Grand Falls-Windsor
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Grand Falls-Windsor 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	21% 14% 5% 9% 5% 5% 4 3 5% 6% 23%	101771
	Night	20% 13% 5% 10% 5% 5% 4 4 5% 6% 24%	97396
Transparency	Day	64% 3 10% 16% 7% 1	105228
	Night	63% 3 10% 16% 7% 1	102050
Seeing	Day	31% 12% 28% 20% 8% 2	18089
	Night	29% 11% 31% 22% 6% 1	24863

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	12% 13% 7% 13% 7% 7% 6% 3 4 4 24%	2279
	11th to 20th	Day	17% 15% 5% 16% 7% 5% 5% 4 4 5% 17%	2530
	21st to end	Day	10% 14% 7% 11% 6% 6% 5% 4 5% 6% 26%	2783
February	1st to 10th	Day	19% 14% 4 10% 8% 6% 5% 4 5% 5% 20%	1520
	11th to 20th	Day	17% 21% 6% 10% 7% 4 5% 4 5% 4 16%	1728
	21st to end	Day	11% 16% 6% 13% 7% 6% 5% 4 4 5% 23%	1570
March	1st to 10th	Day	17% 18% 4 11% 6% 4 5% 3 4 5% 24%	3114
	11th to 20th	Day	22% 21% 9% 12% 7% 5% 4 3 3 3 12%	3347
	21st to end	Day	25% 19% 8% 10% 5% 4 3 2 3 4 17%	4022
April	1st to 10th	Day	19% 21% 7% 12% 7% 5% 4 3 4 4 14%	2280
	11th to 20th	Day	21% 18% 5% 9% 4 3 3 3 4 6% 24%	2402
	21st to end	Day	22% 22% 6% 8% 4 4 3 2 4 4 20%	2470
May	1st to 10th	Day	26% 22% 6% 9% 5% 4 3 2 3 4 15%	4287
	11th to 20th	Day	24% 15% 5% 11% 5% 4 4 3 4 5% 22%	4454
	21st to end	Day	28% 16% 4 8% 4 3 4 3 4 5% 20%	5173
June	1st to 10th	Day	33% 16% 3 7% 5% 4 3 3 4 5% 16%	2850
	11th to 20th	Day	26% 12% 4 8% 5% 4 5% 4 5% 6% 23%	2850
	21st to end	Day	25% 11% 3 8% 6% 5% 4 4 5% 5% 23%	2850
July	1st to 10th	Day	21% 11% 4 8% 5% 5% 5% 4 5% 6% 24%	4750
	11th to 20th	Day	16% 9% 3 8% 6% 5% 6% 5% 7% 8% 27%	4599
	21st to end	Day	15% 7% 2 7% 4 5% 5% 4 6% 9% 37%	4815
August	1st to 10th	Day	22% 9% 3 8% 6% 5% 5% 4 6% 7% 24%	4424
	11th to 20th	Day	18% 9% 3 7% 4 4 4 3 5% 6% 37%	4080
	21st to end	Day	20% 8% 3 8% 5% 4 4 4 5% 7% 32%	4476
September	1st to 10th	Day	19% 9% 3 8% 5% 3 4 4 5% 7% 32%	2280
	11th to 20th	Day	25% 10% 4 7% 5% 4 4 3 5% 6% 28%	2103
	21st to end	Day	18% 11% 4 9% 5% 4 4 4 5% 7% 29%	2090
October	1st to 10th	Day	20% 12% 3 7% 5% 4 4 4 4 6% 31%	2071
	11th to 20th	Day	22% 14% 4 8% 6% 5% 4 3 5% 6% 23%	1710
	21st to end	Day	24% 15% 3 9% 6% 5% 4 3 4 4 22%	1881
November	1st to 10th	Day	25% 14% 5% 9% 6% 5% 5% 4 4 4 20%	1697
	11th to 20th	Day	20% 16% 6% 9% 5% 4 4 3 3 5% 25%	1516
	21st to end	Day	21% 17% 5% 8% 6% 5% 4 3 4 6% 22%	1330
December	1st to 10th	Day	20% 19% 7% 11% 6% 5% 3 4 3 5% 17%	1330
	11th to 20th	Day	29% 13% 4 10% 5% 5% 4 3 4 5% 16%	1668
	21st to end	Day	23% 18% 6% 10% 5% 3 3 4 5% 5% 19%	2442
January	1st to 10th	Night	11% 13% 6% 13% 7% 6% 5% 4 5% 5% 26%	4673
	11th to 20th	Night	13% 13% 5% 13% 7% 5% 5% 5% 5% 6% 20%	4440
	21st to end	Night	10% 11% 6% 11% 5% 7% 6% 4 6% 7% 27%	4884
February	1st to 10th	Night	17% 12% 5% 13% 8% 5% 5% 4 4 6% 21%	2660
	11th to 20th	Night	18% 17% 5% 11% 7% 5% 6% 4 5% 5% 19%	2337
