Niverville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Niverville clear sky chart from 2005-11-06 to 2024-01-16.

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	12% 9% 4 7% 6% 4 5% 5% 6% 7% 34%	74677
	Night	11% 9% 4 8% 7% 4 5% 5% 5% 7% 34%	75163
Transparency	Day	47% 6% 15% 23% 8% 1	74360
	Night	49% 6% 14% 22% 9% 1	74999
Seeing	Day	14% 9% 30% 29% 14% 4	15049
	Night	15% 7% 31% 34% 13% 1	25125

By Month

Percentage Cloud Cover NW (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	7% 14% 6% 9% 8% 4 8% 8% 6% 7% 23%	1329
	11th to 20th	Day	7% 14% 6% 14% 12% 7% 7% 7% 8% 4 15%	1303
	21st to end	Day	12% 15% 7% 12% 9% 6% 9% 7% 6% 6% 11%	1584
February	1st to 10th	Day	7% 11% 7% 11% 9% 5% 9% 7% 8% 7% 19%	1557
	11th to 20th	Day	8% 8% 5% 8% 8% 7% 8% 7% 8% 8% 24%	1574
	21st to end	Day	7% 8% 4 13% 10% 6% 7% 8% 7% 6% 24%	1402
March	1st to 10th	Day	12% 12% 6% 10% 10% 4 5% 6% 5% 7% 24%	1846
	11th to 20th	Day	7% 9% 6% 10% 11% 4 6% 6% 5% 6% 30%	1978
	21st to end	Day	12% 11% 4 9% 8% 4 5% 5% 5% 7% 29%	2178
April	1st to 10th	Day	10% 11% 5% 7% 6% 4 5% 5% 4 7% 34%	2186
	11th to 20th	Day	12% 10% 4 8% 7% 4 5% 4 5% 7% 35%	2312
	21st to end	Day	16% 10% 3 8% 5% 3 5% 4 5% 7% 33%	2340
May	1st to 10th	Day	16% 9% 4 6% 5% 3 4 4 5% 5% 39%	2409
	11th to 20th	Day	17% 7% 3 5% 5% 3 4 5% 5% 7% 38%	2583
	21st to end	Day	18% 7% 3 6% 4 3 4 4 6% 6% 38%	2918
June	1st to 10th	Day	14% 6% 2 6% 6% 3 5% 5% 7% 10% 37%	2700
	11th to 20th	Day	15% 7% 3 6% 5% 3 5% 6% 6% 9% 36%	2700
	21st to end	Day	12% 5% 3 6% 6% 3 6% 7% 7% 8% 37%	2700
July	1st to 10th	Day	7% 3 2 4 5% 3 6% 5% 7% 9% 48%	2700
	11th to 20th	Day	10% 5% 2 5% 5% 4 5% 6% 6% 8% 45%	2700
	21st to end	Day	6% 4 2 4 5% 3 5% 5% 6% 8% 52%	2905
August	1st to 10th	Day	7% 5% 3 4 4 3 5% 6% 7% 9% 47%	2410
	11th to 20th	Day	10% 5% 2 4 4 2 5% 5% 7% 9% 47%	2301
	21st to end	Day	13% 5% 2 5% 4 3 4 4 5% 7% 48%	2574
September	1st to 10th	Day	10% 5% 2 4 5% 3 4 4 6% 8% 50%	2232
	11th to 20th	Day	13% 7% 2 5% 5% 3 5% 4 6% 9% 42%	1980
	21st to end	Day	17% 6% 3 5% 5% 3 3 5% 6% 8% 41%	1980
October	1st to 10th	Day	18% 10% 3 6% 6% 3 4 5% 5% 7% 34%	1832
	11th to 20th	Day	14% 10% 4 8% 6% 3 4 5% 5% 7% 34%	1775
	21st to end	Day	15% 13% 5% 9% 6% 4 5% 5% 5% 7% 26%	1782
November	1st to 10th	Day	16% 13% 5% 8% 6% 3 4 5% 5% 7% 28%	1515
	11th to 20th	Day	11% 14% 6% 13% 7% 4 4 4 6% 7% 25%	1520
	21st to end	Day	13% 14% 5% 9% 9% 5% 6% 4 5% 5% 25%	1421
December	1st to 10th	Day	8% 15% 7% 12% 10% 5% 8% 5% 5% 5% 20%	1330
	11th to 20th	Day	10% 14% 8% 12% 10% 4 6% 6% 7% 8% 17%	1679
	21st to end	Day	9% 14% 6% 10% 9% 5% 8% 7% 7% 7% 18%	2442
January	1st to 10th	Night	7% 13% 6% 10% 10% 5% 7% 8% 6% 6% 22%	2837
	11th to 20th	Night	9% 14% 7% 13% 10% 5% 6% 7% 5% 5% 19%	2783
	21st to end	Night	8% 13% 8% 11% 10% 5% 6% 7% 7% 7% 17%	2772
February	1st to 10th	Night	8% 10% 5% 10% 9% 5% 9% 8% 5% 6% 25%	2403
