The Islands Provincial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Islands Provincial Park clear sky chart from 2005-11-06 to 2024-11-04.

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	23% 11% 3 7% 4 4 4 3 5% 6% 30%	102032
	Night	22% 11% 3 8% 5% 4 4 3 5% 6% 29%	97029
Transparency	Day	54% 3 11% 20% 11% 1	105621
	Night	55% 3 10% 20% 10% 1	101517
Seeing	Day	28% 16% 32% 18% 6% 1	17133
	Night	27% 14% 29% 22% 7% 1	24663

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	20% 14% 5% 10% 6% 4 5% 4 5% 6% 21%	2533
	11th to 20th	Day	20% 14% 5% 16% 6% 5% 4 4 5% 5% 17%	2840
	21st to end	Day	22% 12% 5% 11% 6% 5% 4 3 4 6% 22%	3124
February	1st to 10th	Day	20% 17% 4 10% 7% 6% 5% 3 4 5% 18%	1710
	11th to 20th	Day	18% 12% 4 12% 8% 6% 4 3 4 6% 21%	1663
	21st to end	Day	15% 15% 4 8% 6% 4 4 3 6% 7% 27%	1498
March	1st to 10th	Day	28% 14% 3 8% 5% 3 4 4 4 4 23%	3396
	11th to 20th	Day	19% 18% 4 7% 5% 4 4 3 5% 5% 26%	3480
	21st to end	Day	31% 13% 5% 10% 4 4 3 2 3 4 22%	3816
April	1st to 10th	Day	25% 16% 2 7% 4 4 3 2 4 5% 28%	2205
	11th to 20th	Day	21% 10% 2 6% 4 4 4 3 4 6% 35%	2380
	21st to end	Day	24% 9% 2 6% 4 3 3 3 5% 6% 35%	2470
May	1st to 10th	Day	24% 12% 3 8% 4 3 4 3 4 6% 28%	4106
	11th to 20th	Day	25% 12% 3 7% 4 3 4 3 5% 6% 29%	4269
	21st to end	Day	21% 8% 3 6% 4 3 4 3 5% 8% 35%	4836
June	1st to 10th	Day	26% 9% 2 6% 4 4 3 3 5% 6% 32%	2660
	11th to 20th	Day	21% 9% 3 5% 4 3 3 2 5% 6% 38%	2812
	21st to end	Day	27% 8% 2 5% 5% 4 4 4 5% 8% 28%	2850
July	1st to 10th	Day	25% 9% 3 6% 4 3 4 4 6% 6% 31%	4738
	11th to 20th	Day	31% 9% 2 5% 3 3 4 3 4 7% 28%	4358
	21st to end	Day	21% 9% 3 6% 4 4 4 3 5% 7% 33%	4467
August	1st to 10th	Day	31% 10% 3 6% 3 3 3 3 4 6% 28%	4105
	11th to 20th	Day	18% 7% 3 7% 4 4 4 3 5% 7% 36%	4045
	21st to end	Day	13% 6% 2 5% 3 3 4 3 5% 8% 48%	4418
September	1st to 10th	Day	16% 7% 2 5% 4 4 3 3 5% 7% 44%	2280
	11th to 20th	Day	19% 6% 3 5% 3 4 3 3 4 5% 45%	2109
	21st to end	Day	20% 8% 2 5% 4 4 3 3 4 6% 41%	2088
October	1st to 10th	Day	20% 7% 2 5% 4 4 4 3 4 7% 38%	1900
	11th to 20th	Day	20% 7% 2 6% 4 5% 4 4 5% 7% 36%	1900
	21st to end	Day	21% 9% 3 7% 6% 4 5% 3 5% 6% 32%	2086
November	1st to 10th	Day	21% 10% 3 5% 5% 3 4 3 5% 6% 34%	1641
	11th to 20th	Day	21% 13% 3 8% 6% 4 4 3 5% 8% 26%	1520
	21st to end	Day	20% 14% 3 9% 6% 5% 5% 4 5% 5% 24%	1520
December	1st to 10th	Day	25% 15% 3 9% 5% 5% 4 3 5% 6% 20%	1520
	11th to 20th	Day	30% 13% 4 8% 5% 4 4 3 4 5% 19%	1906
	21st to end	Day	23% 14% 6% 8% 4 4 4 3 5% 5% 24%	2783
January	1st to 10th	Night	17% 13% 5% 15% 6% 5% 5% 4 5% 5% 20%	4420
	11th to 20th	Night	18% 15% 5% 14% 5% 5% 4 4 5% 6% 18%	4120
	21st to end	Night	20% 14% 5% 12% 5% 5% 5% 4 5% 6% 20%	4532
February	1st to 10th	Night	19% 14% 5% 11% 7% 5% 5% 4 5% 5% 20%	2470
	11th to 20th	Night	18% 12% 4 9% 8% 6% 5% 5% 6% 7% 21%	2403
