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 2024-01-31.

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% 8% 4 6% 6% 3 5% 5% 6% 7% 36%	74928
	Night	16% 10% 4 7% 6% 3 5% 5% 5% 6% 32%	75162
Transparency	Day	46% 7% 13% 20% 12% 1	74639
	Night	52% 6% 12% 18% 11% 1	74971
Seeing	Day	16% 5% 18% 30% 24% 7%	14133
	Night	20% 7% 24% 29% 17% 4	23964

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	18% 14% 6% 10% 9% 4 5% 5% 4 5% 21%	1517
	11th to 20th	Day	18% 15% 6% 12% 9% 5% 5% 4 4 5% 16%	1668
	21st to end	Day	18% 16% 8% 10% 7% 5% 4 4 4 6% 19%	1872
February	1st to 10th	Day	17% 14% 5% 10% 8% 4 4 5% 5% 5% 23%	1620
	11th to 20th	Day	16% 10% 5% 10% 9% 5% 5% 5% 5% 6% 24%	1675
	21st to end	Day	17% 9% 4 9% 7% 3 5% 5% 5% 7% 28%	1480
March	1st to 10th	Day	17% 9% 4 6% 6% 4 5% 5% 6% 8% 30%	1876
	11th to 20th	Day	14% 9% 3 6% 6% 3 5% 5% 5% 7% 37%	1980
	21st to end	Day	20% 9% 3 7% 6% 3 5% 5% 5% 8% 29%	2178
April	1st to 10th	Day	12% 9% 4 6% 6% 3 5% 5% 6% 8% 36%	2034
	11th to 20th	Day	17% 7% 3 6% 5% 4 5% 5% 5% 7% 36%	2302
	21st to end	Day	17% 8% 4 5% 5% 3 4 5% 4 7% 38%	2340
May	1st to 10th	Day	15% 7% 3 6% 6% 4 4 6% 5% 7% 37%	2340
	11th to 20th	Day	16% 7% 3 5% 6% 4 6% 5% 6% 7% 37%	2301
	21st to end	Day	8% 5% 2 5% 6% 3 4 5% 7% 9% 44%	2531
June	1st to 10th	Day	10% 5% 3 4 6% 3 6% 5% 7% 8% 43%	2422
	11th to 20th	Day	8% 5% 2 5% 5% 3 4 6% 6% 9% 45%	2700
	21st to end	Day	9% 4 2 5% 5% 3 5% 6% 7% 10% 44%	2537
July	1st to 10th	Day	8% 4 2 4 5% 3 5% 5% 6% 8% 51%	2520
	11th to 20th	Day	8% 3 2 4 4 3 5% 6% 6% 10% 49%	2439
	21st to end	Day	7% 4 2 6% 4 3 5% 5% 6% 8% 49%	2547
August	1st to 10th	Day	8% 4 2 4 4 4 5% 5% 7% 9% 49%	2327
	11th to 20th	Day	8% 4 2 5% 6% 3 6% 5% 7% 10% 44%	2303
	21st to end	Day	10% 5% 2 4 4 3 4 5% 6% 9% 48%	2574
September	1st to 10th	Day	12% 5% 2 4 4 3 5% 5% 5% 8% 46%	2008
	11th to 20th	Day	10% 6% 2 5% 4 3 4 5% 8% 8% 46%	1980
	21st to end	Day	18% 6% 2 4 4 3 4 5% 6% 7% 41%	1980
October	1st to 10th	Day	15% 6% 3 5% 5% 4 4 4 5% 7% 41%	1905
	11th to 20th	Day	20% 8% 4 6% 5% 3 4 4 5% 7% 34%	1800
	21st to end	Day	22% 9% 4 6% 5% 3 4 5% 6% 7% 28%	1895
November	1st to 10th	Day	11% 11% 4 7% 4 3 4 5% 6% 7% 38%	1672
	11th to 20th	Day	17% 16% 4 7% 5% 3 4 4 3 6% 30%	1710
	21st to end	Day	19% 14% 5% 6% 7% 3 4 5% 6% 6% 24%	1592
December	1st to 10th	Day	17% 16% 10% 11% 7% 3 4 4 5% 5% 17%	1520
	11th to 20th	Day	16% 14% 6% 13% 7% 4 4 5% 6% 6% 20%	1910
	21st to end	Day	23% 19% 7% 11% 8% 4 5% 4 4 5% 12%	2873
January	1st to 10th	Night	18% 14% 6% 11% 7% 3 4 5% 4 5% 22%	2648
	11th to 20th	Night	19% 17% 8% 11% 7% 3 5% 4 4 5% 17%	2506
	21st to end	Night	18% 16% 7% 9% 8% 4 5% 4 4 4 22%	2711
February	1st to 10th	Night	18% 13% 6% 9% 9% 4 5% 5% 4 5% 22%	2340
	11th to 20th	Night	18% 11% 5% 10% 7% 4 5% 5% 5% 5% 25%	2167
	21st to end	Night	22% 10% 5% 9% 5% 4 5% 3 4 5% 29%	1776
