Candiac
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Candiac clear sky chart from 2005-11-06 to 2025-01-22.

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% 9% 3 8% 5% 5% 5% 4 5% 7% 32%	105260
	Night	18% 11% 4 8% 5% 4 4 3 5% 6% 31%	104104
Transparency	Day	50% 5% 12% 22% 10% 1	108736
	Night	54% 4 11% 19% 10% 1	108717
Seeing	Day	22% 11% 29% 23% 11% 3	14771
	Night	24% 9% 29% 27% 10% 1	23848

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% 16% 6% 12% 6% 5% 5% 4 3 5% 22%	2597
	11th to 20th	Day	15% 13% 6% 11% 6% 5% 4 4 6% 6% 24%	2600
	21st to end	Day	16% 17% 5% 9% 5% 5% 5% 4 5% 7% 22%	2780
February	1st to 10th	Day	16% 15% 4 11% 7% 5% 5% 3 5% 5% 24%	1662
	11th to 20th	Day	14% 12% 4 10% 7% 5% 6% 4 5% 5% 27%	1774
	21st to end	Day	17% 16% 4 7% 6% 5% 4 3 4 6% 27%	1570
March	1st to 10th	Day	20% 12% 3 10% 6% 5% 5% 3 5% 5% 27%	3116
	11th to 20th	Day	13% 16% 5% 11% 6% 5% 5% 3 5% 6% 26%	3273
	21st to end	Day	15% 9% 3 8% 5% 4 5% 3 4 6% 38%	4166
April	1st to 10th	Day	21% 11% 3 7% 5% 4 4 3 5% 5% 31%	2280
	11th to 20th	Day	20% 9% 3 6% 5% 3 3 3 4 6% 37%	2254
	21st to end	Day	22% 9% 3 7% 5% 4 5% 4 5% 6% 32%	2440
May	1st to 10th	Day	20% 10% 3 8% 4 5% 5% 4 6% 7% 29%	4330
	11th to 20th	Day	17% 8% 3 7% 5% 5% 4 4 5% 8% 33%	4398
	21st to end	Day	14% 6% 2 7% 4 5% 5% 4 7% 9% 37%	4837
June	1st to 10th	Day	21% 7% 2 7% 5% 5% 5% 4 6% 8% 31%	2660
	11th to 20th	Day	15% 6% 2 6% 5% 4 5% 4 6% 9% 39%	2660
	21st to end	Day	20% 7% 2 8% 5% 4 5% 4 5% 7% 32%	2660
July	1st to 10th	Day	11% 6% 2 7% 5% 6% 5% 4 6% 9% 37%	4440
	11th to 20th	Day	12% 5% 2 7% 5% 4 5% 5% 6% 9% 39%	4440
	21st to end	Day	11% 6% 2 5% 4 5% 5% 4 6% 8% 44%	4814
August	1st to 10th	Day	14% 6% 3 9% 5% 5% 5% 4 7% 9% 33%	4423
	11th to 20th	Day	13% 6% 3 6% 5% 4 4 3 6% 9% 39%	3989
	21st to end	Day	15% 6% 2 6% 4 4 4 4 6% 9% 41%	4180
September	1st to 10th	Day	12% 5% 2 6% 5% 4 5% 5% 6% 8% 44%	2280
	11th to 20th	Day	14% 5% 2 4 3 3 4 3 5% 6% 49%	2191
	21st to end	Day	15% 6% 2 7% 4 4 4 4 6% 7% 41%	2090
October	1st to 10th	Day	19% 7% 3 8% 5% 5% 5% 3 6% 7% 33%	1976
	11th to 20th	Day	17% 9% 3 9% 6% 5% 5% 3 6% 6% 30%	1853
	21st to end	Day	26% 10% 2 7% 4 4 4 3 5% 5% 30%	1881
November	1st to 10th	Day	18% 11% 3 7% 4 4 4 4 6% 6% 32%	1761
	11th to 20th	Day	17% 11% 4 9% 5% 5% 6% 4 6% 6% 28%	1739
	21st to end	Day	23% 13% 4 9% 6% 5% 4 4 6% 6% 22%	1600
December	1st to 10th	Day	20% 21% 6% 11% 6% 4 4 3 4 4 17%	2600
	11th to 20th	Day	19% 14% 5% 10% 4 5% 6% 5% 5% 6% 23%	2986
	21st to end	Day	23% 13% 4 10% 6% 5% 6% 4 5% 5% 18%	3960
January	1st to 10th	Night	17% 18% 6% 10% 6% 5% 5% 3 4 5% 21%	4569
	11th to 20th	Night	12% 14% 4 13% 7% 7% 6% 4 5% 6% 20%	4580
	21st to end	Night	19% 17% 5% 10% 7% 5% 3 3 4 4 24%	4899
February	1st to 10th	Night	15% 16% 5% 13% 8% 5% 4 3 4 5% 21%	2516
	11th to 20th	Night	15% 11% 4 10% 6% 6% 5% 4 5% 6% 28%	2292
