Long Point Provincial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Long Point Provincial Park clear sky chart from 2005-11-06 to 2026-06-01.

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	14% 9% 4 9% 6% 5% 5% 4 5% 7% 32%	132279
	Night	15% 11% 4 9% 6% 5% 5% 4 5% 6% 30%	130851
Transparency	Day	49% 7% 13% 20% 10% 1	135877
	Night	54% 6% 11% 17% 10% 1	135340
Seeing	Day	17% 7% 22% 29% 19% 5%	16448
	Night	21% 9% 25% 28% 15% 3	26082

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	15% 16% 8% 14% 7% 6% 8% 2 4 4 15%	4933
	11th to 20th	Day	10% 21% 10% 26% 12% 5% 5% 2 2 2 5%	5246
	21st to end	Day	15% 14% 6% 15% 8% 8% 6% 4 4 5% 17%	5780
February	1st to 10th	Day	16% 15% 5% 13% 7% 7% 6% 4 5% 6% 19%	1890
	11th to 20th	Day	15% 12% 7% 11% 7% 6% 6% 4 5% 5% 22%	1843
	21st to end	Day	19% 13% 4 9% 6% 5% 6% 4 5% 6% 23%	1683
March	1st to 10th	Day	17% 10% 5% 11% 6% 5% 5% 3 5% 6% 28%	5029
	11th to 20th	Day	11% 11% 4 8% 5% 6% 5% 4 5% 8% 33%	5090
	21st to end	Day	19% 8% 3 8% 6% 6% 5% 4 4 5% 32%	5586
April	1st to 10th	Day	17% 10% 3 7% 6% 5% 4 4 5% 6% 33%	2424
	11th to 20th	Day	16% 9% 3 8% 4 5% 4 3 6% 7% 34%	2613
	21st to end	Day	17% 9% 2 6% 4 4 5% 4 6% 7% 36%	2730
May	1st to 10th	Day	19% 8% 3 8% 5% 5% 5% 4 5% 6% 31%	6018
	11th to 20th	Day	14% 8% 3 8% 5% 5% 5% 4 7% 8% 32%	6116
	21st to end	Day	15% 6% 2 7% 5% 5% 4 4 5% 7% 39%	7103
June	1st to 10th	Day	11% 6% 2 6% 4 5% 5% 4 6% 8% 41%	2800
	11th to 20th	Day	10% 6% 3 7% 5% 4 5% 5% 6% 9% 40%	2800
	21st to end	Day	9% 5% 2 5% 4 4 5% 4 6% 10% 45%	2800
July	1st to 10th	Day	7% 5% 2 6% 4 4 5% 4 7% 10% 46%	6360
	11th to 20th	Day	9% 5% 2 6% 4 4 4 4 6% 10% 45%	6024
	21st to end	Day	7% 4 2 5% 4 5% 4 4 7% 9% 48%	6424
August	1st to 10th	Day	14% 5% 2 5% 4 4 4 4 6% 10% 42%	4234
	11th to 20th	Day	11% 6% 2 6% 4 5% 5% 4 7% 10% 39%	4174
	21st to end	Day	8% 6% 2 6% 4 4 5% 5% 6% 9% 44%	4543
September	1st to 10th	Day	11% 5% 2 6% 4 4 5% 4 5% 7% 46%	2400
	11th to 20th	Day	8% 5% 2 5% 4 4 4 4 5% 8% 50%	2201
	21st to end	Day	15% 6% 3 7% 5% 5% 5% 4 5% 7% 38%	2200
October	1st to 10th	Day	14% 7% 3 6% 6% 5% 5% 3 5% 7% 39%	2005
	11th to 20th	Day	19% 8% 3 8% 6% 5% 5% 4 6% 6% 29%	2000
	21st to end	Day	22% 10% 4 8% 6% 5% 4 4 6% 7% 24%	2200
November	1st to 10th	Day	15% 9% 3 8% 5% 5% 4 4 6% 6% 35%	1876
	11th to 20th	Day	17% 11% 5% 9% 7% 5% 3 5% 5% 6% 27%	1680
	21st to end	Day	21% 16% 4 11% 6% 7% 5% 3 6% 5% 17%	1680
December	1st to 10th	Day	19% 19% 6% 13% 10% 9% 5% 3 3 5% 9%	2680
	11th to 20th	Day	20% 19% 5% 14% 5% 7% 6% 3 4 4 13%	3066
	21st to end	Day	26% 19% 5% 11% 6% 5% 4 4 4 5% 12%	4048
January	1st to 10th	Night	16% 16% 7% 14% 7% 6% 8% 3 4 4 14%	7957
	11th to 20th	Night	11% 20% 8% 20% 12% 6% 4 3 3 3 10%	7639
	21st to end	Night	16% 15% 6% 16% 7% 6% 5% 4 4 4 16%	8401
February	1st to 10th	Night	17% 16% 4 12% 7% 5% 5% 4 4 5% 22%	2730
	11th to 20th	Night	16% 13% 4 10% 7% 5% 5% 5% 5% 6% 23%	2663
