Orillia
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Orillia clear sky chart from 2005-11-06 to 2024-10-25.

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	15% 10% 4 8% 5% 5% 5% 4 5% 7% 33%	102011
	Night	15% 11% 4 9% 5% 5% 5% 4 5% 6% 31%	96792
Transparency	Day	49% 7% 13% 20% 10% 1	101771
	Night	52% 7% 12% 18% 9% 1	96653
Seeing	Day	18% 11% 28% 27% 13% 4	14805
	Night	20% 11% 30% 28% 11% 1	23658

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	16% 16% 8% 11% 6% 5% 4 3 5% 3 23%	2517
	11th to 20th	Day	11% 16% 7% 15% 8% 7% 6% 4 5% 5% 16%	2680
	21st to end	Day	18% 22% 8% 12% 6% 4 3 3 4 3 16%	3124
February	1st to 10th	Day	13% 17% 7% 15% 9% 5% 4 4 5% 4 19%	1710
	11th to 20th	Day	11% 15% 7% 11% 7% 6% 3 3 5% 5% 25%	1663
	21st to end	Day	16% 15% 6% 12% 7% 6% 4 3 3 5% 22%	1443
March	1st to 10th	Day	18% 12% 4 10% 5% 4 4 3 4 5% 31%	3432
	11th to 20th	Day	10% 15% 7% 10% 6% 6% 5% 3 4 6% 27%	3480
	21st to end	Day	14% 10% 3 9% 5% 3 4 3 5% 6% 37%	3815
April	1st to 10th	Day	18% 12% 3 9% 5% 4 5% 3 4 6% 30%	2251
	11th to 20th	Day	20% 11% 2 6% 4 3 4 3 5% 6% 36%	2342
	21st to end	Day	20% 11% 3 7% 5% 4 4 3 4 6% 34%	2470
May	1st to 10th	Day	17% 8% 3 7% 5% 4 5% 4 6% 6% 35%	4155
	11th to 20th	Day	15% 8% 3 7% 5% 4 4 3 6% 8% 37%	4398
	21st to end	Day	14% 6% 2 6% 3 4 4 4 5% 7% 45%	4837
June	1st to 10th	Day	17% 7% 2 6% 5% 5% 4 4 6% 7% 37%	2660
	11th to 20th	Day	12% 5% 2 5% 5% 5% 5% 4 7% 9% 40%	2771
	21st to end	Day	16% 7% 3 6% 5% 5% 4 4 6% 8% 38%	2850
July	1st to 10th	Day	11% 5% 2 7% 5% 6% 5% 5% 7% 10% 37%	4728
	11th to 20th	Day	10% 5% 2 6% 4 5% 4 5% 6% 8% 46%	4440
	21st to end	Day	8% 5% 3 6% 4 5% 4 4 7% 8% 46%	4596
August	1st to 10th	Day	15% 7% 3 6% 4 4 4 4 6% 9% 39%	4104
	11th to 20th	Day	13% 6% 3 6% 4 5% 5% 4 7% 10% 37%	4044
	21st to end	Day	7% 6% 2 7% 4 4 5% 5% 6% 8% 45%	4377
September	1st to 10th	Day	13% 7% 2 8% 4 5% 4 3 5% 8% 41%	2280
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 3 5% 7% 46%	2177
	21st to end	Day	16% 6% 3 7% 5% 5% 5% 5% 6% 6% 37%	2047
October	1st to 10th	Day	17% 9% 3 7% 5% 4 5% 3 6% 7% 33%	1900
	11th to 20th	Day	21% 10% 4 9% 4 6% 5% 4 6% 5% 26%	1900
	21st to end	Day	25% 11% 4 9% 6% 5% 5% 4 5% 5% 22%	2027
November	1st to 10th	Day	16% 12% 4 9% 6% 4 6% 4 6% 7% 25%	1555
	11th to 20th	Day	16% 14% 5% 9% 6% 5% 6% 6% 6% 7% 21%	1520
	21st to end	Day	19% 18% 5% 9% 6% 6% 6% 4 4 6% 17%	1520
December	1st to 10th	Day	15% 19% 8% 13% 7% 6% 5% 3 6% 5% 14%	1520
	11th to 20th	Day	17% 17% 5% 9% 6% 5% 4 3 5% 6% 22%	1906
	21st to end	Day	26% 18% 6% 13% 6% 4 4 3 4 3 13%	2772
January	1st to 10th	Night	15% 20% 8% 14% 7% 5% 5% 3 5% 5% 13%	4429
	11th to 20th	Night	13% 12% 7% 14% 10% 7% 5% 4 4 5% 18%	4276
	21st to end	Night	18% 17% 7% 11% 6% 5% 4 4 5% 5% 18%	4532
February	1st to 10th	Night	12% 18% 5% 13% 9% 6% 6% 4 5% 5% 17%	2470
	11th to 20th	Night	12% 14% 6% 12% 6% 4 5% 4 5% 6% 25%	2403
