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 2024-08-30.

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% 3 8% 5% 5% 5% 4 6% 7% 33%	95595
	Night	16% 11% 4 9% 6% 5% 4 4 5% 7% 31%	93436
Transparency	Day	48% 8% 14% 19% 10% 1	95327
	Night	54% 8% 12% 16% 9% 1	93258
Seeing	Day	17% 7% 22% 29% 20% 5%	14241
	Night	21% 9% 25% 27% 15% 3	23777

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% 20% 10% 12% 6% 6% 4 2 3 3 15%	2649
	11th to 20th	Day	13% 20% 8% 23% 11% 4 4 2 3 4 8%	2840
	21st to end	Day	23% 18% 6% 14% 7% 5% 5% 3 4 3 12%	3124
February	1st to 10th	Day	17% 16% 5% 12% 7% 6% 6% 4 5% 6% 18%	1710
	11th to 20th	Day	15% 12% 7% 11% 7% 6% 6% 3 5% 5% 23%	1663
	21st to end	Day	20% 12% 3 9% 6% 4 6% 4 5% 5% 24%	1527
March	1st to 10th	Day	19% 10% 4 9% 6% 5% 5% 3 5% 6% 27%	3420
	11th to 20th	Day	10% 13% 4 8% 6% 6% 5% 4 6% 8% 31%	3480
	21st to end	Day	18% 8% 3 7% 6% 6% 4 4 5% 6% 34%	3815
April	1st to 10th	Day	15% 10% 3 8% 5% 5% 4 4 5% 6% 33%	2193
	11th to 20th	Day	17% 9% 3 8% 3 5% 4 3 6% 8% 35%	2361
	21st to end	Day	18% 9% 2 6% 4 4 4 4 6% 7% 36%	2470
May	1st to 10th	Day	18% 7% 3 8% 6% 5% 5% 4 6% 7% 32%	4108
	11th to 20th	Day	15% 9% 3 8% 5% 4 5% 4 7% 8% 32%	4162
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 4 6% 9% 46%	4837
June	1st to 10th	Day	11% 6% 2 6% 4 5% 5% 4 6% 8% 40%	2660
	11th to 20th	Day	10% 6% 2 6% 5% 4 5% 5% 6% 9% 41%	2660
	21st to end	Day	10% 5% 2 5% 4 4 4 4 6% 11% 45%	2660
July	1st to 10th	Day	7% 5% 2 6% 4 4 5% 4 7% 10% 46%	4440
	11th to 20th	Day	10% 5% 2 5% 4 4 4 4 6% 11% 46%	4202
	21st to end	Day	6% 4 2 5% 4 5% 5% 4 8% 10% 46%	4466
August	1st to 10th	Day	9% 4 1 5% 4 4 5% 5% 7% 10% 46%	2457
	11th to 20th	Day	9% 4 1 6% 4 5% 6% 5% 8% 10% 42%	2433
	21st to end	Day	10% 6% 2 6% 4 4 4 4 6% 9% 45%	2619
September	1st to 10th	Day	12% 6% 2 6% 4 4 6% 4 5% 7% 44%	2160
	11th to 20th	Day	8% 5% 2 5% 5% 4 4 5% 6% 8% 48%	1981
	21st to end	Day	15% 6% 3 7% 5% 5% 5% 4 6% 7% 39%	1980
October	1st to 10th	Day	15% 7% 3 7% 6% 5% 5% 4 6% 7% 36%	1805
	11th to 20th	Day	20% 8% 3 8% 7% 6% 6% 4 6% 6% 26%	1800
	21st to end	Day	24% 11% 4 8% 6% 5% 4 3 6% 7% 22%	1980
November	1st to 10th	Day	14% 10% 3 8% 5% 5% 4 4 6% 6% 35%	1695
	11th to 20th	Day	17% 11% 5% 9% 8% 4 3 5% 5% 6% 27%	1520
	21st to end	Day	22% 16% 3 10% 6% 7% 4 2 6% 6% 18%	1520
December	1st to 10th	Day	19% 19% 5% 11% 8% 8% 5% 3 4 6% 13%	1520
	11th to 20th	Day	19% 19% 6% 12% 6% 7% 6% 3 5% 5% 13%	1906
	21st to end	Day	28% 20% 5% 11% 5% 5% 4 3 3 4 11%	2772
January	1st to 10th	Night	19% 20% 8% 12% 7% 6% 4 3 4 4 15%	4292
	11th to 20th	Night	16% 20% 8% 17% 13% 5% 3 2 3 3 10%	4120
	21st to end	Night	24% 19% 7% 17% 5% 4 4 2 3 4 11%	4532
February	1st to 10th	Night	17% 16% 4 12% 7% 5% 5% 4 4 5% 21%	2470
	11th to 20th	Night	16% 14% 3 10% 7% 5% 5% 5% 5% 6% 23%	2403
