Nipigon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Nipigon clear sky chart from 2005-11-06 to 2025-02-25.

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% 10% 4 8% 5% 5% 5% 4 6% 7% 32%	108387
	Night	13% 11% 4 10% 6% 5% 5% 4 6% 7% 29%	110486
Transparency	Day	28% 46% 8% 12% 5%	111826
	Night	33% 43% 8% 11% 5%	115196
Seeing	Day	18% 17% 35% 21% 8% 2	16167
	Night	19% 11% 31% 29% 10% 1	25940

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	9% 12% 5% 10% 7% 9% 8% 5% 7% 8% 19%	3617
	11th to 20th	Day	7% 11% 5% 13% 7% 7% 7% 7% 9% 8% 19%	3589
	21st to end	Day	9% 16% 9% 11% 7% 7% 5% 4 6% 7% 19%	3982
February	1st to 10th	Day	7% 11% 4 10% 6% 4 7% 6% 7% 8% 29%	1625
	11th to 20th	Day	7% 10% 5% 11% 7% 4 4 4 7% 8% 32%	1804
	21st to end	Day	6% 10% 4 10% 8% 7% 5% 4 7% 8% 31%	1610
March	1st to 10th	Day	11% 9% 4 9% 5% 5% 5% 3 5% 6% 40%	3118
	11th to 20th	Day	7% 12% 5% 11% 6% 7% 5% 4 5% 5% 32%	3267
	21st to end	Day	17% 13% 4 10% 5% 5% 4 3 4 5% 31%	4165
April	1st to 10th	Day	14% 11% 2 8% 5% 6% 5% 4 5% 6% 33%	2280
	11th to 20th	Day	17% 12% 4 8% 5% 5% 4 4 5% 7% 30%	2304
	21st to end	Day	16% 11% 3 7% 4 4 4 3 5% 6% 35%	2508
May	1st to 10th	Day	17% 9% 3 7% 4 4 4 3 5% 7% 36%	4428
	11th to 20th	Day	14% 8% 3 6% 4 4 4 4 6% 7% 39%	4399
	21st to end	Day	16% 8% 2 6% 4 4 4 4 5% 7% 38%	4926
June	1st to 10th	Day	19% 7% 2 6% 4 4 5% 4 6% 8% 35%	2850
	11th to 20th	Day	14% 7% 3 6% 4 4 4 4 6% 8% 39%	2850
	21st to end	Day	17% 7% 2 7% 5% 5% 4 3 6% 7% 37%	2850
July	1st to 10th	Day	10% 6% 2 6% 4 5% 5% 5% 7% 9% 41%	4571
	11th to 20th	Day	8% 4 2 5% 5% 4 5% 4 7% 8% 46%	4440
	21st to end	Day	13% 6% 2 5% 4 4 5% 4 6% 10% 41%	4814
August	1st to 10th	Day	11% 6% 3 7% 5% 5% 6% 5% 8% 10% 35%	4423
	11th to 20th	Day	12% 4 1 5% 3 4 4 4 6% 8% 48%	4292
	21st to end	Day	14% 7% 2 6% 4 4 5% 4 6% 8% 40%	4244
September	1st to 10th	Day	14% 6% 2 7% 5% 4 5% 3 5% 8% 41%	2280
	11th to 20th	Day	18% 7% 2 6% 5% 4 4 3 5% 9% 35%	2195
	21st to end	Day	17% 9% 3 8% 5% 4 5% 3 6% 7% 33%	2090
October	1st to 10th	Day	21% 12% 3 8% 4 3 4 4 5% 9% 27%	1956
	11th to 20th	Day	20% 12% 4 10% 7% 7% 5% 4 5% 7% 21%	1788
	21st to end	Day	20% 14% 4 11% 6% 5% 5% 3 5% 5% 21%	1881
November	1st to 10th	Day	17% 13% 5% 9% 7% 5% 4 4 6% 7% 22%	1762
	11th to 20th	Day	20% 17% 5% 12% 6% 4 3 3 6% 5% 18%	1602
	21st to end	Day	17% 15% 6% 11% 8% 7% 6% 3 5% 4 17%	1436
December	1st to 10th	Day	10% 14% 6% 17% 8% 6% 4 4 6% 7% 16%	2280
	11th to 20th	Day	10% 15% 5% 13% 7% 6% 5% 4 6% 7% 21%	2621
	21st to end	Day	19% 21% 7% 12% 4 3 3 3 5% 6% 16%	3540
January	1st to 10th	Night	7% 13% 5% 12% 9% 8% 7% 5% 6% 8% 21%	6348
	11th to 20th	Night	5% 11% 6% 17% 10% 8% 8% 7% 8% 6% 15%	6316
	21st to end	Night	7% 13% 7% 13% 8% 6% 6% 5% 6% 7% 21%	6996
February	1st to 10th	Night	8% 11% 5% 9% 6% 7% 7% 6% 6% 7% 28%	2775
