Summerside
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Summerside clear sky chart from 2005-11-06 to 2026-05-17.

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 9% 5% 5% 4 4 5% 6% 31%	132434
	Night	18% 12% 4 9% 5% 4 4 3 5% 6% 29%	130548
Transparency	Day	37% 36% 8% 14% 6%	135979
	Night	39% 35% 7% 12% 6% 1	135092
Seeing	Day	23% 12% 29% 24% 10% 2	19098
	Night	25% 12% 30% 25% 7% 1	26586

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	14% 22% 6% 13% 8% 6% 4 3 4 5% 15%	4093
	11th to 20th	Day	17% 17% 8% 12% 6% 5% 4 3 4 4 22%	4594
	21st to end	Day	8% 10% 4 10% 5% 5% 6% 4 5% 7% 36%	5724
February	1st to 10th	Day	15% 14% 4 10% 5% 4 5% 3 4 6% 30%	1890
	11th to 20th	Day	14% 16% 4 8% 6% 6% 4 4 4 6% 29%	1843
	21st to end	Day	11% 12% 5% 8% 5% 5% 4 3 6% 7% 34%	1573
March	1st to 10th	Day	19% 12% 5% 10% 5% 7% 4 3 4 6% 25%	4949
	11th to 20th	Day	13% 13% 5% 12% 6% 5% 5% 4 6% 7% 24%	5090
	21st to end	Day	23% 15% 4 9% 5% 3 4 4 5% 6% 22%	5622
April	1st to 10th	Day	19% 12% 3 8% 5% 4 4 3 4 5% 31%	2520
	11th to 20th	Day	18% 11% 3 6% 4 4 4 3 5% 8% 32%	2595
	21st to end	Day	20% 11% 3 7% 5% 4 5% 4 6% 7% 30%	2730
May	1st to 10th	Day	24% 14% 3 6% 4 4 4 3 4 6% 28%	6330
	11th to 20th	Day	19% 10% 3 7% 5% 4 4 3 4 6% 34%	6402
	21st to end	Day	17% 10% 3 7% 5% 5% 5% 4 6% 7% 32%	6948
June	1st to 10th	Day	23% 10% 2 7% 5% 5% 4 4 6% 7% 27%	2887
	11th to 20th	Day	18% 8% 2 7% 5% 4 4 4 6% 7% 36%	3000
	21st to end	Day	24% 8% 2 7% 5% 4 4 4 5% 6% 32%	3000
July	1st to 10th	Day	14% 9% 3 8% 6% 5% 6% 4 7% 8% 30%	6820
	11th to 20th	Day	13% 5% 2 6% 4 4 4 4 6% 7% 43%	6553
	21st to end	Day	11% 6% 2 7% 4 4 5% 4 7% 9% 41%	6927
August	1st to 10th	Day	14% 9% 3 8% 5% 4 4 4 6% 7% 35%	4241
	11th to 20th	Day	12% 5% 2 7% 5% 5% 5% 5% 6% 8% 40%	4175
	21st to end	Day	12% 5% 2 5% 4 4 5% 3 6% 9% 46%	4517
September	1st to 10th	Day	16% 5% 2 5% 3 4 4 4 6% 8% 43%	2400
	11th to 20th	Day	17% 8% 3 6% 4 4 3 3 5% 6% 41%	2345
	21st to end	Day	17% 6% 2 7% 5% 4 4 3 4 6% 42%	2124
October	1st to 10th	Day	17% 8% 3 7% 4 4 4 4 6% 7% 37%	2000
	11th to 20th	Day	18% 12% 3 9% 5% 5% 5% 3 6% 6% 27%	2000
	21st to end	Day	19% 12% 4 9% 7% 5% 5% 3 5% 7% 26%	2165
November	1st to 10th	Day	19% 13% 4 8% 6% 7% 4 3 4 6% 26%	1651
	11th to 20th	Day	20% 17% 6% 9% 6% 4 5% 3 5% 6% 19%	1680
	21st to end	Day	19% 15% 6% 12% 8% 5% 4 3 5% 6% 18%	1680
December	1st to 10th	Day	18% 13% 6% 21% 7% 4 3 3 3 4 18%	2690
	11th to 20th	Day	17% 15% 6% 13% 7% 5% 4 3 3 3 24%	3076
	21st to end	Day	15% 14% 8% 16% 8% 6% 5% 3 3 4 19%	3600
January	1st to 10th	Night	16% 18% 5% 13% 7% 5% 4 3 4 4 22%	8831
	11th to 20th	Night	17% 17% 6% 12% 6% 4 4 3 4 4 23%	8316
	21st to end	Night	7% 13% 4 10% 6% 5% 5% 4 5% 5% 35%	8446
February	1st to 10th	Night	16% 14% 4 10% 5% 4 4 4 5% 5% 28%	2730
	11th to 20th	Night	16% 16% 4 10% 6% 4 4 3 5% 5% 26%	2663