	21st to end	Night	17% 14% 4 9% 5% 5% 4 3 4 4 32%	1884
March	1st to 10th	Night	21% 11% 3 7% 5% 4 4 3 4 5% 34%	3724
	11th to 20th	Night	19% 19% 4 8% 5% 4 3 2 4 4 28%	3670
	21st to end	Night	13% 10% 4 8% 6% 4 4 3 5% 5% 38%	3466
April	1st to 10th	Night	24% 10% 3 7% 4 5% 4 3 5% 7% 29%	1900
	11th to 20th	Night	23% 9% 2 8% 4 3 4 4 5% 6% 33%	1875
	21st to end	Night	21% 9% 3 6% 5% 4 4 3 5% 5% 35%	1739
May	1st to 10th	Night	22% 9% 3 8% 5% 3 5% 3 5% 6% 31%	2625
	11th to 20th	Night	23% 8% 3 7% 4 3 4 2 4 7% 35%	2495
	21st to end	Night	16% 7% 3 7% 4 5% 4 4 5% 8% 38%	2738
June	1st to 10th	Night	22% 8% 3 8% 4 4 3 4 7% 6% 32%	1520
	11th to 20th	Night	16% 6% 2 7% 4 4 4 4 6% 7% 39%	1520
	21st to end	Night	19% 6% 2 7% 6% 5% 5% 5% 5% 7% 33%	1520
July	1st to 10th	Night	14% 8% 3 8% 6% 4 5% 4 7% 7% 35%	2520
	11th to 20th	Night	13% 5% 2 5% 4 5% 5% 5% 7% 7% 41%	2520
	21st to end	Night	12% 6% 3 7% 5% 4 4 4 6% 8% 42%	2739
August	1st to 10th	Night	16% 7% 3 8% 5% 4 4 4 5% 6% 37%	2506
	11th to 20th	Night	15% 7% 3 8% 4 5% 5% 4 5% 7% 38%	2806
	21st to end	Night	16% 6% 2 6% 4 5% 4 4 5% 7% 40%	3476
September	1st to 10th	Night	13% 6% 2 7% 5% 4 4 4 5% 6% 44%	1900
	11th to 20th	Night	15% 5% 2 6% 4 3 3 2 5% 7% 49%	1988
	21st to end	Night	16% 7% 2 6% 4 5% 4 3 5% 6% 43%	2090
October	1st to 10th	Night	18% 7% 3 7% 5% 5% 4 4 4 6% 38%	2202
	11th to 20th	Night	22% 8% 2 7% 5% 5% 5% 4 5% 5% 34%	2327
	21st to end	Night	23% 9% 4 8% 4 4 4 4 4 5% 30%	2717
November	1st to 10th	Night	19% 11% 4 7% 5% 4 4 3 5% 6% 31%	2537
	11th to 20th	Night	19% 10% 4 9% 5% 4 4 3 4 5% 33%	2660
	21st to end	Night	22% 13% 4 9% 5% 5% 5% 3 5% 5% 24%	2800
December	1st to 10th	Night	18% 20% 6% 12% 6% 5% 4 3 4 4 16%	4580
	11th to 20th	Night	23% 14% 5% 9% 5% 4 4 3 5% 5% 24%	5208
	21st to end	Night	24% 15% 5% 9% 4 3 4 4 6% 6% 20%	6996

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	65% 8% 11% 14% 3	2598
	11th to 20th	Day	61% 6% 12% 14% 7%	2600
	21st to end	Day	62% 8% 12% 13% 5%	2780
February	1st to 10th	Day	63% 3 9% 19% 5% 1	1662
	11th to 20th	Day	57% 5% 10% 18% 7% 1	1783
	21st to end	Day	59% 4 11% 15% 9% 1	1570
March	1st to 10th	Day	58% 7% 8% 19% 7% 1	3119
	11th to 20th	Day	58% 6% 11% 13% 10% 2	3273
	21st to end	Day	46% 7% 7% 21% 17% 2	4166
April	1st to 10th	Day	55% 5% 7% 19% 12% 2	2280
	11th to 20th	Day	48% 5% 8% 22% 15% 2	2254
	21st to end	Day	53% 4 10% 18% 12% 3	2440
May	1st to 10th	Day	53% 7% 8% 21% 10% 1	4344
	11th to 20th	Day	49% 7% 15% 19% 9% 2	4402
	21st to end	Day	43% 7% 12% 24% 13% 2	4837
June	1st to 10th	Day	51% 6% 10% 20% 11% 2	2660
	11th to 20th	Day	42% 6% 11% 25% 14% 3	2660
	21st to end	Day	52% 4 12% 21% 10% 1	2660
July	1st to 10th	Day	43% 4 14% 29% 10% 1	4370
	11th to 20th	Day	40% 5% 16% 31% 8%	4365
	21st to end	Day	39% 5% 13% 33% 9%	4661
August	1st to 10th	Day	47% 4 16% 24% 8%	4409
