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 2025-02-25.

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	16% 11% 4 8% 5% 4 4 3 5% 6% 32%	109090
	Night	16% 14% 5% 10% 5% 5% 4 3 5% 6% 29%	109561
Transparency	Day	51% 7% 12% 20% 9% 1	112714
	Night	55% 6% 11% 17% 9% 1	114101
Seeing	Day	23% 16% 31% 19% 8% 3	15227
	Night	23% 13% 29% 24% 9% 1	24336

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	12% 17% 9% 10% 5% 4 4 3 4 5% 26%	3258
	11th to 20th	Day	10% 20% 8% 19% 9% 7% 5% 3 3 4 11%	3770
	21st to end	Day	12% 19% 8% 15% 7% 7% 5% 3 4 4 16%	4466
February	1st to 10th	Day	12% 20% 6% 16% 8% 5% 4 3 3 3 20%	1800
	11th to 20th	Day	13% 16% 6% 14% 6% 5% 4 3 4 5% 25%	1753
	21st to end	Day	17% 17% 6% 12% 5% 5% 5% 3 3 3 22%	1472
March	1st to 10th	Day	19% 15% 4 8% 5% 4 4 3 5% 5% 29%	3429
	11th to 20th	Day	10% 17% 6% 10% 6% 5% 4 3 5% 5% 27%	3480
	21st to end	Day	14% 10% 5% 7% 4 4 4 3 5% 6% 38%	3815
April	1st to 10th	Day	20% 14% 3 7% 5% 4 4 3 4 6% 29%	2250
	11th to 20th	Day	22% 11% 2 6% 5% 4 4 3 4 5% 36%	2364
	21st to end	Day	22% 11% 2 6% 4 4 4 3 4 5% 35%	2470
May	1st to 10th	Day	19% 8% 3 7% 5% 4 5% 4 6% 7% 34%	4167
	11th to 20th	Day	14% 8% 3 6% 4 4 4 3 5% 8% 39%	4398
	21st to end	Day	17% 6% 2 5% 4 4 4 4 5% 7% 42%	4837
June	1st to 10th	Day	18% 7% 2 6% 4 5% 5% 4 5% 6% 37%	2672
	11th to 20th	Day	14% 6% 2 6% 5% 4 5% 5% 6% 9% 39%	2850
	21st to end	Day	19% 8% 3 6% 5% 4 3 4 6% 8% 36%	2850
July	1st to 10th	Day	14% 6% 3 6% 5% 5% 5% 5% 6% 9% 37%	4760
	11th to 20th	Day	14% 6% 2 6% 4 4 4 4 5% 7% 44%	4541
	21st to end	Day	11% 6% 2 6% 4 4 4 4 6% 8% 47%	4626
August	1st to 10th	Day	13% 7% 3 7% 4 5% 6% 4 6% 8% 38%	4104
	11th to 20th	Day	16% 7% 3 6% 3 4 5% 4 6% 10% 36%	4044
	21st to end	Day	9% 5% 2 6% 4 4 5% 5% 6% 9% 45%	4404
September	1st to 10th	Day	15% 6% 2 6% 4 4 5% 4 6% 7% 41%	2280
	11th to 20th	Day	15% 5% 2 5% 4 4 4 4 5% 6% 45%	2171
	21st to end	Day	20% 8% 3 7% 4 4 5% 3 4 6% 36%	2051
October	1st to 10th	Day	21% 9% 2 7% 4 4 4 4 4 6% 34%	1900
	11th to 20th	Day	27% 11% 3 8% 5% 5% 4 3 5% 7% 23%	1900
	21st to end	Day	31% 12% 3 8% 5% 4 4 3 4 5% 21%	2090
November	1st to 10th	Day	20% 14% 3 8% 4 4 4 3 4 7% 26%	1609
	11th to 20th	Day	18% 17% 4 9% 6% 5% 5% 4 4 5% 22%	1600
	21st to end	Day	21% 21% 5% 9% 6% 5% 5% 3 6% 5% 15%	1600
December	1st to 10th	Day	17% 26% 7% 11% 5% 4 4 4 5% 5% 14%	2600
	11th to 20th	Day	18% 23% 7% 14% 5% 4 3 2 3 3 18%	2986
	21st to end	Day	24% 18% 6% 13% 5% 3 3 2 3 4 18%	3723
January	1st to 10th	Night	13% 19% 9% 13% 6% 5% 5% 3 4 5% 19%	6694
	11th to 20th	Night	11% 17% 7% 19% 8% 7% 6% 4 5% 4 12%	6110
	21st to end	Night	12% 20% 9% 13% 6% 6% 4 3 4 5% 17%	6490
February	1st to 10th	Night	12% 19% 6% 12% 7% 5% 5% 3 4 5% 20%	2600
	11th to 20th	Night	12% 17% 6% 12% 7% 5% 5% 3 4 5% 24%	2533
	21st to end	Night	16% 18% 5% 11% 7% 5% 4 3 4 5% 23%	2076
