Pelee Island
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pelee Island clear sky chart from 2005-11-06 to 2026-06-16.

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	13% 9% 3 8% 5% 5% 5% 4 6% 7% 35%	137134
	Night	15% 11% 4 9% 5% 5% 5% 4 5% 6% 32%	134904
Transparency	Day	45% 7% 13% 21% 12% 1	140731
	Night	50% 7% 12% 19% 12% 1	139379
Seeing	Day	15% 6% 19% 30% 24% 7%	17330
	Night	19% 7% 24% 30% 17% 4	27063

By Month

Percentage Cloud Cover SE (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% 6% 19% 6% 4 4 3 5% 6% 17%	4691
	11th to 20th	Day	12% 17% 6% 15% 8% 8% 5% 3 4 5% 17%	5162
	21st to end	Day	18% 14% 5% 11% 7% 7% 5% 4 5% 5% 19%	5780
February	1st to 10th	Day	15% 14% 4 12% 7% 5% 4 4 5% 5% 24%	1890
	11th to 20th	Day	14% 11% 4 12% 8% 6% 4 4 5% 6% 25%	1963
	21st to end	Day	15% 9% 4 10% 6% 5% 5% 4 6% 7% 28%	1730
March	1st to 10th	Day	16% 10% 5% 10% 5% 5% 4 3 4 6% 32%	4786
	11th to 20th	Day	10% 8% 3 9% 6% 5% 5% 4 5% 7% 39%	5090
	21st to end	Day	16% 9% 3 9% 5% 5% 5% 4 6% 7% 30%	5586
April	1st to 10th	Day	13% 10% 3 7% 5% 5% 5% 4 6% 8% 35%	2373
	11th to 20th	Day	16% 7% 3 7% 5% 5% 5% 5% 5% 7% 36%	2691
	21st to end	Day	16% 8% 3 6% 4 5% 4 4 5% 7% 38%	2730
May	1st to 10th	Day	18% 8% 3 7% 5% 4 4 4 5% 7% 35%	7616
	11th to 20th	Day	13% 7% 3 6% 5% 5% 5% 4 7% 9% 35%	7626
	21st to end	Day	14% 6% 2 6% 4 4 4 4 6% 7% 42%	8391
June	1st to 10th	Day	10% 6% 2 5% 5% 5% 5% 5% 7% 8% 42%	2827
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 5% 6% 9% 44%	3076
	21st to end	Day	9% 4 2 6% 4 5% 4 5% 8% 10% 43%	2818
July	1st to 10th	Day	9% 5% 2 6% 4 4 4 4 6% 9% 47%	6360
	11th to 20th	Day	7% 4 2 5% 4 4 5% 5% 6% 10% 47%	6139
	21st to end	Day	8% 5% 2 7% 4 5% 4 4 6% 8% 47%	6424
August	1st to 10th	Day	11% 5% 2 5% 3 4 4 4 7% 9% 46%	4234
	11th to 20th	Day	8% 6% 2 7% 5% 5% 5% 4 7% 9% 42%	4174
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 4 7% 10% 44%	4675
September	1st to 10th	Day	11% 5% 2 5% 4 4 4 4 4 8% 49%	2229
	11th to 20th	Day	9% 6% 2 5% 3 4 4 3 7% 7% 49%	2200
	21st to end	Day	19% 7% 2 5% 3 4 4 4 5% 7% 40%	2200
October	1st to 10th	Day	13% 7% 3 6% 4 5% 4 3 5% 7% 43%	2116
	11th to 20th	Day	19% 8% 3 6% 4 4 5% 3 6% 7% 37%	2000
	21st to end	Day	21% 9% 3 6% 5% 4 4 4 7% 7% 30%	2105
November	1st to 10th	Day	12% 11% 3 7% 4 4 5% 3 6% 7% 38%	1852
	11th to 20th	Day	17% 17% 4 8% 4 4 4 3 3 6% 29%	1890
