night	16% 6% 3 5% 5% 2 4 5% 6% 7% 40%	1260
July	1st to 10th	Night	10% 4 2 3 4 2 4 5% 5% 8% 52%	1260
	11th to 20th	Night	13% 6% 3 5% 4 3 4 5% 5% 7% 44%	1376
	21st to end	Night	11% 5% 2 4 6% 3 5% 5% 5% 8% 46%	1677
August	1st to 10th	Night	11% 5% 2 5% 5% 3 4 5% 6% 7% 48%	1611
	11th to 20th	Night	11% 5% 2 5% 5% 3 5% 5% 6% 7% 46%	1598
	21st to end	Night	16% 5% 3 5% 4 2 5% 4 5% 7% 42%	1836
September	1st to 10th	Night	11% 4 3 6% 5% 3 5% 5% 6% 7% 46%	1800
	11th to 20th	Night	14% 5% 3 5% 4 2 4 5% 6% 8% 45%	1899
	21st to end	Night	18% 7% 2 5% 6% 3 4 4 5% 6% 40%	2016
October	1st to 10th	Night	21% 8% 2 6% 4 3 5% 5% 5% 7% 34%	2160
	11th to 20th	Night	26% 11% 3 8% 6% 3 4 4 5% 5% 25%	2160
	21st to end	Night	28% 13% 5% 7% 5% 3 4 3 4 5% 23%	2376
November	1st to 10th	Night	22% 13% 4 6% 5% 3 3 4 4 6% 30%	2547
	11th to 20th	Night	19% 16% 5% 8% 5% 3 6% 4 5% 6% 24%	2660
	21st to end	Night	24% 18% 6% 9% 5% 4 5% 4 4 5% 17%	2660
December	1st to 10th	Night	21% 23% 7% 10% 5% 3 5% 4 4 4 13%	2660
	11th to 20th	Night	20% 22% 7% 10% 7% 3 3 4 3 5% 16%	3288
	21st to end	Night	26% 21% 7% 11% 6% 3 3 3 4 4 11%	5026

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	73% 4 10% 8% 5%	2270
	11th to 20th	Day	74% 8% 7% 6% 5% 1	2652
	21st to end	Day	72% 6% 7% 8% 6% 1	3124
February	1st to 10th	Day	73% 5% 6% 11% 4 1	1656
	11th to 20th	Day	62% 7% 10% 12% 8% 1	1582
	21st to end	Day	67% 5% 9% 14% 6%	1353
March	1st to 10th	Day	56% 7% 14% 14% 10%	1977
	11th to 20th	Day	55% 6% 10% 18% 10% 2	1980
	21st to end	Day	50% 6% 11% 16% 14% 3	2178
April	1st to 10th	Day	56% 6% 11% 16% 9% 1	2131
	11th to 20th	Day	51% 5% 9% 22% 13% 1	2238
	21st to end	Day	52% 6% 10% 17% 12% 3	2340
May	1st to 10th	Day	48% 7% 10% 20% 12% 2	2371
	11th to 20th	Day	44% 6% 10% 25% 13% 1	2482
	21st to end	Day	40% 8% 14% 21% 13% 3	2725
June	1st to 10th	Day	45% 7% 11% 23% 13%	2531
	11th to 20th	Day	40% 9% 12% 22% 16% 1	2700
	21st to end	Day	44% 9% 15% 21% 11% 1	2700
July	1st to 10th	Day	34% 9% 14% 26% 15% 1	2626
	11th to 20th	Day	37% 9% 16% 27% 11% 1	2500
	21st to end	Day	40% 8% 15% 25% 11% 1	2489
August	1st to 10th	Day	38% 10% 17% 23% 11% 1	2314
	11th to 20th	Day	38% 11% 17% 24% 9% 1	2303
	21st to end	Day	43% 8% 17% 22% 9% 1	2502
September	1st to 10th	Day	40% 9% 14% 26% 10% 1	2160
	11th to 20th	Day	40% 7% 15% 28% 10% 1	2057
	21st to end	Day	49% 9% 11% 25% 7%	1944
October	1st to 10th	Day	51% 9% 11% 17% 10% 1	1800
	11th to 20th	Day	63% 8% 11% 12% 6% 1	1800
	21st to end	Day	66% 6% 9% 12% 6%	1980
November	1st to 10th	Day	57% 7% 16% 15% 5%	1527
	11th to 20th	Day	63% 8% 13% 11% 4 1	1520