	21st to end	Night	12% 13% 4 10% 7% 5% 5% 4 5% 6% 29%	1884
March	1st to 10th	Night	18% 17% 4 11% 6% 6% 5% 3 5% 5% 21%	3726
	11th to 20th	Night	17% 18% 8% 14% 7% 5% 5% 3 5% 4 14%	3612
	21st to end	Night	23% 17% 6% 10% 5% 3 3 3 4 5% 21%	3607
April	1st to 10th	Night	23% 20% 6% 8% 4 4 3 2 4 5% 21%	1900
	11th to 20th	Night	21% 16% 5% 9% 4 3 4 2 4 4 28%	1727
	21st to end	Night	22% 19% 5% 8% 4 4 3 3 4 6% 23%	1710
May	1st to 10th	Night	27% 19% 5% 11% 4 4 4 3 3 5% 15%	2659
	11th to 20th	Night	23% 14% 6% 12% 5% 5% 4 4 4 5% 17%	2450
	21st to end	Night	29% 12% 4 7% 4 4 4 3 4 5% 21%	2412
June	1st to 10th	Night	33% 14% 4 7% 3 4 4 4 3 6% 18%	1330
	11th to 20th	Night	26% 10% 2 7% 4 4 5% 3 7% 7% 25%	1330
	21st to end	Night	28% 11% 3 7% 5% 4 4 4 4 4 26%	1330
July	1st to 10th	Night	25% 11% 2 7% 4 4 4 3 5% 7% 27%	2220
	11th to 20th	Night	15% 10% 3 8% 5% 4 6% 4 6% 8% 30%	2368
	21st to end	Night	15% 8% 3 7% 5% 4 4 3 5% 6% 39%	2750
August	1st to 10th	Night	13% 9% 3 7% 5% 5% 4 4 6% 8% 35%	2516
	11th to 20th	Night	18% 8% 2 7% 4 4 4 4 5% 5% 39%	2756
	21st to end	Night	21% 7% 2 6% 4 4 4 3 5% 6% 38%	3187
September	1st to 10th	Night	20% 8% 3 8% 6% 4 3 3 4 6% 36%	1900
	11th to 20th	Night	22% 10% 2 6% 5% 4 3 3 5% 6% 33%	2076
	21st to end	Night	21% 9% 3 9% 4 4 3 4 6% 7% 30%	2090
October	1st to 10th	Night	21% 10% 3 8% 4 4 5% 3 5% 6% 30%	2108
	11th to 20th	Night	22% 11% 3 8% 4 5% 4 3 5% 6% 29%	2466
	21st to end	Night	26% 13% 3 7% 4 4 4 3 4 5% 26%	2717
November	1st to 10th	Night	22% 14% 4 8% 6% 5% 4 4 6% 6% 20%	2454
	11th to 20th	Night	22% 13% 5% 8% 6% 4 4 4 6% 6% 22%	2661
	21st to end	Night	19% 15% 6% 10% 6% 5% 4 4 5% 6% 20%	2850
December	1st to 10th	Night	19% 18% 5% 11% 6% 5% 4 3 5% 4 19%	2850
	11th to 20th	Night	30% 15% 5% 11% 6% 5% 4 3 4 3 15%	3531
	21st to end	Night	21% 13% 7% 10% 6% 4 5% 4 5% 6% 20%	5225

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	67% 2 5% 14% 9% 3	2280
	11th to 20th	Day	73% 2 5% 11% 9%	2530
	21st to end	Day	62% 1 6% 16% 11% 3	2783
February	1st to 10th	Day	67% 3 9% 12% 7% 2	1520
	11th to 20th	Day	72% 2 6% 12% 7% 1	1735
	21st to end	Day	66% 2 5% 15% 11% 1	1570
March	1st to 10th	Day	66% 2 7% 13% 9% 3	3118
	11th to 20th	Day	80% 1 4 10% 5%	3347
	21st to end	Day	74% 1 5% 13% 6% 1	4022
April	1st to 10th	Day	76% 2 6% 10% 5% 1	2280
	11th to 20th	Day	65% 1 7% 15% 10% 1	2402
	21st to end	Day	70% 2 6% 13% 9% 1	2470
May	1st to 10th	Day	76% 1 8% 11% 4	4302
	11th to 20th	Day	67% 1 9% 17% 5% 1	4458
	21st to end	Day	69% 1 8% 16% 6%	5173
June	1st to 10th	Day	73% 2 6% 13% 5%	2850
	11th to 20th	Day	63% 3 10% 19% 5% 1	2850
	21st to end	Day	63% 3 10% 16% 7% 1	2850
July	1st to 10th	Day	61% 3 12% 18% 6%	4675
	11th to 20th	Day	55% 4 17% 19% 4	4517
	21st to end	Day	45% 3 20% 26% 6% 1	4662
