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 2025-02-21.

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 8% 5% 5% 5% 4 6% 7% 34%	108642
	Night	15% 11% 5% 9% 5% 4 5% 3 5% 6% 31%	109935
Transparency	Day	46% 7% 13% 20% 12% 1	112283
	Night	51% 7% 12% 18% 11% 1	114433
Seeing	Day	15% 5% 18% 30% 24% 7%	15538
	Night	19% 7% 24% 30% 17% 4	25365

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	14% 16% 6% 18% 6% 4 4 3 4 5% 19%	3617
	11th to 20th	Day	13% 18% 6% 15% 8% 9% 6% 3 4 4 15%	3968
	21st to end	Day	22% 15% 6% 12% 6% 6% 5% 3 5% 5% 16%	4466
February	1st to 10th	Day	16% 15% 4 11% 7% 5% 4 4 5% 5% 24%	1800
	11th to 20th	Day	14% 11% 4 12% 9% 6% 5% 4 5% 6% 25%	1867
	21st to end	Day	16% 9% 4 10% 6% 5% 5% 4 6% 7% 28%	1570
March	1st to 10th	Day	20% 11% 4 8% 5% 5% 4 3 5% 6% 30%	3266
	11th to 20th	Day	12% 9% 3 8% 6% 5% 5% 4 5% 6% 37%	3480
	21st to end	Day	18% 9% 3 8% 5% 4 5% 4 5% 7% 31%	3815
April	1st to 10th	Day	12% 10% 3 7% 5% 5% 5% 4 6% 8% 36%	2147
	11th to 20th	Day	17% 7% 3 7% 5% 5% 5% 5% 5% 6% 37%	2432
	21st to end	Day	17% 8% 3 6% 4 4 4 4 4 7% 37%	2470
May	1st to 10th	Day	16% 8% 3 7% 5% 4 5% 4 5% 7% 35%	4082
	11th to 20th	Day	16% 7% 3 6% 5% 5% 5% 5% 6% 9% 33%	4081
	21st to end	Day	8% 5% 2 6% 5% 4 4 4 7% 8% 46%	4476
June	1st to 10th	Day	10% 6% 3 5% 5% 5% 5% 5% 8% 8% 42%	2558
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 5% 7% 9% 45%	2850
	21st to end	Day	10% 4 2 6% 4 5% 4 5% 8% 10% 43%	2677
July	1st to 10th	Day	10% 5% 2 6% 4 4 5% 4 6% 9% 44%	4440
	11th to 20th	Day	7% 3 1 5% 4 4 5% 4 7% 10% 49%	4289
	21st to end	Day	7% 5% 2 7% 4 5% 5% 5% 6% 8% 47%	4466
August	1st to 10th	Day	12% 5% 2 5% 3 4 4 4 6% 9% 46%	4104
	11th to 20th	Day	8% 6% 2 6% 5% 5% 5% 4 7% 9% 42%	4044
	21st to end	Day	8% 5% 2 6% 5% 4 5% 4 7% 10% 44%	4532
September	1st to 10th	Day	12% 5% 2 5% 4 4 4 4 4 8% 48%	2118
	11th to 20th	Day	9% 6% 2 6% 3 4 4 3 7% 7% 48%	2090
	21st to end	Day	19% 7% 2 5% 3 4 4 4 5% 7% 39%	2090
October	1st to 10th	Day	14% 6% 3 7% 4 5% 4 3 5% 7% 43%	2010
	11th to 20th	Day	19% 8% 3 7% 4 4 5% 3 5% 7% 36%	1900
	21st to end	Day	21% 9% 3 6% 5% 4 4 4 6% 7% 29%	2000
November	1st to 10th	Day	11% 11% 3 7% 4 4 5% 3 6% 7% 38%	1762
	11th to 20th	Day	17% 17% 4 8% 4 4 4 3 3 6% 29%	1800
	21st to end	Day	18% 15% 5% 8% 6% 5% 4 4 6% 6% 23%	1675
December	1st to 10th	Day	15% 15% 11% 17% 6% 5% 4 3 4 5% 16%	2600
	11th to 20th	Day	19% 17% 6% 14% 9% 4 4 4 4 5% 14%	2990
	21st to end	Day	23% 19% 6% 12% 7% 5% 4 3 4 4 13%	4110
January	1st to 10th	Night	15% 17% 8% 18% 5% 4 4 3 4 4 19%	6348
	11th to 20th	Night	12% 18% 9% 15% 7% 6% 8% 3 4 4 14%	5976
	21st to end	Night	21% 15% 6% 11% 5% 4 4 3 4 4 22%	6490
February	1st to 10th	Night	17% 14% 5% 11% 7% 6% 5% 4 5% 5% 22%	2600
	11th to 20th	Night	17% 12% 5% 11% 6% 5% 5% 4 5% 5% 25%	2415
	21st to end	Night	21% 11% 4 11% 5% 5% 5% 2 4 5% 28%	1885