	21st to end	Night	18% 13% 4 9% 7% 5% 4 4 5% 6% 23%	2121
March	1st to 10th	Night	16% 10% 4 8% 6% 5% 5% 3 5% 6% 32%	5030
	11th to 20th	Night	12% 8% 3 6% 5% 4 5% 4 6% 8% 38%	5089
	21st to end	Night	16% 11% 4 8% 5% 4 4 3 5% 5% 37%	5588
April	1st to 10th	Night	19% 10% 4 7% 6% 4 4 3 5% 7% 30%	2195
	11th to 20th	Night	18% 8% 3 6% 5% 4 4 3 6% 6% 35%	1974
	21st to end	Night	15% 6% 3 7% 5% 5% 6% 4 6% 7% 36%	1890
May	1st to 10th	Night	21% 10% 3 8% 4 4 4 3 4 5% 32%	4143
	11th to 20th	Night	13% 8% 4 9% 5% 5% 5% 4 5% 6% 36%	3993
	21st to end	Night	17% 6% 2 6% 4 4 3 4 6% 8% 39%	4014
June	1st to 10th	Night	11% 7% 3 5% 5% 5% 5% 4 7% 8% 41%	1600
	11th to 20th	Night	10% 5% 2 6% 6% 4 4 4 7% 9% 42%	1600
	21st to end	Night	10% 5% 2 6% 4 4 6% 4 6% 9% 44%	1600
July	1st to 10th	Night	7% 6% 2 7% 5% 4 5% 4 6% 10% 46%	3600
	11th to 20th	Night	8% 5% 2 6% 5% 4 4 4 6% 9% 46%	3918
	21st to end	Night	7% 5% 2 6% 4 5% 4 4 6% 9% 49%	4428
August	1st to 10th	Night	11% 5% 2 6% 5% 4 4 4 6% 10% 42%	2915
	11th to 20th	Night	12% 5% 3 6% 4 4 4 3 7% 8% 45%	2875
	21st to end	Night	7% 5% 2 5% 5% 5% 4 4 7% 9% 48%	3322
September	1st to 10th	Night	11% 7% 2 6% 4 3 4 3 6% 8% 46%	2000
	11th to 20th	Night	10% 4 1 5% 3 3 4 3 4 8% 54%	2195
	21st to end	Night	16% 7% 3 8% 5% 4 4 4 5% 6% 38%	2200
October	1st to 10th	Night	15% 7% 2 6% 4 4 4 4 5% 7% 42%	2394
	11th to 20th	Night	19% 9% 3 8% 6% 4 4 3 5% 7% 32%	2400
	21st to end	Night	22% 8% 3 8% 5% 4 4 3 5% 7% 31%	2640
November	1st to 10th	Night	16% 7% 3 7% 5% 5% 4 3 5% 7% 37%	2639
	11th to 20th	Night	17% 13% 4 8% 6% 6% 6% 4 5% 8% 25%	2940
	21st to end	Night	21% 15% 4 9% 7% 6% 5% 3 5% 6% 19%	2940
December	1st to 10th	Night	17% 19% 7% 11% 8% 7% 5% 3 4 5% 13%	4720
	11th to 20th	Night	21% 19% 5% 14% 6% 6% 6% 3 4 5% 12%	5348
	21st to end	Night	24% 19% 5% 11% 6% 5% 4 3 4 5% 15%	7150

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	75% 6% 9% 6% 4	4934
	11th to 20th	Day	88% 4 4 3 1	5280
	21st to end	Day	69% 6% 10% 10% 4 1	5780
February	1st to 10th	Day	66% 7% 12% 12% 4	1890
	11th to 20th	Day	63% 6% 11% 14% 6%	1852
	21st to end	Day	60% 6% 13% 16% 5% 1	1683
March	1st to 10th	Day	52% 7% 16% 20% 5%	5032
	11th to 20th	Day	46% 8% 19% 19% 6% 2	5090
	21st to end	Day	50% 7% 10% 22% 10% 1	5586
April	1st to 10th	Day	49% 6% 14% 18% 12% 1	2424
	11th to 20th	Day	47% 6% 12% 21% 13% 1	2613
	21st to end	Day	45% 8% 12% 20% 12% 2	2730
May	1st to 10th	Day	49% 8% 11% 18% 10% 4	6027
	11th to 20th	Day	45% 10% 13% 21% 9% 2	6120
	21st to end	Day	41% 7% 13% 21% 13% 4	7103
June	1st to 10th	Day	38% 9% 13% 24% 15% 2	2800
	11th to 20th	Day	37% 10% 15% 23% 15% 1	2800
	21st to end	Day	32% 8% 16% 27% 16% 1	2800
July	1st to 10th	Day	32% 6% 14% 28% 18% 2	6290
	11th to 20th	Day	33% 6% 16% 27% 17% 1	5952
	21st to end	Day	31% 6% 17% 25% 20% 1	6240
August	1st to 10th	Day	37% 7% 18% 25% 13% 1	4221