	21st to end	Night	19% 12% 4 9% 7% 5% 4 4 5% 6% 24%	1925
March	1st to 10th	Night	19% 10% 4 7% 5% 5% 4 3 4 6% 32%	3419
	11th to 20th	Night	15% 10% 3 6% 5% 4 5% 4 5% 8% 35%	3479
	21st to end	Night	16% 10% 3 7% 4 4 4 3 5% 5% 39%	3817
April	1st to 10th	Night	19% 10% 3 7% 6% 4 4 4 4 7% 32%	1986
	11th to 20th	Night	18% 8% 3 6% 5% 4 4 3 6% 7% 35%	1784
	21st to end	Night	15% 6% 3 7% 5% 5% 6% 4 6% 7% 36%	1710
May	1st to 10th	Night	20% 9% 3 7% 4 3 4 4 5% 7% 36%	2833
	11th to 20th	Night	12% 8% 3 9% 5% 5% 5% 4 6% 7% 35%	2727
	21st to end	Night	10% 6% 2 6% 4 3 3 4 7% 9% 46%	2738
June	1st to 10th	Night	11% 7% 3 5% 5% 5% 4 4 7% 8% 41%	1520
	11th to 20th	Night	10% 5% 2 6% 6% 4 5% 4 7% 9% 42%	1520
	21st to end	Night	11% 5% 2 6% 4 4 5% 4 6% 9% 44%	1520
July	1st to 10th	Night	7% 5% 2 6% 4 4 4 4 5% 10% 48%	2520
	11th to 20th	Night	8% 5% 2 6% 5% 4 4 4 6% 9% 48%	2740
	21st to end	Night	6% 5% 2 7% 4 5% 4 5% 7% 9% 47%	3087
August	1st to 10th	Night	8% 5% 2 5% 5% 5% 5% 4 7% 11% 45%	1701
	11th to 20th	Night	9% 4 3 5% 4 4 4 3 7% 9% 47%	1688
	21st to end	Night	9% 5% 2 5% 5% 5% 4 4 6% 8% 47%	1928
September	1st to 10th	Night	12% 7% 2 6% 4 3 4 3 6% 8% 44%	1800
	11th to 20th	Night	12% 4 1 5% 3 4 4 3 5% 8% 51%	1975
	21st to end	Night	15% 6% 3 8% 5% 4 4 4 5% 6% 40%	1980
October	1st to 10th	Night	16% 7% 2 6% 4 4 5% 4 5% 7% 39%	2154
	11th to 20th	Night	19% 9% 3 8% 7% 5% 4 3 5% 7% 30%	2160
	21st to end	Night	24% 9% 3 8% 5% 4 4 3 5% 7% 28%	2376
November	1st to 10th	Night	17% 7% 3 7% 5% 5% 4 3 5% 7% 37%	2380
	11th to 20th	Night	18% 13% 4 8% 7% 6% 6% 3 4 8% 25%	2660
	21st to end	Night	21% 15% 4 9% 6% 6% 5% 3 5% 6% 20%	2660
December	1st to 10th	Night	22% 19% 5% 10% 6% 6% 4 4 4 6% 14%	2660
	11th to 20th	Night	18% 20% 6% 12% 6% 5% 5% 3 4 6% 15%	3288
	21st to end	Night	27% 20% 6% 11% 6% 4 4 3 4 4 11%	4884

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	74% 9% 6% 5% 5%	2650
	11th to 20th	Day	82% 6% 6% 5% 1	2840
	21st to end	Day	76% 9% 8% 5% 2	3124
February	1st to 10th	Day	66% 8% 12% 10% 3	1710
	11th to 20th	Day	62% 6% 12% 13% 6%	1672
	21st to end	Day	59% 6% 12% 16% 5% 1	1527
March	1st to 10th	Day	53% 9% 12% 21% 4	3423
	11th to 20th	Day	46% 10% 21% 16% 6% 1	3480
	21st to end	Day	48% 9% 13% 20% 9% 1	3815
April	1st to 10th	Day	48% 6% 15% 19% 12%	2193
	11th to 20th	Day	46% 6% 13% 21% 13% 1	2361
	21st to end	Day	46% 8% 13% 18% 13% 2	2470
May	1st to 10th	Day	45% 10% 13% 20% 10% 2	4120
	11th to 20th	Day	45% 12% 14% 20% 8% 1	4166
	21st to end	Day	33% 9% 15% 22% 16% 6%	4837
June	1st to 10th	Day	37% 10% 13% 24% 14% 1	2660
	11th to 20th	Day	36% 10% 15% 23% 16% 1	2660
	21st to end	Day	32% 8% 16% 27% 15% 1	2660
July	1st to 10th	Day	31% 6% 15% 28% 17% 3	4370
	11th to 20th	Day	30% 6% 15% 30% 17% 1	4130
	21st to end	Day	31% 7% 19% 23% 19% 1	4324
August	1st to 10th	Day	30% 9% 19% 29% 12% 1	2444