	11th to 20th	Day	42% 4 18% 28% 7%	4031
	21st to end	Day	41% 4 18% 22% 15%	4180
September	1st to 10th	Day	38% 6% 15% 29% 13%	2280
	11th to 20th	Day	35% 5% 13% 33% 14% 1	2191
	21st to end	Day	42% 5% 15% 27% 11% 1	2090
October	1st to 10th	Day	47% 3 13% 28% 8%	3288
	11th to 20th	Day	45% 4 18% 26% 7%	3056
	21st to end	Day	47% 3 18% 24% 8% 1	3081
November	1st to 10th	Day	52% 5% 13% 21% 9% 1	1761
	11th to 20th	Day	55% 5% 10% 17% 12%	1739
	21st to end	Day	62% 7% 12% 14% 5%	1600
December	1st to 10th	Day	72% 3 9% 14% 2	2600
	11th to 20th	Day	62% 4 9% 16% 9%	2986
	21st to end	Day	68% 5% 9% 12% 6%	3960
January	1st to 10th	Night	65% 6% 13% 11% 4	4569
	11th to 20th	Night	63% 7% 12% 13% 5% 1	4580
	21st to end	Night	65% 4 11% 12% 7%	4899
February	1st to 10th	Night	65% 5% 9% 15% 6% 1	2516
	11th to 20th	Night	57% 4 11% 18% 9% 1	2294
	21st to end	Night	57% 3 9% 18% 12% 1	1884
March	1st to 10th	Night	54% 4 9% 21% 9% 3	3734
	11th to 20th	Night	61% 5% 7% 14% 12% 2	3671
	21st to end	Night	48% 5% 5% 24% 15% 3	3466
April	1st to 10th	Night	56% 4 8% 18% 14% 2	1900
	11th to 20th	Night	53% 4 8% 21% 13% 2	1875
	21st to end	Night	52% 4 8% 18% 14% 4	1739
May	1st to 10th	Night	53% 7% 9% 19% 9% 3	2631
	11th to 20th	Night	49% 6% 11% 20% 12% 2	2496
	21st to end	Night	44% 6% 9% 21% 18% 2	2739
June	1st to 10th	Night	51% 6% 9% 21% 12% 1	1520
	11th to 20th	Night	42% 6% 12% 22% 14% 3	1520
	21st to end	Night	49% 7% 11% 20% 13% 1	1520
July	1st to 10th	Night	48% 4 13% 21% 13% 1	2480
	11th to 20th	Night	40% 5% 16% 30% 10%	2472
	21st to end	Night	41% 5% 17% 24% 13%	2651
August	1st to 10th	Night	49% 4 12% 26% 9%	2496
	11th to 20th	Night	46% 4 19% 22% 9%	2830
	21st to end	Night	44% 3 13% 24% 15% 1	3476
September	1st to 10th	Night	40% 5% 12% 27% 16% 1	1900
	11th to 20th	Night	37% 4 13% 31% 14% 1	1988
	21st to end	Night	43% 5% 11% 26% 15% 1	2090
October	1st to 10th	Night	47% 2 13% 28% 10%	3670
	11th to 20th	Night	46% 3 11% 30% 9%	3863
	21st to end	Night	50% 3 14% 19% 13% 1	4467
November	1st to 10th	Night	53% 4 11% 21% 9% 1	2537
	11th to 20th	Night	54% 4 11% 19% 11% 2	2660
	21st to end	Night	62% 4 11% 17% 6%	2800
December	1st to 10th	Night	73% 2 11% 11% 3	4580
	11th to 20th	Night	63% 3 9% 15% 11%	5208
	21st to end	Night	66% 3 8% 14% 9%	6996

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	32% 14% 30% 16% 8% 1	200
	11th to 20th	Day	26% 15% 36% 19% 4 1	200
	21st to end	Day	24% 15% 32% 22% 8% 1	200
February	1st to 10th	Day	31% 18% 35% 15% 1	247
	11th to 20th	Day	22% 19% 37% 19% 2 1	382
	21st to end	Day	28% 16% 28% 25% 3	382
March	1st to 10th	Day	27% 11% 36% 20% 7%	460
	11th to 20th	Day	22% 17% 35% 19% 6% 1	460
	21st to end	Day	29% 15% 29% 18% 8% 2	506
April	1st to 10th	Day	33% 12% 28% 18% 8% 2	460
	11th to 20th	Day	30% 17% 26% 13% 10% 3	452