	11th to 20th	Day	37% 8% 19% 26% 9% 1	4213
	21st to end	Day	34% 7% 14% 31% 13% 1	4543
September	1st to 10th	Day	35% 8% 17% 26% 13% 1	2400
	11th to 20th	Day	31% 7% 17% 29% 16%	2201
	21st to end	Day	45% 7% 14% 22% 10% 1	2200
October	1st to 10th	Day	34% 6% 16% 26% 16% 1	3265
	11th to 20th	Day	42% 7% 16% 23% 12%	3240
	21st to end	Day	46% 6% 17% 24% 7%	3538
November	1st to 10th	Day	49% 7% 14% 20% 8% 2	1876
	11th to 20th	Day	57% 8% 13% 13% 8% 1	1680
	21st to end	Day	70% 8% 10% 9% 3	1680
December	1st to 10th	Day	82% 5% 7% 6% 1	2680
	11th to 20th	Day	75% 7% 10% 6% 2	3066
	21st to end	Day	76% 6% 9% 7% 2	4048
January	1st to 10th	Night	73% 9% 9% 7% 2	7957
	11th to 20th	Night	81% 5% 6% 5% 2	7680
	21st to end	Night	72% 5% 7% 11% 5%	8401
February	1st to 10th	Night	65% 6% 12% 12% 4	2730
	11th to 20th	Night	61% 7% 12% 14% 5%	2665
	21st to end	Night	60% 7% 13% 14% 6% 1	2121
March	1st to 10th	Night	52% 6% 13% 17% 10% 1	5040
	11th to 20th	Night	41% 7% 18% 22% 11% 1	5090
	21st to end	Night	48% 6% 12% 17% 14% 2	5588
April	1st to 10th	Night	54% 6% 11% 17% 11% 2	2195
	11th to 20th	Night	48% 6% 11% 19% 14% 2	1974
	21st to end	Night	45% 8% 11% 21% 13% 3	1890
May	1st to 10th	Night	54% 6% 9% 14% 11% 7%	4150
	11th to 20th	Night	46% 7% 13% 22% 10% 2	3994
	21st to end	Night	40% 7% 13% 21% 16% 2	4015
June	1st to 10th	Night	38% 9% 13% 23% 13% 4	1600
	11th to 20th	Night	37% 8% 14% 22% 17% 2	1600
	21st to end	Night	37% 9% 13% 22% 18% 1	1600
July	1st to 10th	Night	35% 5% 13% 24% 18% 4	3560
	11th to 20th	Night	35% 5% 12% 29% 17% 2	3868
	21st to end	Night	33% 5% 14% 21% 25% 2	4297
August	1st to 10th	Night	38% 7% 13% 26% 14% 2	2904
	11th to 20th	Night	38% 7% 16% 28% 11% 1	2902
	21st to end	Night	31% 7% 14% 32% 14% 1	3322
September	1st to 10th	Night	36% 8% 12% 26% 16% 2	2000
	11th to 20th	Night	32% 5% 14% 30% 18%	2195
	21st to end	Night	47% 7% 11% 22% 12% 1	2200
October	1st to 10th	Night	34% 6% 9% 27% 23% 2	3914
	11th to 20th	Night	45% 4 13% 23% 14%	3899
	21st to end	Night	42% 5% 16% 23% 13% 1	4252
November	1st to 10th	Night	49% 6% 12% 20% 11% 1	2639
	11th to 20th	Night	59% 8% 11% 14% 7% 1	2940
	21st to end	Night	68% 8% 11% 11% 2	2940
December	1st to 10th	Night	76% 6% 10% 6% 2	4720
	11th to 20th	Night	77% 7% 8% 6% 1	5348
	21st to end	Night	73% 7% 9% 8% 3	7150

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	24% 15% 31% 20% 8% 1	268
	11th to 20th	Day	25% 17% 34% 18% 5% 1	330
	21st to end	Day	20% 12% 35% 25% 7%	363
February	1st to 10th	Day	22% 12% 29% 30% 7% 1	330
	11th to 20th	Day	20% 12% 34% 29% 5%	330
	21st to end	Day	18% 18% 34% 26% 4	273
March	1st to 10th	Day	20% 8% 28% 34% 10%	527
	11th to 20th	Day	20% 9% 31% 32% 7% 1	540
	21st to end	Day	24% 8% 29% 28% 10% 1	594
April	1st to 10th	Day	19% 7% 30% 34% 9% 1	540
	11th to 20th	Day	19% 9% 27% 27% 14% 4	532
	21st to end	Day	21% 6% 23% 36% 14% 1	540