March	1st to 10th	Night	19% 11% 4 8% 4 4 3 3 4 5% 34%	3587
	11th to 20th	Night	11% 8% 3 8% 5% 5% 5% 3 5% 8% 37%	3480
	21st to end	Night	16% 11% 4 8% 4 5% 4 4 5% 6% 34%	3817
April	1st to 10th	Night	16% 12% 2 7% 5% 5% 4 4 5% 5% 34%	2047
	11th to 20th	Night	16% 8% 3 7% 6% 4 5% 4 6% 6% 37%	1697
	21st to end	Night	15% 9% 3 7% 4 4 4 4 5% 6% 38%	1710
May	1st to 10th	Night	18% 9% 3 7% 7% 5% 4 4 5% 8% 30%	2813
	11th to 20th	Night	15% 8% 3 8% 4 4 5% 5% 6% 8% 34%	2812
	21st to end	Night	9% 5% 2 6% 4 5% 4 4 6% 8% 47%	3079
June	1st to 10th	Night	13% 5% 2 6% 5% 3 5% 4 6% 7% 44%	1604
	11th to 20th	Night	8% 6% 2 7% 4 5% 5% 5% 7% 9% 43%	1330
	21st to end	Night	9% 5% 2 5% 6% 5% 5% 4 7% 9% 44%	1489
July	1st to 10th	Night	10% 5% 1 5% 4 3 4 4 7% 10% 47%	2530
	11th to 20th	Night	9% 3 1 5% 4 4 5% 4 7% 10% 48%	2674
	21st to end	Night	6% 4 2 5% 4 5% 6% 4 8% 9% 46%	3087
August	1st to 10th	Night	14% 6% 2 6% 4 4 4 3 5% 9% 42%	2825
	11th to 20th	Night	9% 7% 3 6% 4 5% 5% 3 6% 8% 46%	2785
	21st to end	Night	7% 5% 2 6% 5% 5% 5% 5% 7% 7% 46%	3124
September	1st to 10th	Night	11% 7% 2 5% 4 4 5% 4 5% 8% 46%	2039
	11th to 20th	Night	10% 6% 2 6% 4 4 5% 3 5% 6% 50%	2090
	21st to end	Night	16% 7% 3 7% 5% 5% 5% 3 5% 7% 39%	2090
October	1st to 10th	Night	15% 7% 2 6% 4 4 3 3 6% 6% 43%	2168
	11th to 20th	Night	21% 10% 3 6% 4 4 4 3 5% 5% 34%	2280
	21st to end	Night	23% 9% 3 8% 5% 4 4 4 5% 6% 29%	2593
November	1st to 10th	Night	15% 11% 3 7% 4 4 4 3 5% 6% 37%	2536
	11th to 20th	Night	18% 16% 4 9% 6% 5% 4 3 4 5% 26%	2600
	21st to end	Night	22% 17% 5% 8% 5% 4 4 3 4 6% 22%	2720
December	1st to 10th	Night	14% 19% 12% 15% 5% 4 4 2 4 4 18%	4580
	11th to 20th	Night	18% 17% 7% 13% 6% 5% 4 3 4 5% 18%	5205
	21st to end	Night	25% 18% 6% 11% 6% 5% 4 3 4 5% 13%	6830

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% 9% 11% 4 1	3618
	11th to 20th	Day	72% 5% 9% 6% 7% 1	3968
	21st to end	Day	68% 7% 11% 10% 4	4466
February	1st to 10th	Day	61% 6% 12% 14% 7%	1800
	11th to 20th	Day	59% 5% 12% 16% 7% 1	1876
	21st to end	Day	53% 7% 14% 16% 8% 2	1570
March	1st to 10th	Day	54% 7% 11% 23% 5%	3266
	11th to 20th	Day	45% 8% 17% 21% 8% 2	3480
	21st to end	Day	50% 7% 16% 17% 9% 1	3815
April	1st to 10th	Day	45% 7% 14% 19% 15% 1	2147
	11th to 20th	Day	47% 6% 13% 19% 13% 2	2432
	21st to end	Day	45% 7% 13% 22% 11% 3	2470
May	1st to 10th	Day	45% 8% 12% 23% 10% 2	4120
	11th to 20th	Day	44% 9% 15% 21% 9% 1	4085
	21st to end	Day	32% 10% 13% 21% 17% 7%	4489
June	1st to 10th	Day	37% 8% 13% 27% 13% 2	2558
	11th to 20th	Day	32% 10% 16% 24% 17% 2	2850
	21st to end	Day	34% 8% 15% 24% 16% 3	2677
July	1st to 10th	Day	35% 7% 13% 25% 18% 2	4371
	11th to 20th	Day	27% 8% 14% 31% 19% 1	4214
	21st to end	Day	33% 8% 16% 19% 21% 3	4324
August	1st to 10th	Day	33% 8% 17% 28% 14% 1	4091
	11th to 20th	Day	34% 9% 14% 33% 10% 1	4083