	21st to end	Day	70% 7% 10% 9% 3	1520
December	1st to 10th	Day	73% 6% 8% 9% 4	1520
	11th to 20th	Day	71% 4 8% 11% 6%	1906
	21st to end	Day	77% 5% 6% 10% 3	2613
January	1st to 10th	Night	77% 6% 6% 7% 4	4676
	11th to 20th	Night	71% 9% 8% 7% 4 1	4303
	21st to end	Night	70% 7% 8% 9% 5% 1	4532
February	1st to 10th	Night	68% 5% 10% 12% 4 1	2399
	11th to 20th	Night	62% 5% 9% 16% 7%	2275
	21st to end	Night	63% 5% 11% 14% 6%	1902
March	1st to 10th	Night	53% 6% 13% 16% 11% 1	1982
	11th to 20th	Night	53% 6% 10% 18% 11% 2	1980
	21st to end	Night	48% 5% 10% 19% 15% 3	2178
April	1st to 10th	Night	56% 5% 9% 18% 10% 2	1828
	11th to 20th	Night	48% 5% 9% 21% 15% 2	1687
	21st to end	Night	53% 7% 8% 15% 16% 2	1620
May	1st to 10th	Night	44% 6% 10% 20% 17% 3	1589
	11th to 20th	Night	41% 6% 10% 22% 19% 2	1416
	21st to end	Night	35% 8% 16% 23% 16% 3	1551
June	1st to 10th	Night	45% 7% 10% 21% 15% 1	1423
	11th to 20th	Night	36% 7% 13% 23% 20% 1	1260
	21st to end	Night	43% 7% 15% 23% 11% 1	1260
July	1st to 10th	Night	30% 7% 13% 27% 20% 3	1225
	11th to 20th	Night	37% 6% 14% 28% 14% 1	1332
	21st to end	Night	36% 7% 15% 28% 14% 1	1584
August	1st to 10th	Night	34% 7% 19% 27% 13% 1	1600
	11th to 20th	Night	36% 8% 17% 25% 14% 1	1598
	21st to end	Night	40% 8% 14% 27% 10% 1	1836
September	1st to 10th	Night	35% 9% 17% 24% 13% 1	1800
	11th to 20th	Night	36% 9% 14% 30% 11%	1899
	21st to end	Night	45% 6% 13% 28% 9%	2016
October	1st to 10th	Night	50% 8% 12% 18% 12%	2160
	11th to 20th	Night	59% 9% 11% 16% 4	2160
	21st to end	Night	65% 6% 9% 12% 8%	2376
November	1st to 10th	Night	56% 6% 12% 19% 7% 1	2547
	11th to 20th	Night	60% 8% 12% 13% 6% 1	2660
	21st to end	Night	69% 8% 10% 10% 3	2660
December	1st to 10th	Night	75% 7% 8% 8% 3	2660
	11th to 20th	Night	71% 7% 8% 10% 4	3288
	21st to end	Night	78% 5% 7% 7% 3	5026

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	21% 28% 31% 13% 6% 1	180
	11th to 20th	Day	27% 23% 34% 10% 6%	218
	21st to end	Day	30% 16% 35% 15% 4	297
February	1st to 10th	Day	34% 27% 29% 6% 4 1	252
	11th to 20th	Day	25% 27% 39% 7% 1	240
	21st to end	Day	41% 27% 28% 4	198
March	1st to 10th	Day	24% 21% 36% 15% 3	417
	11th to 20th	Day	23% 21% 35% 17% 4	420
	21st to end	Day	31% 16% 31% 15% 5% 1	462
April	1st to 10th	Day	27% 22% 28% 15% 7%	420
	11th to 20th	Day	31% 20% 24% 15% 8% 3	412
	21st to end	Day	30% 16% 33% 13% 5% 1	420
May	1st to 10th	Day	26% 16% 28% 20% 8% 3	423
	11th to 20th	Day	21% 16% 31% 19% 11% 3	447
	21st to end	Day	18% 15% 31% 23% 11% 2	485
June	1st to 10th	Day	20% 14% 32% 26% 7% 1	461
	11th to 20th	Day	17% 15% 31% 24% 11% 3	630