	11th to 20th	Night	9% 10% 3 9% 7% 8% 7% 5% 7% 7% 28%	2483
	21st to end	Night	6% 13% 6% 13% 6% 6% 5% 4 5% 6% 31%	1939
March	1st to 10th	Night	12% 10% 3 9% 6% 6% 5% 3 6% 8% 33%	3722
	11th to 20th	Night	9% 16% 4 10% 6% 5% 5% 3 5% 6% 32%	3719
	21st to end	Night	16% 12% 4 8% 5% 6% 5% 4 5% 5% 31%	3466
April	1st to 10th	Night	14% 12% 4 9% 6% 5% 5% 4 6% 6% 31%	1900
	11th to 20th	Night	17% 11% 4 7% 5% 3 4 4 6% 7% 33%	1825
	21st to end	Night	17% 10% 2 7% 4 4 3 4 6% 7% 36%	1668
May	1st to 10th	Night	17% 9% 2 6% 4 4 5% 3 5% 7% 39%	2523
	11th to 20th	Night	15% 8% 3 7% 5% 5% 5% 4 6% 7% 36%	2506
	21st to end	Night	22% 6% 2 6% 4 4 4 3 5% 5% 40%	2659
June	1st to 10th	Night	16% 8% 3 7% 5% 5% 4 4 5% 6% 37%	1330
	11th to 20th	Night	15% 7% 3 9% 4 4 4 3 5% 7% 38%	1330
	21st to end	Night	18% 7% 2 5% 5% 5% 5% 4 7% 9% 35%	1330
July	1st to 10th	Night	10% 8% 3 8% 4 4 4 4 7% 8% 40%	2394
	11th to 20th	Night	8% 5% 2 6% 4 5% 6% 4 7% 8% 46%	2530
	21st to end	Night	11% 5% 3 5% 3 3 5% 4 6% 10% 44%	2750
August	1st to 10th	Night	14% 6% 2 5% 4 5% 4 4 7% 9% 41%	2517
	11th to 20th	Night	13% 4 2 4 3 4 3 3 6% 9% 48%	2545
	21st to end	Night	17% 7% 4 6% 3 4 3 3 4 6% 42%	3408
September	1st to 10th	Night	14% 6% 3 5% 3 4 4 3 6% 7% 45%	1900
	11th to 20th	Night	15% 8% 3 6% 4 5% 4 4 5% 7% 40%	1966
	21st to end	Night	19% 8% 3 8% 4 3 4 4 5% 7% 34%	2090
October	1st to 10th	Night	17% 11% 2 7% 5% 4 5% 4 5% 6% 34%	2222
	11th to 20th	Night	18% 10% 3 6% 6% 5% 5% 4 6% 8% 29%	2391
	21st to end	Night	20% 14% 4 9% 6% 5% 5% 3 5% 5% 24%	2717
November	1st to 10th	Night	18% 13% 4 8% 6% 5% 5% 3 6% 7% 25%	2536
	11th to 20th	Night	19% 16% 5% 13% 7% 5% 4 3 5% 5% 19%	2795
	21st to end	Night	16% 17% 6% 13% 7% 5% 5% 3 5% 6% 17%	2961
December	1st to 10th	Night	9% 17% 6% 15% 9% 6% 6% 4 6% 7% 15%	4910
	11th to 20th	Night	10% 14% 6% 13% 6% 5% 5% 4 6% 7% 25%	5586
	21st to end	Night	22% 19% 5% 13% 5% 4 4 3 5% 5% 15%	7433

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	41% 32% 10% 12% 4 1	3618
	11th to 20th	Day	42% 31% 8% 17% 2	3620
	21st to end	Day	48% 32% 7% 7% 5% 1	3982
February	1st to 10th	Day	18% 64% 7% 8% 3	1625
	11th to 20th	Day	21% 62% 5% 9% 3	1813
	21st to end	Day	20% 64% 2 7% 7%	1610
March	1st to 10th	Day	26% 42% 8% 13% 11%	3120
	11th to 20th	Day	29% 43% 8% 14% 5% 1	3267
	21st to end	Day	35% 41% 4 8% 12% 1	4165
April	1st to 10th	Day	16% 65% 4 7% 7% 1	2280
	11th to 20th	Day	17% 66% 4 9% 3 1	2304
	21st to end	Day	16% 65% 4 8% 6% 1	2508
May	1st to 10th	Day	26% 41% 5% 13% 14% 1	4440
	11th to 20th	Day	25% 43% 7% 15% 9% 1	4403
	21st to end	Day	26% 44% 9% 11% 9% 2	4926
June	1st to 10th	Day	19% 65% 4 6% 6%	2850
	11th to 20th	Day	16% 66% 4 10% 4	2850
	21st to end	Day	17% 65% 5% 9% 3	2850
July	1st to 10th	Day	24% 42% 15% 13% 6%	4502
	11th to 20th	Day	20% 39% 15% 22% 4	4365
	21st to end	Day	23% 38% 12% 24% 4	4662