	21st to end	Night	13% 12% 4 9% 6% 5% 4 3 5% 6% 33%	2232
March	1st to 10th	Night	22% 13% 4 11% 6% 5% 4 3 4 5% 23%	5098
	11th to 20th	Night	19% 15% 4 10% 6% 5% 4 4 5% 5% 24%	5089
	21st to end	Night	27% 13% 4 10% 4 4 4 3 4 3 24%	5552
April	1st to 10th	Night	22% 12% 4 9% 5% 4 4 4 5% 5% 26%	2100
	11th to 20th	Night	22% 11% 3 7% 5% 4 4 3 4 6% 31%	1972
	21st to end	Night	21% 13% 3 8% 5% 3 3 3 4 6% 29%	1890
May	1st to 10th	Night	28% 12% 3 8% 4 4 4 3 5% 6% 23%	3842
	11th to 20th	Night	20% 8% 3 7% 5% 4 4 3 5% 6% 35%	3645
	21st to end	Night	16% 10% 3 7% 4 4 4 4 6% 8% 33%	3948
June	1st to 10th	Night	24% 9% 4 7% 4 4 4 3 5% 7% 29%	1529
	11th to 20th	Night	19% 7% 2 5% 5% 4 5% 3 5% 8% 37%	1400
	21st to end	Night	23% 10% 4 8% 4 5% 4 3 5% 6% 28%	1400
July	1st to 10th	Night	16% 7% 3 9% 7% 6% 6% 5% 7% 8% 27%	3160
	11th to 20th	Night	10% 6% 3 8% 5% 5% 6% 5% 8% 8% 37%	3380
	21st to end	Night	14% 5% 2 6% 4 5% 4 4 6% 8% 39%	3948
August	1st to 10th	Night	17% 8% 3 9% 6% 5% 6% 5% 5% 7% 31%	2905
	11th to 20th	Night	10% 5% 3 8% 6% 5% 5% 4 5% 8% 40%	2872
	21st to end	Night	13% 5% 2 6% 4 4 4 3 6% 8% 45%	3380
September	1st to 10th	Night	15% 6% 2 5% 3 4 3 3 6% 7% 43%	2000
	11th to 20th	Night	16% 7% 2 6% 4 3 4 4 5% 7% 43%	2052
	21st to end	Night	16% 6% 1 6% 5% 4 3 4 5% 7% 43%	2275
October	1st to 10th	Night	19% 6% 2 6% 4 4 3 3 5% 7% 39%	2400
	11th to 20th	Night	19% 9% 3 8% 4 4 5% 3 5% 7% 33%	2400
	21st to end	Night	23% 11% 3 9% 5% 4 4 3 5% 6% 28%	2675
November	1st to 10th	Night	20% 12% 4 8% 5% 4 4 4 5% 5% 28%	2863
	11th to 20th	Night	21% 15% 4 8% 6% 5% 4 3 5% 5% 23%	2940
	21st to end	Night	23% 15% 4 10% 5% 4 4 3 5% 7% 20%	2940
December	1st to 10th	Night	14% 13% 5% 14% 7% 5% 5% 4 5% 5% 22%	4720
	11th to 20th	Night	20% 15% 5% 11% 5% 4 4 3 4 5% 26%	5353
	21st to end	Night	20% 15% 6% 13% 5% 4 4 3 4 5% 21%	7602

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	63% 20% 8% 7% 3	4094
	11th to 20th	Day	56% 21% 5% 10% 7% 1	4623
	21st to end	Day	39% 21% 9% 19% 11% 1	5724
February	1st to 10th	Day	25% 59% 2 9% 4 1	1890
	11th to 20th	Day	24% 58% 4 10% 5%	1851
	21st to end	Day	19% 59% 4 10% 6% 1	1573
March	1st to 10th	Day	47% 27% 5% 13% 8% 1	4953
	11th to 20th	Day	48% 27% 12% 9% 4 1	5090
	21st to end	Day	52% 27% 4 11% 6% 1	5622
April	1st to 10th	Day	24% 58% 3 6% 7% 2	2520
	11th to 20th	Day	23% 59% 3 10% 4	2595
	21st to end	Day	24% 59% 3 6% 6% 1	2730
May	1st to 10th	Day	46% 27% 8% 13% 6%	6342
	11th to 20th	Day	41% 27% 12% 18% 3	6406
	21st to end	Day	40% 28% 8% 17% 7%	6948
June	1st to 10th	Day	20% 62% 4 10% 4	2887
	11th to 20th	Day	18% 62% 6% 10% 4	3000
	21st to end	Day	21% 60% 5% 8% 6% 1	3000
July	1st to 10th	Day	42% 25% 13% 13% 6%	6745
	11th to 20th	Day	31% 25% 12% 27% 5%	6472
	21st to end	Day	29% 26% 16% 23% 5%	6730
August	1st to 10th	Day	34% 36% 8% 18% 4	4227