March	1st to 10th	Night	16% 13% 5% 9% 6% 4 4 3 4 6% 31%	3410
	11th to 20th	Night	12% 17% 7% 10% 5% 4 4 3 5% 5% 30%	3479
	21st to end	Night	15% 10% 5% 7% 4 4 4 3 6% 6% 35%	3817
April	1st to 10th	Night	22% 13% 4 6% 4 4 4 3 4 5% 31%	1929
	11th to 20th	Night	18% 11% 4 8% 4 4 3 3 5% 5% 36%	1782
	21st to end	Night	20% 9% 4 7% 5% 5% 4 3 5% 6% 31%	1710
May	1st to 10th	Night	16% 7% 2 7% 4 5% 4 4 5% 7% 38%	2774
	11th to 20th	Night	16% 8% 2 5% 4 4 4 3 6% 7% 40%	2495
	21st to end	Night	12% 7% 2 6% 5% 4 4 4 5% 8% 44%	2738
June	1st to 10th	Night	16% 9% 2 7% 5% 4 4 3 7% 8% 35%	1502
	11th to 20th	Night	12% 7% 2 5% 4 4 3 3 6% 9% 45%	1330
	21st to end	Night	16% 7% 3 7% 4 4 5% 4 6% 7% 39%	1330
July	1st to 10th	Night	10% 7% 3 7% 5% 4 4 4 5% 7% 44%	2210
	11th to 20th	Night	16% 5% 2 5% 3 3 4 3 5% 7% 47%	2417
	21st to end	Night	9% 6% 2 5% 4 4 4 4 5% 8% 50%	2923
August	1st to 10th	Night	11% 6% 2 6% 4 4 4 4 6% 7% 46%	2825
	11th to 20th	Night	16% 7% 2 6% 3 4 3 3 5% 6% 44%	2785
	21st to end	Night	15% 4 2 4 3 3 3 3 5% 8% 48%	3220
September	1st to 10th	Night	12% 4 2 6% 4 4 4 4 5% 7% 46%	1900
	11th to 20th	Night	13% 5% 2 6% 3 3 4 3 5% 7% 48%	2005
	21st to end	Night	19% 7% 2 6% 5% 4 3 3 5% 6% 40%	2128
October	1st to 10th	Night	20% 8% 2 6% 4 5% 4 4 5% 7% 35%	2280
	11th to 20th	Night	24% 11% 3 9% 5% 4 4 4 5% 5% 26%	2280
	21st to end	Night	27% 13% 5% 8% 4 4 4 2 4 5% 23%	2508
November	1st to 10th	Night	22% 14% 3 7% 4 4 3 3 4 6% 29%	2685
	11th to 20th	Night	18% 17% 4 9% 4 5% 5% 3 5% 6% 24%	2800
	21st to end	Night	24% 19% 6% 10% 5% 5% 5% 3 4 5% 16%	2800
December	1st to 10th	Night	19% 25% 6% 11% 5% 4 4 3 4 5% 14%	4580
	11th to 20th	Night	17% 22% 7% 16% 7% 5% 4 3 3 4 12%	5208
	21st to end	Night	23% 20% 6% 13% 5% 4 3 3 3 4 14%	7208

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	61% 5% 8% 18% 9%	3259
	11th to 20th	Day	76% 6% 6% 7% 5%	3802
	21st to end	Day	71% 5% 8% 9% 7%	4466
February	1st to 10th	Day	72% 5% 6% 12% 4 1	1800
	11th to 20th	Day	62% 7% 10% 12% 8% 1	1762
	21st to end	Day	66% 5% 9% 14% 6%	1472
March	1st to 10th	Day	58% 6% 14% 12% 10%	3432
	11th to 20th	Day	58% 7% 12% 15% 7% 1	3480
	21st to end	Day	45% 7% 13% 20% 14% 2	3815
April	1st to 10th	Day	56% 6% 11% 17% 9% 1	2250
	11th to 20th	Day	51% 5% 9% 22% 12% 1	2364
	21st to end	Day	52% 6% 10% 17% 12% 3	2470
May	1st to 10th	Day	47% 9% 11% 20% 11% 1	4179
	11th to 20th	Day	40% 8% 16% 25% 10% 1	4402
	21st to end	Day	41% 7% 14% 19% 16% 3	4837
June	1st to 10th	Day	47% 8% 11% 22% 13%	2672
	11th to 20th	Day	40% 9% 12% 23% 15% 1	2850
	21st to end	Day	45% 9% 14% 20% 11% 1	2850
July	1st to 10th	Day	42% 7% 16% 23% 11% 1	4686
	11th to 20th	Day	37% 7% 16% 30% 10%	4462
	21st to end	Day	34% 6% 12% 30% 17%	4478
August	1st to 10th	Day	42% 7% 16% 24% 10% 1	4091
	11th to 20th	Day	42% 8% 16% 25% 8%	4083