	11th to 20th	Night	7% 9% 4 8% 7% 4 8% 7% 6% 7% 32%	2273
	21st to end	Night	7% 10% 5% 11% 9% 4 6% 5% 6% 6% 31%	1870
March	1st to 10th	Night	12% 11% 5% 10% 7% 4 5% 5% 5% 6% 32%	2113
	11th to 20th	Night	7% 9% 4 7% 7% 3 5% 4 5% 8% 41%	1980
	21st to end	Night	14% 10% 3 7% 6% 3 4 5% 6% 7% 35%	2178
April	1st to 10th	Night	11% 7% 4 5% 6% 3 5% 5% 6% 8% 40%	1772
	11th to 20th	Night	13% 10% 4 7% 6% 3 4 5% 5% 6% 37%	1599
	21st to end	Night	12% 8% 4 6% 6% 4 5% 5% 5% 6% 38%	1620
May	1st to 10th	Night	15% 9% 3 5% 5% 3 5% 3 5% 8% 40%	1549
	11th to 20th	Night	14% 7% 3 5% 5% 3 4 5% 5% 8% 41%	1312
	21st to end	Night	16% 6% 4 4 4 2 4 4 5% 9% 41%	1358
June	1st to 10th	Night	12% 6% 2 4 5% 2 5% 5% 5% 10% 43%	1260
	11th to 20th	Night	12% 6% 2 5% 6% 3 4 4 5% 9% 44%	1260
	21st to end	Night	9% 4 2 7% 6% 4 5% 4 7% 10% 43%	1260
July	1st to 10th	Night	5% 3 2 3 3 2 5% 5% 7% 9% 56%	1260
	11th to 20th	Night	4 4 1 3 4 4 4 6% 7% 10% 52%	1260
	21st to end	Night	6% 3 1 3 4 3 3 6% 7% 7% 56%	1410
August	1st to 10th	Night	7% 3 2 4 4 3 5% 5% 6% 8% 54%	1528
	11th to 20th	Night	9% 3 2 5% 4 3 4 4 5% 8% 53%	1600
	21st to end	Night	10% 5% 2 4 3 2 3 4 5% 8% 54%	1782
September	1st to 10th	Night	8% 4 2 4 5% 2 4 5% 6% 8% 54%	1727
	11th to 20th	Night	12% 5% 2 4 4 3 5% 4 5% 8% 47%	1980
	21st to end	Night	15% 6% 3 5% 6% 3 5% 4 5% 7% 41%	1980
October	1st to 10th	Night	17% 9% 4 6% 5% 3 4 5% 5% 7% 36%	2110
	11th to 20th	Night	16% 10% 3 6% 6% 3 5% 4 6% 7% 36%	2182
	21st to end	Night	14% 11% 4 8% 6% 3 4 5% 5% 6% 32%	2574
November	1st to 10th	Night	13% 13% 6% 9% 7% 4 4 4 4 5% 30%	2563
	11th to 20th	Night	10% 14% 6% 11% 8% 4 5% 5% 4 6% 26%	2660
	21st to end	Night	13% 12% 6% 11% 9% 5% 4 5% 4 6% 26%	2755
December	1st to 10th	Night	8% 12% 6% 11% 11% 5% 6% 6% 6% 6% 21%	2850
	11th to 20th	Night	10% 14% 7% 13% 9% 4 6% 4 5% 6% 21%	3518
	21st to end	Night	9% 11% 5% 10% 11% 6% 6% 6% 6% 6% 23%	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	58% 7% 14% 16% 6%	1329
	11th to 20th	Day	67% 6% 10% 13% 4	1303
	21st to end	Day	71% 5% 6% 11% 7%	1584
February	1st to 10th	Day	60% 6% 12% 14% 8% 1	1557
	11th to 20th	Day	53% 6% 14% 20% 7%	1583
	21st to end	Day	56% 5% 14% 17% 7%	1402
March	1st to 10th	Day	60% 6% 13% 15% 6%	1846
	11th to 20th	Day	52% 7% 13% 20% 7%	1980
	21st to end	Day	53% 7% 13% 19% 7% 1	2178
April	1st to 10th	Day	49% 5% 11% 24% 10% 1	2186
	11th to 20th	Day	49% 5% 11% 22% 11% 2	2312
	21st to end	Day	50% 6% 15% 20% 7% 2	2340
May	1st to 10th	Day	46% 4 11% 24% 13% 1	2409
	11th to 20th	Day	44% 6% 11% 26% 12% 1	2587
	21st to end	Day	45% 7% 12% 23% 12% 1	2918
June	1st to 10th	Day	42% 7% 16% 24% 10% 1	2700
	11th to 20th	Day	45% 6% 15% 23% 10% 1	2700
	21st to end	Day	41% 10% 19% 23% 7%	2700
July	1st to 10th	Day	29% 7% 20% 32% 11% 1	2626
	11th to 20th	Day	34% 7% 18% 31% 10%	2619
	21st to end	Day	30% 7% 18% 33% 11% 1	2743
August	1st to 10th	Day	31% 8% 19% 32% 10% 1	2394