March	1st to 10th	Night	15% 10% 5% 8% 7% 4 5% 4 5% 5% 33%	2084
	11th to 20th	Night	14% 9% 3 7% 5% 3 5% 4 6% 8% 36%	1980
	21st to end	Night	19% 10% 4 7% 6% 4 4 4 4 6% 33%	2178
April	1st to 10th	Night	16% 10% 4 7% 5% 3 5% 5% 5% 6% 35%	1940
	11th to 20th	Night	16% 7% 3 6% 7% 3 5% 5% 6% 6% 37%	1607
	21st to end	Night	16% 8% 4 6% 5% 3 4 5% 5% 7% 38%	1620
May	1st to 10th	Night	17% 9% 3 7% 8% 4 4 5% 6% 8% 30%	1620
	11th to 20th	Night	17% 8% 3 6% 5% 2 3 5% 5% 7% 37%	1592
	21st to end	Night	9% 4 2 5% 5% 3 5% 6% 6% 9% 44%	1744
June	1st to 10th	Night	12% 4 3 5% 5% 2 5% 6% 6% 7% 44%	1520
	11th to 20th	Night	8% 6% 2 6% 5% 3 4 6% 6% 10% 44%	1260
	21st to end	Night	10% 4 2 4 7% 3 5% 5% 6% 9% 45%	1410
July	1st to 10th	Night	9% 5% 2 5% 5% 2 4 5% 6% 8% 49%	1440
	11th to 20th	Night	9% 3 1 5% 5% 3 6% 5% 6% 10% 48%	1519
	21st to end	Night	7% 3 2 4 5% 3 5% 6% 7% 9% 49%	1771
August	1st to 10th	Night	8% 4 1 5% 5% 3 5% 5% 5% 10% 50%	1611
	11th to 20th	Night	8% 5% 2 6% 5% 3 6% 5% 6% 9% 45%	1598
	21st to end	Night	9% 4 2 5% 6% 3 5% 6% 7% 6% 48%	1782
September	1st to 10th	Night	11% 6% 2 4 5% 3 5% 5% 5% 7% 45%	1930
	11th to 20th	Night	11% 5% 2 5% 5% 3 6% 4 5% 6% 48%	1980
	21st to end	Night	15% 6% 2 6% 6% 4 5% 4 5% 7% 41%	1980
October	1st to 10th	Night	15% 8% 2 5% 5% 3 4 4 6% 7% 41%	2053
	11th to 20th	Night	22% 10% 3 6% 5% 3 4 4 5% 6% 33%	2160
	21st to end	Night	25% 9% 4 6% 6% 3 5% 5% 4 5% 28%	2456
November	1st to 10th	Night	15% 10% 4 7% 4 3 4 4 6% 6% 37%	2406
	11th to 20th	Night	19% 15% 5% 9% 7% 3 4 4 4 5% 26%	2470
	21st to end	Night	23% 15% 5% 7% 6% 3 4 4 4 6% 23%	2584
December	1st to 10th	Night	19% 18% 10% 11% 6% 3 4 3 4 4 18%	2660
	11th to 20th	Night	18% 16% 6% 9% 6% 4 5% 4 5% 6% 22%	3285
	21st to end	Night	28% 18% 7% 9% 8% 3 4 4 4 4 12%	4774

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% 7% 11% 12% 4 1	1518
	11th to 20th	Day	70% 7% 13% 7% 2	1668
	21st to end	Day	67% 6% 12% 11% 5%	1872
February	1st to 10th	Day	62% 6% 12% 13% 6%	1620
	11th to 20th	Day	60% 5% 12% 15% 7% 1	1684
	21st to end	Day	54% 7% 13% 16% 8% 2	1480
March	1st to 10th	Day	52% 7% 14% 20% 7% 1	1876
	11th to 20th	Day	47% 7% 13% 19% 11% 2	1980
	21st to end	Day	53% 7% 11% 22% 7% 1	2178
April	1st to 10th	Day	45% 7% 14% 18% 15% 1	2034
	11th to 20th	Day	47% 6% 13% 18% 13% 3	2302
	21st to end	Day	45% 7% 13% 21% 10% 3	2340
May	1st to 10th	Day	45% 8% 11% 22% 12% 2	2340
	11th to 20th	Day	46% 8% 12% 17% 15% 2	2305
	21st to end	Day	34% 10% 15% 26% 15% 2	2531
June	1st to 10th	Day	37% 8% 13% 27% 13% 2	2422
	11th to 20th	Day	33% 10% 16% 23% 16% 2	2700
	21st to end	Day	34% 8% 15% 24% 16% 3	2537
July	1st to 10th	Day	31% 7% 12% 28% 19% 3	2451
	11th to 20th	Day	29% 7% 15% 28% 19% 2	2364
	21st to end	Day	32% 8% 14% 25% 19% 2	2405
August	1st to 10th	Day	29% 8% 17% 31% 15%	2314
	11th to 20th	Day	33% 8% 17% 27% 12% 2	2303