	21st to end	Day	18% 16% 5% 8% 6% 5% 4 4 6% 6% 23%	1759
December	1st to 10th	Day	15% 15% 11% 17% 6% 5% 4 3 4 5% 15%	2680
	11th to 20th	Day	19% 18% 6% 14% 9% 4 4 4 4 5% 14%	3070
	21st to end	Day	23% 19% 7% 12% 7% 5% 4 3 4 4 13%	4201
January	1st to 10th	Night	15% 17% 7% 17% 5% 4 4 3 4 4 19%	8232
	11th to 20th	Night	10% 16% 9% 15% 7% 6% 8% 3 4 5% 18%	7784
	21st to end	Night	17% 14% 6% 10% 5% 4 4 3 5% 6% 24%	8401
February	1st to 10th	Night	16% 14% 5% 11% 7% 6% 5% 4 5% 5% 23%	2730
	11th to 20th	Night	16% 12% 5% 11% 6% 5% 5% 4 5% 6% 24%	2539
	21st to end	Night	20% 11% 4 11% 4 5% 5% 3 4 5% 28%	2076
March	1st to 10th	Night	17% 11% 4 8% 5% 4 4 3 5% 6% 34%	5287
	11th to 20th	Night	10% 7% 3 8% 5% 5% 5% 4 6% 8% 39%	5090
	21st to end	Night	15% 10% 4 8% 4 6% 5% 4 5% 6% 35%	5588
April	1st to 10th	Night	17% 12% 3 7% 5% 5% 4 4 5% 6% 33%	2263
	11th to 20th	Night	15% 8% 3 8% 6% 4 5% 3 6% 6% 36%	1878
	21st to end	Night	16% 8% 3 7% 4 4 4 4 5% 6% 38%	1890
May	1st to 10th	Night	20% 10% 4 8% 7% 5% 5% 4 5% 7% 27%	5237
	11th to 20th	Night	14% 7% 3 7% 4 4 5% 4 6% 8% 37%	5234
	21st to end	Night	14% 7% 2 6% 5% 5% 5% 4 5% 7% 40%	5761
June	1st to 10th	Night	12% 5% 2 6% 5% 3 5% 4 6% 7% 44%	1772
	11th to 20th	Night	8% 6% 2 7% 4 5% 4 5% 7% 9% 43%	1435
	21st to end	Night	9% 5% 2 5% 6% 5% 5% 4 7% 9% 45%	1568
July	1st to 10th	Night	8% 5% 2 5% 4 4 5% 5% 7% 11% 44%	3618
	11th to 20th	Night	8% 4 2 7% 5% 4 5% 4 7% 10% 44%	3826
	21st to end	Night	8% 5% 2 5% 4 4 5% 4 7% 9% 48%	4427
August	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 9% 43%	2915
	11th to 20th	Night	9% 7% 3 6% 4 5% 5% 3 6% 8% 46%	2875
	21st to end	Night	7% 5% 2 6% 5% 5% 5% 5% 7% 7% 46%	3223
September	1st to 10th	Night	11% 7% 2 5% 4 4 5% 4 5% 7% 47%	2146
	11th to 20th	Night	9% 5% 2 5% 4 4 5% 3 5% 6% 52%	2200
	21st to end	Night	15% 7% 3 7% 5% 5% 5% 3 5% 6% 39%	2200
October	1st to 10th	Night	15% 7% 2 6% 4 4 3 3 5% 6% 45%	2282
	11th to 20th	Night	20% 10% 3 7% 4 4 4 3 5% 6% 35%	2400
	21st to end	Night	23% 9% 3 8% 5% 4 4 4 4 6% 30%	2730
November	1st to 10th	Night	14% 11% 3 7% 4 4 4 3 5% 6% 38%	2666
	11th to 20th	Night	18% 16% 4 9% 6% 5% 4 3 4 5% 26%	2730
	21st to end	Night	22% 17% 5% 8% 5% 4 4 3 4 6% 22%	2856
December	1st to 10th	Night	14% 19% 12% 15% 5% 4 4 2 4 4 18%	4720
	11th to 20th	Night	18% 17% 7% 13% 6% 5% 4 3 4 5% 18%	5345
	21st to end	Night	25% 18% 6% 11% 6% 4 4 3 4 5% 13%	6980

