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 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% 10% 4 9% 5% 4 4 4 5% 7% 31%	105470
	Night	18% 12% 4 9% 5% 4 4 3 5% 6% 29%	103989
Transparency	Day	31% 44% 7% 12% 5%	109033
	Night	34% 43% 7% 11% 5%	108517
Seeing	Day	23% 11% 29% 25% 10% 2	17295
	Night	25% 12% 30% 25% 8% 1	24838

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% 15% 6% 14% 11% 6% 5% 3 4 4 18%	2277
	11th to 20th	Day	12% 14% 5% 12% 6% 5% 4 4 4 5% 29%	2550
	21st to end	Day	11% 10% 4 13% 6% 4 5% 3 5% 6% 32%	3101
February	1st to 10th	Day	17% 13% 4 9% 4 4 5% 4 4 6% 31%	1710
	11th to 20th	Day	15% 15% 4 8% 6% 6% 5% 4 4 6% 28%	1663
	21st to end	Day	11% 12% 5% 8% 5% 6% 4 3 6% 7% 33%	1427
March	1st to 10th	Day	21% 13% 5% 7% 4 5% 4 3 4 6% 28%	3369
	11th to 20th	Day	12% 16% 6% 14% 8% 5% 5% 4 5% 5% 20%	3480
	21st to end	Day	24% 15% 4 7% 5% 3 4 4 5% 6% 22%	3837
April	1st to 10th	Day	18% 13% 3 8% 5% 4 5% 3 4 6% 31%	2280
	11th to 20th	Day	18% 11% 3 6% 4 3 4 3 5% 8% 33%	2345
	21st to end	Day	20% 11% 3 7% 5% 4 5% 4 6% 7% 30%	2470
May	1st to 10th	Day	21% 15% 3 6% 4 4 4 3 4 7% 29%	4316
	11th to 20th	Day	15% 9% 3 7% 6% 4 4 3 4 6% 38%	4398
	21st to end	Day	15% 9% 3 8% 5% 6% 6% 5% 6% 8% 31%	4836
June	1st to 10th	Day	24% 10% 2 7% 5% 5% 4 4 6% 6% 26%	2742
	11th to 20th	Day	19% 9% 2 7% 5% 4 4 4 6% 7% 35%	2850
	21st to end	Day	24% 8% 2 7% 5% 4 4 4 5% 6% 31%	2850
July	1st to 10th	Day	14% 8% 3 7% 5% 5% 6% 4 7% 8% 34%	4760
	11th to 20th	Day	15% 6% 2 6% 5% 5% 5% 4 6% 8% 38%	4577
	21st to end	Day	12% 7% 2 7% 5% 4 5% 4 7% 9% 39%	4815
August	1st to 10th	Day	15% 10% 4 8% 5% 4 5% 5% 6% 7% 33%	4111
	11th to 20th	Day	13% 5% 2 7% 5% 5% 5% 5% 6% 8% 39%	4045
	21st to end	Day	12% 5% 2 5% 4 4 5% 3 6% 9% 46%	4379
September	1st to 10th	Day	16% 5% 2 5% 3 4 4 4 6% 8% 42%	2280
	11th to 20th	Day	18% 8% 3 6% 4 4 3 3 5% 6% 40%	2228
	21st to end	Day	18% 6% 2 7% 5% 4 4 3 4 6% 41%	2018
October	1st to 10th	Day	17% 8% 3 7% 4 4 4 4 6% 7% 36%	1900
	11th to 20th	Day	19% 12% 3 8% 5% 5% 5% 3 6% 6% 27%	1900
	21st to end	Day	19% 12% 4 9% 7% 5% 4 3 5% 7% 26%	2057
November	1st to 10th	Day	19% 12% 4 9% 6% 7% 5% 3 4 6% 25%	1571
	11th to 20th	Day	20% 16% 6% 9% 6% 5% 5% 3 5% 6% 18%	1600
	21st to end	Day	19% 16% 6% 12% 8% 5% 4 3 5% 6% 17%	1600
December	1st to 10th	Day	18% 12% 6% 21% 7% 4 3 3 3 5% 18%	2610
	11th to 20th	Day	17% 15% 5% 13% 7% 5% 4 3 3 3 24%	2996
	21st to end	Day	15% 14% 8% 15% 8% 6% 5% 3 3 4 19%	3522
January	1st to 10th	Night	13% 13% 4 13% 8% 5% 5% 4 4 5% 25%	4898
	11th to 20th	Night	15% 14% 5% 11% 6% 5% 4 4 5% 5% 28%	4635
	21st to end	Night	11% 14% 4 13% 7% 4 5% 3 5% 5% 29%	4578
February	1st to 10th	Night	17% 14% 4 9% 5% 4 4 3 5% 6% 28%	2470
	11th to 20th	Night	16% 16% 4 10% 6% 5% 4 3 5% 5% 25%	2403