	21st to end	Day	32% 8% 15% 24% 18% 3	2574
September	1st to 10th	Day	36% 6% 18% 22% 16% 2	2008
	11th to 20th	Day	34% 7% 15% 28% 15% 1	1980
	21st to end	Day	41% 7% 12% 22% 17%	1980
October	1st to 10th	Day	42% 8% 12% 23% 15% 1	1905
	11th to 20th	Day	48% 7% 14% 20% 11% 1	1800
	21st to end	Day	54% 8% 13% 16% 8%	1895
November	1st to 10th	Day	44% 7% 13% 20% 14% 1	1672
	11th to 20th	Day	56% 5% 12% 16% 9% 1	1710
	21st to end	Day	59% 7% 13% 16% 5%	1592
December	1st to 10th	Day	69% 7% 11% 9% 3	1520
	11th to 20th	Day	63% 7% 12% 14% 3	1906
	21st to end	Day	75% 7% 8% 7% 2	2873
January	1st to 10th	Night	63% 7% 9% 15% 6%	2648
	11th to 20th	Night	70% 6% 11% 11% 2	2506
	21st to end	Night	66% 5% 11% 12% 5%	2711
February	1st to 10th	Night	64% 6% 11% 13% 5% 1	2340
	11th to 20th	Night	61% 6% 10% 15% 7% 1	2169
	21st to end	Night	58% 5% 11% 17% 8% 1	1776
March	1st to 10th	Night	52% 5% 11% 21% 9%	2084
	11th to 20th	Night	46% 7% 12% 20% 13% 2	1980
	21st to end	Night	53% 5% 9% 22% 10% 2	2178
April	1st to 10th	Night	49% 6% 11% 18% 13% 2	1940
	11th to 20th	Night	45% 7% 11% 17% 17% 3	1607
	21st to end	Night	45% 6% 11% 19% 15% 3	1620
May	1st to 10th	Night	51% 8% 11% 17% 10% 3	1620
	11th to 20th	Night	45% 7% 10% 17% 17% 3	1593
	21st to end	Night	35% 8% 14% 26% 16% 2	1745
June	1st to 10th	Night	38% 7% 11% 25% 16% 3	1520
	11th to 20th	Night	34% 8% 15% 24% 16% 3	1260
	21st to end	Night	34% 7% 12% 26% 19% 1	1410
July	1st to 10th	Night	32% 7% 13% 25% 19% 4	1400
	11th to 20th	Night	31% 8% 12% 29% 17% 3	1471
	21st to end	Night	28% 10% 17% 22% 19% 4	1672
August	1st to 10th	Night	29% 7% 16% 30% 16% 1	1600
	11th to 20th	Night	34% 8% 15% 28% 13% 2	1598
	21st to end	Night	34% 7% 14% 22% 20% 3	1782
September	1st to 10th	Night	36% 7% 15% 24% 14% 4	1930
	11th to 20th	Night	35% 7% 11% 26% 20% 1	1980
	21st to end	Night	43% 7% 11% 21% 17% 1	1980
October	1st to 10th	Night	42% 7% 12% 19% 19% 1	2053
	11th to 20th	Night	52% 5% 10% 18% 14% 1	2160
	21st to end	Night	56% 7% 10% 17% 9% 1	2456
November	1st to 10th	Night	47% 6% 13% 19% 14% 1	2406
	11th to 20th	Night	61% 6% 10% 14% 8% 1	2470
	21st to end	Night	62% 6% 12% 16% 4	2584
December	1st to 10th	Night	70% 5% 9% 11% 4	2660
	11th to 20th	Night	64% 6% 14% 13% 3	3288
	21st to end	Night	76% 6% 10% 6% 2	4774

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	22% 10% 29% 30% 9% 1	270
	11th to 20th	Day	22% 10% 34% 27% 7% 1	270
	21st to end	Day	28% 7% 26% 28% 11% 1	294
February	1st to 10th	Day	22% 7% 31% 35% 5%	240
	11th to 20th	Day	22% 7% 35% 30% 7%	240
	21st to end	Day	21% 7% 33% 34% 6%	198
March	1st to 10th	Day	21% 6% 24% 37% 11%	316
	11th to 20th	Day	17% 7% 27% 33% 14% 1	420
	21st to end	Day	24% 8% 23% 34% 11% 1	462
April	1st to 10th	Day	13% 7% 24% 38% 17% 2	420
	11th to 20th	Day	19% 5% 24% 33% 15% 5%	412
	21st to end	Day	21% 4 23% 31% 19% 1	420