	21st to end	Day	28% 12% 30% 18% 10% 2	460
May	1st to 10th	Day	25% 11% 32% 22% 10% 2	463
	11th to 20th	Day	18% 10% 31% 27% 10% 4	487
	21st to end	Day	19% 12% 32% 24% 10% 2	529
June	1st to 10th	Day	25% 9% 27% 27% 10% 2	490
	11th to 20th	Day	15% 11% 28% 29% 14% 2	490
	21st to end	Day	22% 11% 29% 23% 13% 3	490
July	1st to 10th	Day	13% 7% 28% 30% 19% 4	485
	11th to 20th	Day	14% 7% 30% 31% 14% 4	484
	21st to end	Day	14% 6% 28% 30% 19% 3	532
August	1st to 10th	Day	15% 5% 24% 33% 19% 5%	486
	11th to 20th	Day	13% 4 24% 33% 18% 9%	479
	21st to end	Day	14% 9% 24% 28% 16% 9%	539
September	1st to 10th	Day	13% 7% 29% 28% 16% 8%	490
	11th to 20th	Day	16% 7% 20% 24% 21% 12%	490
	21st to end	Day	17% 8% 28% 24% 17% 7%	490
October	1st to 10th	Day	20% 11% 31% 20% 13% 4	490
	11th to 20th	Day	21% 16% 31% 19% 12% 1	465
	21st to end	Day	35% 12% 24% 23% 6%	429
November	1st to 10th	Day	30% 12% 26% 24% 7% 1	395
	11th to 20th	Day	23% 20% 32% 16% 7% 1	339
	21st to end	Day	32% 13% 32% 18% 6% 1	200
December	1st to 10th	Day	37% 9% 24% 23% 7% 2	200
	11th to 20th	Day	27% 22% 35% 13% 4	200
	21st to end	Day	29% 18% 28% 18% 5% 3	220
January	1st to 10th	Night	28% 11% 34% 22% 5%	800
	11th to 20th	Night	26% 12% 35% 21% 6%	800
	21st to end	Night	21% 11% 36% 25% 7% 1	841
February	1st to 10th	Night	24% 11% 35% 26% 4 1	760
	11th to 20th	Night	22% 12% 38% 23% 4	743
	21st to end	Night	26% 11% 34% 26% 4	628
March	1st to 10th	Night	26% 10% 32% 26% 5%	760
	11th to 20th	Night	29% 10% 32% 22% 6%	760
	21st to end	Night	25% 9% 31% 25% 8% 1	836
April	1st to 10th	Night	28% 11% 29% 26% 5%	760
	11th to 20th	Night	28% 13% 29% 23% 7% 1	751
	21st to end	Night	26% 12% 29% 24% 9% 1	599
May	1st to 10th	Night	27% 6% 32% 25% 9% 1	452
	11th to 20th	Night	22% 8% 31% 30% 9% 1	374
	21st to end	Night	18% 9% 32% 30% 10%	411
June	1st to 10th	Night	27% 3 28% 32% 10% 1	380
	11th to 20th	Night	21% 4 29% 33% 13%	380
	21st to end	Night	20% 5% 27% 34% 13% 1	380
July	1st to 10th	Night	15% 5% 26% 37% 16%	370
	11th to 20th	Night	11% 3 26% 44% 15% 2	368
	21st to end	Night	13% 4 21% 47% 14% 1	416
August	1st to 10th	Night	15% 4 15% 49% 16% 1	378
	11th to 20th	Night	14% 4 22% 34% 24% 2	569
	21st to end	Night	17% 3 22% 36% 20% 2	836
September	1st to 10th	Night	16% 3 26% 38% 17% 1	760
	11th to 20th	Night	17% 5% 18% 35% 21% 3	760
	21st to end	Night	20% 6% 27% 29% 16% 2	760
October	1st to 10th	Night	21% 9% 29% 27% 14% 1	760
	11th to 20th	Night	27% 8% 28% 27% 9%	760
	21st to end	Night	29% 11% 30% 25% 5%	836
November	1st to 10th	Night	26% 14% 30% 21% 8% 1	780
	11th to 20th	Night	25% 13% 30% 22% 9% 1	800
	21st to end	Night	31% 14% 29% 19% 8% 1	800
December	1st to 10th	Night	33% 11% 30% 21% 5%	800
	11th to 20th	Night	32% 13% 31% 17% 6% 1	800
	21st to end	Night	34% 13% 30% 19% 5% 1	880

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