	21st to end	Day	34% 7% 14% 34% 10% 1	4404
September	1st to 10th	Day	40% 8% 14% 26% 11% 1	2280
	11th to 20th	Day	39% 7% 14% 28% 12% 1	2171
	21st to end	Day	49% 9% 11% 23% 9%	2051
October	1st to 10th	Day	46% 6% 13% 24% 10% 1	3160
	11th to 20th	Day	52% 7% 12% 23% 6%	3140
	21st to end	Day	59% 6% 14% 16% 5%	3428
November	1st to 10th	Day	57% 6% 15% 16% 5%	1609
	11th to 20th	Day	63% 7% 12% 12% 4 1	1600
	21st to end	Day	71% 6% 10% 10% 3	1600
December	1st to 10th	Day	71% 7% 12% 8% 2	2600
	11th to 20th	Day	73% 3 8% 12% 4	2986
	21st to end	Day	73% 4 5% 12% 6%	3723
January	1st to 10th	Night	68% 6% 7% 13% 7%	6694
	11th to 20th	Night	73% 8% 7% 6% 5% 1	6153
	21st to end	Night	69% 6% 8% 8% 8% 1	6490
February	1st to 10th	Night	66% 6% 10% 13% 5% 1	2600
	11th to 20th	Night	62% 6% 9% 15% 7%	2535
	21st to end	Night	63% 6% 11% 14% 6%	2076
March	1st to 10th	Night	53% 6% 14% 15% 10% 1	3420
	11th to 20th	Night	55% 8% 14% 15% 7% 2	3480
	21st to end	Night	46% 7% 13% 21% 12% 1	3817
April	1st to 10th	Night	56% 6% 9% 18% 10% 2	1929
	11th to 20th	Night	49% 5% 9% 20% 15% 2	1782
	21st to end	Night	53% 7% 8% 14% 16% 1	1710
May	1st to 10th	Night	42% 8% 14% 23% 12% 2	2781
	11th to 20th	Night	40% 8% 14% 23% 14% 1	2496
	21st to end	Night	36% 8% 13% 24% 17% 2	2739
June	1st to 10th	Night	46% 7% 10% 21% 15% 1	1502
	11th to 20th	Night	36% 7% 14% 24% 19% 1	1330
	21st to end	Night	44% 7% 14% 23% 11% 1	1330
July	1st to 10th	Night	39% 6% 13% 23% 16% 2	2175
	11th to 20th	Night	36% 5% 14% 33% 11% 1	2373
	21st to end	Night	33% 6% 11% 31% 19% 1	2830
August	1st to 10th	Night	36% 6% 17% 24% 15% 1	2814
	11th to 20th	Night	40% 6% 18% 24% 12% 1	2812
	21st to end	Night	34% 6% 12% 35% 12% 1	3220
September	1st to 10th	Night	35% 9% 17% 24% 14% 1	1900
	11th to 20th	Night	34% 8% 14% 30% 13%	2005
	21st to end	Night	45% 6% 13% 27% 10%	2128
October	1st to 10th	Night	39% 6% 12% 27% 16%	3800
	11th to 20th	Night	50% 7% 15% 22% 7%	3779
	21st to end	Night	55% 6% 16% 17% 6%	4120
November	1st to 10th	Night	56% 6% 12% 19% 7% 1	2685
	11th to 20th	Night	60% 7% 12% 13% 6% 1	2800
	21st to end	Night	69% 8% 10% 10% 3	2800
December	1st to 10th	Night	73% 5% 12% 7% 2	4580
	11th to 20th	Night	75% 5% 8% 8% 4	5208
	21st to end	Night	75% 4 7% 8% 5%	7208

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	20% 27% 35% 14% 6% 1	200
	11th to 20th	Day	26% 22% 35% 12% 5%	243
	21st to end	Day	27% 18% 36% 15% 4	330
February	1st to 10th	Day	32% 27% 31% 6% 3 1	300
	11th to 20th	Day	26% 26% 39% 8% 1	300
	21st to end	Day	40% 24% 32% 5%	237
March	1st to 10th	Day	24% 22% 36% 15% 3	457
	11th to 20th	Day	22% 23% 35% 16% 4	460
	21st to end	Day	31% 17% 30% 15% 5% 1	506
April	1st to 10th	Day	28% 22% 28% 15% 7%	460
	11th to 20th	Day	35% 19% 22% 14% 7% 2	452
	21st to end	Day	31% 17% 33% 12% 6% 1	460