	11th to 20th	Day	33% 10% 19% 27% 10% 1	2433
	21st to end	Day	33% 8% 16% 28% 13% 2	2619
September	1st to 10th	Day	37% 8% 18% 23% 12% 1	2160
	11th to 20th	Day	32% 8% 17% 28% 15%	1981
	21st to end	Day	43% 8% 14% 23% 11% 1	1980
October	1st to 10th	Day	46% 8% 15% 18% 12% 1	1805
	11th to 20th	Day	56% 9% 14% 15% 6% 1	1800
	21st to end	Day	63% 8% 12% 12% 4 1	1980
November	1st to 10th	Day	49% 8% 14% 20% 8% 2	1695
	11th to 20th	Day	58% 8% 14% 12% 8% 1	1520
	21st to end	Day	69% 8% 10% 9% 3	1520
December	1st to 10th	Day	76% 7% 9% 8% 1	1520
	11th to 20th	Day	73% 10% 9% 6% 2	1906
	21st to end	Day	78% 8% 8% 6% 1	2772
January	1st to 10th	Night	71% 14% 7% 6% 2	4292
	11th to 20th	Night	80% 8% 6% 5% 2	4120
	21st to end	Night	79% 7% 6% 6% 2	4532
February	1st to 10th	Night	66% 7% 13% 11% 3	2470
	11th to 20th	Night	61% 8% 11% 15% 5%	2405
	21st to end	Night	59% 7% 13% 14% 6% 1	1925
March	1st to 10th	Night	53% 7% 13% 19% 7%	3429
	11th to 20th	Night	44% 9% 18% 18% 10% 1	3480
	21st to end	Night	45% 7% 13% 19% 14% 2	3817
April	1st to 10th	Night	52% 6% 11% 18% 11% 2	1986
	11th to 20th	Night	47% 6% 12% 19% 14% 2	1784
	21st to end	Night	46% 8% 11% 19% 13% 3	1710
May	1st to 10th	Night	47% 7% 11% 19% 12% 4	2840
	11th to 20th	Night	45% 9% 15% 20% 9% 2	2728
	21st to end	Night	31% 9% 15% 23% 20% 3	2739
June	1st to 10th	Night	38% 9% 13% 23% 14% 3	1520
	11th to 20th	Night	37% 8% 13% 22% 18% 2	1520
	21st to end	Night	37% 9% 13% 23% 17% 1	1520
July	1st to 10th	Night	35% 6% 12% 23% 20% 6%	2480
	11th to 20th	Night	33% 5% 13% 30% 17% 2	2690
	21st to end	Night	34% 6% 17% 22% 20% 2	2988
August	1st to 10th	Night	32% 8% 15% 29% 14% 1	1690
	11th to 20th	Night	34% 9% 17% 27% 12% 1	1688
	21st to end	Night	33% 9% 14% 28% 14% 2	1928
September	1st to 10th	Night	38% 8% 13% 23% 15% 3	1800
	11th to 20th	Night	35% 5% 14% 28% 17% 1	1975
	21st to end	Night	45% 7% 12% 23% 13% 1	1980
October	1st to 10th	Night	45% 7% 12% 22% 14% 1	2154
	11th to 20th	Night	55% 6% 13% 17% 9%	2160
	21st to end	Night	59% 7% 11% 15% 7% 1	2376
November	1st to 10th	Night	50% 7% 12% 20% 11% 1	2380
	11th to 20th	Night	60% 8% 10% 13% 6% 1	2660
	21st to end	Night	66% 9% 11% 11% 2	2660
December	1st to 10th	Night	75% 8% 10% 6% 2	2660
	11th to 20th	Night	72% 10% 10% 6% 1	3288
	21st to end	Night	78% 8% 9% 5% 1	4884

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	26% 13% 31% 19% 10% 1	218
	11th to 20th	Day	27% 13% 33% 20% 6% 1	270
	21st to end	Day	22% 11% 33% 26% 7%	297
February	1st to 10th	Day	22% 13% 29% 31% 5%	270
	11th to 20th	Day	20% 13% 36% 27% 4	270
	21st to end	Day	20% 18% 34% 24% 4	225
March	1st to 10th	Day	20% 9% 28% 33% 10%	448
	11th to 20th	Day	20% 9% 30% 33% 7% 2	460
	21st to end	Day	25% 8% 28% 27% 11% 1	506
April	1st to 10th	Day	17% 7% 31% 35% 9% 2	460
	11th to 20th	Day	19% 10% 26% 27% 13% 4	452