	21st to end	Day	32% 8% 17% 28% 12% 2	4531
September	1st to 10th	Day	35% 6% 18% 23% 16% 2	2118
	11th to 20th	Day	33% 7% 15% 28% 17% 1	2090
	21st to end	Day	43% 7% 12% 21% 16%	2090
October	1st to 10th	Day	28% 7% 15% 31% 19% 1	3335
	11th to 20th	Day	39% 7% 13% 24% 17% 1	3140
	21st to end	Day	43% 6% 13% 22% 15%	3276
November	1st to 10th	Day	44% 7% 13% 21% 14% 1	1762
	11th to 20th	Day	57% 5% 12% 16% 9% 1	1800
	21st to end	Day	60% 7% 13% 15% 5%	1675
December	1st to 10th	Day	71% 7% 12% 7% 3	2600
	11th to 20th	Day	71% 6% 10% 10% 2	2986
	21st to end	Day	74% 7% 7% 8% 4	4110
January	1st to 10th	Night	66% 7% 9% 13% 5%	6348
	11th to 20th	Night	73% 5% 9% 8% 5% 1	5976
	21st to end	Night	65% 6% 12% 9% 8%	6490
February	1st to 10th	Night	62% 7% 11% 14% 6% 1	2600
	11th to 20th	Night	59% 6% 11% 16% 7% 1	2417
	21st to end	Night	59% 5% 11% 16% 8% 1	1885
March	1st to 10th	Night	52% 5% 13% 22% 8%	3587
	11th to 20th	Night	41% 9% 18% 18% 12% 1	3480
	21st to end	Night	48% 6% 13% 22% 10% 1	3817
April	1st to 10th	Night	50% 7% 11% 17% 13% 2	2047
	11th to 20th	Night	45% 7% 11% 18% 16% 3	1697
	21st to end	Night	45% 6% 11% 19% 15% 3	1710
May	1st to 10th	Night	50% 7% 11% 17% 12% 3	2840
	11th to 20th	Night	44% 9% 13% 22% 11% 2	2813
	21st to end	Night	32% 7% 13% 24% 19% 5%	3087
June	1st to 10th	Night	38% 7% 11% 25% 16% 3	1604
	11th to 20th	Night	35% 8% 14% 24% 15% 4	1330
	21st to end	Night	35% 7% 12% 26% 19% 1	1489
July	1st to 10th	Night	31% 7% 13% 28% 16% 6%	2490
	11th to 20th	Night	29% 8% 14% 29% 17% 3	2626
	21st to end	Night	29% 9% 18% 21% 20% 3	2988
August	1st to 10th	Night	38% 8% 13% 25% 14% 2	2814
	11th to 20th	Night	35% 8% 11% 32% 13% 1	2812
	21st to end	Night	34% 8% 13% 27% 16% 2	3124
September	1st to 10th	Night	35% 7% 14% 24% 15% 4	2039
	11th to 20th	Night	33% 7% 11% 26% 21% 2	2090
	21st to end	Night	45% 7% 11% 20% 16% 1	2090
October	1st to 10th	Night	27% 5% 9% 30% 27% 1	3623
	11th to 20th	Night	42% 5% 11% 24% 17%	3779
	21st to end	Night	41% 6% 10% 28% 14% 2	4267
November	1st to 10th	Night	47% 6% 13% 19% 14% 1	2536
	11th to 20th	Night	61% 6% 10% 14% 9% 1	2600
	21st to end	Night	63% 6% 11% 15% 4	2720
December	1st to 10th	Night	70% 6% 10% 10% 3	4580
	11th to 20th	Night	68% 6% 12% 11% 3	5208
	21st to end	Night	73% 7% 10% 8% 3	6830

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% 29% 30% 8% 1	300
	11th to 20th	Day	22% 10% 34% 27% 7% 1	300
	21st to end	Day	26% 7% 27% 29% 10% 1	330
February	1st to 10th	Day	20% 6% 30% 34% 8% 1	300
	11th to 20th	Day	20% 7% 33% 30% 9%	300
	21st to end	Day	20% 8% 31% 34% 7%	225
March	1st to 10th	Day	21% 7% 24% 35% 13%	351
	11th to 20th	Day	17% 8% 27% 33% 14% 1	460
	21st to end	Day	24% 8% 23% 34% 10% 1	506
April	1st to 10th	Day	13% 7% 23% 40% 15% 2	460
	11th to 20th	Day	19% 5% 25% 34% 13% 4	452
	21st to end	Day	19% 5% 23% 32% 19% 2	460