August	1st to 10th	Day	27% 40% 9% 19% 4	4408
	11th to 20th	Day	20% 39% 15% 19% 7%	4334
	21st to end	Day	26% 41% 10% 18% 6%	4243
September	1st to 10th	Day	18% 60% 7% 10% 4	2280
	11th to 20th	Day	18% 63% 9% 8% 1	2195
	21st to end	Day	20% 61% 7% 7% 4	2090
October	1st to 10th	Day	26% 40% 11% 13% 10%	3242
	11th to 20th	Day	31% 39% 12% 17% 2	2952
	21st to end	Day	38% 39% 12% 9% 1	3081
November	1st to 10th	Day	28% 58% 7% 6% 1	1762
	11th to 20th	Day	31% 59% 5% 4 2	1602
	21st to end	Day	33% 58% 3 4 2	1436
December	1st to 10th	Day	48% 40% 8% 3 1	2280
	11th to 20th	Day	41% 36% 11% 9% 3	2621
	21st to end	Day	52% 30% 5% 12% 1	3540
January	1st to 10th	Night	46% 31% 9% 10% 3 1	6348
	11th to 20th	Night	50% 29% 6% 13% 2	6360
	21st to end	Night	44% 33% 7% 12% 4 1	6996
February	1st to 10th	Night	20% 64% 6% 7% 3	2775
	11th to 20th	Night	21% 62% 6% 7% 3	2484
	21st to end	Night	21% 63% 4 6% 5%	1939
March	1st to 10th	Night	30% 42% 9% 9% 9% 1	3733
	11th to 20th	Night	32% 41% 8% 13% 5% 1	3720
	21st to end	Night	33% 42% 6% 10% 10% 1	3466
April	1st to 10th	Night	17% 66% 4 7% 5%	1900
	11th to 20th	Night	16% 66% 4 7% 6% 1	1825
	21st to end	Night	15% 66% 4 10% 5%	1668
May	1st to 10th	Night	24% 41% 8% 16% 10% 1	2530
	11th to 20th	Night	27% 42% 7% 18% 4 2	2507
	21st to end	Night	28% 42% 6% 14% 10%	2660
June	1st to 10th	Night	17% 66% 3 8% 6%	1330
	11th to 20th	Night	16% 65% 5% 8% 7%	1330
	21st to end	Night	18% 65% 5% 8% 5%	1330
July	1st to 10th	Night	28% 39% 14% 11% 7%	2354
	11th to 20th	Night	20% 40% 15% 20% 4 1	2482
	21st to end	Night	21% 38% 9% 25% 7%	2662
August	1st to 10th	Night	24% 39% 10% 23% 4	2508
	11th to 20th	Night	20% 39% 17% 20% 5%	2569
	21st to end	Night	30% 39% 11% 12% 7%	3408
September	1st to 10th	Night	16% 62% 5% 11% 5%	1900
	11th to 20th	Night	18% 63% 9% 8% 1	1966
	21st to end	Night	20% 62% 5% 9% 4	2090
October	1st to 10th	Night	21% 39% 10% 17% 12%	3703
	11th to 20th	Night	28% 39% 9% 19% 5%	3966
	21st to end	Night	41% 39% 11% 7% 2	4467
November	1st to 10th	Night	29% 58% 7% 5% 1	2536
	11th to 20th	Night	30% 59% 6% 4 1	2795
	21st to end	Night	32% 59% 5% 3 1	2961
December	1st to 10th	Night	50% 39% 6% 4 1	4910
	11th to 20th	Night	40% 34% 11% 12% 3	5585
	21st to end	Night	56% 28% 5% 10% 2	7433

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	17% 11% 45% 21% 5%	300
	11th to 20th	Day	12% 15% 41% 24% 7% 1	300
	21st to end	Day	15% 16% 45% 17% 7% 1	330
February	1st to 10th	Day	13% 19% 43% 20% 5%	300
	11th to 20th	Day	10% 22% 44% 19% 4	300
	21st to end	Day	14% 29% 40% 13% 3	237
March	1st to 10th	Day	15% 25% 35% 20% 4	270
	11th to 20th	Day	19% 23% 36% 16% 4 1	286
	21st to end	Day	17% 15% 39% 20% 7% 3	506
April	1st to 10th	Day	20% 20% 30% 22% 7% 1	460
	11th to 20th	Day	26% 20% 26% 17% 9% 1	452
	21st to end	Day	21% 18% 31% 18% 9% 3	498