	21st to end	Night	14% 14% 5% 10% 7% 6% 5% 4 5% 5% 26%	2008
March	1st to 10th	Night	16% 12% 4 9% 5% 4 5% 3 4 6% 31%	3408
	11th to 20th	Night	11% 14% 6% 9% 5% 5% 5% 4 5% 6% 31%	3479
	21st to end	Night	15% 8% 4 9% 5% 4 5% 4 6% 6% 35%	3817
April	1st to 10th	Night	19% 12% 4 8% 5% 5% 3 3 5% 6% 30%	1929
	11th to 20th	Night	17% 9% 3 7% 4 3 5% 4 5% 5% 37%	1801
	21st to end	Night	17% 10% 3 9% 5% 5% 5% 3 5% 6% 33%	1710
May	1st to 10th	Night	17% 7% 2 6% 4 4 4 3 5% 7% 40%	2783
	11th to 20th	Night	15% 7% 3 6% 4 4 4 4 6% 8% 40%	2495
	21st to end	Night	10% 5% 2 5% 4 4 4 4 5% 8% 49%	2738
June	1st to 10th	Night	14% 7% 3 6% 4 4 4 5% 6% 7% 39%	1520
	11th to 20th	Night	9% 6% 2 7% 4 4 5% 4 7% 9% 43%	1401
	21st to end	Night	13% 7% 2 8% 5% 5% 5% 4 6% 8% 38%	1330
July	1st to 10th	Night	7% 5% 2 6% 5% 5% 5% 4 6% 6% 49%	2236
	11th to 20th	Night	12% 5% 1 5% 4 4 4 3 5% 7% 50%	2520
	21st to end	Night	8% 5% 2 5% 4 5% 5% 4 6% 9% 48%	2953
August	1st to 10th	Night	10% 6% 2 6% 4 4 5% 4 6% 8% 47%	2825
	11th to 20th	Night	12% 6% 3 6% 3 4 4 3 5% 6% 48%	2785
	21st to end	Night	12% 5% 2 6% 4 4 4 4 6% 7% 46%	3247
September	1st to 10th	Night	9% 5% 2 7% 3 4 5% 4 6% 8% 46%	1900
	11th to 20th	Night	11% 5% 2 5% 5% 4 4 4 5% 8% 50%	2000
	21st to end	Night	16% 7% 2 7% 4 4 3 4 5% 6% 41%	2133
October	1st to 10th	Night	17% 6% 2 7% 5% 5% 5% 4 5% 6% 36%	2280
	11th to 20th	Night	18% 12% 4 9% 5% 5% 5% 3 5% 7% 28%	2280
	21st to end	Night	21% 10% 3 11% 6% 5% 5% 4 6% 6% 24%	2435
November	1st to 10th	Night	17% 11% 3 7% 5% 5% 5% 3 5% 6% 32%	2517
	11th to 20th	Night	16% 15% 4 8% 6% 6% 5% 4 6% 7% 24%	2660
	21st to end	Night	19% 15% 5% 9% 6% 6% 6% 5% 6% 7% 19%	2660
December	1st to 10th	Night	18% 16% 6% 13% 7% 6% 5% 4 5% 5% 15%	2660
	11th to 20th	Night	15% 19% 6% 12% 7% 6% 4 4 6% 6% 17%	3288
	21st to end	Night	26% 20% 7% 13% 6% 4 4 3 3 4 10%	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	64% 7% 14% 9% 6%	2518
	11th to 20th	Day	70% 7% 10% 8% 5%	2680
	21st to end	Day	70% 8% 8% 8% 5% 1	3124
February	1st to 10th	Day	68% 7% 9% 13% 4 1	1710
	11th to 20th	Day	59% 7% 10% 15% 8% 1	1672
	21st to end	Day	65% 5% 9% 14% 6%	1443
March	1st to 10th	Day	54% 8% 14% 14% 10%	3435
	11th to 20th	Day	54% 7% 14% 16% 7% 1	3480
	21st to end	Day	43% 7% 12% 21% 14% 2	3815
April	1st to 10th	Day	55% 6% 10% 19% 10% 1	2251
	11th to 20th	Day	49% 6% 10% 21% 14% 1	2342
	21st to end	Day	51% 6% 10% 19% 12% 3	2470
May	1st to 10th	Day	45% 8% 12% 21% 12% 1	4167
	11th to 20th	Day	42% 9% 14% 24% 10% 1	4402
	21st to end	Day	38% 8% 13% 22% 16% 3	4837
June	1st to 10th	Day	44% 7% 12% 23% 13%	2660
	11th to 20th	Day	38% 8% 13% 25% 15% 1	2771
	21st to end	Day	42% 7% 15% 22% 12% 1	2850
July	1st to 10th	Day	39% 7% 18% 22% 13% 1	4655
	11th to 20th	Day	35% 6% 16% 34% 9% 1	4365
	21st to end	Day	34% 7% 13% 29% 16% 1	4449