	21st to end	Day	19% 12% 37% 22% 8% 1	630
July	1st to 10th	Day	10% 12% 33% 29% 14% 2	621
	11th to 20th	Day	16% 11% 27% 28% 13% 5%	499
	21st to end	Day	14% 9% 33% 29% 10% 5%	488
August	1st to 10th	Day	12% 9% 28% 29% 14% 7%	446
	11th to 20th	Day	15% 5% 25% 31% 14% 10%	439
	21st to end	Day	17% 8% 32% 23% 14% 6%	495
September	1st to 10th	Day	15% 10% 30% 24% 14% 7%	450
	11th to 20th	Day	15% 10% 28% 24% 17% 6%	450
	21st to end	Day	19% 14% 26% 26% 12% 3	450
October	1st to 10th	Day	26% 14% 27% 17% 13% 3	450
	11th to 20th	Day	31% 20% 31% 12% 4 1	450
	21st to end	Day	36% 21% 27% 14% 2	495
November	1st to 10th	Day	31% 20% 32% 15% 2	201
	11th to 20th	Day	29% 24% 35% 11% 2	180
	21st to end	Day	32% 22% 38% 7% 2	180
December	1st to 10th	Day	28% 23% 33% 14% 2	180
	11th to 20th	Day	35% 29% 23% 11% 2 1	180
	21st to end	Day	35% 27% 28% 8% 3	198
January	1st to 10th	Night	29% 19% 31% 17% 4 1	904
	11th to 20th	Night	30% 18% 31% 18% 4 1	760
	21st to end	Night	21% 12% 36% 23% 7% 1	836
February	1st to 10th	Night	24% 19% 34% 19% 3	739
	11th to 20th	Night	21% 18% 35% 20% 6%	703
	21st to end	Night	26% 21% 29% 19% 4	592
March	1st to 10th	Night	23% 17% 35% 22% 4	720
	11th to 20th	Night	21% 18% 35% 21% 5% 1	720
	21st to end	Night	21% 14% 31% 25% 9%	792
April	1st to 10th	Night	29% 14% 30% 23% 5%	720
	11th to 20th	Night	26% 13% 29% 22% 10% 1	623
	21st to end	Night	24% 12% 29% 25% 10%	540
May	1st to 10th	Night	23% 6% 26% 32% 12% 1	509
	11th to 20th	Night	18% 10% 32% 29% 11%	354
	21st to end	Night	12% 6% 32% 34% 15%	389
June	1st to 10th	Night	18% 7% 32% 33% 10% 1	360
	11th to 20th	Night	14% 9% 26% 37% 14%	360
	21st to end	Night	17% 6% 27% 35% 15%	360
July	1st to 10th	Night	11% 4 23% 43% 19% 1	350
	11th to 20th	Night	13% 7% 26% 34% 20% 1	348
	21st to end	Night	11% 4 26% 37% 20% 1	497
August	1st to 10th	Night	13% 5% 18% 37% 25% 2	537
	11th to 20th	Night	11% 5% 19% 38% 25% 3	534
	21st to end	Night	17% 6% 26% 29% 20% 2	648
September	1st to 10th	Night	13% 7% 28% 31% 18% 3	720
	11th to 20th	Night	15% 7% 24% 32% 18% 4	720
	21st to end	Night	21% 8% 21% 31% 17% 2	720
October	1st to 10th	Night	23% 12% 28% 24% 13% 1	720
	11th to 20th	Night	29% 16% 26% 20% 8% 1	720
	21st to end	Night	33% 17% 29% 19% 3	792
November	1st to 10th	Night	31% 12% 27% 22% 7% 1	740
	11th to 20th	Night	28% 20% 30% 17% 5%	760
	21st to end	Night	35% 14% 29% 18% 3	760
December	1st to 10th	Night	34% 21% 28% 13% 4	760
	11th to 20th	Night	29% 20% 35% 12% 3 1	760
	21st to end	Night	34% 16% 30% 18% 2	926

Page generated at 2024-02-02 05:20:27. Version ac07

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