	11th to 20th	Day	27% 36% 9% 17% 10%	4214
	21st to end	Day	25% 36% 10% 19% 11%	4517
September	1st to 10th	Day	15% 57% 8% 14% 6%	2400
	11th to 20th	Day	22% 56% 7% 10% 4	2345
	21st to end	Day	18% 57% 4 14% 8%	2124
October	1st to 10th	Day	32% 35% 8% 20% 5%	3260
	11th to 20th	Day	37% 35% 4 18% 5%	3240
	21st to end	Day	33% 35% 12% 14% 6%	3481
November	1st to 10th	Day	31% 53% 6% 9% 2	1651
	11th to 20th	Day	35% 54% 5% 4 2	1680
	21st to end	Day	33% 54% 6% 4 2	1680
December	1st to 10th	Day	47% 35% 4 14% 1	2690
	11th to 20th	Day	48% 31% 6% 9% 6% 1	3075
	21st to end	Day	54% 26% 7% 11% 2	3600
January	1st to 10th	Night	55% 20% 8% 14% 3	8831
	11th to 20th	Night	56% 20% 6% 12% 6%	8362
	21st to end	Night	43% 21% 7% 14% 13% 2	8446
February	1st to 10th	Night	26% 58% 3 6% 5% 1	2730
	11th to 20th	Night	25% 57% 3 9% 5%	2666
	21st to end	Night	21% 59% 2 9% 7% 2	2232
March	1st to 10th	Night	50% 27% 2 9% 10% 2	5107
	11th to 20th	Night	50% 27% 7% 9% 6% 1	5090
	21st to end	Night	52% 27% 2 10% 8%	5552
April	1st to 10th	Night	25% 59% 3 7% 5% 1	2100
	11th to 20th	Night	25% 59% 3 9% 3 1	1972
	21st to end	Night	25% 58% 3 6% 6% 2	1890
May	1st to 10th	Night	51% 27% 5% 10% 8%	3847
	11th to 20th	Night	39% 28% 10% 18% 5% 1	3646
	21st to end	Night	39% 27% 13% 17% 4	3949
June	1st to 10th	Night	19% 62% 5% 10% 4	1529
	11th to 20th	Night	17% 62% 5% 12% 4	1400
	21st to end	Night	22% 61% 2 8% 6%	1400
July	1st to 10th	Night	45% 25% 10% 12% 7% 1	3125
	11th to 20th	Night	33% 26% 15% 19% 7%	3338
	21st to end	Night	32% 26% 16% 19% 6%	3831
August	1st to 10th	Night	38% 37% 9% 12% 3	2894
	11th to 20th	Night	27% 37% 11% 14% 10% 1	2899
	21st to end	Night	26% 35% 11% 18% 10%	3379
September	1st to 10th	Night	16% 57% 5% 15% 6%	2000
	11th to 20th	Night	21% 57% 6% 12% 5%	2052
	21st to end	Night	17% 57% 5% 15% 6%	2275
October	1st to 10th	Night	35% 35% 8% 17% 4	3920
	11th to 20th	Night	31% 36% 6% 20% 7%	3899
	21st to end	Night	33% 35% 11% 15% 7%	4311
November	1st to 10th	Night	31% 53% 6% 7% 3	2863
	11th to 20th	Night	31% 55% 6% 6% 2	2940
	21st to end	Night	34% 54% 5% 4 2	2940
December	1st to 10th	Night	40% 34% 8% 15% 2	4720
	11th to 20th	Night	44% 31% 6% 13% 6% 1	5355
	21st to end	Night	52% 25% 9% 10% 4	7602

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	29% 20% 30% 17% 4	220
	11th to 20th	Day	29% 16% 29% 19% 6%	395
	21st to end	Day	17% 15% 37% 26% 4 1	473
February	1st to 10th	Day	25% 14% 34% 21% 4 2	430
	11th to 20th	Day	24% 15% 33% 21% 5%	426
	21st to end	Day	17% 16% 32% 26% 7% 1	355
March	1st to 10th	Day	24% 14% 33% 22% 6% 1	518
	11th to 20th	Day	20% 16% 32% 24% 7% 1	540
	21st to end	Day	28% 14% 30% 20% 6% 1	594
April	1st to 10th	Day	28% 17% 33% 17% 6%	540
	11th to 20th	Day	25% 15% 32% 18% 8% 1	532
	21st to end	Day	24% 14% 27% 22% 11% 1	540
May	1st to 10th	Day	33% 10% 28% 20% 6% 2	676