	21st to end	Night	13% 12% 4 9% 6% 5% 4 4 5% 5% 33%	2026
March	1st to 10th	Night	22% 12% 4 12% 5% 5% 4 3 4 4 25%	3458
	11th to 20th	Night	19% 18% 5% 10% 7% 5% 4 3 4 4 20%	3479
	21st to end	Night	27% 13% 4 10% 4 4 5% 4 5% 3 23%	3795
April	1st to 10th	Night	22% 13% 4 8% 5% 4 4 4 5% 4 26%	1900
	11th to 20th	Night	20% 11% 3 7% 5% 4 4 3 4 7% 31%	1782
	21st to end	Night	21% 13% 4 8% 6% 3 3 3 4 6% 29%	1710
May	1st to 10th	Night	25% 13% 3 8% 4 4 4 3 4 5% 25%	2629
	11th to 20th	Night	16% 7% 2 7% 5% 4 4 3 6% 6% 40%	2506
	21st to end	Night	15% 10% 4 8% 6% 6% 5% 4 7% 8% 28%	2749
June	1st to 10th	Night	24% 10% 4 7% 4 4 5% 3 5% 7% 28%	1453
	11th to 20th	Night	19% 7% 2 5% 5% 4 5% 3 5% 8% 37%	1330
	21st to end	Night	22% 10% 4 8% 5% 5% 4 3 5% 6% 28%	1330
July	1st to 10th	Night	15% 7% 2 8% 7% 5% 6% 5% 7% 7% 31%	2210
	11th to 20th	Night	13% 7% 3 7% 5% 5% 7% 5% 8% 8% 32%	2360
	21st to end	Night	12% 6% 3 6% 4 4 4 4 5% 8% 43%	2750
August	1st to 10th	Night	17% 8% 3 9% 6% 5% 6% 5% 5% 7% 29%	2815
	11th to 20th	Night	10% 5% 3 8% 6% 5% 5% 4 5% 9% 40%	2782
	21st to end	Night	13% 5% 2 6% 4 4 4 3 6% 8% 45%	3276
September	1st to 10th	Night	16% 7% 3 5% 3 4 3 3 6% 7% 43%	1900
	11th to 20th	Night	16% 7% 2 6% 4 3 4 4 4 7% 42%	1949
	21st to end	Night	17% 6% 1 6% 4 4 3 4 5% 6% 42%	2161
October	1st to 10th	Night	20% 6% 2 7% 4 4 3 3 5% 7% 38%	2280
	11th to 20th	Night	19% 8% 3 8% 4 4 5% 3 5% 7% 34%	2280
	21st to end	Night	23% 11% 3 8% 5% 4 4 3 5% 5% 28%	2541
November	1st to 10th	Night	21% 12% 4 8% 5% 4 5% 4 5% 6% 28%	2723
	11th to 20th	Night	21% 14% 4 9% 6% 5% 4 3 5% 5% 23%	2800
	21st to end	Night	24% 16% 4 10% 5% 4 4 3 5% 7% 20%	2800
December	1st to 10th	Night	15% 13% 5% 14% 7% 6% 5% 4 5% 5% 22%	4580
	11th to 20th	Night	20% 15% 5% 11% 5% 4 4 3 4 5% 26%	5213
	21st to end	Night	21% 15% 6% 13% 5% 4 4 3 4 5% 21%	7438

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	47% 35% 8% 7% 2	2278
	11th to 20th	Day	36% 36% 3 14% 10% 1	2550
	21st to end	Day	36% 38% 11% 8% 7% 1	3101
February	1st to 10th	Day	20% 65% 2 9% 3 1	1710
	11th to 20th	Day	20% 64% 4 8% 4	1671
	21st to end	Day	16% 65% 3 8% 6% 1	1427
March	1st to 10th	Day	36% 39% 5% 15% 3 1	3373
	11th to 20th	Day	46% 39% 4 7% 4	3480
	21st to end	Day	43% 39% 3 9% 5% 1	3837
April	1st to 10th	Day	21% 64% 3 5% 5% 2	2280
	11th to 20th	Day	18% 66% 3 9% 4 1	2345
	21st to end	Day	21% 65% 3 5% 5% 1	2470
May	1st to 10th	Day	36% 39% 9% 13% 4	4331
	11th to 20th	Day	30% 38% 11% 18% 3	4402
	21st to end	Day	35% 39% 8% 12% 5%	4836
June	1st to 10th	Day	20% 65% 4 8% 3	2742
	11th to 20th	Day	17% 64% 6% 9% 3	2850
	21st to end	Day	19% 63% 4 8% 6%	2850
July	1st to 10th	Day	34% 36% 12% 10% 8% 1	4685
	11th to 20th	Day	31% 36% 10% 19% 4	4496
	21st to end	Day	25% 37% 15% 18% 5%	4662
August	1st to 10th	Day	35% 37% 8% 17% 3	4097