August	1st to 10th	Day	58% 4 13% 21% 4	4410
	11th to 20th	Day	49% 3 14% 23% 10% 1	4120
	21st to end	Day	52% 3 14% 26% 5%	4476
September	1st to 10th	Day	53% 3 11% 23% 9% 2	2280
	11th to 20th	Day	59% 2 12% 19% 7%	2103
	21st to end	Day	56% 3 14% 19% 8% 1	2090
October	1st to 10th	Day	59% 4 10% 18% 8%	3449
	11th to 20th	Day	59% 6% 11% 18% 6%	2832
	21st to end	Day	62% 4 9% 16% 9% 1	3092
November	1st to 10th	Day	69% 3 11% 12% 5%	1697
	11th to 20th	Day	65% 2 10% 14% 8% 1	1516
	21st to end	Day	67% 3 11% 10% 8% 1	1330
December	1st to 10th	Day	73% 3 8% 10% 7%	1330
	11th to 20th	Day	72% 3 8% 10% 6%	1667
	21st to end	Day	71% 1 8% 15% 4	2442
January	1st to 10th	Night	65% 2 5% 15% 10% 4	4673
	11th to 20th	Night	67% 2 7% 15% 8% 1	4440
	21st to end	Night	60% 2 10% 12% 12% 4	4884
February	1st to 10th	Night	67% 2 7% 14% 8% 1	2660
	11th to 20th	Night	70% 2 8% 13% 7% 1	2341
	21st to end	Night	57% 2 8% 18% 14% 1	1884
March	1st to 10th	Night	68% 2 7% 15% 7% 1	3735
	11th to 20th	Night	76% 2 6% 11% 5% 1	3613
	21st to end	Night	69% 1 7% 16% 6%	3607
April	1st to 10th	Night	70% 2 4 12% 11% 1	1900
	11th to 20th	Night	63% 1 7% 18% 10%	1727
	21st to end	Night	65% 3 7% 14% 10% 1	1710
May	1st to 10th	Night	75% 1 9% 11% 4	2664
	11th to 20th	Night	72% 1 8% 14% 5%	2451
	21st to end	Night	67% 2 8% 17% 5%	2413
June	1st to 10th	Night	71% 3 9% 12% 5%	1330
	11th to 20th	Night	59% 3 14% 18% 6%	1330
	21st to end	Night	61% 3 11% 18% 7% 1	1330
July	1st to 10th	Night	58% 3 15% 20% 4	2186
	11th to 20th	Night	55% 5% 16% 18% 7%	2326
	21st to end	Night	47% 4 16% 28% 5%	2663
August	1st to 10th	Night	49% 5% 20% 23% 4	2505
	11th to 20th	Night	47% 3 17% 25% 7% 1	2782
	21st to end	Night	48% 3 16% 28% 5%	3186
September	1st to 10th	Night	51% 3 12% 24% 10%	1900
	11th to 20th	Night	54% 3 13% 19% 10% 1	2076
	21st to end	Night	54% 3 13% 20% 9% 1	2090
October	1st to 10th	Night	59% 4 15% 16% 6% 1	3511
	11th to 20th	Night	54% 6% 13% 18% 8%	4093
	21st to end	Night	58% 4 12% 17% 9% 1	4467
November	1st to 10th	Night	66% 4 10% 15% 6%	2454
	11th to 20th	Night	64% 3 9% 17% 6%	2661
	21st to end	Night	67% 3 8% 13% 8%	2850
December	1st to 10th	Night	70% 3 7% 14% 6%	2850
	11th to 20th	Night	77% 2 6% 11% 5%	3533
	21st to end	Night	70% 2 10% 14% 4	5225

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	28% 16% 32% 17% 6% 1	370
	11th to 20th	Day	30% 17% 28% 21% 4	370
	21st to end	Day	29% 14% 30% 21% 5%	407
February	1st to 10th	Day	31% 18% 28% 15% 7% 1	370
	11th to 20th	Day	29% 20% 31% 15% 3 1	366
	21st to end	Day	22% 19% 36% 16% 5% 2	307
March	1st to 10th	Day	29% 18% 33% 14% 5% 1	370
	11th to 20th	Day	31% 15% 24% 18% 11% 3	370
	21st to end	Day	38% 14% 26% 16% 5% 2	463
April	1st to 10th	Day	33% 16% 30% 16% 5%	460
	11th to 20th	Day	34% 12% 26% 21% 6% 1	600
	21st to end	Day	36% 12% 30% 17% 5% 1	650