	11th to 20th	Day	32% 7% 21% 33% 7%	2301
	21st to end	Day	35% 6% 17% 33% 9%	2574
September	1st to 10th	Day	32% 6% 17% 33% 11% 1	2232
	11th to 20th	Day	40% 6% 20% 27% 6% 1	1980
	21st to end	Day	42% 5% 16% 31% 5%	1980
October	1st to 10th	Day	49% 6% 16% 21% 7%	1832
	11th to 20th	Day	49% 6% 15% 22% 7% 1	1775
	21st to end	Day	57% 7% 17% 16% 3	1782
November	1st to 10th	Day	56% 6% 16% 17% 4 1	1515
	11th to 20th	Day	59% 6% 17% 13% 4	1520
	21st to end	Day	62% 5% 16% 15% 3	1421
December	1st to 10th	Day	64% 6% 15% 11% 3	1330
	11th to 20th	Day	63% 6% 15% 12% 4	1680
	21st to end	Day	61% 6% 12% 16% 5%	2442
January	1st to 10th	Night	59% 6% 13% 15% 6%	2837
	11th to 20th	Night	65% 6% 9% 16% 4	2783
	21st to end	Night	63% 6% 11% 13% 6%	2772
February	1st to 10th	Night	57% 6% 13% 15% 9%	2403
	11th to 20th	Night	48% 6% 17% 19% 10%	2274
	21st to end	Night	54% 5% 11% 20% 10%	1870
March	1st to 10th	Night	54% 5% 13% 20% 8%	2113
	11th to 20th	Night	42% 4 14% 27% 11% 1	1980
	21st to end	Night	47% 7% 14% 20% 11% 1	2178
April	1st to 10th	Night	42% 4 12% 24% 15% 3	1772
	11th to 20th	Night	47% 5% 8% 21% 17% 2	1599
	21st to end	Night	45% 5% 12% 25% 10% 2	1620
May	1st to 10th	Night	43% 5% 11% 25% 15% 1	1549
	11th to 20th	Night	41% 6% 11% 26% 13% 3	1312
	21st to end	Night	40% 7% 13% 21% 18% 2	1358
June	1st to 10th	Night	37% 8% 16% 25% 13% 1	1260
	11th to 20th	Night	38% 6% 17% 24% 13% 2	1260
	21st to end	Night	36% 8% 21% 27% 8% 1	1260
July	1st to 10th	Night	22% 7% 18% 37% 14% 2	1225
	11th to 20th	Night	25% 8% 20% 30% 15% 1	1218
	21st to end	Night	25% 6% 15% 39% 14% 2	1332
August	1st to 10th	Night	26% 6% 17% 37% 12% 1	1520
	11th to 20th	Night	29% 6% 21% 32% 12% 1	1600
	21st to end	Night	29% 5% 15% 35% 14% 1	1782
September	1st to 10th	Night	28% 6% 17% 34% 15% 1	1727
	11th to 20th	Night	36% 7% 17% 28% 11% 1	1980
	21st to end	Night	42% 6% 14% 29% 10%	1980
October	1st to 10th	Night	48% 7% 14% 23% 8% 1	2110
	11th to 20th	Night	48% 5% 14% 26% 7%	2182
	21st to end	Night	52% 6% 15% 22% 4	2574
November	1st to 10th	Night	56% 6% 14% 17% 6% 1	2563
	11th to 20th	Night	59% 6% 15% 14% 5% 1	2660
	21st to end	Night	61% 6% 14% 13% 6%	2755
December	1st to 10th	Night	61% 7% 16% 13% 4	2850
	11th to 20th	Night	62% 5% 14% 13% 5%	3516
	21st to end	Night	57% 6% 12% 18% 6%	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	11% 8% 34% 30% 15% 2	270
	11th to 20th	Day	12% 8% 30% 35% 15% 1	257
	21st to end	Day	16% 9% 25% 33% 13% 3	264
February	1st to 10th	Day	11% 11% 38% 31% 8% 1	240
	11th to 20th	Day	10% 13% 34% 29% 13% 2	240
	21st to end	Day	9% 5% 44% 31% 11%	198
March	1st to 10th	Day	12% 7% 33% 35% 13% 1	240
	11th to 20th	Day	13% 8% 31% 30% 13% 4	240
	21st to end	Day	15% 8% 34% 28% 13% 2	264
April	1st to 10th	Day	15% 13% 31% 30% 9% 2	446
	11th to 20th	Day	17% 11% 32% 26% 13% 2	590
	21st to end	Day	18% 10% 32% 27% 11% 2	600