	11th to 20th	Day	28% 37% 9% 16% 10%	4084
	21st to end	Day	24% 37% 10% 18% 11%	4379
September	1st to 10th	Day	14% 60% 7% 12% 6%	2280
	11th to 20th	Day	21% 59% 7% 9% 4	2228
	21st to end	Day	17% 59% 4 12% 7%	2018
October	1st to 10th	Day	32% 36% 8% 19% 5%	3160
	11th to 20th	Day	36% 36% 4 18% 5%	3140
	21st to end	Day	32% 36% 12% 13% 6%	3373
November	1st to 10th	Day	29% 55% 6% 8% 2	1571
	11th to 20th	Day	33% 57% 5% 3 2	1600
	21st to end	Day	32% 57% 6% 4 2	1600
December	1st to 10th	Day	46% 36% 4 14% 1	2610
	11th to 20th	Day	47% 31% 6% 9% 6% 1	2995
	21st to end	Day	53% 26% 7% 11% 2	3522
January	1st to 10th	Night	39% 35% 10% 13% 2	4898
	11th to 20th	Night	39% 35% 4 15% 7%	4635
	21st to end	Night	39% 38% 7% 11% 4	4578
February	1st to 10th	Night	22% 65% 3 5% 4 1	2470
	11th to 20th	Night	22% 63% 3 8% 4	2406
	21st to end	Night	18% 65% 2 7% 6% 2	2026
March	1st to 10th	Night	40% 40% 3 11% 4 2	3467
	11th to 20th	Night	48% 39% 3 6% 4 1	3480
	21st to end	Night	46% 39% 2 8% 5%	3795
April	1st to 10th	Night	21% 65% 3 6% 4 1	1900
	11th to 20th	Night	20% 66% 3 7% 3 1	1782
	21st to end	Night	21% 64% 2 5% 5% 1	1710
May	1st to 10th	Night	42% 39% 7% 9% 3	2634
	11th to 20th	Night	27% 38% 12% 18% 5%	2507
	21st to end	Night	37% 39% 11% 9% 3	2750
June	1st to 10th	Night	19% 65% 5% 8% 4	1453
	11th to 20th	Night	15% 65% 5% 11% 4	1330
	21st to end	Night	20% 64% 2 8% 5%	1330
July	1st to 10th	Night	37% 36% 9% 10% 7% 1	2175
	11th to 20th	Night	31% 37% 15% 13% 4	2318
	21st to end	Night	23% 37% 16% 16% 9%	2663
August	1st to 10th	Night	39% 39% 9% 11% 2	2804
	11th to 20th	Night	27% 38% 11% 13% 10% 1	2809
	21st to end	Night	26% 36% 12% 17% 10%	3275
September	1st to 10th	Night	15% 60% 5% 13% 6%	1900
	11th to 20th	Night	20% 60% 6% 11% 4	1949
	21st to end	Night	16% 60% 5% 14% 5%	2161
October	1st to 10th	Night	35% 36% 8% 17% 4	3800
	11th to 20th	Night	30% 37% 6% 20% 7%	3779
	21st to end	Night	32% 36% 11% 14% 7%	4177
November	1st to 10th	Night	29% 56% 6% 7% 2	2723
	11th to 20th	Night	29% 58% 7% 5% 2	2800
	21st to end	Night	33% 57% 5% 3 2	2800
December	1st to 10th	Night	40% 36% 8% 15% 2	4580
	11th to 20th	Night	43% 32% 6% 13% 6% 1	5215
	21st to end	Night	52% 25% 9% 10% 4	7438

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	30% 20% 29% 18% 4 1	200
	11th to 20th	Day	28% 15% 30% 21% 6%	366
	21st to end	Day	18% 12% 36% 28% 5% 1	410
February	1st to 10th	Day	27% 13% 33% 19% 4 2	370
	11th to 20th	Day	24% 16% 34% 22% 4	366
	21st to end	Day	17% 16% 32% 27% 7% 1	307
March	1st to 10th	Day	24% 13% 33% 24% 6% 1	442
	11th to 20th	Day	17% 16% 32% 27% 8% 1	460
	21st to end	Day	28% 13% 29% 22% 7% 1	506
April	1st to 10th	Day	27% 16% 32% 18% 7%	460
	11th to 20th	Day	22% 15% 32% 20% 10% 2	452
	21st to end	Day	23% 14% 27% 22% 12% 1	460
May	1st to 10th	Day	32% 9% 28% 22% 7% 3	583