May	1st to 10th	Day	42% 11% 20% 18% 8% 2	653
	11th to 20th	Day	31% 10% 24% 22% 8% 4	674
	21st to end	Day	38% 10% 29% 17% 5% 1	735
June	1st to 10th	Day	43% 8% 22% 16% 8% 2	680
	11th to 20th	Day	35% 8% 27% 19% 11% 1	680
	21st to end	Day	29% 10% 28% 19% 9% 5%	680
July	1st to 10th	Day	31% 8% 27% 20% 12% 3	670
	11th to 20th	Day	27% 7% 26% 27% 12% 1	668
	21st to end	Day	27% 6% 25% 30% 11% 1	740
August	1st to 10th	Day	24% 9% 29% 24% 12% 2	675
	11th to 20th	Day	27% 4 25% 26% 14% 4	667
	21st to end	Day	26% 7% 24% 26% 14% 3	718
September	1st to 10th	Day	21% 12% 33% 22% 8% 3	490
	11th to 20th	Day	37% 9% 28% 20% 5% 2	396
	21st to end	Day	22% 14% 36% 20% 7% 2	390
October	1st to 10th	Day	26% 13% 32% 22% 5% 2	390
	11th to 20th	Day	34% 8% 27% 19% 9% 3	390
	21st to end	Day	32% 14% 28% 16% 8% 2	429
November	1st to 10th	Day	40% 12% 26% 16% 6% 1	374
	11th to 20th	Day	31% 16% 27% 19% 6% 1	370
	21st to end	Day	35% 18% 31% 12% 4	370
December	1st to 10th	Day	29% 12% 32% 17% 9%	370
	11th to 20th	Day	29% 19% 30% 16% 4	370
	21st to end	Day	27% 16% 31% 20% 5% 2	407
January	1st to 10th	Night	27% 15% 30% 21% 6% 1	850
	11th to 20th	Night	26% 18% 33% 19% 4	850
	21st to end	Night	23% 16% 36% 22% 4	935
February	1st to 10th	Night	27% 16% 36% 17% 4	850
	11th to 20th	Night	30% 16% 33% 18% 3 1	787
	21st to end	Night	21% 12% 38% 22% 6% 2	628
March	1st to 10th	Night	27% 18% 34% 17% 4	760
	11th to 20th	Night	24% 13% 30% 25% 8%	651
	21st to end	Night	33% 13% 30% 19% 5%	627
April	1st to 10th	Night	34% 16% 28% 17% 4 1	570
	11th to 20th	Night	31% 9% 33% 21% 5% 1	564
	21st to end	Night	33% 11% 31% 21% 4	570
May	1st to 10th	Night	36% 6% 29% 21% 7% 1	570
	11th to 20th	Night	32% 7% 30% 22% 8%	562
	21st to end	Night	36% 9% 30% 20% 5%	616
June	1st to 10th	Night	42% 7% 24% 22% 5%	570
	11th to 20th	Night	35% 6% 26% 25% 8%	570
	21st to end	Night	34% 6% 30% 21% 8% 1	570
July	1st to 10th	Night	28% 8% 31% 24% 8% 1	556
	11th to 20th	Night	22% 7% 34% 32% 5%	552
	21st to end	Night	26% 6% 33% 29% 7%	623
August	1st to 10th	Night	22% 5% 28% 34% 11% 1	568
	11th to 20th	Night	25% 5% 28% 30% 12%	562
	21st to end	Night	22% 6% 28% 33% 10% 1	627
September	1st to 10th	Night	26% 4 33% 29% 7%	570
	11th to 20th	Night	31% 9% 29% 27% 4	570
	21st to end	Night	28% 8% 34% 26% 5%	570
October	1st to 10th	Night	30% 8% 32% 25% 5%	580
	11th to 20th	Night	32% 8% 28% 23% 8% 1	856
	21st to end	Night	35% 11% 27% 20% 7%	946
November	1st to 10th	Night	33% 13% 29% 20% 5% 1	848
	11th to 20th	Night	31% 11% 31% 20% 6% 1	850
	21st to end	Night	29% 19% 31% 20% 2	850
December	1st to 10th	Night	30% 13% 28% 20% 7% 1	850
	11th to 20th	Night	35% 15% 29% 16% 4	850
	21st to end	Night	26% 13% 33% 21% 6% 1	935

Page generated at 2024-11-02 00:47:49. Version ac07

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