May	1st to 10th	Day	23% 5% 19% 36% 15% 3	543
	11th to 20th	Day	16% 3 21% 31% 24% 5%	567
	21st to end	Day	15% 2 14% 32% 29% 8%	617
June	1st to 10th	Day	13% 3 21% 37% 23% 4	530
	11th to 20th	Day	12% 4 18% 33% 28% 6%	530
	21st to end	Day	12% 4 14% 37% 28% 5%	530
July	1st to 10th	Day	7% 2 13% 32% 34% 12%	525
	11th to 20th	Day	12% 5% 11% 32% 31% 10%	524
	21st to end	Day	7% 2 11% 36% 36% 7%	576
August	1st to 10th	Day	11% 2 9% 31% 36% 12%	526
	11th to 20th	Day	12% 3 11% 28% 36% 10%	519
	21st to end	Day	11% 3 13% 31% 34% 8%	583
September	1st to 10th	Day	12% 3 18% 26% 26% 15%	530
	11th to 20th	Day	9% 4 10% 23% 35% 19%	530
	21st to end	Day	15% 6% 20% 26% 25% 8%	530
October	1st to 10th	Day	15% 7% 18% 28% 21% 10%	530
	11th to 20th	Day	19% 12% 26% 28% 12% 3	530
	21st to end	Day	28% 10% 26% 24% 11%	583
November	1st to 10th	Day	22% 12% 26% 25% 12% 2	356
	11th to 20th	Day	25% 16% 28% 20% 8% 2	220
	21st to end	Day	30% 13% 30% 22% 5%	220
December	1st to 10th	Day	30% 19% 27% 18% 5%	220
	11th to 20th	Day	29% 19% 32% 17% 3	220
	21st to end	Day	27% 17% 31% 20% 6%	242
January	1st to 10th	Night	28% 16% 35% 16% 5%	840
	11th to 20th	Night	29% 15% 32% 21% 3	840
	21st to end	Night	21% 12% 36% 25% 6%	924
February	1st to 10th	Night	27% 9% 32% 28% 4	840
	11th to 20th	Night	22% 10% 35% 28% 4	823
	21st to end	Night	23% 10% 36% 26% 5%	692
March	1st to 10th	Night	20% 7% 32% 31% 9%	840
	11th to 20th	Night	21% 7% 33% 30% 8% 1	840
	21st to end	Night	20% 8% 28% 32% 10% 2	924
April	1st to 10th	Night	21% 8% 28% 33% 9% 1	840
	11th to 20th	Night	20% 7% 26% 33% 11% 2	730
	21st to end	Night	18% 4 24% 40% 13% 2	630
May	1st to 10th	Night	20% 6% 23% 31% 18% 2	630
	11th to 20th	Night	17% 4 18% 37% 21% 3	570
	21st to end	Night	15% 2 13% 34% 29% 7%	455
June	1st to 10th	Night	14% 3 21% 35% 25% 3	400
	11th to 20th	Night	12% 3 16% 38% 29% 3	400
	21st to end	Night	12% 3 19% 35% 29% 3	400
July	1st to 10th	Night	7% 3 11% 38% 32% 10%	390
	11th to 20th	Night	9% 3 15% 34% 32% 7%	522
	21st to end	Night	11% 2 12% 37% 33% 5%	657
August	1st to 10th	Night	9% 2 12% 32% 37% 7%	597
	11th to 20th	Night	9% 2 14% 29% 37% 8%	594
	21st to end	Night	11% 2 15% 34% 29% 8%	720
September	1st to 10th	Night	15% 5% 15% 26% 29% 10%	800
	11th to 20th	Night	13% 3 13% 27% 34% 12%	800
	21st to end	Night	17% 6% 18% 30% 22% 7%	800
October	1st to 10th	Night	18% 7% 20% 27% 21% 6%	800
	11th to 20th	Night	24% 11% 26% 27% 10% 3	800
	21st to end	Night	29% 10% 29% 24% 7% 1	880
November	1st to 10th	Night	23% 12% 27% 25% 11% 2	820
	11th to 20th	Night	25% 16% 30% 22% 6% 1	840
	21st to end	Night	32% 16% 29% 18% 5%	840
December	1st to 10th	Night	33% 18% 28% 15% 5% 1	840
	11th to 20th	Night	28% 19% 32% 17% 3	840
	21st to end	Night	30% 13% 35% 20% 3	924

Page generated at 2026-05-29 01:53:26. Version ac07

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