	21st to end	Day	21% 6% 23% 37% 12% 1	460
May	1st to 10th	Day	23% 5% 19% 33% 17% 3	463
	11th to 20th	Day	17% 2 20% 30% 24% 6%	487
	21st to end	Day	12% 3 13% 31% 31% 9%	529
June	1st to 10th	Day	12% 3 21% 36% 23% 4	490
	11th to 20th	Day	12% 3 18% 33% 28% 6%	490
	21st to end	Day	12% 4 15% 38% 27% 4	490
July	1st to 10th	Day	6% 1 13% 32% 34% 13%	485
	11th to 20th	Day	12% 4 11% 31% 31% 10%	484
	21st to end	Day	7% 2 12% 38% 35% 6%	532
August	1st to 10th	Day	12% 2 9% 32% 34% 11%	486
	11th to 20th	Day	12% 2 12% 29% 37% 8%	479
	21st to end	Day	12% 3 14% 30% 34% 8%	532
September	1st to 10th	Day	13% 2 17% 29% 26% 13%	450
	11th to 20th	Day	9% 4 12% 27% 32% 17%	450
	21st to end	Day	14% 7% 22% 26% 23% 8%	450
October	1st to 10th	Day	16% 8% 19% 26% 20% 10%	450
	11th to 20th	Day	21% 13% 27% 26% 11% 2	450
	21st to end	Day	30% 11% 25% 24% 10%	495
November	1st to 10th	Day	22% 12% 26% 23% 14% 3	295
	11th to 20th	Day	27% 17% 26% 20% 8% 2	180
	21st to end	Day	30% 13% 29% 24% 4	180
December	1st to 10th	Day	31% 18% 29% 16% 6% 1	180
	11th to 20th	Day	29% 19% 31% 18% 3	180
	21st to end	Day	27% 18% 30% 19% 6%	198
January	1st to 10th	Night	29% 15% 35% 15% 6%	760
	11th to 20th	Night	29% 14% 30% 22% 4	760
	21st to end	Night	22% 11% 35% 25% 6%	836
February	1st to 10th	Night	27% 9% 33% 26% 4	760
	11th to 20th	Night	22% 10% 35% 28% 4	743
	21st to end	Night	24% 10% 36% 26% 5%	628
March	1st to 10th	Night	20% 7% 32% 31% 9%	760
	11th to 20th	Night	21% 7% 34% 29% 9% 1	760
	21st to end	Night	20% 8% 28% 32% 10% 2	836
April	1st to 10th	Night	21% 8% 29% 33% 9% 1	760
	11th to 20th	Night	20% 8% 27% 32% 12% 2	660
	21st to end	Night	18% 4 24% 40% 13% 1	570
May	1st to 10th	Night	19% 5% 23% 30% 20% 3	570
	11th to 20th	Night	18% 3 18% 36% 22% 3	515
	21st to end	Night	14% 2 13% 32% 31% 8%	411
June	1st to 10th	Night	14% 3 21% 34% 25% 3	380
	11th to 20th	Night	12% 3 16% 37% 29% 3	380
	21st to end	Night	12% 3 19% 36% 28% 3	380
July	1st to 10th	Night	7% 3 11% 37% 31% 11%	370
	11th to 20th	Night	9% 3 15% 34% 32% 7%	495
	21st to end	Night	10% 2 12% 38% 33% 5%	624
August	1st to 10th	Night	9% 2 13% 32% 37% 7%	567
	11th to 20th	Night	9% 2 15% 30% 37% 7%	564
	21st to end	Night	11% 3 16% 33% 29% 8%	680
September	1st to 10th	Night	16% 5% 14% 26% 29% 9%	720
	11th to 20th	Night	14% 3 15% 29% 31% 9%	720
	21st to end	Night	17% 6% 19% 29% 22% 7%	720
October	1st to 10th	Night	19% 8% 21% 26% 20% 6%	720
	11th to 20th	Night	24% 13% 25% 26% 11% 2	720
	21st to end	Night	31% 11% 29% 22% 6% 1	792
November	1st to 10th	Night	23% 12% 25% 26% 12% 2	740
	11th to 20th	Night	25% 16% 31% 21% 6% 2	760
	21st to end	Night	31% 16% 29% 18% 6%	760
December	1st to 10th	Night	34% 18% 29% 14% 5% 1	760
	11th to 20th	Night	28% 19% 33% 18% 4	760
	21st to end	Night	31% 13% 34% 19% 2	836

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