	11th to 20th	Day	25% 9% 27% 22% 13% 3	754
	21st to end	Day	23% 9% 32% 26% 8% 1	790
June	1st to 10th	Day	30% 7% 25% 27% 10% 2	730
	11th to 20th	Day	22% 8% 29% 28% 11% 2	730
	21st to end	Day	28% 7% 20% 30% 12% 3	730
July	1st to 10th	Day	19% 5% 30% 28% 15% 2	720
	11th to 20th	Day	16% 5% 27% 33% 16% 3	718
	21st to end	Day	18% 6% 24% 34% 15% 2	795
August	1st to 10th	Day	14% 5% 24% 34% 18% 5%	532
	11th to 20th	Day	16% 4 24% 29% 21% 5%	519
	21st to end	Day	14% 8% 27% 28% 18% 5%	583
September	1st to 10th	Day	15% 5% 30% 32% 13% 4	530
	11th to 20th	Day	21% 10% 25% 26% 15% 2	530
	21st to end	Day	22% 9% 30% 25% 11% 4	488
October	1st to 10th	Day	21% 10% 27% 25% 14% 3	420
	11th to 20th	Day	25% 15% 26% 22% 10% 2	420
	21st to end	Day	26% 15% 31% 20% 7% 1	462
November	1st to 10th	Day	26% 18% 34% 16% 5% 1	425
	11th to 20th	Day	33% 17% 28% 16% 6% 1	430
	21st to end	Day	32% 17% 30% 17% 3 1	430
December	1st to 10th	Day	31% 18% 31% 17% 3	430
	11th to 20th	Day	31% 23% 33% 11% 3	430
	21st to end	Day	21% 20% 35% 20% 4 1	263
January	1st to 10th	Night	26% 16% 32% 20% 5%	950
	11th to 20th	Night	27% 15% 30% 22% 5%	950
	21st to end	Night	19% 17% 34% 22% 7% 1	934
February	1st to 10th	Night	24% 14% 33% 22% 6% 1	840
	11th to 20th	Night	24% 16% 34% 22% 4	823
	21st to end	Night	21% 10% 35% 26% 8% 1	692
March	1st to 10th	Night	24% 13% 35% 25% 3	840
	11th to 20th	Night	23% 14% 30% 25% 8% 1	840
	21st to end	Night	28% 13% 29% 22% 8% 1	914
April	1st to 10th	Night	27% 14% 31% 22% 5%	630
	11th to 20th	Night	28% 10% 30% 24% 8%	624
	21st to end	Night	29% 9% 30% 23% 8% 1	630
May	1st to 10th	Night	30% 7% 28% 23% 9% 2	630
	11th to 20th	Night	25% 7% 27% 28% 10% 2	611
	21st to end	Night	19% 9% 38% 28% 5%	649
June	1st to 10th	Night	29% 6% 27% 32% 5% 1	529
	11th to 20th	Night	21% 6% 28% 36% 9% 1	400
	21st to end	Night	27% 5% 26% 32% 9% 1	400
July	1st to 10th	Night	19% 6% 32% 29% 14% 1	390
	11th to 20th	Night	13% 6% 33% 38% 10%	478
	21st to end	Night	18% 5% 29% 37% 11% 1	656
August	1st to 10th	Night	16% 3 30% 35% 16% 1	598
	11th to 20th	Night	16% 4 26% 37% 16% 1	592
	21st to end	Night	17% 5% 24% 34% 18% 1	660
September	1st to 10th	Night	18% 7% 34% 32% 10% 1	600
	11th to 20th	Night	19% 9% 21% 37% 12% 1	652
	21st to end	Night	20% 9% 30% 29% 11% 1	800
October	1st to 10th	Night	23% 8% 28% 30% 11% 1	800
	11th to 20th	Night	24% 11% 30% 25% 9% 1	800
	21st to end	Night	31% 15% 28% 19% 6%	899
November	1st to 10th	Night	33% 15% 29% 18% 4 1	930
	11th to 20th	Night	33% 18% 25% 17% 5% 1	950
	21st to end	Night	32% 18% 26% 20% 3 1	950
December	1st to 10th	Night	30% 17% 30% 19% 3	950
	11th to 20th	Night	27% 24% 32% 13% 3	950
	21st to end	Night	29% 18% 29% 20% 3 1	1045

Page generated at 2026-05-14 02:58:58. Version ac07

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