August	1st to 10th	Day	41% 7% 16% 24% 11% 1	4091
	11th to 20th	Day	40% 7% 18% 24% 10%	4083
	21st to end	Day	34% 7% 15% 33% 10% 1	4377
September	1st to 10th	Day	40% 6% 14% 28% 10% 1	2280
	11th to 20th	Day	36% 7% 15% 30% 12%	2177
	21st to end	Day	46% 9% 13% 24% 9%	2047
October	1st to 10th	Day	50% 7% 13% 19% 10% 1	1900
	11th to 20th	Day	58% 8% 13% 15% 6% 1	1900
	21st to end	Day	63% 7% 12% 12% 5%	2027
November	1st to 10th	Day	56% 8% 14% 16% 6%	1555
	11th to 20th	Day	59% 11% 12% 12% 5% 1	1520
	21st to end	Day	67% 10% 11% 10% 2	1520
December	1st to 10th	Day	72% 8% 10% 8% 2	1520
	11th to 20th	Day	64% 9% 10% 10% 6%	1906
	21st to end	Day	75% 7% 8% 8% 2	2772
January	1st to 10th	Night	73% 8% 9% 8% 2	4429
	11th to 20th	Night	68% 9% 11% 9% 3	4276
	21st to end	Night	67% 8% 12% 9% 4 1	4532
February	1st to 10th	Night	66% 7% 10% 13% 3 1	2470
	11th to 20th	Night	59% 7% 12% 16% 6%	2405
	21st to end	Night	58% 7% 13% 16% 6%	2008
March	1st to 10th	Night	52% 7% 12% 19% 9% 1	3418
	11th to 20th	Night	52% 8% 14% 17% 7% 2	3480
	21st to end	Night	45% 7% 13% 20% 13% 1	3817
April	1st to 10th	Night	55% 5% 9% 19% 10% 1	1929
	11th to 20th	Night	46% 6% 9% 21% 15% 2	1801
	21st to end	Night	50% 7% 11% 14% 16% 1	1710
May	1st to 10th	Night	42% 7% 14% 18% 17% 2	2790
	11th to 20th	Night	40% 9% 14% 24% 12% 2	2496
	21st to end	Night	33% 8% 13% 27% 18% 2	2739
June	1st to 10th	Night	42% 7% 12% 22% 15% 2	1520
	11th to 20th	Night	35% 7% 14% 25% 18% 1	1401
	21st to end	Night	43% 7% 13% 22% 13% 1	1330
July	1st to 10th	Night	35% 7% 15% 24% 18% 2	2201
	11th to 20th	Night	34% 5% 14% 32% 15%	2472
	21st to end	Night	32% 7% 13% 31% 17% 1	2859
August	1st to 10th	Night	36% 6% 16% 26% 16% 1	2814
	11th to 20th	Night	36% 7% 17% 25% 14% 1	2812
	21st to end	Night	36% 7% 12% 33% 11% 1	3247
September	1st to 10th	Night	35% 9% 16% 27% 12% 1	1900
	11th to 20th	Night	33% 7% 14% 30% 15%	2000
	21st to end	Night	43% 6% 13% 27% 10%	2133
October	1st to 10th	Night	47% 9% 13% 19% 12% 1	2280
	11th to 20th	Night	57% 8% 12% 18% 5%	2280
	21st to end	Night	61% 8% 10% 14% 8%	2435
November	1st to 10th	Night	52% 8% 13% 18% 8%	2517
	11th to 20th	Night	59% 9% 12% 13% 6% 1	2660
	21st to end	Night	65% 10% 13% 10% 2	2660
December	1st to 10th	Night	71% 9% 10% 8% 2	2660
	11th to 20th	Night	68% 8% 12% 10% 3	3288
	21st to end	Night	79% 5% 7% 7% 2	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	17% 21% 37% 17% 8% 2	180
	11th to 20th	Day	20% 19% 36% 18% 6% 1	225
	21st to end	Day	26% 12% 30% 25% 6% 1	297
February	1st to 10th	Day	23% 20% 37% 15% 4	270
	11th to 20th	Day	18% 19% 38% 23% 2	270
	21st to end	Day	25% 25% 27% 22%	234
March	1st to 10th	Day	20% 11% 40% 26% 4	460
	11th to 20th	Day	14% 19% 35% 25% 6%	460
	21st to end	Day	25% 11% 33% 21% 9%	506
April	1st to 10th	Day	19% 14% 35% 24% 8% 1	460
	11th to 20th	Day	26% 15% 25% 21% 9% 3	452