	21st to end	Night	13% 12% 4 8% 6% 5% 5% 4 5% 7% 29%	1951
March	1st to 10th	Night	26% 12% 3 7% 7% 5% 4 3 3 4 26%	3443
	11th to 20th	Night	17% 16% 5% 9% 5% 3 4 4 5% 7% 25%	3479
	21st to end	Night	34% 9% 4 8% 3 2 2 2 3 4 27%	3816
April	1st to 10th	Night	23% 13% 3 7% 5% 3 3 2 5% 6% 30%	1973
	11th to 20th	Night	24% 10% 2 5% 3 4 3 3 4 7% 34%	1745
	21st to end	Night	25% 9% 3 6% 4 3 4 3 4 7% 32%	1710
May	1st to 10th	Night	22% 13% 4 7% 4 3 4 3 6% 6% 27%	2834
	11th to 20th	Night	24% 12% 3 8% 4 4 3 3 4 5% 30%	2630
	21st to end	Night	22% 11% 3 8% 4 4 3 3 5% 5% 32%	2749
June	1st to 10th	Night	26% 9% 3 7% 3 3 4 3 5% 8% 29%	1520
	11th to 20th	Night	20% 10% 3 6% 4 4 4 3 5% 6% 35%	1381
	21st to end	Night	29% 10% 3 6% 4 4 4 3 5% 6% 26%	1330
July	1st to 10th	Night	30% 12% 4 7% 4 3 3 3 5% 6% 23%	2210
	11th to 20th	Night	34% 11% 3 5% 4 3 3 3 5% 7% 23%	2591
	21st to end	Night	22% 10% 2 6% 4 4 4 3 5% 7% 32%	3087
August	1st to 10th	Night	30% 11% 3 7% 4 3 3 2 3 7% 29%	2825
	11th to 20th	Night	21% 10% 2 7% 5% 3 4 3 5% 7% 33%	2782
	21st to end	Night	13% 9% 2 5% 3 3 4 3 5% 8% 46%	3238
September	1st to 10th	Night	17% 8% 2 5% 4 4 3 3 5% 7% 42%	1900
	11th to 20th	Night	20% 7% 2 4 3 3 3 4 5% 6% 44%	2066
	21st to end	Night	21% 8% 3 6% 3 3 3 3 5% 6% 39%	2091
October	1st to 10th	Night	21% 7% 3 6% 4 4 4 3 4 7% 38%	2280
	11th to 20th	Night	19% 7% 2 5% 3 4 3 3 5% 6% 43%	2280
	21st to end	Night	23% 8% 2 6% 3 4 4 3 4 7% 35%	2508
November	1st to 10th	Night	19% 8% 3 6% 4 4 4 3 5% 6% 38%	2508
	11th to 20th	Night	20% 10% 3 7% 5% 5% 5% 4 5% 7% 28%	2660
	21st to end	Night	19% 13% 3 8% 5% 4 5% 4 6% 6% 28%	2660
December	1st to 10th	Night	24% 13% 4 9% 6% 5% 5% 3 5% 7% 21%	2660
	11th to 20th	Night	28% 12% 4 8% 4 4 4 4 5% 6% 21%	3293
	21st to end	Night	25% 12% 4 9% 4 4 4 4 4 5% 25%	4884

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	61% 2 13% 19% 5%	2534
	11th to 20th	Day	68% 3 10% 14% 5%	2840
	21st to end	Day	62% 2 8% 19% 8%	3124
February	1st to 10th	Day	65% 3 11% 13% 8% 1	1710
	11th to 20th	Day	61% 3 10% 17% 8% 1	1671
	21st to end	Day	54% 3 11% 20% 9% 3	1498
March	1st to 10th	Day	64% 1 8% 17% 8% 2	3400
	11th to 20th	Day	57% 3 12% 17% 10% 1	3480
	21st to end	Day	68% 2 5% 14% 10% 2	3816
April	1st to 10th	Day	59% 2 8% 16% 13% 1	2205
	11th to 20th	Day	50% 4 10% 22% 14% 1	2380
	21st to end	Day	50% 3 10% 20% 15% 2	2470
May	1st to 10th	Day	60% 2 11% 21% 7%	4120
	11th to 20th	Day	57% 2 11% 20% 9% 1	4273
	21st to end	Day	49% 2 16% 18% 13% 1	4836
June	1st to 10th	Day	54% 3 9% 22% 11% 1	2660
	11th to 20th	Day	49% 3 11% 21% 14% 3	2812
	21st to end	Day	56% 3 13% 17% 10% 1	2850
July	1st to 10th	Day	54% 3 11% 18% 12% 2	4663
	11th to 20th	Day	57% 3 9% 22% 8% 1	4282
	21st to end	Day	50% 4 12% 22% 11% 1	4325
August	1st to 10th	Day	59% 3 9% 19% 9% 1	4092