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	66% 8% 10% 11% 4 1	4692
	11th to 20th	Day	69% 5% 9% 7% 10% 1	5162
	21st to end	Day	65% 7% 11% 12% 5%	5780
February	1st to 10th	Day	60% 6% 12% 15% 7%	1890
	11th to 20th	Day	58% 5% 12% 16% 8% 1	1972
	21st to end	Day	53% 7% 15% 16% 8% 2	1730
March	1st to 10th	Day	52% 6% 12% 21% 8%	4786
	11th to 20th	Day	42% 7% 17% 24% 9% 2	5090
	21st to end	Day	50% 7% 14% 17% 11% 1	5586
April	1st to 10th	Day	46% 7% 13% 19% 14% 1	2373
	11th to 20th	Day	46% 6% 13% 20% 13% 2	2691
	21st to end	Day	44% 7% 13% 22% 11% 2	2730
May	1st to 10th	Day	46% 7% 11% 22% 12% 1	7651
	11th to 20th	Day	41% 9% 16% 21% 11% 2	7630
	21st to end	Day	38% 8% 11% 20% 17% 6%	8405
June	1st to 10th	Day	36% 8% 13% 28% 13% 3	2827
	11th to 20th	Day	33% 9% 15% 24% 16% 2	3076
	21st to end	Day	33% 8% 15% 24% 16% 3	2818
July	1st to 10th	Day	32% 7% 12% 30% 18% 2	6291
	11th to 20th	Day	29% 8% 16% 28% 18% 1	6064
	21st to end	Day	33% 8% 14% 22% 21% 2	6240
August	1st to 10th	Day	32% 8% 17% 28% 14% 1	4221
	11th to 20th	Day	34% 9% 14% 33% 10% 1	4213
	21st to end	Day	32% 8% 17% 29% 12% 2	4674
September	1st to 10th	Day	34% 6% 17% 24% 17% 1	2229
	11th to 20th	Day	32% 7% 15% 30% 17% 1	2200
	21st to end	Day	43% 7% 12% 21% 17%	2200
October	1st to 10th	Day	28% 7% 14% 31% 19% 1	3441
	11th to 20th	Day	39% 7% 12% 24% 17% 1	3240
	21st to end	Day	43% 7% 13% 22% 15%	3381
November	1st to 10th	Day	44% 7% 12% 22% 14% 1	1852
	11th to 20th	Day	57% 5% 12% 16% 9% 1	1890
	21st to end	Day	61% 6% 12% 16% 5%	1759
December	1st to 10th	Day	71% 7% 12% 7% 3	2680
	11th to 20th	Day	71% 6% 10% 10% 2	3066
	21st to end	Day	74% 7% 7% 8% 4	4201
January	1st to 10th	Night	67% 7% 9% 12% 5%	8233
	11th to 20th	Night	67% 5% 10% 10% 7% 1	7784
	21st to end	Night	59% 6% 12% 15% 8%	8401
February	1st to 10th	Night	61% 7% 11% 15% 6% 1	2730
	11th to 20th	Night	59% 6% 11% 16% 7% 1	2541
	21st to end	Night	59% 5% 12% 16% 8% 1	2076
March	1st to 10th	Night	50% 5% 14% 20% 10% 1	5287
	11th to 20th	Night	39% 8% 15% 25% 11% 1	5090
	21st to end	Night	48% 6% 12% 19% 14% 1	5588
April	1st to 10th	Night	51% 6% 11% 17% 13% 2	2263
	11th to 20th	Night	46% 7% 11% 18% 16% 3	1878
	21st to end	Night	45% 7% 11% 20% 15% 3	1890
May	1st to 10th	Night	54% 7% 10% 13% 13% 3	5264
	11th to 20th	Night	43% 8% 12% 23% 13% 2	5235
	21st to end	Night	41% 7% 11% 21% 17% 3	5771
June	1st to 10th	Night	38% 6% 10% 24% 17% 4	1772
	11th to 20th	Night	34% 8% 14% 24% 15% 3	1435
	21st to end	Night	34% 7% 12% 26% 20% 1	1568
July	1st to 10th	Night	31% 9% 15% 25% 16% 5%	3580
	11th to 20th	Night	34% 8% 14% 27% 15% 2	3781
	21st to end	Night	30% 8% 15% 22% 23% 3	4297
August	1st to 10th	Night	37% 8% 13% 25% 15% 2	2904
	11th to 20th	Night	34% 8% 11% 32% 13% 1	2902
	21st to end	Night	34% 8% 13% 27% 16% 2	3223
September	1st to 10th	Night	35% 7% 14% 26% 15% 4	2146
	11th to 20th	Night	32% 7% 11% 28% 21% 2	2200
	21st to end	Night	45% 7% 11% 19% 17% 1	2200
October	1st to 10th	Night	27% 5% 9% 30% 27% 1	3737
	11th to 20th	Night	42% 5% 11% 24% 18%	3899
	21st to end	Night	40% 6% 10% 27% 15% 2	4404
November	1st to 10th	Night	46% 6% 13% 20% 14% 1	2666
	11th to 20th	Night	60% 5% 10% 15% 9% 1	2730
	21st to end	Night	64% 6% 11% 15% 4	2856
December	1st to 10th	Night	70% 6% 10% 10% 3	4720
	11th to 20th	Night	68% 6% 12% 11% 3	5348
	21st to end	Night	73% 6% 10% 8% 3	6980