	21st to end	Day	24% 12% 30% 24% 8% 2	460
May	1st to 10th	Day	21% 9% 27% 28% 12% 2	463
	11th to 20th	Day	16% 6% 27% 31% 18% 3	487
	21st to end	Day	15% 6% 23% 33% 17% 5%	529
June	1st to 10th	Day	18% 6% 26% 33% 16% 1	490
	11th to 20th	Day	13% 6% 25% 35% 16% 4	601
	21st to end	Day	17% 7% 26% 34% 13% 2	680
July	1st to 10th	Day	9% 6% 21% 38% 21% 5%	653
	11th to 20th	Day	14% 3 23% 33% 19% 8%	484
	21st to end	Day	8% 4 23% 39% 18% 7%	532
August	1st to 10th	Day	13% 4 19% 33% 23% 7%	486
	11th to 20th	Day	13% 6% 15% 31% 26% 9%	479
	21st to end	Day	11% 8% 22% 29% 23% 7%	539
September	1st to 10th	Day	15% 7% 23% 29% 20% 7%	490
	11th to 20th	Day	11% 4 20% 27% 25% 13%	490
	21st to end	Day	16% 9% 27% 23% 21% 4	490
October	1st to 10th	Day	20% 11% 28% 22% 13% 6%	490
	11th to 20th	Day	20% 18% 31% 22% 7% 2	490
	21st to end	Day	28% 16% 31% 21% 5%	514
November	1st to 10th	Day	23% 22% 23% 24% 8%	226
	11th to 20th	Day	19% 23% 33% 19% 5% 1	180
	21st to end	Day	24% 18% 40% 16% 1	180
December	1st to 10th	Day	22% 24% 35% 16% 4	180
	11th to 20th	Day	25% 24% 30% 16% 4 1	180
	21st to end	Day	28% 22% 35% 13% 2	198
January	1st to 10th	Night	24% 19% 33% 19% 5% 1	760
	11th to 20th	Night	27% 13% 32% 23% 5% 1	760
	21st to end	Night	20% 10% 31% 31% 7% 1	836
February	1st to 10th	Night	20% 12% 40% 24% 3	760
	11th to 20th	Night	18% 13% 38% 26% 6%	743
	21st to end	Night	23% 13% 35% 25% 4	628
March	1st to 10th	Night	19% 13% 36% 29% 4	760
	11th to 20th	Night	18% 13% 37% 26% 5% 1	760
	21st to end	Night	20% 10% 32% 29% 9%	836
April	1st to 10th	Night	25% 10% 32% 28% 5%	760
	11th to 20th	Night	21% 10% 30% 27% 11% 1	677
	21st to end	Night	20% 9% 32% 28% 12%	570
May	1st to 10th	Night	19% 5% 23% 36% 15% 1	546
	11th to 20th	Night	19% 5% 25% 37% 13% 1	374
	21st to end	Night	12% 4 25% 40% 18%	411
June	1st to 10th	Night	15% 6% 28% 36% 14% 1	380
	11th to 20th	Night	11% 6% 26% 40% 17% 1	380
	21st to end	Night	14% 8% 22% 38% 16% 1	380
July	1st to 10th	Night	8% 4 19% 46% 22% 2	370
	11th to 20th	Night	11% 6% 20% 40% 21% 2	368
	21st to end	Night	10% 3 22% 40% 24% 1	542
August	1st to 10th	Night	11% 3 18% 38% 28% 2	567
	11th to 20th	Night	6% 5% 20% 36% 30% 3	564
	21st to end	Night	13% 5% 23% 32% 24% 2	698
September	1st to 10th	Night	12% 5% 24% 34% 21% 4	760
	11th to 20th	Night	13% 5% 21% 31% 23% 7%	760
	21st to end	Night	19% 8% 20% 30% 18% 5%	760
October	1st to 10th	Night	19% 7% 33% 25% 14% 2	760
	11th to 20th	Night	24% 14% 31% 22% 8% 1	760
	21st to end	Night	27% 15% 32% 22% 4	812
November	1st to 10th	Night	23% 14% 29% 23% 9% 1	740
	11th to 20th	Night	23% 18% 34% 18% 6% 1	760
	21st to end	Night	27% 17% 32% 20% 4	760
December	1st to 10th	Night	27% 21% 32% 16% 4	760
	11th to 20th	Night	23% 18% 38% 15% 4 1	760
	21st to end	Night	31% 15% 35% 18% 2	836

Page generated at 2024-10-22 20:21:01. Version ac07

Copyright © 2024 Attilla Danko.