May	1st to 10th	Day	21% 5% 17% 32% 20% 5%	423
	11th to 20th	Day	16% 3 19% 29% 28% 6%	447
	21st to end	Day	10% 2 10% 31% 33% 14%	485
June	1st to 10th	Day	11% 2 12% 36% 32% 7%	473
	11th to 20th	Day	12% 2 11% 36% 30% 8%	630
	21st to end	Day	11% 3 12% 33% 33% 8%	630
July	1st to 10th	Day	8% 2 7% 27% 37% 18%	621
	11th to 20th	Day	10% 2 7% 28% 41% 13%	537
	21st to end	Day	8% 2 8% 31% 40% 11%	488
August	1st to 10th	Day	10% 3 6% 27% 38% 15%	446
	11th to 20th	Day	9% 2 9% 29% 38% 12%	439
	21st to end	Day	8% 3 8% 28% 39% 13%	495
September	1st to 10th	Day	13% 2 12% 24% 34% 16%	450
	11th to 20th	Day	11% 3 9% 22% 37% 18%	450
	21st to end	Day	18% 6% 16% 22% 28% 10%	450
October	1st to 10th	Day	14% 4 17% 25% 28% 13%	450
	11th to 20th	Day	19% 10% 22% 28% 17% 4	450
	21st to end	Day	24% 10% 26% 26% 12% 2	410
November	1st to 10th	Day	14% 7% 22% 26% 23% 7%	270
	11th to 20th	Day	24% 12% 23% 25% 14% 2	270
	21st to end	Day	23% 7% 35% 28% 7%	214
December	1st to 10th	Day	19% 11% 33% 30% 8%	180
	11th to 20th	Day	20% 15% 38% 19% 8%	180
	21st to end	Day	24% 11% 30% 27% 8%	283
January	1st to 10th	Night	25% 11% 33% 23% 8% 1	950
	11th to 20th	Night	26% 11% 33% 24% 6%	796
	21st to end	Night	24% 8% 31% 29% 7%	835
February	1st to 10th	Night	24% 5% 36% 30% 5%	720
	11th to 20th	Night	23% 8% 31% 33% 5%	703
	21st to end	Night	24% 8% 35% 28% 4	592
March	1st to 10th	Night	20% 4 32% 33% 10% 1	720
	11th to 20th	Night	18% 6% 31% 32% 10% 3	720
	21st to end	Night	21% 6% 24% 34% 12% 2	792
April	1st to 10th	Night	18% 9% 28% 34% 10% 1	680
	11th to 20th	Night	19% 5% 25% 35% 14% 2	533
	21st to end	Night	17% 5% 25% 34% 16% 2	540
May	1st to 10th	Night	20% 5% 20% 36% 17% 3	540
	11th to 20th	Night	22% 4 16% 31% 22% 5%	531
	21st to end	Night	11% 2 13% 29% 33% 12%	584
June	1st to 10th	Night	12% 3 16% 38% 28% 4	468
	11th to 20th	Night	10% 1 14% 38% 32% 6%	360
	21st to end	Night	12% 1 15% 36% 31% 5%	510
July	1st to 10th	Night	11% 2 8% 31% 36% 11%	525
	11th to 20th	Night	10% 2 11% 35% 33% 9%	522
	21st to end	Night	6% 2 12% 38% 38% 5%	591
August	1st to 10th	Night	8% 3 9% 36% 33% 10%	537
	11th to 20th	Night	10% 1 12% 33% 33% 11%	534
	21st to end	Night	10% 2 11% 33% 34% 11%	594
September	1st to 10th	Night	14% 4 13% 28% 31% 10%	685
	11th to 20th	Night	12% 3 11% 29% 34% 10%	720
	21st to end	Night	17% 5% 17% 28% 25% 8%	720
October	1st to 10th	Night	20% 4 19% 26% 23% 8%	720
	11th to 20th	Night	27% 11% 22% 26% 13% 2	720
	21st to end	Night	28% 11% 26% 26% 9% 1	792
November	1st to 10th	Night	20% 9% 26% 28% 14% 3	740
	11th to 20th	Night	24% 14% 31% 21% 8% 2	760
	21st to end	Night	30% 12% 28% 23% 7% 1	760
December	1st to 10th	Night	27% 14% 29% 23% 6% 1	760
	11th to 20th	Night	26% 12% 35% 21% 6%	760
	21st to end	Night	29% 11% 29% 25% 5%	950

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