	11th to 20th	Day	46% 4 13% 28% 8%	4084
	21st to end	Day	34% 4 12% 29% 20% 1	4418
September	1st to 10th	Day	41% 3 11% 25% 18% 2	2280
	11th to 20th	Day	42% 3 10% 25% 17% 3	2109
	21st to end	Day	45% 3 7% 24% 18% 2	2088
October	1st to 10th	Day	44% 6% 11% 26% 13% 1	3160
	11th to 20th	Day	40% 3 9% 25% 22% 1	3140
	21st to end	Day	44% 4 12% 25% 12% 4	3412
November	1st to 10th	Day	51% 3 12% 23% 11% 1	1641
	11th to 20th	Day	55% 4 11% 20% 9%	1520
	21st to end	Day	58% 4 12% 20% 5% 1	1520
December	1st to 10th	Day	64% 3 11% 16% 6%	1520
	11th to 20th	Day	67% 3 8% 14% 7%	1905
	21st to end	Day	61% 2 14% 15% 7% 1	2783
January	1st to 10th	Night	63% 2 10% 20% 5% 1	4420
	11th to 20th	Night	65% 3 10% 15% 6%	4120
	21st to end	Night	64% 2 11% 16% 6%	4532
February	1st to 10th	Night	64% 3 11% 15% 7%	2470
	11th to 20th	Night	59% 3 10% 19% 8% 1	2406
	21st to end	Night	52% 3 11% 21% 11% 1	1951
March	1st to 10th	Night	63% 3 7% 15% 11% 1	3452
	11th to 20th	Night	59% 2 13% 15% 10% 1	3480
	21st to end	Night	63% 1 7% 16% 11% 2	3816
April	1st to 10th	Night	57% 2 8% 16% 13% 4	1973
	11th to 20th	Night	50% 3 8% 25% 12% 1	1745
	21st to end	Night	52% 3 10% 20% 12% 3	1710
May	1st to 10th	Night	59% 2 12% 21% 6%	2840
	11th to 20th	Night	58% 2 9% 23% 7% 1	2631
	21st to end	Night	56% 2 11% 24% 6%	2750
June	1st to 10th	Night	55% 2 7% 25% 9% 1	1520
	11th to 20th	Night	51% 3 12% 21% 13% 1	1381
	21st to end	Night	61% 4 8% 15% 10% 1	1330
July	1st to 10th	Night	64% 3 9% 16% 9%	2175
	11th to 20th	Night	64% 3 7% 15% 9% 1	2544
	21st to end	Night	54% 5% 10% 20% 10% 1	2989
August	1st to 10th	Night	60% 2 9% 20% 9%	2813
	11th to 20th	Night	51% 5% 13% 24% 6%	2809
	21st to end	Night	38% 3 11% 29% 18% 1	3237
September	1st to 10th	Night	43% 3 8% 27% 17% 3	1900
	11th to 20th	Night	42% 3 8% 27% 19% 2	2066
	21st to end	Night	48% 2 6% 26% 17% 1	2091
October	1st to 10th	Night	46% 5% 11% 23% 13% 1	3800
	11th to 20th	Night	34% 2 11% 27% 25% 1	3779
	21st to end	Night	41% 2 11% 28% 17% 1	4120
November	1st to 10th	Night	47% 3 14% 25% 11%	2508
	11th to 20th	Night	53% 3 12% 21% 10%	2660
	21st to end	Night	53% 5% 15% 19% 7%	2660
December	1st to 10th	Night	63% 2 12% 17% 6%	2660
	11th to 20th	Night	63% 3 9% 17% 6% 1	3295
	21st to end	Night	61% 2 11% 20% 5% 1	4884

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% 25% 28% 14% 4	370
	11th to 20th	Day	31% 21% 31% 14% 3	370
	21st to end	Day	21% 27% 32% 16% 3	407
February	1st to 10th	Day	32% 22% 30% 14% 3	370
	11th to 20th	Day	30% 26% 28% 13% 3	366
	21st to end	Day	29% 22% 32% 15% 3	348
March	1st to 10th	Day	33% 20% 33% 11% 3	460
	11th to 20th	Day	31% 22% 31% 10% 4 1	460
	21st to end	Day	29% 23% 31% 10% 5% 1	506
April	1st to 10th	Day	34% 24% 30% 11% 2	460
	11th to 20th	Day	29% 20% 37% 11% 2	452
	21st to end	Day	29% 20% 32% 13% 5% 1	460