May	1st to 10th	Day	25% 15% 29% 20% 8% 3	463
	11th to 20th	Day	19% 16% 31% 21% 10% 3	487
	21st to end	Day	18% 15% 32% 22% 11% 2	529
June	1st to 10th	Day	21% 14% 32% 26% 6% 1	502
	11th to 20th	Day	16% 15% 31% 25% 10% 2	680
	21st to end	Day	21% 12% 37% 21% 8% 1	680
July	1st to 10th	Day	11% 11% 34% 28% 13% 2	671
	11th to 20th	Day	16% 11% 27% 29% 13% 4	542
	21st to end	Day	14% 9% 32% 28% 11% 5%	532
August	1st to 10th	Day	12% 10% 28% 29% 14% 7%	486
	11th to 20th	Day	15% 6% 25% 30% 14% 10%	479
	21st to end	Day	16% 8% 32% 23% 15% 6%	539
September	1st to 10th	Day	17% 10% 29% 24% 13% 6%	490
	11th to 20th	Day	13% 9% 26% 24% 19% 9%	490
	21st to end	Day	20% 13% 26% 25% 12% 4	490
October	1st to 10th	Day	25% 15% 28% 17% 12% 3	490
	11th to 20th	Day	29% 20% 32% 13% 6% 1	490
	21st to end	Day	35% 21% 28% 14% 2	539
November	1st to 10th	Day	32% 21% 31% 14% 2	223
	11th to 20th	Day	29% 25% 35% 10% 2	200
	21st to end	Day	31% 23% 37% 9% 2	200
December	1st to 10th	Day	29% 22% 33% 15% 3	200
	11th to 20th	Day	35% 28% 24% 11% 2 1	200
	21st to end	Day	35% 24% 28% 10% 3	220
January	1st to 10th	Night	28% 18% 32% 17% 4 1	951
	11th to 20th	Night	29% 17% 32% 18% 3 1	800
	21st to end	Night	21% 12% 36% 23% 7% 1	880
February	1st to 10th	Night	23% 20% 34% 20% 3	800
	11th to 20th	Night	22% 18% 35% 20% 5%	783
	21st to end	Night	25% 21% 30% 19% 4	647
March	1st to 10th	Night	22% 18% 35% 22% 3	760
	11th to 20th	Night	21% 18% 35% 22% 4 1	760
	21st to end	Night	20% 15% 32% 24% 8%	836
April	1st to 10th	Night	29% 14% 30% 22% 5%	760
	11th to 20th	Night	26% 13% 29% 22% 9% 1	658
	21st to end	Night	24% 12% 29% 25% 10%	570
May	1st to 10th	Night	22% 7% 27% 32% 12% 1	537
	11th to 20th	Night	18% 9% 31% 30% 11%	374
	21st to end	Night	12% 7% 31% 35% 14%	411
June	1st to 10th	Night	18% 7% 32% 32% 10% 1	380
	11th to 20th	Night	14% 10% 26% 37% 13%	380
	21st to end	Night	18% 7% 27% 35% 14%	380
July	1st to 10th	Night	11% 5% 22% 43% 18% 1	370
	11th to 20th	Night	13% 7% 25% 35% 20% 1	368
	21st to end	Night	11% 4 26% 38% 21% 1	525
August	1st to 10th	Night	13% 5% 18% 37% 25% 2	567
	11th to 20th	Night	12% 5% 19% 36% 24% 3	564
	21st to end	Night	17% 6% 26% 30% 20% 2	684
September	1st to 10th	Night	14% 7% 28% 30% 18% 2	760
	11th to 20th	Night	14% 7% 23% 31% 20% 4	760
	21st to end	Night	22% 8% 21% 31% 16% 2	760
October	1st to 10th	Night	22% 12% 28% 24% 13% 1	760
	11th to 20th	Night	28% 16% 26% 21% 8% 1	760
	21st to end	Night	32% 18% 29% 18% 3	836
November	1st to 10th	Night	31% 13% 27% 22% 7% 1	780
	11th to 20th	Night	28% 20% 30% 17% 5%	800
	21st to end	Night	35% 15% 29% 18% 3	800
December	1st to 10th	Night	34% 21% 28% 13% 4 1	800
	11th to 20th	Night	28% 20% 35% 13% 3 1	800
	21st to end	Night	34% 16% 30% 18% 2	975

Page generated at 2025-02-22 06:51:36. Version ac07

Copyright © 2025 Attilla Danko.