May	1st to 10th	Day	20% 5% 17% 33% 20% 4	463
	11th to 20th	Day	15% 3 18% 28% 29% 6%	487
	21st to end	Day	9% 2 11% 31% 33% 13%	529
June	1st to 10th	Day	10% 2 14% 36% 31% 7%	515
	11th to 20th	Day	11% 2 11% 38% 31% 8%	680
	21st to end	Day	12% 3 12% 33% 33% 8%	680
July	1st to 10th	Day	8% 3 7% 29% 36% 17%	671
	11th to 20th	Day	9% 2 7% 29% 40% 13%	582
	21st to end	Day	8% 2 8% 30% 40% 12%	532
August	1st to 10th	Day	10% 3 8% 27% 37% 15%	486
	11th to 20th	Day	9% 3 9% 30% 38% 11%	479
	21st to end	Day	8% 3 8% 28% 40% 13%	539
September	1st to 10th	Day	12% 2 12% 24% 34% 16%	490
	11th to 20th	Day	10% 2 8% 22% 38% 20%	490
	21st to end	Day	20% 6% 17% 21% 27% 10%	490
October	1st to 10th	Day	13% 3 17% 27% 28% 12%	490
	11th to 20th	Day	18% 10% 22% 27% 18% 5%	490
	21st to end	Day	22% 10% 26% 26% 13% 3	449
November	1st to 10th	Day	14% 7% 24% 27% 22% 6%	300
	11th to 20th	Day	25% 11% 25% 25% 13% 2	300
	21st to end	Day	24% 9% 33% 27% 7%	237
December	1st to 10th	Day	19% 11% 32% 31% 8%	200
	11th to 20th	Day	21% 16% 36% 21% 8%	200
	21st to end	Day	24% 10% 30% 26% 9%	315
January	1st to 10th	Night	24% 12% 34% 23% 7% 1	1000
	11th to 20th	Night	24% 11% 34% 24% 6%	837
	21st to end	Night	24% 8% 33% 29% 7%	880
February	1st to 10th	Night	23% 5% 36% 31% 6%	800
	11th to 20th	Night	22% 8% 31% 34% 5%	783
	21st to end	Night	23% 9% 34% 28% 5%	629
March	1st to 10th	Night	20% 4 31% 33% 11% 1	760
	11th to 20th	Night	17% 7% 32% 32% 9% 2	760
	21st to end	Night	21% 7% 25% 34% 12% 2	836
April	1st to 10th	Night	18% 9% 28% 34% 10% 1	717
	11th to 20th	Night	19% 5% 25% 35% 13% 2	563
	21st to end	Night	17% 6% 24% 35% 16% 2	570
May	1st to 10th	Night	19% 5% 20% 36% 17% 3	570
	11th to 20th	Night	21% 4 16% 30% 22% 6%	561
	21st to end	Night	10% 2 13% 30% 32% 12%	617
June	1st to 10th	Night	13% 3 16% 37% 27% 4	494
	11th to 20th	Night	9% 1 13% 38% 33% 6%	380
	21st to end	Night	11% 1 16% 37% 30% 5%	539
July	1st to 10th	Night	11% 2 8% 33% 35% 10%	555
	11th to 20th	Night	10% 2 12% 35% 33% 9%	552
	21st to end	Night	6% 1 11% 37% 39% 5%	624
August	1st to 10th	Night	9% 3 10% 36% 32% 10%	567
	11th to 20th	Night	10% 2 12% 33% 33% 10%	564
	21st to end	Night	10% 2 11% 33% 34% 11%	627
September	1st to 10th	Night	13% 4 14% 28% 31% 10%	724
	11th to 20th	Night	12% 3 10% 29% 35% 11%	760
	21st to end	Night	18% 6% 18% 27% 25% 7%	760
October	1st to 10th	Night	19% 5% 20% 26% 23% 8%	760
	11th to 20th	Night	26% 11% 22% 25% 14% 2	760
	21st to end	Night	27% 10% 25% 26% 10% 1	836
November	1st to 10th	Night	19% 9% 27% 28% 14% 3	780
	11th to 20th	Night	25% 14% 30% 22% 8% 2	800
	21st to end	Night	30% 12% 28% 22% 7% 1	800
December	1st to 10th	Night	27% 15% 29% 23% 7% 1	800
	11th to 20th	Night	25% 12% 35% 21% 6%	800
	21st to end	Night	29% 11% 29% 26% 5%	1000

Page generated at 2025-02-18 03:26:28. Version ac07

Copyright © 2025 Attilla Danko.