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	20% 10% 30% 31% 8% 1	330
	11th to 20th	Day	22% 12% 34% 26% 6% 1	330
	21st to end	Day	25% 7% 28% 30% 9% 1	363
February	1st to 10th	Day	19% 6% 29% 35% 9% 1	330
	11th to 20th	Day	18% 8% 32% 32% 9%	330
	21st to end	Day	17% 7% 33% 36% 7%	273
March	1st to 10th	Day	20% 6% 26% 36% 11%	419
	11th to 20th	Day	16% 9% 28% 33% 13% 1	540
	21st to end	Day	22% 8% 24% 36% 10% 1	594
April	1st to 10th	Day	15% 8% 24% 37% 14% 1	540
	11th to 20th	Day	18% 6% 25% 35% 13% 4	532
	21st to end	Day	18% 5% 23% 33% 20% 1	540
May	1st to 10th	Day	20% 6% 17% 35% 18% 4	543
	11th to 20th	Day	15% 4 19% 29% 28% 5%	567
	21st to end	Day	11% 3 13% 31% 30% 11%	617
June	1st to 10th	Day	10% 3 13% 35% 32% 7%	598
	11th to 20th	Day	11% 2 12% 38% 30% 7%	756
	21st to end	Day	11% 3 12% 32% 34% 9%	730
July	1st to 10th	Day	8% 3 7% 29% 36% 16%	721
	11th to 20th	Day	9% 3 7% 29% 40% 12%	627
	21st to end	Day	8% 3 8% 29% 41% 12%	576
August	1st to 10th	Day	9% 3 7% 27% 39% 15%	526
	11th to 20th	Day	8% 3 9% 29% 38% 12%	519
	21st to end	Day	8% 3 8% 30% 39% 13%	583
September	1st to 10th	Day	12% 2 12% 23% 33% 18%	530
	11th to 20th	Day	9% 2 8% 21% 40% 20%	530
	21st to end	Day	19% 6% 15% 21% 28% 10%	530
October	1st to 10th	Day	12% 3 16% 27% 28% 13%	530
	11th to 20th	Day	17% 9% 22% 29% 18% 5%	530
	21st to end	Day	22% 10% 26% 27% 13% 2	488
November	1st to 10th	Day	15% 7% 24% 28% 21% 5%	330
	11th to 20th	Day	24% 13% 25% 25% 12% 2	330
	21st to end	Day	23% 11% 33% 26% 7%	261
December	1st to 10th	Day	20% 10% 32% 30% 8%	220
	11th to 20th	Day	20% 16% 38% 20% 7%	220
	21st to end	Day	24% 11% 31% 26% 8%	347
January	1st to 10th	Night	24% 12% 34% 24% 7% 1	1050
	11th to 20th	Night	24% 11% 35% 23% 6%	879
	21st to end	Night	23% 8% 34% 29% 6%	924
February	1st to 10th	Night	22% 5% 35% 32% 6%	840
	11th to 20th	Night	22% 8% 32% 34% 5%	823
	21st to end	Night	22% 9% 35% 28% 5%	692
March	1st to 10th	Night	20% 5% 32% 33% 10% 1	840
	11th to 20th	Night	17% 7% 32% 32% 9% 2	840
	21st to end	Night	20% 7% 26% 34% 11% 2	924
April	1st to 10th	Night	20% 9% 27% 33% 9% 1	793
	11th to 20th	Night	18% 6% 26% 35% 13% 2	623
	21st to end	Night	18% 5% 24% 35% 16% 2	630
May	1st to 10th	Night	19% 5% 22% 35% 16% 3	630
	11th to 20th	Night	21% 4 17% 31% 21% 5%	621
	21st to end	Night	11% 3 14% 32% 30% 11%	683
June	1st to 10th	Night	13% 3 16% 38% 27% 4	546
	11th to 20th	Night	10% 13% 40% 32% 5%	410
	21st to end	Night	11% 1 15% 36% 31% 5%	568
July	1st to 10th	Night	10% 3 8% 32% 36% 10%	585
	11th to 20th	Night	10% 2 12% 34% 33% 9%	582
	21st to end	Night	7% 2 11% 37% 39% 5%	657
August	1st to 10th	Night	9% 3 10% 35% 34% 10%	597
	11th to 20th	Night	10% 2 11% 32% 34% 10%	594
	21st to end	Night	9% 2 11% 33% 33% 11%	660
September	1st to 10th	Night	13% 4 14% 27% 32% 10%	762
	11th to 20th	Night	11% 3 10% 28% 36% 12%	800
	21st to end	Night	17% 6% 17% 28% 25% 8%	800
October	1st to 10th	Night	18% 5% 19% 27% 24% 8%	800
	11th to 20th	Night	26% 11% 22% 25% 14% 2	800
	21st to end	Night	27% 10% 25% 27% 10% 1	880
November	1st to 10th	Night	19% 10% 28% 28% 13% 2	820
	11th to 20th	Night	24% 14% 30% 22% 8% 2	840
	21st to end	Night	30% 13% 28% 23% 6%	840
December	1st to 10th	Night	26% 15% 29% 23% 7%	840
	11th to 20th	Night	25% 12% 36% 21% 6%	840
	21st to end	Night	29% 11% 29% 26% 5%	1050

Page generated at 2026-06-13 02:31:43. Version ac07

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