May	1st to 10th	Day	30% 22% 32% 14% 3 1	463
	11th to 20th	Day	27% 18% 31% 18% 4 1	597
	21st to end	Day	31% 12% 32% 18% 7% 1	735
June	1st to 10th	Day	32% 10% 33% 19% 5%	680
	11th to 20th	Day	24% 10% 35% 22% 7% 1	680
	21st to end	Day	34% 9% 31% 21% 5% 1	680
July	1st to 10th	Day	29% 7% 29% 25% 9% 1	670
	11th to 20th	Day	30% 5% 32% 23% 10% 1	625
	21st to end	Day	24% 7% 35% 25% 8% 1	532
August	1st to 10th	Day	20% 8% 37% 24% 9% 2	486
	11th to 20th	Day	25% 8% 33% 20% 11% 2	479
	21st to end	Day	22% 8% 33% 21% 12% 3	539
September	1st to 10th	Day	20% 11% 33% 27% 8% 2	490
	11th to 20th	Day	25% 10% 31% 21% 9% 3	490
	21st to end	Day	22% 12% 36% 21% 7% 3	488
October	1st to 10th	Day	22% 11% 34% 21% 10% 2	390
	11th to 20th	Day	21% 18% 31% 21% 7% 2	390
	21st to end	Day	25% 17% 34% 17% 6%	429
November	1st to 10th	Day	23% 20% 32% 17% 7% 1	374
	11th to 20th	Day	29% 24% 27% 13% 6%	370
	21st to end	Day	30% 22% 29% 16% 3 1	370
December	1st to 10th	Day	37% 17% 29% 14% 3	370
	11th to 20th	Day	39% 24% 23% 11% 3	370
	21st to end	Day	31% 24% 28% 13% 3 1	407
January	1st to 10th	Night	28% 22% 29% 17% 4	846
	11th to 20th	Night	29% 17% 29% 21% 3	760
	21st to end	Night	24% 22% 32% 18% 4	836
February	1st to 10th	Night	29% 22% 28% 19% 2	760
	11th to 20th	Night	26% 24% 32% 15% 2	743
	21st to end	Night	23% 17% 35% 19% 6%	628
March	1st to 10th	Night	28% 19% 34% 17% 3	760
	11th to 20th	Night	24% 18% 33% 19% 6%	760
	21st to end	Night	26% 19% 32% 18% 6%	836
April	1st to 10th	Night	30% 14% 35% 19% 3	643
	11th to 20th	Night	29% 13% 37% 16% 3 1	564
	21st to end	Night	30% 11% 30% 21% 7% 1	570
May	1st to 10th	Night	31% 11% 34% 19% 5% 1	570
	11th to 20th	Night	29% 9% 31% 24% 6% 1	562
	21st to end	Night	30% 7% 31% 24% 7% 1	616
June	1st to 10th	Night	29% 8% 33% 25% 5%	570
	11th to 20th	Night	24% 7% 31% 31% 6%	431
	21st to end	Night	35% 2 27% 28% 7% 1	380
July	1st to 10th	Night	30% 2 26% 31% 9% 1	370
	11th to 20th	Night	28% 3 29% 30% 10%	539
	21st to end	Night	29% 4 28% 33% 7%	623
August	1st to 10th	Night	22% 4 29% 35% 9% 1	568
	11th to 20th	Night	23% 6% 23% 34% 13% 1	562
	21st to end	Night	23% 4 25% 29% 17% 2	627
September	1st to 10th	Night	20% 6% 29% 32% 11% 2	570
	11th to 20th	Night	23% 6% 25% 27% 15% 3	736
	21st to end	Night	26% 8% 26% 26% 13% 2	760
October	1st to 10th	Night	26% 7% 29% 28% 11% 1	760
	11th to 20th	Night	23% 16% 26% 24% 9% 2	760
	21st to end	Night	28% 16% 27% 24% 6%	836
November	1st to 10th	Night	25% 14% 28% 24% 8% 1	782
	11th to 20th	Night	25% 19% 29% 21% 6%	850
	21st to end	Night	27% 21% 27% 18% 6%	850
December	1st to 10th	Night	31% 17% 29% 18% 5%	850
	11th to 20th	Night	32% 23% 28% 14% 2	850
	21st to end	Night	30% 22% 26% 18% 4	935

Page generated at 2024-11-01 23:47:31. Version ac07

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