May	1st to 10th	Day	19% 20% 35% 18% 6% 1	653
	11th to 20th	Day	18% 19% 35% 19% 6% 2	675
	21st to end	Day	20% 19% 35% 21% 5% 1	734
June	1st to 10th	Day	20% 14% 40% 19% 5% 2	680
	11th to 20th	Day	16% 19% 36% 21% 7% 1	680
	21st to end	Day	18% 12% 38% 22% 8% 2	680
July	1st to 10th	Day	11% 10% 39% 28% 10% 3	671
	11th to 20th	Day	11% 13% 42% 22% 9% 2	668
	21st to end	Day	12% 12% 34% 26% 12% 4	739
August	1st to 10th	Day	12% 14% 36% 26% 9% 3	676
	11th to 20th	Day	16% 11% 29% 28% 12% 4	627
	21st to end	Day	20% 13% 31% 23% 11% 3	539
September	1st to 10th	Day	16% 13% 31% 25% 12% 3	490
	11th to 20th	Day	22% 14% 29% 22% 12% 1	490
	21st to end	Day	20% 16% 28% 21% 11% 3	490
October	1st to 10th	Day	25% 23% 29% 15% 6% 2	356
	11th to 20th	Day	23% 22% 35% 16% 3	300
	21st to end	Day	28% 28% 32% 10% 3	330
November	1st to 10th	Day	21% 24% 34% 17% 4	300
	11th to 20th	Day	31% 21% 34% 11% 3	300
	21st to end	Day	22% 26% 33% 15% 4	217
December	1st to 10th	Day	19% 16% 34% 24% 7% 2	200
	11th to 20th	Day	21% 22% 31% 18% 7% 1	200
	21st to end	Day	22% 17% 31% 22% 7% 1	233
January	1st to 10th	Night	16% 12% 39% 27% 6% 1	1000
	11th to 20th	Night	17% 13% 35% 26% 8% 2	1000
	21st to end	Night	15% 10% 35% 29% 10% 1	1100
February	1st to 10th	Night	14% 11% 36% 29% 9% 1	1000
	11th to 20th	Night	14% 12% 36% 26% 11% 1	929
	21st to end	Night	13% 12% 39% 27% 9% 1	647
March	1st to 10th	Night	13% 12% 37% 27% 11% 1	760
	11th to 20th	Night	17% 15% 34% 27% 6% 1	736
	21st to end	Night	17% 9% 30% 30% 13% 2	627
April	1st to 10th	Night	18% 10% 31% 32% 6% 1	570
	11th to 20th	Night	22% 11% 28% 27% 11% 1	563
	21st to end	Night	22% 7% 28% 30% 13% 1	570
May	1st to 10th	Night	22% 8% 29% 32% 8% 1	570
	11th to 20th	Night	19% 9% 28% 34% 9% 1	561
	21st to end	Night	22% 9% 24% 34% 9% 1	565
June	1st to 10th	Night	14% 9% 34% 30% 11% 1	380
	11th to 20th	Night	17% 9% 30% 36% 7% 1	380
	21st to end	Night	19% 7% 30% 36% 7% 1	380
July	1st to 10th	Night	13% 5% 30% 38% 13% 1	471
	11th to 20th	Night	13% 6% 27% 40% 13% 1	552
	21st to end	Night	10% 5% 24% 42% 19% 2	624
August	1st to 10th	Night	14% 4 25% 42% 14%	567
	11th to 20th	Night	15% 4 21% 35% 24% 2	564
	21st to end	Night	18% 6% 29% 30% 15% 1	627
September	1st to 10th	Night	15% 8% 24% 35% 16% 3	570
	11th to 20th	Night	20% 10% 30% 28% 11% 2	636
	21st to end	Night	22% 10% 27% 28% 13% 1	760
October	1st to 10th	Night	23% 14% 30% 24% 9% 1	760
	11th to 20th	Night	24% 13% 31% 22% 8% 1	760
	21st to end	Night	28% 11% 32% 22% 6%	836
November	1st to 10th	Night	24% 16% 32% 22% 6%	780
	11th to 20th	Night	29% 14% 30% 20% 6% 1	995
	21st to end	Night	24% 18% 29% 23% 5%	1000
December	1st to 10th	Night	18% 15% 36% 23% 7% 1	1000
	11th to 20th	Night	18% 14% 32% 27% 9% 1	1000
	21st to end	Night	24% 12% 29% 27% 7% 1	1100

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