	11th to 20th	Day	23% 9% 26% 24% 15% 3	674
	21st to end	Day	23% 9% 32% 26% 8% 1	735
June	1st to 10th	Day	30% 6% 25% 27% 10% 2	680
	11th to 20th	Day	22% 7% 28% 29% 12% 2	680
	21st to end	Day	28% 5% 20% 31% 13% 3	680
July	1st to 10th	Day	19% 5% 29% 28% 16% 2	670
	11th to 20th	Day	16% 4 27% 32% 17% 3	668
	21st to end	Day	19% 6% 23% 35% 15% 2	740
August	1st to 10th	Day	15% 5% 24% 34% 18% 4	492
	11th to 20th	Day	17% 5% 23% 30% 21% 5%	479
	21st to end	Day	14% 7% 25% 29% 19% 5%	539
September	1st to 10th	Day	16% 6% 31% 31% 13% 3	490
	11th to 20th	Day	22% 10% 25% 25% 15% 2	490
	21st to end	Day	22% 9% 29% 25% 12% 4	452
October	1st to 10th	Day	21% 11% 26% 24% 15% 3	390
	11th to 20th	Day	25% 16% 26% 22% 9% 2	390
	21st to end	Day	26% 15% 32% 19% 7% 1	429
November	1st to 10th	Day	24% 18% 35% 17% 6% 1	395
	11th to 20th	Day	32% 17% 28% 16% 6% 1	400
	21st to end	Day	33% 17% 30% 17% 3	400
December	1st to 10th	Day	31% 18% 31% 18% 3	400
	11th to 20th	Day	30% 22% 34% 12% 3	400
	21st to end	Day	20% 19% 36% 21% 3 1	240
January	1st to 10th	Night	27% 16% 32% 20% 5%	900
	11th to 20th	Night	25% 15% 31% 23% 5%	900
	21st to end	Night	19% 16% 34% 23% 8% 1	850
February	1st to 10th	Night	25% 14% 32% 22% 6% 1	760
	11th to 20th	Night	24% 16% 35% 21% 3	743
	21st to end	Night	20% 11% 34% 27% 8% 1	628
March	1st to 10th	Night	24% 11% 35% 26% 4	760
	11th to 20th	Night	22% 14% 29% 26% 8% 1	760
	21st to end	Night	28% 12% 28% 23% 8% 1	827
April	1st to 10th	Night	27% 14% 30% 23% 6%	570
	11th to 20th	Night	26% 9% 30% 25% 9%	564
	21st to end	Night	28% 9% 30% 23% 8% 1	570
May	1st to 10th	Night	29% 7% 27% 25% 10% 2	570
	11th to 20th	Night	24% 7% 26% 30% 11% 2	562
	21st to end	Night	19% 9% 39% 28% 5%	616
June	1st to 10th	Night	29% 5% 28% 31% 6% 1	503
	11th to 20th	Night	21% 5% 28% 37% 9% 1	380
	21st to end	Night	26% 5% 26% 32% 10% 1	380
July	1st to 10th	Night	19% 6% 32% 29% 13%	370
	11th to 20th	Night	14% 6% 32% 39% 10%	453
	21st to end	Night	17% 4 29% 38% 11% 1	623
August	1st to 10th	Night	16% 3 30% 35% 15% 1	568
	11th to 20th	Night	15% 4 27% 36% 16% 1	562
	21st to end	Night	17% 5% 24% 34% 19% 1	627
September	1st to 10th	Night	18% 7% 34% 31% 9% 1	570
	11th to 20th	Night	20% 9% 21% 37% 12% 1	619
	21st to end	Night	21% 9% 29% 29% 11% 1	760
October	1st to 10th	Night	23% 7% 28% 30% 11% 1	760
	11th to 20th	Night	24% 11% 31% 25% 8% 1	760
	21st to end	Night	32% 16% 28% 19% 6%	853
November	1st to 10th	Night	32% 15% 28% 19% 4 1	880
	11th to 20th	Night	32% 18% 26% 18% 5% 1	900
	21st to end	Night	33% 18% 26% 20% 3	900
December	1st to 10th	Night	30% 16% 30% 19% 4	900
	11th to 20th	Night	26% 24% 32% 14% 3	900
	21st to end	Night	30% 17% 29% 20% 3 1	990

Page generated at 2025-01-19 04:06:47. Version ac07

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