May	1st to 10th	Day	17% 12% 31% 26% 12% 2	603
	11th to 20th	Day	20% 10% 27% 27% 13% 4	625
	21st to end	Day	20% 8% 25% 28% 15% 4	679
June	1st to 10th	Day	14% 10% 28% 27% 15% 7%	630
	11th to 20th	Day	15% 13% 30% 28% 11% 3	630
	21st to end	Day	12% 7% 26% 32% 17% 6%	630
July	1st to 10th	Day	10% 4 29% 31% 18% 8%	621
	11th to 20th	Day	11% 7% 29% 28% 21% 5%	618
	21st to end	Day	5% 5% 27% 33% 20% 8%	684
August	1st to 10th	Day	7% 6% 27% 32% 22% 7%	626
	11th to 20th	Day	10% 6% 24% 31% 20% 9%	615
	21st to end	Day	13% 6% 27% 30% 19% 5%	693
September	1st to 10th	Day	10% 8% 34% 32% 14% 3	522
	11th to 20th	Day	15% 11% 37% 25% 9% 3	270
	21st to end	Day	22% 9% 33% 27% 7% 1	270
October	1st to 10th	Day	22% 13% 24% 26% 10% 4	270
	11th to 20th	Day	14% 13% 33% 30% 9% 2	270
	21st to end	Day	26% 8% 34% 21% 9% 1	297
November	1st to 10th	Day	25% 8% 29% 27% 9% 1	270
	11th to 20th	Day	17% 12% 36% 26% 9%	270
	21st to end	Day	18% 12% 41% 23% 6%	270
December	1st to 10th	Day	14% 6% 37% 27% 14% 2	270
	11th to 20th	Day	14% 11% 37% 30% 7% 1	270
	21st to end	Day	13% 8% 29% 31% 14% 5%	297
January	1st to 10th	Night	11% 8% 33% 31% 14% 2	950
	11th to 20th	Night	15% 7% 31% 36% 10% 1	930
	21st to end	Night	14% 8% 33% 32% 12% 1	990
February	1st to 10th	Night	13% 7% 29% 35% 15% 1	900
	11th to 20th	Night	11% 7% 30% 35% 13% 4	879
	21st to end	Night	10% 6% 34% 33% 16% 1	686
March	1st to 10th	Night	15% 6% 30% 32% 14% 3	673
	11th to 20th	Night	11% 7% 39% 29% 12% 1	540
	21st to end	Night	19% 7% 26% 29% 15% 3	594
April	1st to 10th	Night	14% 9% 29% 37% 10% 1	540
	11th to 20th	Night	16% 8% 29% 35% 12%	533
	21st to end	Night	16% 6% 30% 36% 11%	540
May	1st to 10th	Night	18% 6% 33% 33% 9% 1	540
	11th to 20th	Night	17% 7% 30% 33% 13% 1	531
	21st to end	Night	18% 6% 32% 32% 11%	584
June	1st to 10th	Night	14% 5% 29% 35% 16% 1	540
	11th to 20th	Night	15% 5% 32% 32% 15% 1	540
	21st to end	Night	10% 5% 23% 41% 21% 1	540
July	1st to 10th	Night	6% 2 26% 45% 20% 1	525
	11th to 20th	Night	7% 4 26% 43% 17% 2	522
	21st to end	Night	7% 3 23% 43% 21% 3	591
August	1st to 10th	Night	9% 2 23% 47% 18% 2	537
	11th to 20th	Night	9% 4 22% 39% 22% 4	534
	21st to end	Night	12% 6% 24% 38% 20% 1	594
September	1st to 10th	Night	10% 4 30% 37% 17% 2	540
	11th to 20th	Night	16% 6% 26% 38% 15%	540
	21st to end	Night	18% 5% 32% 33% 11% 1	540
October	1st to 10th	Night	22% 9% 31% 29% 9%	670
	11th to 20th	Night	20% 8% 33% 30% 9% 1	742
	21st to end	Night	20% 10% 31% 29% 9% 1	990
November	1st to 10th	Night	19% 10% 34% 26% 10%	925
	11th to 20th	Night	18% 9% 34% 30% 8% 2	950
	21st to end	Night	18% 9% 39% 26% 7% 1	950
December	1st to 10th	Night	14% 6% 32% 33% 13% 2	950
	11th to 20th	Night	17% 7% 34% 32% 9% 2	950
	21st to end	Night	19% 8% 30% 29% 11% 2	1045

Page generated at 2024-01-13 18:28:28. Version ac07

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